Quality control of bolted joints of metal structures. Cn bolted joints of metal structures

As you know, depending on the design, purpose, method of joining materials, field of application and other factors, contact joints are distinguished: bolted, welded, brazed and made by compression (pressed and twisted).
Contact connections include remote wire spacers.

During the operation of contact joints made by welding, the causes of defects in them may be: deviations from the specified parameters, undercuts, bubbles, caverns, lack of penetration, sagging, cracks, slag and gas inclusions (cavities), unsealed craters, burnout of the core wires, misalignment of the connected conductors, wrong choice of ferrules, lack of protective coatings on the connections, etc.
Thermal welding technology does not provide reliable operation of welded connectors for wires of large cross-sections (240 mm2 and more). This is due to the fact that due to insufficient heating during welding of the wires to be connected and the uneven approach of their ends, the outer layers of wires are burned out, lack of penetration, and shrinkage cavities and slags appear at the welding site. As a result, the mechanical strength of the welded joint is reduced. When mechanical loads are less than the calculated ones, a break (burnout) of the wire occurs in the loop of the anchor support, which leads to emergency shutdowns of overhead lines with a short service life. If individual conductors of the wire break in the welded joint, this leads to an increase in the contact resistance and an increase in its temperature.
The rate of defect development in this case will significantly depend on a number of factors: the value of the load current, wire tension, wind and vibration effects, etc.
Based on the experiments carried out, it was found that:

a decrease in the active cross-section of the wire by 20 - 25% due to the breakage of individual conductors may not be detected during IR control from a helicopter, which is associated with the low emissivity of the wire, the distance of the thermal imager from the route by 50 - 80 m, the influence of wind, solar radiation, and other factors;
when rejecting defective contact joints made by welding using a thermal imager or pyrometer, it must be borne in mind that the rate of development of a defect of these joints is much higher than that of bolted contact joints with pressing;
defects in welded contact joints detected by a thermal imager during inspection of overhead lines from a helicopter must be classified as dangerous if their excess temperature is 5 ° C;
steel bushings not removed from the welded section of the wires can give a false impression of possible heating due to the high emissivity of the annealed surface.

In contact connections made by crimping, incorrect selection of ferrules or sleeves, incomplete insertion of the core into the ferrule, insufficient degree of crimping, displacement of the steel core in the wire connector, etc. are observed. As you know, one of the ways to control molded connectors is to measure their DC resistance.
The criterion for an ideal contact connection is the equality of its resistance to the resistance of an equivalent section of a whole wire. A crimped connector is considered serviceable if its resistance is no more than 1.2 times the equivalent length of the entire wire. When the connector is pressed, its resistance drops sharply, but with an increase in pressure, it stabilizes and changes insignificantly.
The resistance of the connector is very sensitive to the state of the contact surface of the crimped wires. The appearance of aluminum oxides on the contact surfaces leads to a sharp increase in the contact resistance of the connector and increased heat generation.
Insignificant changes in the contact resistance of the contact joint during the process of pressing them, as well as the associated low heat release in the contact joint, indicate the insufficient efficiency of detecting defects in them immediately after installation using infrared devices. During the operation of the pressed contact joints, the presence of defects in them will contribute to a more intense formation of oxide films and increase the transition resistance, which can lead to the appearance of local heating. Therefore, we can assume that the IR control of new crimped contact connections does not allow detecting crimping defects and should be carried out for connectors that have worked for a certain period (1 year or more).
The main characteristics of crimped connectors are crimp strength and mechanical strength. As the mechanical strength of the connector increases, its contact resistance decreases. The maximum mechanical strength of the connector corresponds to the minimum electrical contact resistance.

Contact connections made with bolts most often have defects due to the absence of washers at the junction of the copper conductor with a flat terminal made of copper or aluminum alloy, the absence of Belleville springs, the direct connection of the aluminum tip to the copper terminals of the equipment in rooms with an aggressive or humid environment , as a result of insufficient tightening of bolts, etc.
Bolted contact joints of aluminum buses for high currents (3000 A and above) are not sufficiently stable in operation. If contact connections for currents up to 1500 A require tightening the bolts once every 1 - 2 years, then similar connections for currents of 3000 A and above require an annual overhaul with the indispensable cleaning of the contact surfaces. The need for such an operation is due to the fact that in multi-ampere bus ducts (busbars of power plants, etc.) made of aluminum, the process of formation of oxide films on the surface of contact joints is more intensive.
The process of formation of oxide films on the surface of bolted contact joints is facilitated by various temperature coefficients of linear expansion of steel bolts and aluminum bus. Therefore, when the short-circuit current passes through the bus duct, when it is operated with a variable current load, deformation (compaction) of the contact surface of the aluminum bus occurs as a result of vibration effects in it with a large length. In this case, the force pulling together the two contact surfaces of the busbar is weakened, the lubricant layer between them evaporates, etc.
Due to the formation of oxide films, the contact area of the contacts, i.e. the number and size of contact pads (number of points) through which the current passes decreases and, at the same time, the current density increases, which can reach thousands of amperes per square centimeter, as a result of which the heating of these points increases greatly.
The temperature of the last point reaches the melting point of the contact material, and a drop of liquid metal is formed between the contact surfaces. The droplet temperature, rising, reaches a boil, the space around the contact connection is ionized, and there is a danger of a multiphase short circuit in the reactor plant. Under the influence of magnetic forces, the arc can move along the RU tires with all the ensuing consequences.
Operational experience shows that along with multi-ampere bus ducts, single-bolt contact connections also have insufficient reliability. The latter, in accordance with GOST 21242-75, are allowed for use at a rated current of up to 1 000 A, however, they are damaged already at currents of 400 - 630 A. Improving the reliability of single-bolt contact connections requires a number of technical measures to stabilize their electrical resistance.
The process of defect development in a bolted contact connection, as a rule, takes a long time and depends on a number of factors: load current, operating mode (stable load or variable), exposure to chemicals, wind loads, bolt tightening forces, stabilization of contact pressure, etc.
The transition resistance of the bolted contact connection depends on the duration of the current load. The transient resistance of the contact joints gradually increases up to a certain point, after which there is a sharp deterioration of the contact surface of the contact joint with intense heat generation, indicating the emergency state of the contact joint.
Similar results were obtained by specialists from Inframetrix (USA) during thermal tests of bolted contact joints. The increase in the heating temperature during the tests was gradual throughout the year, and then a period of a sharp increase in heat release began.

Failures of contact connections made by twisting occur mainly due to installation defects. Incomplete twisting of wires in oval connectors (less than 4.5 turns) will pull the wire out of the connector and break it. Untreated wires create a high contact resistance, as a result of which the wire in the connector overheats with possible burnout. Cases of pulling out the lightning protection cable АЖС-70/39, twisted by a smaller number of turns, from the oval connector of the СОАС-95-3 brand of 220 kV overhead lines were repeatedly noted.

Rice. Photo of the place of attachment of the distance spacer with a break in the conductors as a result of vibration effects (a) and the diagram of the flow of load currents in the two-wire phase of the switchgear or overhead line when the conductors are broken at the point of attachment of the spacers (b)

Distance spacers.

The unsatisfactory design of some versions of spacers, the impact of vibration forces and other factors can lead to chafing or breaking of the conductors of the wire (Fig. 34). In this case, a current will flow through the spacer, the value of which will be determined by the nature and degree of the defect development.

Analysis of the results of thermal imaging control of contact connections

Welded contact connections.

During thermal imaging control of contact joints, the assessment of their condition in accordance with the “Scope and Norms of Electrical Equipment Testing” can be carried out according to the coefficient of defectiveness or according to the value of excess temperature. The experiments carried out by Yuzhtechenergo revealed the insufficient efficiency of the thermal imaging method for detecting a defect in a welded contact joint at an early stage of development, especially when inspecting the contact joints of overhead lines from a helicopter. For welded contact joints, it is preferable to assess their condition by the value of excess temperature.

Crimped contact connections.

At one time, the values of the defectiveness coefficients were used as the criteria for assessing the state of the pressed contact connections at the outdoor switchgear and overhead lines, i.e. the ratio of the measured resistance or voltage drop across a connector to the resistance of an identical section of a whole wire.
With the advent of devices and CT, the state of pressed contact joints can be assessed by the value of the excess temperature or by the coefficient of defectiveness.
The question arises about the degree of effectiveness of each of these methods for assessing the state of pressed contact joints. To solve this problem, Mosenergo carried out stress tests of a section of an ASU-400 wire with serviceable and defective connectors.
Defectiveness ratios for direct current (Kx - 9) and voltage drop (K2 = 5) were preliminarily determined. The results of stress tests (Table 1) showed that for crimped connectors, the most preferable method for assessing contact joints by the value of excess temperature.

Current value	Heating temperature, "С			Coefficient
load, A		good contact connection	defective contact connection	defectiveness

So, at a current (0.3 - 0.4) / nom, the excess temperature is 7-16 ° C, which is quite confidently recorded by the ICT device.
The results of the experiments carried out are in good agreement with the recommendations of the “Scope and norms of testing of electrical equipment”. When assessing the state of the pressed contact joints according to the values of the defectiveness coefficients, it should be borne in mind that at the initial stage of manufacturing (during installation) the contact joints have a defectiveness coefficient of 0.8 - 0.9.

The failure of the crimped contact connection develops gradually and largely depends on the observance of the compression technology and the pressure developed at the same time. The optimal condition is considered when the maximum degree of reduction corresponds to the minimum value of the contact resistance of the contact connection.

Bolted contact connections.

Both in domestic and foreign practice, the most widespread is the assessment of the state of the bolted contact joint by the value of the excess temperature.
The process of defect development in a bolted contact connection was investigated by Inframetrix (USA) on an operating connection at a load current of 200 A. The experiment showed that the process of defect development in the absence of external climatic, vibration and other factors and a load that is stable over time can take a very long time ...
Based on the test results, the company proposed the following overtemperature limit values at rated current:
a)< 10 °С - нормальная периодичность тепловизионного контроля;
b) 10 - 20 ° С - more frequent thermal imaging control;
c) 20 - 40 ° С - thermal imaging control every month;
d)> 40 ° C - emergency heating.
The system for assessing the state of bolted contact joints by heating temperature proposed by the company, in principle, does not differ from the one regulated by the “Scope and norms of testing of electrical equipment”.

Rice. 2. Dependence of the excess temperature of the bolted connector on the load current:
1 - when reducing the area of contact of contact surfaces by 40%; 2 - the same, 80%

The influence of the heating temperature of bolted contact joints on the degree of defect development was investigated by Yuzhtekhenergo. For this purpose, stress tests of bolted contact joints were carried out while simulating their reduction by 40 and 80%, the contact surfaces of the contact surfaces were flat (Fig. 35). The possibility of detecting defects of this kind during thermal imaging control was confirmed and it was shown that defects at an early stage of development can be clearly detected at load currents (0.3 - 0.4) / nom.
Cyclic long-term tests of bolted contact joints show that the stability of their contact transition resistance is largely determined by the design of the fastening fittings (the presence of spring washers, etc.). When carrying out thermal imaging control, the identification of contact connections with increased heating requires the adoption of certain stabilization measures, for example, taking out of service or temporarily reducing the load. In the latter case, the current / additional allowable for a given defective contact connection can be determined from the ratio

Monitored nodes
	heating temperature, ° С		temperature rise, "С
1. Current-carrying (except for contacts and contact connections) and non-current-carrying metal parts:
uninsulated and not in contact with insulating materials
insulated or in contact with insulating materials of heat resistance classes according to GOST 8865-93:






2. Copper and copper alloy contacts: uncoated (in air / insulating oil)
with overlaid silver plates (in air / in insulating oil)
silver or nickel plated (in air / insulating oil)
with a silver coating with a thickness of at least 24 microns

3. Contacts sintered tungsten- and molybdenum-containing insulating oil based on copper / silver
4. Hardware leads made of copper, aluminum and their alloys, intended for connection with external conductors of electrical circuits:
without cover
tin, silver or nickel plated
5. Bolted contact connections made of copper, aluminum and their alloys:
uncoated (in air / in insulating oil)
tin plated (in air / in insulating oil)
Monitored nodes		Highest allowable value
		temperature heating, “С		exceeding temperature, "С
silver or nickel plated (in air / insulating oil)
6. AC fuses for voltage 3 kV and higher:
compounds of copper, aluminum and their alloys (in uncoated / tinned air):
with detachable contact connection carried out by springs
with dismountable connection (pressing with bolts or screws), including fuse terminals
metal parts used as springs:

of phosphor bronze and similar alloys
7. Insulating oil in top layer switching devices
8. Built-in current transformers:

magnetic cores
9. Bolted connection of current-carrying leads of removable inputs (in oil / in air)
10. Connections of power transformer on-load tap-changers
formers made of copper, its alloys and copper-containing compositions without silver coating when operating in air / in oil:
with pressing bolts or other elements ensuring the rigidity of the connection
spring-loaded and self-cleaning during shifting
spring-loaded and not self-cleaning during shifting
11. Current-carrying conductors of power cables in continuous / emergency mode with insulation:
made of polyvinyl chloride plastic and polyethylene

Monitored nodes	Highest allowable value
Monitored nodes	heating temperature, ° С	temperature rise, “С
vulcanized polyethylene
rubber
made of rubber of increased heat resistance
with impregnated paper insulation with viscous / depleted impregnation and rated voltage, kV:





12. Collectors and slip rings, unprotected and protected by insulation, heat resistance classes:


13. Plain / rolling bearings

Note. The data given in the table apply if no other standards have been established for specific types of equipment.
where / load, ΔTmeas - current and temperature rise of the measured contact connection, respectively; ΔTnorm - the temperature rise of the contact connection, regulated by the “Scope and norms of testing electrical equipment”, depending on the type of coating of contact surfaces and the environment in which they are located.
Detection of the thermal state of electrical equipment and live parts, depending on the conditions of their operation and design, can be carried out: according to the normalized heating temperatures (temperature rises), excess temperature, defectiveness coefficient, the dynamics of temperature change over time, with a change in load, by comparing the measured temperature values within phases and between phases with temperature values in known good sections.
The limiting values of the heating temperature for / nom and its excess are given in table. sixteen.

For contacts and bolted contact connections, the standards given in table. 16, should be used at load currents (0.6 - 1.0) / nom after appropriate conversion. The recalculation of the excess of the measured temperature value to the normalized one is carried out according to the ratio

where ΔTnom - temperature rise at / nom; ΔTwork - the same, at r
slave-
Thermal imaging control of electrical equipment and live parts at load currents of 0.3 / nom and below does not help to identify defects at an early stage of their development.
For contacts and bolted contact connections at load currents (0.3 - 0.6) / nom, their condition is assessed by excess temperature. The temperature value converted to 0.5 / nom is used as a standard.
For recalculation, the ratio is used

where ΔT0.5 is the excess temperature at a load current of 0.5 / nom.
When assessing the state of contacts and bolted contact connections by excess temperature at a load current of 0.5 / nom, the following areas are distinguished according to the degree of failure:

excess temperature 5-10 ° C. The initial degree of malfunction, which should be monitored and corrective measures taken during scheduled repairs;
excess temperature 10 - 30 ° C. Developed defect. Measures should be taken to eliminate the malfunction at the next withdrawal of the electrical equipment from operation;
excess temperature over 30 ° C. Emergency defect. Requires immediate elimination.

It is recommended to evaluate the condition of welded and crimped contact joints by excess temperature or coefficient of defectiveness.
When assessing the thermal state of live parts, the following degrees of malfunction are distinguished, based on the given values of the defect ratio:
No more than 1.2 ............................................. ... Initial failure rate, Forward

6.2.16.1 The control of the tightening of bolted joints of the nodal linings of aluminum dome roofs is carried out when dismantling the cards for the control of beams and support crowns (Table 6.4, lines 12 and 27 and Table 6.5, line 20). Additionally, the tightening of bolted connections in four nodal linings is checked according to the diagram shown in Figure 6.18.

Figure 6.18 - Scheme of places for dismantling the nodal caps (top view of the domed roof)

6.2.16.2 Before checking the tightening, the protective caps must be dismantled and visual control bolted connection. There should be no cracks, scale, rust, burrs, dents or nicks on the threads on the surface of bolts, nuts and washers. The bolts must be marked with the tensile strength, the conventional designation of the melt number, the manufacturer's stamp must be affixed, the marking of the bolts of climatic modification ХЛ (according to GOST 15150) must contain the designation "ХЛ".

6.2.16.3 Check the tightening of bolted connections by measuring the tightening torque with a torque wrench and a feeler gauge. The number of monitored bolted connections in the assembly must be at least:

When the number of bolts in the connection is up to four - all bolts;

From five to nine - at least three bolts;

From 10 and more - 10% of bolts, but not less than three in each connection.

When one bolted connection is detected with an inadequate tightening
(subparagraph 6.2.16.6), the double number of bolted connections is subject to control. If, upon re-checking, one bolt is found with an abnormal tightening, all bolts in all controlled units must be checked to bring the tightening torque of each to the required value.

6.2.16.4 To check the tightening threaded connections with a controlled torque of the tightening force of the high-strength bolts of the upper nodal linings, torque wrenches of scale and limit types and probes are used that meet the requirements given in Table 6.10.

Table 6.10 - Requirements for means of control of bolted connections

Torque wrenches to control the tightening of high-strength bolts must be calibrated at least once per shift in the absence of mechanical damage, as well as after each replacement of the control measuring instrument or repair of the wrench, in accordance with SNiP 3.03.01-87 (paragraph 4.27).

6.2.16.5 Before checking the bolted connection, it is necessary to set the tightening torque on the torque wrench, established in the design documentation, upon reaching which a click will occur. In the absence of the data specified in the design documentation, the torque M, Nm, is determined by the formula:

M = K ∙ P ∙ d, (6.11)

where K is the average value of the torsion coefficient established for each batch of bolts in the manufacturer's certificate or determined at the installation site using control measuring instruments. For bolts in accordance with GOST R 52644 K = 0.18;

P is the calculated bolt tension specified in the working drawings, N (kgf). In the absence of design data, the design bolt tension is determined in accordance with SNiP 2.03.06-85, 8.10 by the formula:

P = Rbh × Abn, (6.12)

where R bh is the calculated tensile strength of a high-strength bolt, determined by the formula:

R bh = 0.7 ∙ R bun, (6.13)

where R bun is the smallest ultimate tensile strength of the bolt, taken by
SNiP II-23-81 * (table 6.1) and given in table 6.12.

A bn - bolt sectional area taken according to GOST 9150, GOST 8724 and
GOST 24705, taken from the values given in SNiP II-23-81 * (see table 6.2) and are given in table 6.11.

Table 6.11 - The value of the smallest ultimate tensile strength of the bolt

Table 6.12 - Bolt cross-sectional areas

d, mm
A bn, cm 2	1,57	1,92	2,45	3,03	3,52	4,59	5,60	8,16	11,20	14,72

6.2.16.6 The criterion for the conformity of the tightening of the bolted connection is the absence of rotation of the nut or bolt.

6.2.16.7 The tightness of the screed of the upper knot lining and the aluminum profile, at the joints, should be checked with a 0.3 mm thick feeler, which should not pass between the assembled parts to a depth of more than 20 mm according to (SNiP 3.03.01-87). The scheme for checking the junction of the upper nodal lining and the aluminum profile with a probe is shown in Figure 6.19.

1 - the junction of the upper knot lining and the aluminum profile

Figure 6.19 - Scheme of checking with a probe (this place is designated by number 1) of the junction of the upper nodal lining and the aluminum profile

4.11. When assembling the joints, the holes in the structural parts must be aligned and the parts must be fixed against displacement with assembly plugs (at least two), and the packages are tightly tightened with bolts. In connections with two holes, the assembly plug is installed in one of them.

4.12. In the assembled package, the bolts of the specified diameter in the project must pass through 100% of the holes. It is allowed to clean 20% of the holes with a drill, the diameter of which is equal to the hole diameter specified in the drawings. At the same time, in joints with the operation of bolts for shear and connected elements for crushing, blackness is allowed (mismatch of holes in adjacent parts of the assembled package) up to 1 mm - in 50% of the holes, up to 1.5 mm - in 10% of the holes.

In case of non-observance of this requirement, with the permission of the organization - the developer of the project, the holes should be drilled to the nearest larger diameter with the installation of a bolt of the corresponding diameter.

In joints where the bolts work in tension, as well as in joints where the bolts are structurally installed, the blackness should not exceed the difference between the diameters of the hole and the bolt.

4.13. It is prohibited to use bolts and nuts that do not have the manufacturer's brand and mark indicating the strength class.

4.14. No more than two round washers (GOST 11371-78) should be installed under the bolt nuts.

It is allowed to install one of the same washers under the bolt head.

Where necessary, oblique washers should be installed (GOST 10906-78).

The thread of the bolts should not enter into the depth of the hole by more than half of the thickness of the outermost element of the package from the nut side.

4.15. Solutions to prevent self-loosening of nuts - setting a spring washer (GOST 6402-70) or lock nuts - should be indicated in the working drawings.

The use of spring washers is not allowed with oval holes, when the difference between the diameters of the hole and the bolt is more than 3 mm, as well as when installed together with a round washer (GOST 11371-78).

It is prohibited to lock the nuts by driving the bolt threads or welding them to the bolt shank.

4.16. Nuts and locknuts should be tightened all the way from the middle of the joint to its edges.

4.17. The heads and nuts of bolts, including foundation bolts, should, after tightening, tightly (without gaps) touch the planes of washers or structural elements, and the bolt rod should protrude from the nut by at least 3 mm.

4.18. The tightness of the screed of the assembled package should be checked with a 0.3 mm thick feeler, which, within the area bounded by the washer, should not pass between the assembled parts to a depth of more than 20 mm.

4.19. The tightness of the permanent bolts should be checked by tapping them with a hammer weighing 0.4 kg, while the bolts should not move.

High-strength bolted assembly connections with controlled tension1

4.20. Workers who have undergone special training, confirmed by a corresponding certificate, may be allowed to make connections on bolts with controlled tension.

4.21. In shear-resistant joints, the contacting surfaces of the parts must be processed in the manner provided for in the project.

From surfaces to be, and also not to be treated with steel brushes, it is necessary to first remove oil contamination.

The condition of surfaces after processing and before assembly should be monitored and recorded in the log (see mandatory Appendix 5).

Before assembling the joints, the treated surfaces must be protected from dirt, oil, paint and ice formation. If this requirement is not observed or the assembly of the joint begins after more than 3 days after the preparation of the surfaces, their processing should be repeated.

4.22. The difference in surfaces (deplanation) of the abutting parts over 0.5 and up to 3 mm must be eliminated by machining by forming a smooth bevel with a slope not steeper than 1:10.

With a difference of more than 3 mm, it is necessary to install gaskets of the required thickness, processed in the same way as the connection parts. The use of gaskets is subject to agreement with the organization - the developer of the project.

4.23. During assembly, the holes in the parts must be aligned and secured against displacement with plugs. The number of plugs is determined by calculating the effect of assembly loads, but there must be at least 10% of them with the number of holes 20 or more and at least two with a smaller number of holes.

In the assembled package, fixed with plugs, blackness (mismatch of holes) is allowed, which does not prevent the bolts from being positioned freely without skewing. A gauge with a diameter of 0.5 mm larger than the nominal diameter of the bolt must pass through 100% of the holes of each joint.

It is allowed to clean the holes of tightly tightened packages with a drill, the diameter of which is equal to the nominal diameter of the hole, provided that the blackness does not exceed the difference between the nominal diameters of the hole and the bolt.

The use of water, emulsions and oil when cleaning the holes is prohibited.

4.24. It is forbidden to use bolts that do not have the factory marking of ultimate resistance on the head, the manufacturer's mark, the symbol of the heat number, and on the bolts of the climatic version ХЛ (according to GOST 15150-69) - also the letters "ХЛ".

4.25. Bolts, nuts and washers must be prepared before installation.

4.26. The bolt tension specified by the project should be ensured by tightening the nut or rotating the bolt head up to the calculated tightening torque, or by turning the nut by a certain angle, or in another way that guarantees a given tension force.

The order of tension should exclude the formation of leaks in the bags being pulled together.

4.27. Torque wrenches for tensioning and controlling the tension of high-strength bolts must be calibrated at least once a shift in the absence of mechanical damage, as well as after each replacement of the control device or repair of the key.

4.28. Design torque M required to tighten the bolt should be determined by the formula

M = KRd, Hm (kgf × m), (1)

where TO- the average value of the tightening factor established for each batch of bolts in the manufacturer's certificate or determined at the installation site using control devices;

R- design bolt tension specified in the working drawings, N (kgf);

d- nominal bolt diameter, m

4.29. The tightening of the bolts according to the angle of rotation of the nut should be done in the following order:

hand-tighten all the bolts in the connection to failure using an assembly wrench with a handle length of 0.3 m;

turn the bolt nuts 180 ± 30 °.

The specified method is applicable for bolts with a diameter of 24 mm with a package thickness of up to 140 mm and the number of parts in a package up to 7.

4.30. One washer must be installed under the head of a high-strength bolt and a high-strength nut in accordance with GOST 22355-77. If the difference between the diameters of the hole and the bolt is not more than 4 mm, it is allowed to install one washer only under the element (nut or bolt head), the rotation of which provides the bolt tension.

4.31. Nuts that are tightened to the design torque or by turning a certain angle should not be additionally secured with anything.

4.32. After tensioning all the bolts in the connection, the senior assembly worker (foreman) is obliged to put a stamp (the number or sign assigned to him) in the prescribed place.

4.33. The tension of the bolts should be controlled:

with the number of bolts in the connection up to 4 - all bolts, from 5 to 9 - at least three bolts, 10 or more - 10% of the bolts, but not less than three in each connection.

The actual torque of twisting must be at least the calculated one determined by the formula (1), and not exceed it by more than 20%. The deviation of the nut rotation angle is allowed within  30 °.

If at least one bolt is found that does not meet these requirements, double the number of bolts is subject to inspection. If, upon re-checking, one bolt with a lower torque value or with a lower nut rotation angle is found, all bolts should be checked to bring the tightening torque or rotation angle of each nut to the required value.

The 0.3 mm thick probe should not enter the gaps between the connection parts.

4.34. After checking the tension and accepting the joint, all the outer surfaces of the joints, including the bolt heads, nuts and the parts of the bolt threads protruding from them, should be cleaned, primed, painted, and the slots in the places of thickness differences and the gaps in the joints should be filled.

4.35. All tensioning and tension control work should be recorded in the Tension Controlled Bolt Connection Log.

4.36. Bolts in flange connections must be tightened to the forces indicated in the working drawings by rotating the nut to the calculated torque. 100% of the bolts are subject to tension control.

The actual torque of twisting must not be less than the calculated one determined by the formula (1), and not exceed it by more than 10%.

The gap between the contacting planes of the flanges at the locations of the bolts is not allowed. The 0.1 mm thick stylus must not penetrate the 40 mm radius from the bolt axis.

Bolt types. Bolts are usually used to connect metal, less often reinforced concrete structures. The following types of bolts are used to connect metal structures: normal, coarse, high-precision and high-strength bolts with appropriate nuts and washers.

Rough precision bolts are stamped from round carbon steel with a diameter not exceeding 20 mm. They are placed in holes with a gap of 2-3 mm. Such bolts have increased deformability and in multi-bolt joints do not work well for shear, therefore, they are not allowed to be used in joints with alternating forces. Bolts of coarse precision are used, as a rule, in nodes with the support of one element on another, with a transfer through a support table, as well as in joints where they do not work or work only in tension.

Bolts of increased accuracy are machined by turning on lathe with a tolerance of + 0.1 mm. Such bolts are made with a diameter of 10-48 mm and a length of up to 300 mm.

High-strength bolts (otherwise they are called friction bolts) are designed to transfer forces acting on the connection through friction. Such bolts are made from high-strength steels and heat-treated as a finished product. The bolts are placed in holes 2-3 mm larger than the bolt diameter, but the nuts are tightened with a torque wrench. Such connections are simple, but reliable enough and are used in critical structures.

The diameters for bolts of increased accuracy are assigned equal to the nominal diameters of the bolts. The holes for such bolts have only positive deviations, which allows the bolt to be installed without difficulty. Unlike bolts of normal and coarse precision, the working part of the bolt of the bolt of increased precision does not have a thread, which ensures a sufficiently complete filling of the hole and Good work on a cut. To distinguish high-strength bolts from others, a raised mark is applied to their head.

Assembling connections. The assembly of bolted connections includes the following operations: preparation of abutting surfaces, alignment of bolt holes, preliminary tightening of the joint parts to be joined, reaming of the holes (if necessary) to the design size, installation of bolts and final assembly.

Preparation of mating surfaces consists in cleaning the mating elements from rust, dirt, oil and dust. In addition, they correct irregularities, dents, bends, and also remove burrs on the edges of parts and holes with a file or chisel. These operations are especially carefully performed when connecting parts on high strength bolts, where the tight abutment of all abutting elements is one of the main conditions for the reliability of the bolted connection.

The surfaces to be joined are cleaned with dry quartz or metal sand using a sandblasting machine; firing gas burners, steel brushes, chemical treatment.

Sandblasting is more effective than other methods, since it provides a high coefficient of friction of the abutting surfaces, but this method is the most laborious.

The most commonly used firing method of processing using universal burners that operate both on natural gas and on an oxygen-acetylene mixture and create a temperature of 1600-1800 ° C, which burns fat spots and flakes off scale and rust.

One way to clean bolts, nuts and washers is to submerge them in a tank of boiling water and then in a container filled with unleaded gasoline with 10-15% mineral oil. After the gasoline evaporates, a thin continuous film of grease remains on the surface of the hardware.

The accuracy of the alignment of the holes of the mounting parts is achieved with the help of through mandrels, which are a rod with cylindrical parts. The diameter of the mandrels should be 0.2-0.5 mm less than the hole diameter.

To fix the relative position of the mounted elements and prevent their displacement, 1/10 of the total number of holes is filled with plugs with a diameter equal to the diameter of the holes. The length of the plugs must exceed the total thickness of the elements to be connected. After setting the plugs, the mandrels are knocked out. Packages of elements to be connected are tightened with permanent or temporary bolts, which are placed through every third hole, but at least every 500 mm.

The holes are drilled with hand-held pneumatic and electric machines.

Pneumatic machines are straight, used for work in places where there are no restrictions on dimensions, and angular, adapted for work in confined spaces. Pneumatic installations drill holes with a diameter of up to 20 mm.

Electric machines operate on a 220 V alternating current network. In the open air, such machines are used complete with a protective-disconnecting device, and in closed dry rooms they are grounded, the installer works with electric tools in gloves and standing on a rubber mat. The safest machines are double insulated; they can be used without additional protective measures and when working outdoors.

After reaming the holes free from the assembly bolts, the bolts are unscrewed, and permanent bolts are put in their place.

The nuts of all bolts (permanent and temporary) are tightened with hand wrenches (conventional or ratchet). In this case, one worker keeps the bolt head from rotating, and the second tightens the nut. Washers are installed on bolts of normal and increased accuracy - one under the bolt head and no more than two under the nut. With a large number of bolts in one joint, electric wrenches are used. The bolts are installed from the middle of the joint to the edges. There should be at least one full thread thread on the nut side. The tightening quality is checked by tapping the bolts with a hammer weighing 0.3-0.4 kg. In this case, the bolts should not move and tremble.

The nuts are secured against self-loosening with locknuts or spring washers. However, with dynamic and vibration loads, these measures are not enough, therefore, during operation, the condition of the mounting connections should be systematically monitored and the nuts should be tightened on the loosened bolts.

High-strength bolted connections are available in shear-resistant and bearing bolts. In shear-resistant joints, the bolts are not directly involved in the transfer of forces: all the forces applied to the mating elements are perceived only due to the friction forces arising between the shear planes. In the connection with the bearing bolts, along with the friction forces between the shear planes, the bolts themselves also participate in the transfer of forces, which makes it possible to increase the bearing capacity of one bolt by 1.5-2 times compared to a bolt in shear-resistant joints.

In these cases, the surfaces of the elements to be connected are treated as for conventional bolted connections. Remove preservative grease before installing bolts, washers and nuts. To do this, they are dipped in a trellised container into boiling water, and then into a container with a mixture of 15% mineral oil and 85% unleaded gasoline.

When assembling, installing metal structures, special attention is paid to the tension of the elements to be connected. There are several ways to determine bolt tension forces. On the construction site, a method is often used to indirectly estimate the tensile forces through the torque that must be applied to the nut.

The torque M is determined from the expression: M = KP · a, where P is the tension force of the bolt, N; d is the nominal bolt diameter, mm; K is the screw tightening factor.

The tension of the bolts is controlled selectively: with the number of bolts in the connection up to 5 - all bolts, with 6-20 - at least 5 bolts and with a larger number - at least 25% of the bolts in the connection. If during the inspection it is found that at least one bolt does not meet the established requirements, then all the bolts are checked. The heads of the checked bolts are painted, and all joints are putty along the contour.

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BEARING AND GUARDING STRUCTURES- BUILDING STANDARDS AND RULES- SNiP 3-03-01-87 (approved by the Decree of the USSR State Construction Committee of 04-12-87 ... Actual in 2017

High-strength bolted assembly connections with controlled tension

4.20. Workers who have undergone special training, confirmed by a corresponding certificate, may be allowed to make connections on bolts with controlled tension.

4.21. In shear-resistant joints, the contacting surfaces of the parts must be processed in the manner provided for in the project.

From surfaces to be, and also not to be treated with steel brushes, it is necessary to first remove oil contamination.

The condition of surfaces after processing and before assembly should be monitored and recorded in the log (see mandatory Appendix 5).

4.22. The difference in surfaces (deplanation) of the abutting parts over 0.5 and up to 3 mm must be eliminated by machining by forming a smooth bevel with a slope not steeper than 1:10.

4.23. During assembly, the holes in the parts must be aligned and secured against displacement with plugs. The number of plugs is determined by calculating the effect of assembly loads, but there must be at least 10% of them with the number of holes 20 or more and at least two with a smaller number of holes.

The use of water, emulsions and oil when cleaning the holes is prohibited.

4.24. It is forbidden to use bolts that do not have the factory marking of ultimate resistance on the head, the manufacturer's mark, the symbol of the heat number, and on the bolts of the climatic version ХЛ (according to GOST 15150-69) - also the letters "ХЛ".

4.25. Bolts, nuts and washers must be prepared before installation.

4.26. The bolt tension specified by the project should be ensured by tightening the nut or rotating the bolt head up to the calculated tightening torque, or by turning the nut by a certain angle, or in another way that ensures the specified tension force is obtained.

The order of tension should exclude the formation of leaks in the bags being pulled together.

4.27. Torque wrenches for tensioning and controlling the tension of high-strength bolts must be calibrated at least once a shift in the absence of mechanical damage, as well as after each replacement of the control device or repair of the key.

4.28. The design torque M required to tighten the bolt should be determined by the formula

where K is the average value of the tightening factor established for each batch of bolts in the manufacturer's certificate or determined at the installation site using control devices;

P is the calculated bolt tension specified in the working drawings, N (kgf);

d - nominal bolt diameter, m.

4.29. The tightening of the bolts according to the angle of rotation of the nut should be done in the following order:

hand-tighten all the bolts in the connection to failure using an assembly wrench with a handle length of 0.3 m;

turn the bolt nuts 180 ° ± 30 °.

The specified method is applicable for bolts with a diameter of 24 mm with a package thickness of up to 140 mm and the number of parts in a package up to 7.

4.30. One washer must be installed under the head of a high-strength bolt and a high-strength nut in accordance with GOST 22355-77. If the difference between the diameters of the hole and the bolt is not more than 4 mm, it is allowed to install one washer only under the element (nut or bolt head), the rotation of which provides the bolt tension.

4.31. Nuts that are tightened to the design torque or by turning a certain angle should not be additionally secured with anything.

4.32. After tensioning all the bolts in the connection, the senior assembly worker (foreman) is obliged to put a stamp (the number or sign assigned to him) in the prescribed place.

4.33. The tension of the bolts should be controlled:

with the number of bolts in the connection up to 4 - all bolts, from 5 to 9 - at least three bolts, 10 and more -10% of the bolts, but not less than three in each connection.

The 0.3 mm thick probe should not enter the gaps between the connection parts.

4.34. After checking the tension and accepting the joint, all the outer surfaces of the joints, including the bolt heads, nuts and the parts of the bolt threads protruding from them, should be cleaned, primed, painted, and the slots in the places of thickness differences and the gaps in the joints should be filled.

4.35. All tensioning and tension control work should be recorded in the Tension Controlled Bolt Connection Log.

4.36. The bolts in the flange connections must be tightened to the forces indicated in the working drawings by rotating the nut to the calculated torque. 100% of the bolts are subject to tension control.

The actual torque of twisting must not be less than the calculated one determined by the formula (1), and not exceed it by more than 10%.

The gap between the contacting planes of the flanges at the locations of the bolts is not allowed. The 0.1 mm thick stylus must not penetrate the 40 mm radius from the bolt axis.

In accordance with the document “MDS 12-22.2005. Recommendations for the application in construction production of the requirements of regulatory legal and other regulatory acts containing state and regulatory requirements for labor protection "Appendix 5, all data relating to construction and installation work in production should be entered daily tension control bolt connection log. This requirement cannot be ignored or neglected. In the event of any legal action, this journal will carry legal weight and be considered an official document.

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Title page:
- name of the organization performing the work
- name of the construction object
- position, surname, initials and signature of the person responsible for the execution of work and keeping the journal
- the organization that developed the design documentation, KM drawings
- project code
- the organization that developed the project for the production of works
- project code
- the enterprise that developed the structural design drawings and manufactured the structures
- order code
- customer (organization), position, surname, initials and signature of the head (representative) of technical supervision

Sections 1
List of link (assemblers) who are busy installing bolts.

Graphs tension control bolt connection log:

2. Assigned rank

3. Assigned number or mark

4-5. Qualification certificate

date of issue

Issued by

6. Note

Main part

Columns to fill in:
1. Date
2. The number of the KMD drawing and the name of the node (joint) in the joint
3-6. Bolt placement
- number of supplied bolts in the connection
- number of the certificate for bolts
- method of processing contact surfaces
- calculated torque or rotation angle of the nut

7-12. Control results
- processing of contact surfaces
- number of checked bolts
- results of checking the tightening torque or the angle of rotation of the nut
- stamp number, signature of the foreman
- signature of the person responsible for bolting
- signature of the customer's representative

The document "MDS 12-22.2005. Recommendations for the application in construction production of the requirements of regulatory legal and other regulatory acts containing state regulatory requirements for labor protection" says:
1.5. Data on the performance of construction and installation works should be entered daily in

INDUSTRY STANDARD

STEEL CONSTRUCTIONS. INSTALLATION

HIGH STRENGTH BOLT CONNECTIONS

Typical technological process

OST 36-72-82

By order of the Ministry of Assembly and Special Construction Works of the USSR dated December 7, 1982, the introduction date was set from July 1, 1983.

APPROVED AND INTRODUCED BY THE ORDER of the Ministry of Assembly and Special construction works USSR from December 7, 1982, No. 267

Contractors: VNIPI Promstalkonstruktsiya

K.I. Lukyanov, Ph.D., A.F. Knyazhev, Ph.D., G.N. Pavlova

Co-executors: Central Research Institute Proektstalkonstruktsiya

B.G. Pavlov, Ph.D., V.V. Volkov, Ph.D., V.M. Babushkin

B.M. Weinblat, Ph.D.

Introduced for the first time

This standard applies to a typical workflow for making shear resistant erection joints on high strength bolts in building steel structures.

The standard establishes technical requirements for the materials used, structural elements to be joined, tools, as well as the sequence of operations of the technological process, quality control, and safety fundamentals.

1. GENERAL PROVISIONS

1.1. High-strength bolts, nuts and washers should be used in accordance with the instructions of the working (KM) or detailing (KMD) drawings of the steel structures of the mounted object.

1.2. Projects for the production of work (PPR) should contain work flow diagrams or flow charts that provide for the implementation of connections on high-strength bolts in the specific conditions of the facility being mounted.

1.3. Preparation, assembly and acceptance of connections on high-strength bolts should be carried out under the guidance of a person (foreman, foreman) appointed by the order of the installation organization responsible for the implementation of this type of connection at the facility.

1.4. Fitters are allowed to make connections on high-strength bolts at least 18 years old, who have undergone special theoretical and practical training, confirmed by a personal certificate for the right to perform these works, issued by the installation organization.

2. TECHNICAL REQUIREMENTS

2.1.1. High-strength bolts, nuts, washers must be supplied to the object being mounted in batches supplied with certificates in accordance with the requirements of GOST 22353-77, GOST 22354-77, GOST 22355-77, GOST 22356-77.

2.1.2. For sandblasting (shot blasting) processing of the contact surfaces of the connected structural elements, quartz sand should be used in accordance with GOST 8736-77 or shot from cast iron or steel in accordance with GOST 11964-81 E.

2.1.3. To form a glue-friction coating on the contact surfaces of the linings, glue based on epoxy-dianic resin ED-20 in accordance with GOST 10587-76 and carborundum powder of KZ and KCh grades, fractions No. 8, 10, 12 in accordance with GOST3647-80 should be used.

2.1.4. For flame treatment of surfaces, acetylene in accordance with GOST 5457-75 and oxygen in accordance with GOST 6331-78 should be used. Acetylene and oxygen must be supplied to the workplace in steel cylinders in accordance with GOST 15860-70.

2.2.1. The possibility of free supply of high-strength bolts and screwing nuts using wrenches and torque wrenches should be ensured by the constructive solution of the connections.

2.2.2. Mounting of connections is not allowed if there are burrs on the structural elements around and inside the holes, as well as along the edges of the elements.

The contact surfaces of the elements are not subject to priming and painting. The distance between the axis of the bolts of the last row and the primed surface should not be less than 70mm.

2.2.3. It is not allowed to use in joints elements with dimensional deviations that do not meet the requirements of SNiP III-18-75 “Rules for the production and acceptance of work. Metal constructions". The difference in the planes of the elements connected by overlays should not exceed 0.5 mm inclusive.

2.2.4. In joints made of rolled profiles with non-parallel flange surfaces, leveling shims must be used.

2.2.5. The nominal diameters and blackness of the holes (mismatch of holes in individual parts of the assembled package) should not exceed the requirements specified in the chapter SNiP III-18-75 "Rules for production and acceptance of work. Metal structures".

2.2.6. Control and calibration torque wrenches must be numbered, calibrated and provided with calibration charts or tables. Pneumatic and electric wrenches must meet passport requirements.

3.1.1. Preparatory operations include: de-preservation and cleaning of high-strength bolts; preparation of structural elements; control and calibration check of the tool.

3.1.2. High-strength bolts, nuts, washers must be cleaned from factory preservation, dirt, rust and covered with a thin layer of grease. Preservation and cleaning are carried out according to the following technology.

3.1.3. Place high-strength bolts, nuts and washers with a maximum weight of 30 kg in a wire rack.

3.1.4. Submerge the lattice container filled with hardware in a tank with boiling water for 8 - 10 minutes (see drawing).

3.1.5. After boiling, rinse hot hardware in a mixture consisting of 85% unleaded gasoline in accordance with GOST 2084-77 and 15% of machine oil (autol type) in accordance with GOST 20799-75 by 2 - 3-fold immersion followed by drying.

3.1.6. Place the machined bolts, nuts and washers separately in closed boxes with handles with a capacity of no more than 20 kg for transferring them to the workplace.

3.1.7. On the portable packaging, indicate the standard sizes, the number of bolts, nuts and washers, the date of processing, the certificate and batch numbers.

3.1.8. Cleaned bolts, nuts and washers should be stored in closed boxes for no more than 10 days, after which it is necessary to re-process in accordance with paragraphs. 3.1.4 and 3.1.5.

3.1.9. Burrs found around and inside holes and around the edges of elements must be removed completely. Deburring around holes and along the edges of elements should be done with pneumatic or electric stripping machines without forming a depression that breaks the contact of the contacting surfaces, and if there are burrs inside the hole, with a drill, the diameter of which is equal to the diameter of the bolt.

3.1.10. With a difference in the planes of the elements to be connected over 0.5 to 3.0 mm, inclusive, on the protruding element, it is necessary to make a bevel with a stripping pneumatic or electric machine at a distance of up to 30.0 mm from the edge of the element. When the plane difference is more than 3.0 mm, leveling shims should be used.

3.1.11. Calibration (calibration check) of control and calibration torque wrenches should be performed once per shift before starting work on special stands or devices in accordance with recommended Appendix 1. Wrenches are calibrated in accordance with Recommended Appendix 2.

1 - heating element; 2 - lattice container for bolts; 3 - water tank;

4 - drain plug

3.2.1. The main technological operations include:

Contact surface treatment;

Assembly of connections;

Installation of high strength bolts;

Bolt tension and tension control.

3.2.2. The method of processing contact surfaces is selected in accordance with the coefficient of friction specified in the drawings of the KM or KMD, and the chapter of SNiP II-23-81 “Steel structures. Design standards ".

The following methods of treatment of contact surfaces, performed at the installation site, have been established: sand-blasting (shot-blasting); metal brushes; glue friction.

3.2.3. Sandblasting (shot blasting) treatment of the contact surfaces of the elements to be connected should be carried out with sandblasting or shot blasting machines in accordance with GOST 11046-69 (ST SEV 3110-81).

When sandblasting (shot blasting) the contact surfaces, mill scale and rust must be completely removed until a uniform light gray surface is obtained.

3.2.4. Flame treatment of contact surfaces must be carried out with wide-range gas-flame burners GAO-60 or GAO-2-72 in accordance with GOST 17357-71.

Flame treatment is allowed with a metal thickness of at least 5.0 mm.

The speed of the torch movement is 1 m / min with a metal thickness of more than 10 mm and 1.5-2 m / min - with a metal thickness of up to 10 mm inclusive.

Combustion products and scale should be swept away with a soft wire brush and then a hair brush.

The surface after flame treatment must be free from dirt, paint, oil stains and easily peelable scale. Complete removal of mill scale is optional.

The equipment of the gas-flame treatment station and a brief technical characteristics of the equipment are given in the recommended appendix 3.

3.2.5. The processing of contact surfaces with metal brushes should be carried out using pneumatic or electric cleaning machines, the brands of which are indicated in the recommended Appendix 4.

It is not allowed to bring the contact surfaces to be cleaned to a metallic sheen.

3.2.6. As a rule, a glue-friction coating is applied to the contact surfaces of the linings at the factories that manufacture metal structures.

The technological process for obtaining an adhesive friction coating provides for:

Treatment of contact surfaces of linings in sandblasting (shot blasting) devices in accordance with GOST 11046-69 (ST SEV 3110-81);

Application of epoxy-polyamide glue to the treated contact surfaces;

Application over uncured glue with carborundum powder.

The safety of the adhesive coating must be ensured by packing the linings for the entire period of their loading, transportation, unloading and storage at the construction site.

The shelf life of pads with an adhesive friction coating is not limited.

The composition of the friction coating is given in the recommended appendix 5.

The contact surfaces of the main elements to be connected before assembly must be treated with metal brushes in accordance with clause 3.2.5.

3.2.7. Metallization processing of the contact surfaces of the joined structural elements (galvanizing, aluminizing), as a rule, is carried out at the factories that manufacture metal structures.

3.2.8. The treated surfaces must be protected from dirt, oil and ice formation. The shelf life of structures treated with sandblasting (shot blasting), flame methods or metal brushes should not exceed three days before assembly, after which the surfaces should be re-treated in accordance with paragraphs. 3.2.3 -3.2.5.

Surfaces treated by sandblasting (shot-blasting) are allowed to be cleaned by a gas-flame method during repeated processing.

3.2.9. The contact surfaces without treatment must be cleaned of dirt and peeling scale with metal brushes; from oil - unleaded gasoline, from ice - chipping.

3.2.10. The assembly of high-strength bolted connections includes the following operations:

Alignment of holes and fixation in the design position of the connection elements using assembly plugs, the number of which should be 10% of the number of holes, but not less than 2 pcs .;

Installation of high-strength bolts in holes free from assembly plugs;

Dense bag screed;

Tension of the installed high-strength bolts to the force indicated in the KM and KMD drawings;

Removing assembly plugs, placing high-strength bolts in the vacant holes and tensioning them to the design force;

Connection priming.

3.2.11. Under the heads and nuts of high-strength bolts, it is necessary to place only one heat-treated washer in accordance with GOST 22355-77.

The protruding end of the bolt must have at least one thread above the nut.

3.2.12. If the holes do not match, their reaming in elements with machined surfaces should be done without using coolants.

3.2.13. The preliminary and final tension of high-strength bolts must be performed from the middle of the joint to the edges or from the most rigid part of the joint towards its free edges.

3.2.14. The tensioning method for high-strength bolts should be specified in the KM or KMD drawings.

3.2.15. In the absence of instructions, the tensioning method is selected by the installer according to the recommended appendix 2.

4.1. After completing the installation connection on high-strength bolts, the foreman is obliged to put a personal stamp on the connection (a set of numbers) and present the finished connection to the person in charge.

4.2. The person in charge (foreman, foreman), after inspection and verification, must present the finished connection to the customer's representative. If the customer does not have any comments, the connection should be considered accepted and the person in charge enters all the necessary information about it in the log of installation connections on high-strength bolts (see mandatory Appendix 6).

4.3. After acceptance, the finished joint should be primed and painted. Soil grades and paint material are accepted according to the "List of polymeric materials and products permitted for use in construction", approved by the USSR Ministry of Health, the same as for priming and painting metal structures. The marks of soil and paint must be indicated in the drawings of the CM and KMD.

4.4. The quality of the connections on high-strength bolts is checked by the responsible person through operational control. Subject to control:

The quality of the processing of contact surfaces;

Compliance of installed bolts, nuts and washers with the requirements of GOST 22353-77, GOST 22354-77, GOST 22355-77, GOST 22356-77, as well as other requirements specified in the KM and KMD drawings;

The presence of washers under the bolt heads and nuts;

The presence of the manufacturer's mark on the bolt heads;

The length of the protruding part of the bolt thread above the nut;

The presence of the hallmark of the foreman in charge of the assembly of the compound.

4.5. The processing quality of the contact surfaces is checked by visual inspection just before assembling the connections. The control results must be recorded in the log (see mandatory Appendix 6).

4.6. The compliance of the bolt tension with the design one is checked depending on the tension method. The deviation of the actual tightening torque from the moment specified in the KM and KMD drawings should not exceed 20%.

The nut rotation angle is determined by the position of the marks on the protruding end of the bolt and nut. With a two-stage tension of the bolts, the deviation of the angle of rotation should be within ± 15 °, with a single-stage tension - ± 30 °.

Bolts with the position of the marks outside the specified limits must be loosened and tightened again.

4.7. The tension of high-strength bolts is checked with a calibrated torque wrench or a control calibrated wrench.

The tension of the bolts should be controlled by random inspection: with the number of bolts in the connection up to 5 inclusive, 100% of the bolts are controlled, with the number of bolts from 6 to 20 - at least 5, with more- at least 25% of the bolts in the connection.

4.8. If the inspection reveals at least one bolt, the tension of which does not meet the requirements of Clause 4.6 of this standard, then 100% of the bolts in the joint are subject to inspection. In this case, the tension of the bolts must be brought to the required value.

4.9. The density of the bundle being pulled together is controlled with 0.3mm probes. The probe should not pass between the planes along the contour of the connected elements.

4.10. The documentation presented upon acceptance of the finished object, in addition to the documentation provided for by the chapter of SNiP III-18-75 "Rules for the production and acceptance of work. Metal structures", must contain:

High-strength bolt assembly log;

Certificates for bolts, nuts and washers;

Certificates for materials for the formation of adhesive friction coatings.

5. SAFETY REQUIREMENTS

5.1. The organization of the section for the enlarged assembly of structures with assembly joints on high-strength bolts should ensure the safety of workers at all stages of work.

Work on the installation of structures on high-strength bolts must be carried out in accordance with the PPR containing the following safety solutions:

Organization of workplaces and walkways;

The sequence of technological operations;

Methods and devices for the safe work of installers;

Location and coverage of assembly mechanisms;

Warehousing methods building materials and structural elements.

5.2. The placement of working equipment and the organization of workplaces must ensure the safety of the evacuation of workers in emergency situations, taking into account the current building codes.

5.3. All work at height on making assembly connections on high-strength bolts should be carried out from a scaffold that provides free access to the connection with the tool.

Paving means and other devices ensuring the safety of work must comply with the requirements of the chapter SNiPIII-4-80 "Rules for the production and acceptance of work. Safety in construction", GOST 12.2.012-75, GOST 24259-80 and GOST 24258-80.

5.4. Electrical safety at the installation site must be ensured in accordance with the requirements of GOST 12.1.013-78.

5.5. When processing contact surfaces with sandblasting (shot blasting) devices, the "Rules for the Design and Safety of Operation of Pressure Vessels" approved by the USSR Gosgortekhnadzor should be followed.

5.6. The place of production of sandblasting (shotblasting) works should be fenced and appropriate warning signs and inscriptions should be posted near it.

5.7. Materials for sandblasting (shot blasting) surface treatment (sand, shot, metal sand) should be stored in containers with a tightly closed lid.

5.8. The operator of the sandblasting (shot blasting) apparatus and the auxiliary worker are supplied with spacesuits or helmets with a forced supply of clean air.

5.9. The air supplied to the spacesuit must first be passed through a filter to remove dust, water and oil.

5.10. Between the workplaces of the operator and the auxiliary worker, located near the sandblasting (shot blasting) apparatus, an audible or light alarm should be provided.

5.11. When treating contact surfaces with metal brushes (manual and mechanical), workers should be provided with goggles in accordance with GOST 12.4.003-80 or masks, gloves and respirators.

5.12. When processing contact surfaces with a flame method, it is necessary to comply with the requirements of the chapter SNiP III-4-80 “Rules for the production and acceptance of work. Safety in construction ", as well as sanitary rules for welding and cutting metals, approved by the USSR Ministry of Health.

5.13. Places of production of gas-flame works must be free from combustible materials within a radius of at least 5 m, and from explosive materials and installations (including gas cylinders and gas generators) - within a radius of 10m.

5.14. It is not allowed to carry out work on gas-flame treatment of surfaces of structural elements in rainy weather outside without a canopy.

5.15. When performing gas-flame treatment of contact surfaces, workers must be provided with closed-type goggles with glass-light filters of the G-1 or G-2 brands.

Auxiliary workers must be provided with protective glasses with glass-light filters grades B-1 or B-2.

5.16. The application of an adhesive layer to the surface of the linings, as a rule, should be carried out at the manufacturing plants. In this case, safety requirements in accordance with GOST 12.3.008-75, GOST 12.3.016-79 and GOST 10587-76, as well as safety rules when working with synthetic adhesives, must be observed.

5.17. Glue preparation and application of glue friction coatings should be carried out in a separate room equipped with exchange and local ventilation.

5.18. Persons working with epoxy-diane resins must be provided with protective clothing and gloves.

To protect the skin from the effects of epoxy-diane resins, protective pastes and ointments based on lanolin, petroleum jelly or castor oil should be used.

5.19. The room for applying glue-friction coatings must be provided with fire extinguishing means - carbon dioxide and foam fire extinguishers.

5.20. De-preservation of bolts, nuts and washers should be carried out in an open area with a canopy.

5.21. When boiling hardware in water, the bath must be grounded. Workers performing the de-preservation of hardware should not have direct contact with baths for boiling and lubrication. The loading process must be mechanized.

5.22. When performing assembly operations, the alignment of holes and verification of their coincidence in the mounted structural elements should be performed using a special tool - tapered mandrels, assembly plugs, etc. It is not allowed to check the alignment of holes with fingers.

5.23. Operation of mechanisms, means of small-scale mechanization, including Maintenance, should be carried out in accordance with the requirements of the chapter SNiP III-4-80 “Rules for the production and acceptance of work. Safety in construction ”and the instructions of the manufacturers.

5.24. When using hand-held machines, one should observe the safety rules stipulated by GOST 12.1.012-79 (ST SEV 1932-79, ST SEV 2602-80) and GOST 12.2.010-75, as well as the instructions of the manufacturers.

5.25. The working regime when working with manual electric and pneumatic machines and wrenches should be established in accordance with the "Recommendations for the development of the Regulations on the working regime of workers in vibration-hazardous professions", approved in December 1971 by the All-Union Central Council of Trade Unions, the USSR Ministry of Health, the State Committee of the USSR Council of Ministers on Labor and wages, as well as instructions from manufacturers for performing work with specific types of machines.

5.26. Finished joints on high-strength bolts should be primed and painted at the assembly site of metal structures.

5.27. Only workers who know the rules of safe handling of the equipment and materials used and are familiar with the fire safety rules are allowed to work on priming the joints.

5.28. Workers engaged in priming and painting compounds must undergo a medical examination in accordance with the requirements of Order No. 400 of the USSR Ministry of Health dated 05/30/1969 "On conducting preliminary and periodic medical examinations of workers upon admission to work."

5.29. Temporary production and auxiliary premises should be equipped with ventilation and lighting, as well as equipped with fire extinguishing equipment in accordance with the requirements of GOST 12.4.009-75.

ANNEX 1

An example of calibration of a torque wrench type KTR-3 1

_________________

1 Keys KTR-3 are manufactured by installation companies according to the drawings of the Central Research Institute of Proektstalkonstruktsii.

Torque wrenches are calibrated on special calibration stands or by hanging a load of a given size from its handle. A torque wrench is hung on a hexagonal mandrel or a tightened high-strength bolt so that its handle is in a horizontal position (see drawing).

At a fixed point at the end of the key, a weight is suspended

where M s - estimated torque of twisting;

Δ M z- the moment equal to the product of the key mass by the distance from its center of gravity to the axis of the mandrel or bolt;

l- the distance from the center of gravity of the load to the axis of the mandrel or bolt.

With a suspended load, the counting is carried out according to a recording device, for example, a dial indicator ICh 10 mm in accordance with GOST 577-68. The measurement is carried out 2-3 times until a stable result is obtained. The calibration results are entered into the control calibration log of the keys (see mandatory Appendix 7).

1 - welded hexagon or tightened high-strength bolt;

2 - rigid support; 3 - indicator; 4 - a tared key; 5 - tared cargo

APPENDIX 2

M s required for tensioning high-strength bolts is determined by the formula:

M z= kPd,

k- the average value of the tightening factor for each batch of bolts according to the certificate or set using control devices at the installation site;

R- bolt tension force specified in the KM and KMD drawings;

d- the nominal diameter of the bolt.

1.2. To pre-tighten the nuts, use the pneumatic or electric wrenches specified in Recommended Appendix 4 and torque wrenches.

1.3. When tightening the bolt, the head or nut should be kept from turning with a mounting wrench. If turning does not stop as the bolt is tightened, then the bolt and nut must be replaced.

1.4. The torque should be recorded as the key moves in the direction that increases the tension.

Tightening should be done smoothly, without jerking.

1.5. Torque wrenches must be numbered and calibrated. They should be calibrated at the beginning of the shift.

2.1. High-strength bolts must be installed in the holes free from assembly plugs and tightened with a nut wrench, adjusted at a torque of 800 N ⋅ m. Tightening of each bolt must be done before the nut stops rotating. After removing the assembly plugs and replacing them with bolts, the latter should be tightened at the moment of tightening 800 N⋅ m.

2.2. To control the angle of rotation of the nuts, it is necessary to mark them and the protruding ends of the bolts with a aligned center punch (see drawing) or paint.

Combined center punch

1 - center punch; 2 - nut; 3 - high strength bolt; 4 - package

2.3. The final tightening is carried out with a nutrunner adjusted at the moment of tightening 1600 N ⋅ m, while the nut must turn through the angle indicated in the table.

Number of gaps in the package	Package thickness, mm	Angle of rotation, hail

3.1. Wrenches should be calibrated using a special calibration package consisting of three bodies with at least 20 holes.

High-strength bolts are inserted into the holes of the calibration package and tightened with a nutrunner until the nut stops rotating. A group of bolts (calibration bolts) in the amount of at least 5 pcs. do not tighten.

The adjusting bolts must be tightened by hand with an assembly wrench with a handle length of 0.3 m to failure (initial position).

3.2. On the prepared calibration bolts, the wrench is calibrated.

3.3. The compressed air pressure is set so that when the nut is turned through an angle of 180 ± 30 ° from the initial position, the wrench fails.

The air pressure should be checked periodically.

Air pressure control should be carried out according to the GOST 2405-72 pressure gauge installed at the point where the nutrunner hose is connected to the line.

3.4. When calibrating the nutrunner (to observe the angle of rotation of the nut), risks should be applied to its replaceable head.

3.5. The wrench is considered calibrated if the angle of rotation of the nut in the process of tensioning all bolts at the moment of failure of the wrench is 180 ± 30 °.

3.6. The results of calibration of the nutrunner must be entered in the calibration logbook of the nutrunners (see mandatory Appendix 8).

3.7. If the compressed air pressure changes after the malfunction in the nutrunner has been eliminated, it is necessary to perform a check calibration.

APPENDIX 3

equipment identification
Burner GAO-60, GAO-2-72 GOST 17357-71 (1 pc.)	Wide-grip, multi-flame, grip width 100 mm.
Oxygen cylinders (3 pcs.)
Acetylene cylinders (2 pcs.)
	Maximum overpressure at the inlet - 1962 ⋅ 10 4 Pa; working overpressure - 78.48⋅ 10 4 Pa; throughput at maximum pressure - 23m 3 / h
	Maximum overpressure at the inlet - 245.25 ⋅ 10 4 Pa; working overpressure - from 0.981⋅ 10 4 Pa to 14.715 ⋅ 10 4 Pa; throughput - 5 m 3 / h
Rubber hoses for oxygen supply (GOST 9356-75) with an inner diameter of 9.0, an outer diameter of 18 mm	Working overpressure 147.15 ⋅ 10 4 Pa

APPENDIX 4

Equipment, mechanisms and tools used, connected elements and tension of high-strength bolts

The vibration levels of electric and pneumatic hand-held grinding machines and wrenches (Table 1) do not exceed those established in GOST 16519-79 (ST SEV 716-77) and GOST 12.1.012-78.

Table 1

Name	Brand, standard	Appointment
Electric impact wrenches	IE-3115A IE-3119U2 IE-3112A
Pneumatic impact wrenches	GOST 15150-69 IP-3106A IP-3205A GOST 10210-74
Spanners
Electric Hand Sanders	IE-2004UZ	For stripping work
Electric angle grinders	IE-2102A
Pneumatic stripping hand-held machines		For cleaning metal surfaces from rust and scale
Gas burners	GAO-2-72 GOST 17357-71	For processing contact surfaces

The noise levels of electric and pneumatic hand-held grinding machines and wrenches do not exceed those established in GOST 12.1.003-76 Vibration parameters and noise characteristics of electric and pneumatic hand-held machines used in processing the contact surfaces of the connected elements and for tensioning high-strength bolts are given in Table 1, respectively. 2 and 3.

table 2

Vibration parameters

Brand


IE-3115A
IE-3119U2
IE-3112A
IE-3120A
IE-2009
IE-2004AUZ
IE-2102A

Table 3

Noise characteristics

Brand
cars
	Sound power level, dB
IE-3115A
IE-3119U2
IE-3112A
IE-3120A
IP-3106A
IP-3205A

APPENDIX 5

Name		Cooking method
Epoxy-polyamide adhesive
	Hardener I-5M (I-6M) according to VTU OP-2382-65-60 (50 wt. H) Accelerator UP-606-2 according to MRTU 6-09-6101-69 (2 - 3 wt. H)
Abrasive material
Solvent	Acetone according to GOST 2768-79

APPENDIX 6

obligatory

Headquarters

_______________________________________

Object name

_______________________________________

Manufacturer of structures, order no.

High-strength bolt assembly control log

date	KMD drawing number and name of the unit, joint in the joint	Number of supplied bolts per connection	Bolt certificate numbers	Contact surface treatment method	Standard tightening torque or turning angle of the nut	Control results
date	KMD drawing number and name of the unit, joint in the joint	Number of supplied bolts per connection	Bolt certificate numbers	Contact surface treatment method	Standard tightening torque or turning angle of the nut	Contact surface treatment	Number of bolts tested	Torque test results	Brand number, signature of the foreman	Brand number, signature of the person in charge	Signature of the customer's representative

Ch. installation engineer _______________________________________

Place of printing

editing room

organization

APPENDIX 7

obligatory

_______________________________________

Headquarters

_______________________________________

Object name

Magazine 1 control calibration of keys for tension and tension control of high-strength bolts

______________

1 The magazine is issued for all keys used when performing installation connections at each facility.

During the control calibration, the journal must be kept by the responsible person performing the work.

The responsible person fills in the journal after each key calibration. The journal is kept until the delivery of the object.

date	Change	Key		Twisting moment	Readings on the key device	Signature of the person responsible for the calibration
		a type	room

Ch. installation engineer _

Place of printing

installation organization

APPENDIX 8

obligatory

Headquarters

________________________________________

Installation organization (trust, management)

________________________________________

Object name

Magazine 1 calibration of nutrunners for tensioning high-strength bolts with control of forces by the nut rotation angle or by axial tension

________________

1 The magazine is issued for all nutrunners used when performing assembly connections at each facility, designed to tension high-strength bolts by the angle of rotation of the nut or by axial tension.

When calibrating nut runners, the journal must be kept by the responsible person performing the work.

The responsible person fills in the log after each check calibration of the impact wrenches.

The journal is kept until the delivery of the object.

date	Change	Excessive pressure of compressed air at the inlet of the nutrunner, Pa	A set of plates in a tightly tightened bag	Initial tension wrench	Turning angle of the nut with a wrench	Signature of the responsible person who performed the calibration

In this magazine, __________________ pages are laced and numbered

Place of printing

editing room

organization

Content

1. General Provisions

2. Technical requirements

3. The content of the technological process

4. Acceptance rules and control methods

5. Safety requirements

Applications

1. An example of calibration of a torque wrench type KTR-3

2. Methods of tensioning high-strength bolts

3. Equipment for the post fire cleaning

4. Equipment, mechanisms and tools used for processing contact surfaces, connected elements and tension of high-strength bolts

5. Composition of friction coating

6. Log of control over the implementation of erection connections on high-strength bolts

7. Log of control calibration of keys for tension and tension control of high-strength bolts

8. Calibration log for nutrunners for tensioning high-strength bolts with control of efforts by the nut rotation angle or by axial tension

APPROVED

Director___________________

___________ .___________________

1. GENERAL PROVISIONS

1.1. High-strength bolts, nuts and washers should be used in accordance with the instructions of the working (KM) or detailing (KMD) drawings of the steel structures of the mounted object.

1.2. Work production projects (PPR) must contain work production schemes or technological maps, providing for the implementation of connections on high-strength bolts in the specific conditions of the mounted object.

1.3. Preparation, assembly and acceptance of connections on high-strength bolts should be carried out under the guidance of a person (foreman, foreman) appointed by the order of the installation organization responsible for performing this type of connection at the facility.

1.4. Fitters must be at least 18 years old, who have undergone special theoretical and practical training, confirmed by a personal certificate for the right to perform these works, issued by the installation organization, to make connections on high-strength bolts.

2. TECHNICAL REQUIREMENTS

2.1. Requirements for the materials used

2.1.3. To form a glue-friction coating on the contact surfaces of the linings, glue based on epoxy-dianic resin ED-20 according to GOST 10587-76 and carborundum powder grades KZ and KCh, fractions No. 8, 10, 12 according to GOST 3647-80 should be used.

2.2. Requirements for the connected structural members and tools

2.2.1. The possibility of free supply of high-strength bolts and screwing nuts using wrenches and torque wrenches should be ensured by the constructive solution of the connections.

2.2.2. Mounting of connections is not allowed if there are burrs on the structural elements around and inside the holes, as well as along the edges of the elements.

The contact surfaces of the elements are not subject to priming and painting. The distance between the axis of the bolts of the last row and the primed surface should not be less than 70 mm.

2.2.4. In joints made of rolled profiles with non-parallel flange surfaces, leveling shims must be used.

2.2.5. Nominal diameters and blackness of holes (mismatch of holes in individual parts of the assembled package) should not exceed the requirements specified in chapter SNiP III-18-75 “Rules for production and acceptance of work. Metal constructions".

2.2.6. Control and calibration torque wrenches must be numbered, calibrated and supplied with calibration charts or tables. Pneumatic and electric wrenches must meet passport requirements.

3.1. Preparatory operations

3.1.1. Preparatory operations include: de-preservation and cleaning of high-strength bolts; preparation of structural elements; control and calibration check of the tool.

3.1.2. High-strength bolts, nuts, washers should be cleaned from factory preservation, dirt, rust and covered with a thin layer of grease. De-preservation and cleaning are carried out using the following technology.

3.1.3. Place high-strength bolts, nuts and washers with a maximum weight of 30 kg in a wire rack.

3.1.4. Submerge the lattice container filled with hardware in a tank with boiling water for 8 - 10 minutes (see drawing).

3.1.6. Place the machined bolts, nuts and washers separately in closed boxes with handles with a capacity of no more than 20 kg for transferring them to the workplace.

3.1.7. On the portable packaging, indicate the standard sizes, the number of bolts, nuts and washers, the date of processing, the certificate and batch numbers.

3.1.8. Cleaned bolts, nuts and washers should be stored in closed boxes for no more than 10 days, after which it is necessary to re-process in accordance with paragraphs. 3.1.4 and 3.1.5.

3.1.9. Burrs found around and inside holes and around the edges of elements must be removed completely. Deburring around holes and along the edges of elements should be done with pneumatic or electric stripping machines without forming a depression that breaks the contact of the contacting surfaces, and in the case of the presence of burrs inside the hole - with a drill, the diameter of which is equal to the diameter of the bolt.

Boiler for high strength bolts, nuts and washers

1 - heating element; 2 - lattice container for bolts; 3 - water tank;

4 - drain plug

3.2. Basic technological operations

3.2.1. The main technological operations include:

Contact surface treatment;

Assembly of connections;

Installation of high strength bolts;

Bolt tension and tension control.

The following methods of treatment of contact surfaces, performed at the assembly site, have been established: sandblasting (shot blasting); gas flame; metal brushes; glue friction.

When sandblasting (shot blasting) the contact surfaces, mill scale and rust must be completely removed until a uniform light gray surface is obtained.

3.2.4. Flame treatment of contact surfaces must be carried out with wide-range gas-flame burners GAO-60 or GAO-2-72 in accordance with GOST 17357-71.

Flame treatment is allowed with a metal thickness of at least 5.0 mm.

The speed of movement of the torch is 1 m / min with a metal thickness of more than 10 mm and 1.5-2 m / min - with a metal thickness of up to 10 mm inclusive.

Combustion products and scale should be swept away with a soft wire brush and then a hair brush.

The surface after flame treatment must be free from dirt, paint, oil stains and easily peelable scale. Complete removal of mill scale is optional.

The equipment of the gas-flame treatment station and a brief technical characteristics of the equipment are given in the recommended Appendix 3.

3.2.5. The processing of contact surfaces with metal brushes should be carried out using pneumatic or electric cleaning machines, the brands of which are indicated in the recommended Appendix 4.

It is not allowed to bring the contact surfaces to be cleaned to a metallic sheen.

3.2.6. As a rule, a glue-friction coating is applied to the contact surfaces of the linings at the factories that manufacture metal structures.

The technological process for obtaining an adhesive friction coating provides for:

Treatment of contact surfaces of linings in sandblasting (shot blasting) devices in accordance with GOST 11046-69 (ST SEV 3110-81);

Application of epoxy-polyamide glue to the treated contact surfaces;

Application over uncured glue with carborundum powder.

The safety of the adhesive coating must be ensured by packing the linings for the entire period of their loading, transportation, unloading and storage at the construction site.

The shelf life of pads with an adhesive friction coating is not limited.

The composition of the friction coating is given in the recommended appendix 5.

The contact surfaces of the main connected elements before assembly must be treated with metal brushes in accordance with clause 3.2.5.

3.2.7. Metallization processing of the contact surfaces of the joined structural elements (galvanizing, aluminizing), as a rule, is carried out at the factories that manufacture metal structures.

Surfaces treated by sandblasting (shot-blasting) are allowed to be cleaned by a gas-flame method during repeated processing.

3.2.9. The contact surfaces without treatment must be cleaned of dirt and peeling scale with metal brushes; from oil - with unleaded gasoline, from ice - by chipping.

3.2.10. The assembly of high-strength bolted connections includes the following operations:

Alignment of holes and fixing in the design position of the connection elements using assembly plugs, the number of which should be 10% of the number of holes, but not less than 2 pcs;

Installation of high-strength bolts in holes free from assembly plugs;

Dense bag screed;

Tension of the installed high-strength bolts to the force indicated in the KM and KMD drawings;

Removing assembly plugs, placing high-strength bolts in the vacant holes and tensioning them to the design force;

Connection priming.

3.2.11. Under the heads and nuts of high-strength bolts, it is necessary to place only one heat-treated washer in accordance with GOST 22355-77.

The protruding end of the bolt must have at least one thread above the nut.

3.2.12. If the holes do not match, their reaming in elements with machined surfaces should be done without using coolants.

3.2.13. The preliminary and final tension of high-strength bolts must be performed from the middle of the joint to the edges or from the most rigid part of the joint towards its free edges.

3.2.14. The tensioning method for high-strength bolts should be specified in the KM or KMD drawings.

3.2.15. In the absence of instructions, the tensioning method is selected by the installer according to the recommended appendix 2.

4. RULES OF ACCEPTANCE AND CONTROL METHODS

4.3. After acceptance, the finished joint should be primed and painted. Grades of soil and paint and varnish material are taken according to the "List of polymeric materials and products permitted for use in construction", approved by the USSR Ministry of Health, the same as for priming and painting metal structures. The grades of soil and paint must be indicated in the KM and KMD drawings.

4.4. The quality of the connections on high-strength bolts is checked by the responsible person through operational control. Subject to control:

The quality of the processing of contact surfaces;

The presence of washers under the bolt heads and nuts;

The presence of the manufacturer's mark on the bolt heads;

The length of the protruding part of the bolt thread above the nut;

The presence of the hallmark of the foreman in charge of the assembly of the compound.

4.5. The quality of processing of the contact surfaces is checked by visual inspection immediately before assembling the connections. The results of the control must be recorded in the journal (see mandatory Appendix 6).

4.6. The compliance of the bolt tension with the design is checked depending on the tension method. Deviation of the actual torque from the torque specified in the drawings of the CM and KMD should not exceed 20%.

Bolts with the position of the marks outside the specified limits must be loosened and tightened again.

4.7. The tension of high-strength bolts is checked with a calibrated torque wrench or a control calibrated wrench.

The tension of the bolts should be controlled by random inspection: with the number of bolts in the joint up to 5 inclusive, 100% of the bolts are controlled, with the number of bolts from 6 to 20 - at least 5, with a larger number - at least 25% of the bolts in the joint.

4.8. If during the inspection at least one bolt is found whose tension does not meet the requirements of clause 4.6 of this standard, then 100% of the bolts in the joint are subject to inspection. In this case, the tension of the bolts must be brought to the required value.

4.9. The density of the bundle being pulled together is controlled with 0.3 mm probes. The probe should not pass between the planes along the contour of the connected elements.

4.10. Documentation presented upon acceptance of the finished object, except for the documentation provided for by chapter SNiP III-18-75 “Rules for production and acceptance of works. Metal structures ", should contain:

High-strength bolt assembly log;

Certificates for bolts, nuts and washers;

Certificates for materials for the formation of adhesive friction coatings.

5. SAFETY REQUIREMENTS

5.1. The organization of the section for the enlarged assembly of structures with assembly joints on high-strength bolts should ensure the safety of workers at all stages of work.

Work on the installation of structures on high-strength bolts must be carried out in accordance with the PPR containing the following safety solutions:

Organization of workplaces and walkways;

The sequence of technological operations;

Methods and devices for the safe work of installers;

Location and coverage of assembly mechanisms;

Ways of storage of building materials and structural elements.

5.2. The placement of working equipment and the organization of workplaces must ensure the safety of the evacuation of workers in emergency situations, taking into account the current building codes.

5.3. All work at height on making assembly connections on high-strength bolts should be carried out from a scaffold that provides free access to the connection with the tool.

Paving means and other devices that ensure the safety of work must comply with the requirements of the chapter of SNiP III-4-80 “Rules for the production and acceptance of work. Safety in construction ", GOST 12.2.012-75, GOST 24259-80 and GOST 24258-80.

5.4. Electrical safety at the installation site must be ensured in accordance with the requirements of GOST 12.1.013-78.

5.6. The place of production of sandblasting (shotblasting) works should be fenced and appropriate warning signs and inscriptions should be posted near it.

5.7. Materials for sandblasting (shot blasting) surface treatment (sand, shot, metal sand) should be stored in containers with a tightly closed lid.

5.8. The operator of the sandblasting (shot blasting) apparatus and the auxiliary worker are supplied with spacesuits or helmets with a forced supply of clean air.

5.9. The air supplied to the spacesuit must first be passed through a filter to remove dust, water and oil.

5.10. Between the workplaces of the operator and the auxiliary worker, located near the sandblasting (shot blasting) apparatus, an audible or light alarm should be provided.

5.11. When treating contact surfaces with metal brushes (manual and mechanical), workers should be provided with goggles in accordance with GOST 12.4.003-80 or masks, gloves and respirators.

5.13. The places of production of gas-flame works must be free from combustible materials within a radius of at least 5 m, and from explosive materials and installations (including gas cylinders and gas generators) - within a radius of 10 m.

5.14. It is not allowed to carry out work on gas-flame treatment of surfaces of structural elements in rainy weather outside without a canopy.

5.15. When performing gas-flame treatment of contact surfaces, workers must be provided with closed-type goggles with glass-light filters brands G-1 or G-2.

Auxiliary workers must be provided with protective glasses with glass-light filters grades B-1 or B-2.

5.17. Glue preparation and application of glue friction coatings should be carried out in a separate room equipped with exchange and local ventilation.

5.18. Persons working with epoxy-diane resins must be provided with protective clothing and gloves.

To protect the skin from the effects of epoxy-diane resins, protective pastes and ointments based on lanolin, petroleum jelly or castor oil should be used.

5.19. The room for applying glue-friction coatings must be provided with fire extinguishing means - carbon dioxide and foam fire extinguishers.

5.20. De-preservation of bolts, nuts and washers should be carried out in an open area with a canopy.

5.21. When boiling hardware in water, the bath must be grounded. Workers who are de-preserving hardware should not have direct contact with boiling and lubricating baths. The loading process must be mechanized.

5.23. The operation of mechanisms, small-scale mechanization, including maintenance, must be carried out in accordance with the requirements of the chapter of SNiP III-4-80 “Rules for the production and acceptance of work. Safety in construction ”and the instructions of the manufacturers.

5.25. The working regime when working with manual electric and pneumatic machines and wrenches should be established in accordance with the "Recommendations for the development of the Regulations on the working regime of workers in vibration hazardous professions", approved in December 1971 by the All-Union Central Council of Trade Unions, the USSR Ministry of Health, the State Committee of the USSR Council of Ministers on Labor and wages, as well as instructions from manufacturers for performing work with specific types of machines.

5.26. Finished joints on high-strength bolts should be primed and painted at the assembly site of metal structures.

5.27. Only workers who know the rules of safe handling of the equipment and materials used and are familiar with the fire safety rules are allowed to work on priming the joints.

An example of calibration of a torque wrench type KTR-3 1

_________________

1 Keys KTR-3 are manufactured by assembly organizations according to the drawings of the Central Research Institute of Proektstalkonstruktsiya.

At a fixed point at the end of the key, a weight is suspended

where M z- calculated torque of twisting;

D M z- moment equal to the product of the key mass by the distance from its center of gravity to the axis of the mandrel or bolt;

l- the distance from the center of gravity of the load to the axis of the mandrel or bolt.

With a suspended load, the counting is carried out according to a recording device, for example, a dial indicator ICh 10 mm in accordance with GOST 577-68. The measurement is carried out 2-3 times until a stable result is obtained. The calibration results are entered into the key calibration control log (see mandatory Appendix 7).

Torque wrench calibration scheme

1 - welded hexagon or tightened high-strength bolt;

2 - rigid support; 3 - indicator; 4 - a tared key; 5 - tared cargo

Tensioning Methods for High Strength Bolts

1. Tightening high-strength bolts by tightening torque

1.1. The tension of high-strength bolts to the design force should be done by tightening the nuts with a torque wrench to the calculated value of the tightening torque. Torque value M z required for tensioning high-strength bolts is determined by the formula:

M z = kPd,

k- the average value of the tightening factor for each batch of bolts according to the certificate or set using control devices at the installation site;

R- bolt tension force specified in the KM and KMD drawings;

d- nominal bolt diameter.

1.2. To pre-tighten the nuts, use the pneumatic or electric wrenches specified in Recommended Appendix 4 and torque wrenches.

1.3. When tightening the bolt, the head or nut should be kept from turning by the mounting wrench... If turning as the bolt is tightened does not stop, then the bolt and nut must be replaced.

1.4. The torque should be recorded as the key moves in the direction that increases the tension.

Tightening should be done smoothly, without jerking.

1.5. Torque wrenches must be numbered and calibrated. They should be calibrated at the beginning of the shift.

2. Tension of high-strength bolts on the angle of rotation of the nut

2.1. High-strength bolts must be installed in the holes free of assembly plugs and tightened with a nutrunner adjusted at a torque of 800 N × m. Each bolt must be tightened until the nut stops rotating. After removing the assembly plugs and replacing them with bolts, the latter should be tightened at the moment of tightening 800 N × m.

2.2. To control the angle of rotation of the nuts, it is necessary to mark them and the protruding ends of the bolts with a aligned center punch (see drawing) or paint.

Combined center punch

1 - center punch; 2 - nut; 3 - high-strength bolt; 4 - package

2.3. The final tightening is carried out with a nutrunner, adjusted at the moment of tightening 1600 N × m, while the nut should turn by the angle indicated in the table.

3. Calibration of nutrunners according to the angle of rotation of the nut

3.1. Wrenches should be calibrated using a special calibration package consisting of three bodies with at least 20 holes.

The adjusting bolts must be tightened by hand with an assembly wrench with a handle length of 0.3 m to failure (initial position).

3.2. On the prepared calibration bolts, the wrench is calibrated.

3.3. The compressed air pressure is set so that when the nut is turned through an angle of 180 ± 30 ° from the initial position, the wrench fails.

The air pressure should be checked periodically.

Air pressure control should be carried out according to the GOST 2405-72 pressure gauge installed at the point where the nutrunner hose is connected to the line.

3.4. When calibrating the nutrunner (to observe the angle of rotation of the nut), risks should be applied to its replaceable head.

3.5. The wrench is considered calibrated if the angle of rotation of the nut in the process of tensioning all bolts at the moment of failure of the wrench is 180 ± 30 °.

3.6. The results of calibration of the nutrunner must be entered in the calibration logbook of the nutrunners (see mandatory Appendix 8).

3.7. If the compressed air pressure changes after the malfunction in the nutrunner has been eliminated, it is necessary to perform a check calibration.

APPENDIX 3

Fire cleaning post equipment

equipment identification	Brief technical characteristics
Burner GAO-60, GAO-2-72 GOST 17357-71 (1 pc.)	Wide-grip, multi-flame, grip width 100 mm.
Oxygen cylinders (3 pcs.)
Acetylene cylinders (2 pcs.)
Balloon oxygen reducer DKD15-65 or RKD-15-81	Maximum overpressure at the inlet - 1962 × 10 4 Pa; working overpressure - 78.48 × 10 4 Pa; throughput at maximum pressure - 23 m 3 / h
Acetylene balloon reducer RD-2AM, DAP-1-65	Maximum overpressure at the inlet - 245.25 × 10 4 Pa; operating overpressure - from 0.981 × 10 4 Pa to 14.715 × 10 4 Pa; throughput - 5 m 3 / h
Rubber-fabric hoses for oxygen supply (GOST 9356-75) with an inner diameter of 9.0, an outer diameter of 18 mm	Working overpressure 147.15 × 10 4 Pa

APPENDIX 4

Equipment, mechanisms and tools used for processing contact surfaces, connected elements and tension of high-strength bolts

The vibration levels of electric and pneumatic hand-held grinding machines and wrenches (Table 1) do not exceed those established in GOST 16519-79 (ST SEV 716-77) and GOST 12.1.012-78.

Table 1

Name	Brand, standard	Appointment
Electric impact wrenches		For tightening high-strength bolts during assembly and assembly work
Pneumatic impact wrenches	GOST 15150-69 GOST 10210-74
Spanners		For pre-assembling connections
Electric Hand Sanders		For stripping work
Electric angle grinders
Pneumatic stripping hand-held machines		For cleaning metal surfaces from rust and scale
Gas burners	GOST 17357-71	For processing contact surfaces

The noise levels of electric and pneumatic hand-held grinding machines and wrenches do not exceed those established in GOST 12.1.003-76. Vibration parameters and noise characteristics of electric and pneumatic hand-held machines used in processing the contact surfaces of the connected elements and for tensioning high-strength bolts are given, respectively, in table. 2 and 3.

table 2

Vibration parameters



Logarithmic levels of vibration velocity values, dB

Table 3

Noise characteristics

	Average geometric frequencies of octane bands, Hz

	Sound power level, dB

The composition of the friction coating

Name		Cooking method
Epoxy-polyamide adhesive	Epoxy resin ED-20 in accordance with GOST 10587-76 (100 wt.h)	A hardener and an accelerator are introduced into the epoxy resin; the resulting mixture is thoroughly mixed
	Hardener I-5M (I-6M) according to VTU OP-2382-65-60 (50 wt. H) Accelerator UP-606-2 according to MRTU 6-09-6101-69 (2 - 3 wt. H)
Abrasive material	Carborundum powder grade KZ or KCh
Solvent	Acetone according to GOST 2768-79

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