Chief Engineer of the Institute S.K. Kanevsky

A large number of welds of short length has become a serious obstacle to the mechanization and automation of welding processes at installation. Bolted mounting joints allow, under the conditions of the mounting site, to use hard-welded high strength steels in structures. Bolted connections allow you to work simultaneously on a large number of nodes by unskilled workers. The effectiveness of the use of bolted joints is formed at the design and manufacturing stage of the assembly units. According to the USSR Gosstroy, the estimated volume of the possible use of metal structures on bolts is 60 - 65% of the total steel produced by the industry building structures. However, due to the low technical equipment of a number of metalwork factories, poor design quality and a number of other reasons in the Soviet Union, only 15 - 20% of structures are manufactured with bolted mounting joints.

The constructions of objects of ferrous metallurgy in recent years (except for sheet ones) are mainly designed with joints on high-strength bolts).

When supervising mounting joints on high-strength bolts, special attention should be paid to the ultra-high-strength bolts supplied by the industry in the 1970s and 1980s. with a temporary resistance of 120, 135 and 155 kg / mm 2. Such bolts are installed in a number of designs of the Cherepovets, Lipetsk metallurgical plants, Magnitogorsk and others. These bolts due to the lack of restrictions on the upper limit of hardness have an increased ability to ZHR (delayed brittle fracture).

The most dangerous period is the first 1 to 3 years after the start of operation. Bolts "shoot" without a visible application of external load. In all constructions of recent years, attention has been paid to ZHR.

Studies conducted at a number of facilities after years of operation have shown that the drop in bolt tension is negligible. But since in the process of performing installation work, a shortage of bolts is possible, then in the process of operating the structures, a selective check of the tension of the installed bolts is required. The control of bolted mounting joints is much simpler than that of welded joints, since in welded joints there is a greater likelihood of hidden weld defects than in bolted connections. The main way to control bolted connections is visual.

1. GENERAL PROVISIONS

1.1. These Recommendations were developed in accordance with Order No. 759 of 9.XII.1988 according to the USSR Ministry of Industry and Agreement No. P47-6882 concluded between the Central Scientific Research Institute of Steel Construction named after Melnikov Gosstroy of the USSR and the Cherepovets Iron and Steel Works of the Ministry of Industry of the USSR on April 19, 1989 and are the development of section 7 of the industry guidance document ORD 00 00089 “Technical operation steel structures   industrial buildings. "

1.2. The recommendations cover oversight and technical operation metal structures of buildings and structures of ferrous metallurgy enterprises with connections on high-strength bolts, designed according to the standards of the USSR, operated in areas with an estimated temperature of -65 ° C.

1.3. When accepting structures with connections on high-strength bolts in the acceptance committee, the participation of a service representative is required technical supervision   on the operation of buildings and structures of the enterprise.

1.4. Responsibility for technical condition mounting connections   on high-strength bolts, the order for the workshop entrusts the engineering and technical workers of the workshop, who must undergo appropriate theoretical and practical training, are familiar with the rules for making connections on high-strength bolts and have a certificate (Appendix No. 7; 8).

1.5. Direct inspection of installation connections and restoration (repair) should be carried out by specially trained specialists with the appropriate skills and certification. In hard-to-reach places at a height, examinations are carried out with the participation of climbers.

1.6. Specialists in the operation of buildings and structures participating directly in the survey must undergo appropriate training, have a certificate and permission to stay at their best.

The number of specialists is determined at the rate of 1 engineering per 100 thousand high-strength bolts.

1.7. A feature of frictional joints on high-strength bolts is that the forces are perceived not by shear of bolts and crushing of the wall, but by frictional forces arising between the contacting surfaces pulled together by a high-strength bolt. In this regard, the magnitude of the tension of high-strength bolts and the quality of preparation of the friction surfaces of the connected elements is crucial and is controlled during the test. Insufficient tension of high-strength bolts in frictional joints can lead to “slipping” of the elements, while the bolts will work to shear, the elements to collapse. In addition, a geometric shape violation due to the mutual displacement of the elements is possible - the bolts will come into operation unevenly, since the difference in the diameters of the holes and bolts can reach 6 mm in accordance with SNiP III-18-75 table. 4 and there may be cases of successive failure of the bolts.

1.8. The studies found that the decisive influence on the reliability of the bolts is exerted by the levels of their mechanical characteristics (temporary tensile strength, elongation and contraction, impact strength), determined by the heat treatment conditions.

The main of these characteristics is the temporary tensile strength, controlled by its upper limit. Excessively strong bolts (marked 135 and 155), which have increased hardness, are prone to delayed brittle fracture and require more careful monitoring and more frequent examination of the joint.

2. MATERIALS, PRODUCTS AND CONDITIONS OF THEIR APPLICATION

2.1. To connect the elements of steel building structures, high-strength bolts, nuts and washers made in accordance with the requirements of GOST 22353-77 are used? 22356-77 or TU 14-4-1345-85 and bolts of normal strength according to GOST 1759-70 (Fig. 1).

2.2. According to GOST 22356-77, the bolts must have the brand of the manufacturer, as well as a marking showing the temporary resistance in kgf / mm 2, and the symbol of the melting number. Bolts of climatic modification of HL are in addition marked.

2.3. To control the mechanical properties of bolts, nuts and washers at the factory, 5 samples are taken from each batch for each type of test.

Bolts are tested for tearing, tensile specimens, determining toughness (CL), tearing on an oblique washer, determining the twisting coefficient and hardness.

2.4. High strength bolts, nuts and washers are supplied in batches consisting of parts of the same designation made of steel of the same heat, processed in one mode. The mass of a batch of bolts should not exceed 1000 kg, nuts and washers - 500 kg.

2.5. Each batch of hardware should be provided with a certificate stating:

Certificate Number name of the manufacturer; name, type and size of products; steel grade; batch number; heat number; test results; Net weight.

2.6. For structures with a design temperature below minus 40 ° C and up to minus 65 ° C, high-strength CL bolts should be used. On the head of these bolts there is a sign "CL".

2.7. The strength class of bolts of normal strength is indicated by two numbers. The first number, multiplied by 10, determines the value of the minimum tensile strength in kgf / mm 2, the second number, multiplied by 10, determines the ratio of the yield strength to tensile strength in percent. The product of numbers determines the yield strength. This type includes bolts marked 10.9; 8.8; 5.8 (Fig. 1).

Fig. 1 Marking of bolts of various strength classes, including high-strength ones.

a. High-strength bolt of the Druzhkovsky plant; b. High-strength bolt of the Magnitogorsk plant; c. High-strength bolt of the Shchelkovo plant; D. High-strength bolt of the Voronezh plant; e. Bolt strength class 10.9 Magnitogorsk plant; g. Bolt strength class 8.8 Automobile them. Likhachev; h. Bolt strength class 5.8 Magnitogorsk plant.

For example, a bolt strength class of 5.8 indicates that the minimum tensile strength of the metal? c, from which the bolt is made, is 5 × 10 \u003d 50 kgf / mm 2, and the ratio of yield strength? t to temporary resistance? in percent it is equal 8? 10 \u003d 80%. The first number of marking, multiplied by the second, determines the yield strength

T \u003d 5? 8 \u003d 40 kgf / mm 2

2.8. High-strength bolts are marked 110, which indicates the minimum temporary resistance in kgf / mm 2 of the material of the bolt.

2.9. In the absence of bolts specified in the project, replacement of bolts of strength class 5.8 with bolts of 8.8 is permitted; 10.9 and high strength. Bolts 8.8 can be replaced by 10.9 and high strength. Bolts 10.9 - for high strength. Reverse replacement without appropriate recounting of structures is prohibited.

3. SUPERVISION OF THE CONDITION OF THE CONNECTIONS

3.1. Supervision of the condition of the connections is carried out by the workshop service for the technical operation of steel structures of industrial buildings through ongoing inspections.

3.2. Routine inspections of compounds are carried out selectively once every six months in flight   converter, open-hearth and other shops, whose designs are subject to dynamic effects. In other workshops, departments and spans at least once a year.

Inspection of nodes on high-strength bolts, as a rule, is carried out in conjunction with the examination of steel building structures in the time provided by the ARD 00 000-89.

3.3. The condition of high-strength bolts and connected elements is monitored visually and consists in checking the presence of bolts in the nodes, as well as in randomly checking their tension and safety (absence of cracks, gusts) of the connected elements. The bolts are checked in accordance with table. 3 in every tenth node (10% of nodes). Subsequent checks verify previously unverified nodes.

Particular attention should be paid to the identification of defects in accordance with table. 1.

	Defect name		Remedy
	non-emergency	emergency *
	No bolts less than 10% in the joint	More than 10% of bolts in the connection are missing	Install new bolts, tighten the design effort with a control wrench
	Less than 10% of bolts are not tightened on design effort	More than 10% of bolts are not tightened on design effort	Retighten bolts with a control key
	When controlling tension, bolts with nuts turn		Install new bolts. Tighten the bolts to the design effort with a control wrench
	Probe 0.3 mm passes into the gap between the connected elements		Check the tension of the bolts in the assembly. Tighten bolts to design effort. Paint joints along the contour
	Cracks in the body of less than 10% of bolts, nuts or washers in the joint	Cracks in the body of more than 10% of bolts, nuts or washers in the joint	Replace damaged bolts, nuts, or washers. Tighten the bolts to the design effort with a control key
		Crack in connectable structures detected	Strengthen or replace an element in accordance with the decision of the authors of the project

3.4. In case of defect detection emergencywhen more than 10% of the bolts are loosened in the joint, defects are detected or more than 10% of the bolts are missing, cracks or gusts in the connected structures are detected, immediate measures must be taken to eliminate them.

3.5. In the first two to three years of operation of buildings or structures, a selective instrumental check is carried out in accordance with Section 4, in order to identify possible defects made during installation work.

Table 1

List of possible defects in joints with high-strength bolts

* - The emergency nature of the defect is determined conditionally, the final decision on the nature of the influence of the defect on the bearing capacity and integrity of the structures is determined by the author of the project.

3.6. In the process of instrumental testing, the tension of the bolts is controlled (table. 2).

3.7. Bolt tension control is carried out at the time of tightening with torque wrenches. The tightening torque applied to the nut or bolt head must be at least the value indicated in the table. 2.

3.8. The results of checking joints on high-strength bolts are recorded in the log of technical inspections of joints, if necessary, the outer surfaces of the joints are primed with the most common soil GF-020, FL-03K or others that do not contain oil.

3.9. Work to eliminate defects associated with the installation of new bolts is carried out in accordance with the technological process of assembling joints on high-strength bolts (section 4).

3.10. If it is necessary to check the quality of surface preparation or to determine the strength class of bolts and study working drawings, one should be guided by the documents (Appendix 3) stored at the factory with the certificate of completion of the structures.

3.11. When checking mounting connections on bolts, particular attention should be paid to the following components:

(Appendix 9)

Mounting points for ties in columns (for bolts); fig. 5, 7 (nodes 1, 2, 3, 5);

Attachment points for crane beams (for bolts and possible loosening of their tension) fig. 6, fig. 7 (node \u200b\u200b6);

Knots of PPF (crane-girder trusses), truss and truss trusses of large spans (the presence of bolts and selective control of their tension) Fig. 12;

Knots of beam cells (the presence of bolts and selective control of their tension), Fig. 3;

Joint of columns (presence of bolts and selective control of their tension), fig. 4.

3.12. If it is necessary to establish the causes of defects and develop measures to eliminate them, as well as to examine compounds, specialists of research and design organizations may be contracted.

4. TECHNOLOGY OF RESTORING THE CONNECTION

The restoration of joints on high-strength bolts and their acceptance should be carried out under the direction of the person designated as responsible for the implementation of this type of joints by order of the organization performing these works.

To make connections on high-strength bolts, personnel who have undergone appropriate training and have a certificate of admission to these works are allowed.

Technological process   making connections on high-strength bolts when restoring nodes without completely disassembling them includes the following operations:

Preparation of high-strength bolts, nuts and washers;

Assembly of connections;

Tension;

Acceptance and sealing of joints.

The resulting bolts must have a marking showing the temporary resistance in kgf / mm 2 and the brand of the manufacturer.

Each batch of bolts must be equipped with a certificate stating:

Certificate Number

Name of the manufacturer;

Product designation with symbol   melting and batch numbers;

Test results;

Spin factors;

Net weight.

4.1. Preparation of high strength bolts, nuts and washers

4.1.1. The technological process for the preparation of hardware includes de-preservation, cleaning of dirt and rust, threading of discarded bolts and nuts, and lubrication.

4.1.2. There are two ways to handle hardware. Hardware in lattice containers (for small volumes - in a bucket with punched holes); in a clean barrel, water is boiled, if possible, with a washing solution or household washing powder. A bucket is dipped in water and boiled for 10 - 15 minutes. After that, when the water merges, the hardware is lowered for 1 - 2 minutes into a container with a mixture of gasoline (85%) and mineral oil of the Avtol type (15%), then removed. From heated hardware, gasoline quickly evaporates, and oil in the form of a thin film remains on the surface. This method provides equalization of the coefficient of twist to 0.18.

4.1.3. A reduction in the coefficient of twisting to 0.12 and its stabilization is done by waxing the nuts. After cleaning the hardware using the aforementioned technology, only nuts are lowered into the bath with molten paraffin (they are kept for 10-15 minutes), the nuts are removed and allowed to drain excess paraffin and cooled to ambient temperature.

4.2. Assembly of joints on high-strength bolts, if necessary, complete disassembly of joints

If it is necessary to completely disassemble the connections, the design load should be removed according to a specially developed project and the unit restored using the following technology:

4.2.1. The assembly assembly process includes:

Inspection of structures and verification of their compliance with the requirements of the project and chapter SNiP III-18-75 (in terms of accuracy of manufacturing structures);

Alignment of holes and fixing in the design position of the elements and parts of the connection using mounting plugs (10% of the number of holes, but not less than 2 pcs.);

Installation of high-strength bolts in plug-free holes;

Checking the geometric dimensions of assembled structures;

Tight screed package;

The tension of the delivered high-strength bolts to the force provided by the project;

Removing plugs, placing high-strength bolts in the released holes and tensioning them to the design effort.

4.2.2. The difference in the thicknesses of the elements overlapped by the overlays, determined before setting the overlays with a ruler and probe, shall not exceed 0.5 mm.

4.2.3. When the difference in the planes of the parts to be joined is from 0.5 to 3 mm, to ensure a smooth bending of the lining, the edge of the protruding part must be smoothed with an emery stone at a distance of up to 30 mm from the edge of the part, with a slope not steeper than 1:10. In case of a plane difference of more than 3 mm, gaskets should be used. The use of gaskets must be agreed with the design organization.

4.2.4. The lengths of the bolts used are selected depending on the thickness of the bag (Appendix 2).

4.2.5. When drilling holes in elements with machined surfaces, coolants containing oil should not be used.

4.2.6. The assembly of joints should be carried out immediately on high-strength bolts and plugs. The use of other bolts as assembly is prohibited.

4.2.7. Each bolt is installed in connection with two high-strength washers (one is placed under the head of the bolt, the other under the nut).

4.2.8. Nuts tightened to the design effort are not further secured.

4.2.9. At the time of installation of high-strength bolts, the nuts should turn freely (by hand) on the thread. Otherwise, the nut or bolt should be replaced, and the rejected bolts and nuts should be sent for re-training.

4.3. Tightening high-strength bolts, with torque control

4.3.1. The specified method is based on measuring the twisting moment applied to the nut or bolt head when the design axial force is reached in the bolt shaft. The required value of the twisting moment is determined by the formula

M \u003d P · d · K,

where P is a given bolt tension force, kgf;

d is the nominal diameter of the bolt, m;

K is the twisting coefficient, taken equal to 0.18 for all types of bolts supplied in accordance with GOST 22353-77 - GOST 22356-77 and processed according to the proposed technology in clause 3.1.3 and equal to 0.12 when processing in accordance with clause 3.1.3. The twisting coefficient for the certificate is not taken into account in the calculations.

4.3.2. With the number of bolts in the assembly up to 10 - 15 pcs. and in hard-to-reach places, the tension of the bolts is allowed to be performed with torque wrenches in one go (dash key. Appendix 6).

4.3.3. The tightening torque transmitted by the key should be recorded while the key is moving in a direction that increases tension. Tighten smoothly without jerking.

4.3.4. Torque wrenches must be numbered and calibrated.

Keys can be made either at a specialized factory or on their own. Calibration should be carried out at the beginning of the shift.

4.3.5. The deviation of the actual tightening torque from the calculated one should not exceed 20%.

4.3.6. Shortage of bolts is prohibited.

table 2

4.4. Torque wrench calibration

4.4.1. Torque wrenches are calibrated by hanging a specified amount of cargo to the handle of the wrench or using special calibration stands.

4.4.2. According to the first method, calibration should be performed in the following order:

hang a torque wrench on a hexagonal mandrel or on a tightened high-strength bolt so that its handle occupies a horizontal position (Fig. 2). At a fixed point on the end of the key, hang a weight of P (kg)

Fig. 2 Calibration torque wrenches

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

M s - estimated torque;

M s - the moment of twisting of the mass of the key, equal to the product of the mass of the key at a distance from its center of gravity to the axis of the mandrel or bolt.

When the load is suspended, the countdown is taken on the key registering device. Repeat the measurement 2 to 3 times until a stable result is obtained. Log calibration results.

4.5. Acceptance and sealing of joints subject to complete disassembly

4.5.1. Regardless of the method of tension, the controller should first of all conduct an external inspection of all supplied high-strength bolts and make sure that all bolts are marked, all washers are placed under all heads and nuts; the parts of the bolts protruding beyond the nut have at least one thread turn over the nut and two under the nut; on the assembled unit there is a stamp of the team that performed these works (Fig. 3).

4.5.2. The number of bolts in the assembly to be monitored is indicated in the table. 3.

Table 3

4.5.3. If the results of the control do not meet the requirements of clause 3.5.1, for at least one bolt, a double number of bolts is controlled. If, in this case, a defective bolt is detected, all the bolts of this connection are monitored.

4.5.4. The control results, regardless of the method of tension, should be entered in a special journal (Appendix No. 1).

4.5.5. Responsibility for the quality of the bolts is the manufacturer of the work.

4.5.6. The density of the package tie is checked with a 0.3 mm thick probe against the tightened bolt in the area bounded by the washer. The probe should not pass between the assembled parts into the area bounded by the washer (hereinafter formed washer).

4.5.7. On each connection, as a rule, the core is stamped with the team that performed the connection and the person who made the control. The stigma number is assigned by order of the unit performing the connections. If the bolts are prepared by waxing, the letter “P” is placed next to the stigma.

4.5.8. After accepting the connection by the controller, all joints along the contour should be primed. If there is no primer mark in the project design, the use of primers FL-03K, GF-021 with the addition of dry pigment to a consistency that excludes the primer from flowing inside the package is allowed.

4.5.9. The tool for tightening bolts and preparing surfaces is adopted in accordance with the “Guidelines for the use of a tool kit for setting high-strength bolts”. MMSS USSR Moscow 1985 (Appendix No. 10).

4.6. Bolt tension on the angle of rotation of the nut

4.6.1. For small volumes of work, the adjustment of the tension of the bolts by the angle of rotation of the nut can be performed with a hand tool for bolts with a diameter of 20, 22 and 24 mm, with a thickness of the bag up to 140 mm and the number of bodies in the bag up to 7.

4.6.2. The tension of the bolts is carried out in the following order:

Tighten all installed bolts to failure with a wrench with a handle length of 300 mm; (Starting position);

Risks are applied to nuts and protruding parts of bolts with paint or chalk;

Nuts tightened to the initial position of the bolts are rotated through an angle of 180 ° ± 30 °;

Tensioning can be done with any available wrench.

4.6.3. Tension control is performed only at the time of twisting.

TIGHTEN THE BOLT UNLOCKING WITH A KEY WITH HANDLE LENGTH 0.3 m. GUIDANCE ONLY ~ 20 kg · m.

EXPOSURE RISKS TO THE SPEED OF THE BOLT AND THE NUT. INSTALL A KEY WITH HANDLE 1.8 M LENGTH IN THE ORIGINAL POSITION.

Gently rotate the NUT WRENCH with a 180? WRENCH, MONITORING THE TURN ANGLE ON THE RISK MOVEMENT ON THE NUT.

Fig. 4 Tighten the bolts along the angle of rotation of the nut

5. TECHNOLOGY OF RESTORING INSTALLATION COMPOUNDS OF METAL STRUCTURES PERFORMED ON RIVETS, FEATURES OF PERFORMANCE OF BOLT-RIPPED COMPOUNDS

5.1. Bolt-riveted joints are not an independent type of mounting joints, but are introduced in the process of replacing defective rivets with high-strength bolts during repair or in order to increase the endurance of joints of riveted steel building structures.

5.2. The diameters of high-strength bolts should be taken according to the table. 4.

Table 4

5.3. When replacing defective rivets, it is unacceptable to create such mixed bolt joints in which the bolts are located only on one side of the longitudinal axis of symmetry of the structural element. Therefore, at the same time as defective ones, it is necessary to replace symmetrically located non-defective rivets.

5.4. Removing the rivet heads and knocking out the rod is performed in the following sequence (Fig. 5):

Mutually perpendicular slots are made on the rivet head to be removed, with a quadrangle being formed in the center of the head of a diagonal smaller than the diameter of the rod. The depth of the slot is less than the height of the head by 1 - 2 mm;

After the formation of slots on the rivet head, the rod, together with a part of the head in the form of a quadrangle, is knocked out of the opening of the packet.

Fig. 5 Rivet removal method

5.5. The rivet rods are knocked out with heat-treated (40 - 45 units) conical mandrels with a diameter of 0.5 mm less than the diameter of the holes.

5.6. Removable rivets should be dispersed across the joint field. The simultaneous removal of two or more adjacent rivets is prohibited. There must be at least two rivets between the holes (these include high-strength bolts that are tightened to the design force).

5.7. If there are burrs, the holes are cleaned with a drill with a diameter equal to the diameter of the rivets. When drilling holes, coolants must not be used.

5.8. The burrs around the holes are removed with an emery stone attached to the shaft of a pneumatic or electric machine.

5.9. Preparation of high-strength bolts, their installation in the structure and tension should be performed, as with the device friction joints.

5.10. Other rivet removal methods are allowed to ensure structural integrity and their fixation when replacing rivets with bolts.

Annex 1

INSPECTION MAGAZINE
  metalwork joints on high-strength bolts

Appendix 2

Bolt lengths depending on the thickness of the bag being pulled together

Bolt length mm	The thickness of the package in the connection on high-strength bolts with a diameter, mm

Appendix 3

LIST OF DOCUMENTS PRESENTED AT DELIVERY OF MOUNTED METAL STRUCTURES WITH CONNECTIONS ON HIGH-STRENGTH BOLTS (INTERMEDIATE RECEPTION)

1. The certificate of acceptance of metal structures.

2. Journal of installation work.

3. The magazine staging high-strength bolts.

4. Calibration log of wrenches and torque wrenches.

5. The journal for the preparation of high-strength bolts (or an entry in the journal for the production of high-strength bolts) about the methods for preparing hardware with an indication of the adopted twisting coefficient.

6. A copy of the order of the installation organization on the appointment of responsible performers for making connections on high-strength bolts and controllers, indicating the number of brands assigned to performers and controllers.

7. A set of drawings of KM with all corrections and changes made by the design organization.

8. A set of KMD drawings with the stamp “Executive Drawing” and the signature of the chief engineer of the mounting organization.

9. Certificate for completed metalwork.

10. A copy of the certificate for high-strength bolts, nuts and washers.

Appendix 4

LIST OF TECHNICAL DOCUMENTATION OF THE OPERATIONAL PERIOD

1. Act of technical change.

2. Certificates for structures, bolts, welding consumables, etc.

3. Executive drawings KM and KMD.

5. The log of inspections of metal structures on high-strength bolts (Appendix 1).

Appendix 5

LIST OF MATERIALS, TOOLS AND ACCESSORIES REQUIRED WHEN CHECKING THE CONDITION OF MOUNTING CONNECTIONS ON HIGH-STRENGTH BOLTS

1. Torque wrench KTR-3 with a set of control loads weighing 10 - 20 kg in an amount of 3 - 6 pieces.

2. A set of probes (0.1 mm; 0.3 mm; 1 mm).

3. Chisel, sledgehammer.

4. A hacksaw for metal with blades (to replace defective rivets) or a grinder.

5. Assembly mandrels.

6. A control hammer of 0.3 - 0.4 kg with a handle of 600 mm.

7. A set of mounting keys.

8. A set of bolts with nuts and washers.

9. Lattice containers and containers for the preparation of hardware.

10. Brush, paint.

11. The binoculars.

12. Magnifying glass.

13. Safety belt.

14. Protective helmet.

15. Overalls.

Appendix 6

Torque wrench KTR-3 (control)

1 - lever head; 2 - bar; 3 - tongue welded to the bar; 4 - handle; 5 - bracket for mounting the indicator; 6 - indicator of the sentry type ICh-10 GOST 577-60.

Note

Lever pos. No. 1 may be made of steel of grades: 09G2S; 10G2S1D; 13x SND; 14G2. All items are shown in table 1.

Welding assembly drawing

Table 1

Certification

			Designation	Name
				Welding assembly
				Key lever
				Boss 40? 20? 20
				M6 bolt? 14 with a washer		GOST 7798-62
				Indicator 0 - 10 mm
				Bracket
				M6 bolt? 25 with nut		GOST 7798-62
				Sleeve? 12? 6 under the screw M6
						GOST 1490-62
				End nozzle

Notes:

The length of the nozzle, depending on the height of the protruding parts of the connected elements, is allowed within l   \u003d 100? 250 mm

2. Heat treatment:

Hardening, vacation up to 30 ~ 40 units. HRC

End nozzle pos. eleven

Appendix 7

SAMPLE IDENTIFICATION

Certificate No. 336

Issued to KISELEV, Ivan Petrovich

Profession: Overseer Engineer

Passed a TRAINING on surface preparation, control and installation of high-strength bolts in a 40-hour program.

M.P. Deputy chief engineer

combine (Petrov)

Appendix 8

AN EXAMPLE 40 HOUR TRAINING PROGRAM

1. Types of joints of steel structures, features of the work of shear-resistant joints on high-strength bolts - 3 hours.

2. Materials, products, conditions for their use - 3 hours.

3. The technology of connection with high-strength bolts

theoretical classes - 10 hours

practical exercises - 12 hours

4. Tools and fixtures - 3 hours.

5. Acceptance and sealing of joints - 2 hours.

6. Technical executive documentation - 2 hours.

7. Safety measures - 5 hours.

Appendix 9

Mounting joint of trusses on high-strength bolts

Flange connection of the lower belt of trusses

Vyborg Electric Power Plant

Pneumatic drives of metal brushes

Konakovo Power Tool Plant

Noginsky experimental assembly plant

II. TOOL FOR TENSIONING HIGH STRENGTH BOLTS

	Name		Ultimate moment kgf · m	Manufacturing plant
	Pneumatic Wrenches			Sverdlovsk P / O "Pneumostroy machine" of the USSR Ministry of construction and economy
	Electric Wrenches			Rostov P / O "Power Tools" of the USSR Ministry of Construction and Economy
				Vyborg Electric Tool Plant of the USSR Ministry of Construction and Construction
	Manual control key			Kropotkinsk plant of installation and special construction equipment of the Heads of the SCP of the USSR Ministry of Construction and Special Construction

III. CONTROL TOOL FOR TARGING THE WRENCHES AND DETERMINING THE TURNING COEFFICIENT OF HIGH-STRENGTH BOLTS

Appendix 11

HIGH-STRENGTH BOLT MANUFACTURING PLANTS

1. Hardware and metallurgical plant.

455031, Magnitogorsk, Chelyabinsk Region releases bolts M16 M20 and M24.

2. Druzhkovsky hardware plant

343260, Druzhkovka, Donetsk region, st. Lenin, 3 releases bolts M22, M24, M27

3. Plant of bridge metal structures. E.F. Kozhevnikova

670007, Ulan-Ude produces M22 bolts

4. Voronezh bridge factory

voronezh, 2nd Post Office produces bolts M22 and M24

5. Schelkovsky factory of special installation products “Special installation product”

141100, the city of Schelkovo-2, Moscow region releases bolts M20, M22 and M24

1. General Provisions. 2 2. Materials, products and conditions for their use. 3 3. Monitoring the status of connections. 4 4. Connection recovery technology. 6 4.1. Preparation of high strength bolts, nuts and washers. 6 4.2. Assembly of joints on high-strength bolts if necessary, complete disassembly of joints. 7 4.3. Tensioning of high-strength bolts, with adjustment of efforts at the moment of twisting. 7 4.4. Calibration of torque wrenches. 8 4.5. Acceptance and sealing of joints subject to complete disassembly. 9 4.6. Bolt tension in the angle of rotation of the nut. 10 5. Technology for the restoration of mounting joints of metal structures made on rivets, especially the performance of bolt-riveted joints. eleven Appendix 1. The log of inspections of metal structures on high-strength bolts. 12 Appendix 2. The length of the bolts depending on the thickness of the pulled package. 12 Appendix 3. List of documents required for delivery of assembled metal structures with connection on high-strength bolts (intermediate acceptance) 12 Appendix 4. The list of technical documentation for the operational period. thirteen Appendix 5. The list of materials, tools and devices necessary for checking the condition of mounting joints on high-strength bolts. thirteen Appendix 6. Working drawings of the key KTR-3. thirteen Appendix 7. Sample certificate. fifteen Appendix 8. Approximate 40-hour training program. 16 Appendix 9. The use of high-strength bolts in standard designs of industrial buildings. 17 Appendix 10. Tool for cleaning surfaces of friction joints. Tool for tensioning high strength bolts. A control tool for calibrating wrenches and determining the twisting coefficient of high-strength bolts. 24 Appendix 11. Manufacturers of high-strength bolts. 25

ON SUPERVISION AND TECHNICAL OPERATION OF MOUNTING CONNECTIONS ON HIGH-STRENGTH BOLTS OF STEEL CONSTRUCTION STRUCTURES OF BUILDINGS AND STRUCTURES OF THE USSR MINISTRY OF METALLURGY

Moscow, 1989

1. GENERAL PROVISIONS

2. MATERIALS, PRODUCTS AND CONDITIONS OF THEIR APPLICATION

3. SUPERVISION OF THE CONDITION OF THE CONNECTIONS

4. CONNECTION TECHNOLOGY

4.1. Preparation of high strength bolts, nuts and washers

4.2. Assembly of joints on high-strength bolts, if necessary, complete disassembly of joints

4.3. Tightening high-strength bolts, with torque control

4.4. Torque wrench calibration

4.5. Acceptance and sealing of joints subject to complete disassembly

4.6. Bolt tension on the angle of rotation of the nut

5. the technology of RESTORATION OF INSTALLATION COMPOUNDS OF METAL STRUCTURES RUNNED ON RIVETS. FEATURES OF CARRYING OUT THE BOLT-RIVET COMPOUNDS

Appendix 1 The log of inspections of metal structures on high-strength bolts

Appendix 2 Bolt lengths depending on the thickness of the bag being pulled together

Appendix 3 LIST OF DOCUMENTS PRESENTED AT DELIVERY OF MOUNTED METAL CONSTRUCTIONS WITH CONNECTIONS ON HIGH-STRENGTH BOLTS (INTERMEDIATE ACCEPTANCE)

Appendix 4 LIST tECHNICAL DOCUMENTATION   OPERATING PERIOD.

Appendix 5 LIST OF MATERIALS, TOOLS AND ACCESSORIES REQUIRED WHEN CHECKING THE CONDITION OF MOUNTING CONNECTIONS ON HIGH-STRENGTH BOLTS

Appendix 6 Working drawings of the key KTR-3

Annex 7 SAMPLE IDENTIFICATION

Appendix No. 8 EXAMPLE 40-HOUR TRAINING PROGRAM

Appendix 9 Application of high-strength bolts in standard designs   industrial buildings

Appendices 10 Tool for cleaning surfaces of friction joints. Tool for tensioning high strength bolts. A control tool for calibrating wrenches and determining the twisting coefficient of high-strength bolts.

Appendix 11 PLANT MANUFACTURERS OF HIGH-STRENGTH BOLTS

In recent years, significant changes have occurred in the design and installation of metal structures. In addition to the use of new rolled profiles, high-strength steels and improved calculation, there has been a tendency to increase the volume of metal structures with mounting joints on bolts of various strength classes, including high-strength ones.

A large number of welds of short length has become a serious obstacle to mechanization and automation, welding processes at installation. Bolted mounting joints allow, under the conditions of the mounting site, to use hard-welded high strength steels in structures. Bolted connections allow you to work simultaneously on a large number of nodes by unskilled workers. The effectiveness of the use of bolted joints is formed at the design and manufacturing stage of the assembly units. According to the Gosstroy of the USSR, the estimated volume of the possible use of metal structures on bolts is 60-65% of the total volume of steel building structures manufactured by the industry. However, due to the low technical equipment of a number of metalwork factories, poor design quality, and a number of other reasons in the Soviet Union, only 15-20% of structures are manufactured with bolted mounting joints.

The constructions of objects of ferrous metallurgy in recent years (except for sheet ones) are mainly designed with connections on high-strength bolts.

When supervising mounting joints on high-strength bolts, particular attention should be paid to the ultra-high-strength bolts supplied by the industry in 1970-80. with a temporary resistance of 120, 135 and 155 kg / mm 2. Such bolts are installed in a number of designs of the Cherepovets, Lipetsk metallurgical plants, Magnitogorsk and others. These bolts due to the lack of restrictions on the upper limit of hardness have an increased ability to ZHR (delayed brittle fracture).

The most dangerous period is the first 1-3 years after the start of operation. Bolts "shoot" without a visible external load. In all constructions of recent years, attention has been paid to ZHR.

Studies conducted at a number of facilities after years of operation have shown that the drop in bolt tension is negligible. But since in the process of performing installation work, a shortage of bolts is possible, then in the process of operating structures, a selective check of the tension of the installed bolts is required. The control of bolted mounting joints is much simpler than that of welded joints, since in welded joints there is a greater likelihood of hidden weld defects than in bolted joints. The main way to control bolted connections is visual.

1. GENERAL PROVISIONS

1.1. These Recommendations were developed in accordance with Order III 759 of 9.XII.1988, according to the USSR Ministry of Industry and Agreement No. P47-6882, concluded between the Central Research Institute of Steel Project named after Melnikov Gosstroy of the USSR and the Cherepovets Iron and Steel Works of the Ministry of Industry of the USSR on April 19, 1989 and are the development of section 7 of the industry guidance document ORD 00 00089 "Technical operation of steel structures of industrial buildings".

1.2. The recommendations apply to the supervision and technical operation of the metal structures of buildings and structures of ferrous metallurgy enterprises with connections on high-strength bolts designed according to the standards of the USSR, operated in areas with a design temperature of -65 ° С.

1.3. When accepting structures with connections on high-strength bolts in the acceptance commission, the participation of a representative of the technical supervision service for the operation of buildings and structures of the enterprise is mandatory.

1.4. Responsibility for the technical condition of mounting joints on high-strength bolts by the order of the workshop rests with the engineering and technical workers of the workshop, who must undergo appropriate theoretical and practical training, are familiar with the rules for making connections on high-strength bolts and have a certificate (Appendices No. 7; 8).

1.5. Direct inspection of installation connections and restoration (repair) should be carried out by specially trained specialists with the appropriate skills and certification. In hard-to-reach places at a height, examinations are carried out with the participation of climbers.

1.6. Specialists in the operation of buildings and structures participating directly in the survey must undergo appropriate training, have a certificate and permission to stay at their best.

The number of specialists is determined at the rate of 1 engineering per 100 thousand high-strength bolts.

1.7. A feature of friction joints on high-strength bolts is that the forces are perceived not by shear of bolts and crushing of the wall, but by friction forces arising between the contacting surfaces, tightened by a high-strength bolt. In this regard, the magnitude of the tension of high-strength bolts and the quality of preparation of the friction surfaces of the connected elements is crucial and is controlled during the test. Insufficient tension of high-strength bolts in friction joints can lead to “slipping” of the elements, while the bolts will work for shearing, the elements for shearing. In addition, a geometric shape violation due to the mutual displacement of the elements is possible - the bolts will come into operation unevenly, since the difference in the diameters of the holes and bolts can reach 6 mm in accordance with SNiP III-18-75 table. 4 and there may be cases of successive failure of the bolts.

1.8. The studies found that the decisive influence on the reliability of the bolts is exerted by the levels of their mechanical characteristics (temporary tensile strength, elongation and contraction, impact strength), determined by the heat treatment conditions.

The main of these characteristics is the temporary tensile strength, controlled by its upper limit. Excessively strong bolts (marked 135 and 155), which have increased hardness, are prone to delayed brittle fracture and require more careful monitoring and more frequent examination of the compound.