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Flange connections and fasteners. Overview, general information

USSR

GUIDANCE DOCUMENT

FLANGED CONNECTIONS OF VESSELS AND APPARATUS
FOR PRESSURE OVER 10 TO 100 MPa
(OVER 100 TO 1000 KGS/CM2)

METHODOLOGY FOR CALCULATION OF STUD TIGHTENING MODES

RD 26-01-122-89

GUIDANCE DOCUMENT

Date of introduction 01.01.90

This guidance document applies to flange connections of vessels and apparatus for pressures over 10 to 100 MPa (over 100 to 1000 kgf / cm 2) operating in the chemical, petrochemical and related industries and establishes a methodology for calculating the tightening modes for studs of flange connections with two-cone sealing rings , triangular (delta), octagonal sections and with flat gaskets.

1. GENERAL PROVISIONS

1.1. This guidance document applies to flange connections of vessels and apparatuses, the sealing rings and studs of which are manufactured in accordance with OST 26-01-86 and OST 26-01-138 ¸ OST 26-01-144. 1.2. It is allowed to use the governing document for flanged connections of vessels and apparatuses that differ in design and parameters from those given in OST 26-01-86 upon agreement with IrkutskNIIkhimmash. 1.3. The effectiveness of the use of the governing document is ensured subject to the requirements of the regulatory documents OST 26-01-86 and OST 26-01-138 - OST 26-01-144 to the quality of the contact surfaces of the parts of the flange connection of the vessel or high-pressure apparatus. 1.4. The guidance document provides a method for calculating the tightening modes for the studs of flanged joints of vessels and high-pressure vessels, both by the method of preliminary axial drawing using hydraulic jacks or other loading devices, and by the method using torque when tightening the studs. 1.5. The use of other stud tightening modes that differ from those given in the governing document is allowed after their agreement with IrkutskNIIkhimmash. 1.6. The value of the tightening force of the studs is determined in accordance with RD 26-01-168. 1.7. The main terms used in the guidance document are given in Appendix 1. 1.8. Symbols are given in appendices 2 and 3.

2. CALCULATION OF REGIMES WHEN TIGHTENING STUDS BY THE AXIAL DRAWING METHOD

2.1. Sequence of calculation of tightening modes

2.1.1. Determine the amount of tightening torque for the flange connection studs Q h in accordance with RD 26-01-168. 2.1.2. Select the required number of loading devices (hydraulic jacks) i. The number of loading devices can be accepted: minimum - two and maximum - equal to the number of shutter studs m. The accepted number of loading devices must be a multiple of the number of flange connection studs. The calculation starts at i= 2. The required number of loading devices is specified during the calculation process (clause 2.2.1.2). 2.1.3. Determine the number of hairpin groups n(clause 2.2.1.1). 2.1.4. Determine Final Force Qn attributable to the last group of studs at the end of the tightening process (section 2.2.1.1). 2.1.5. Determine the coefficient of relative compliance of the sealing ring a. To do this, it is necessary to first determine the compliance of the sealing ring (section 5.2) and the group of studs under load on one stud (section 5.1.2). 2.1.6. Determine the unloading factor for each group of studs Kz(section 4). 2.1.7. Determine the value of the current loading force for each group of studs Qz. (items 2.2.1., 2.2.2).

2.2. Calculation of tightening modes

2.2.1. One-way stud tightening mode. 2.2.1.1. Current load force Qz, the next group of hairpins is determined by the formula

. (1)

The current loading force of one stud is determined by the formula

The unloading factor of the studs of the corresponding group is determined according to Section 4. In the case when the loading device has a mechanism for tightening nuts with torque control, the unloading factor value Kz(m) determined in accordance with clause 4.3. Final effort Qn per one group of studs at the end of the tightening process is determined by the formula

Number of stud groups n in the gate is determined by the formula

The coefficient of relative compliance of the sealing ring (gasket) a is determined by the formula

For a two-cone sealing ring, there are two types of axial compliance, depending on its position - a free ring and pressed against a stop - respectively, there are two types of relative compliance coefficient of the sealing ring (gasket). For free ring

For the ring pressed against the stop

The coefficients a c and a y are used in the calculations depending on the position of the sealing ring. Coefficients of axial compliance of the sealing ring l o, , and the group of studs l w (Q) is determined according to section 5. 2.2.1.2. The obtained value of the current loading force of one stud of the first group is compared with the value of the allowable load on one stud [ Q] ¢ , while the condition

The value of the permissible load [ Q] ¢ take the smaller of two values: obtained from the condition of ensuring the strength of the stud section that receives the load, having a minimum cross-sectional area, in particular, the mounting section of the stud thread

, (7)

Where K 1 = 10 6 (10 2); corresponding to the working force of the loading device

[Q ] ¢ £ QWell . (8)

If condition (6) is not met, it is necessary to make a calculation with an increased number of loading devices. An example of calculating a one-way mode for tightening the studs is given in Appendix 12. If condition (6) is not met in this case, then it is necessary to calculate the bypass-equalizing mode for tightening the studs. 2.2.2. Bypass-equalizing mode of tightening the studs. 2.2.2.1. Current load force Qz (N) of any group of hairpins in any bypass is determined by the formula

. (9)

The current loading force of one stud is determined by the formula

Allowable load on a group of studs [ Q] is determined by the formula

[Q] = i × [ Q] ¢ . (eleven)

2.2.2.2. Required number of rounds M determined by the formula

. (12)

Stud unload factor TOz 2 in the bypass-equalization mode, the tightening is determined according to section 4.

2.3. Stud tightening sequence

2.3.1. Install loading devices on the first group of studs. 2.3.2. Load the studs of the first group with the current force for the first group. 2.3.3. Tighten the nuts to the stop. In the case when the loading device has a mechanism for tightening, tighten the nuts with a torque of the appropriate value (see paragraph 4.3). 2.3.4. The efforts developed by the loading devices should be reduced to zero. 2.3.5. Move the loading devices to the second group of studs according to the diagram (see Appendix 4). 2.3.6. Load the studs of the second group with the current force for the second group. 2.3.7. Repeat the operations specified in paragraphs 2.3.3 - 2.3.4. 2.3.8. The studs of the remaining groups of the flange connection are loaded with the forces corresponding to them in the same sequence. 2.3.9. When tightening the studs by the bypass-equalizing method, the first bypass of groups of studs by loading devices is carried out in the same sequence as with the one-bypass tightening method. On subsequent rounds, the first group of studs is loaded with the same amount of force as the first group on the first round. The current loading forces of each subsequent group of studs during each round have the corresponding values (see clause 2.2.2.1).

3. CALCULATION OF MODES WHEN TIGHTENING THE STUDS WITH A TORQUE

3.1. Calculation of tightening modes

3.1.1. The technique allows you to calculate the current torque Mz for torque tightening of studs according to the corresponding current loading forces of one stud , calculated in accordance with Section 2. 3.1.2. When calculating the current loading forces of each stud of the next group in accordance with the formulas in Section 2, the unloading factor Kz, is taken equal to 1. For the case of using only one torque wrench, the number of loading devices is conventionally assumed to be 2. If the number of torque wrenches is more than one, the calculation takes into account the actual number of wrenches used during tightening, a multiple of the number of studs. 3.1.3. current torque Mz determined by the formula

, (13)

Where K 2 = 10 3 . 3.1.3.1. Nominal friction diameter DT the end surface of the nut is determined by the formula:

. (14)

3.1.3.2. Thread friction coefficient f 1 and coefficient of friction on the bearing surface of the nut f 2 are taken in accordance with the table. 1 .

Table 1

3.2. Stud tightening sequence

3.2.1. The procedure for tightening the studs with one torque wrench. In order to exclude possible distortion of the cover during tightening of the studs with one torque wrench, each stud of one group is tightened in two steps, applying torque alternately to each stud of the group. In order to determine the serial number of the tightened stud in the group, before tightening the next group of studs, the axial clearance between the end surfaces of the cover and the housing flange in the area of the studs of the tightened group must be measured. In this case, the stud is first tightened, in the zone of which the axial clearance is maximum. Then tighten the second pin of the group. 3.2.1.1. Install the cover parallel to the plane of the flange. Parallelism tolerance according to OST 26-01-86. Tighten all the stud nuts by hand until it stops. 3.2.1.2. Install a torque wrench on the first stud of the first group. 3.2.1.3. Load the stud with a torque equal to 50% of the torque calculated for one stud of the first group. 3.2.1.4. Move the key to the second pin of the first group according to the diagram (see Appendix 5, Fig. 3). 3.2.1.5. Load the second pin of the first group with the calculated moment for one pin of the first group. 3.2.1.6. Tighten the nuts of the remaining studs by hand until they stop. 3.2.1.7. Rearrange the key again on the first hairpin of the first group. 3.2.1.8. Load the stud with the full design moment for one stud of the first group. 3.2.1.9. Tighten all nuts by hand until tight. 3.2.1.10. Measure the gaps between the ends of the cover and the flange of the vessel or apparatus body in the area of the studs of the second group. 3.2.1.11. Install the key on the stud of the second group from the side of the larger gap. 3.2.1.12. Repeat operations p.p. 3.2.1.3 - 3.2.1.9 for studs of the second group with torque values corresponding to this group. 3.2.1.13. Repeat operations p.p. 3.2.1.10 - 3.2.1.12 for studs of other groups at their respective torque values. 3.2.2. The procedure for tightening the studs with two torque wrenches. 3.2.2.1. Install the cover parallel to the plane of the flange. Parallelism tolerance according to OST 26-01-86. Tighten all the stud nuts by hand until it stops. 3.2.2.2. Install torque wrenches on the studs of the first group. 3.2.2.3. Load the studs with the appropriate torque. 3.2.2.4. Tighten the nuts of the remaining studs by hand until they stop. 3.2.2.5. Rearrange the keys on the studs of the second group according to the diagram (see Appendix 5, Fig. 4). 3.2.2.6. Load the studs of the second group with a torque of the appropriate value. 3.2.2.7. Repeat step 3.2.2.4. 3.2.2.8. The studs of the remaining groups of the flange connection are loaded with the corresponding torques in the same sequence.

4. STUD UNLOADING FACTOR

4.1. Coefficient of unloading of studs in single-pass tightening mode. The maximum value of the unloading factor of the studs for the types of sealing rings under consideration is taken equal to K n= 1.5. The value of the unloading coefficient for the corresponding serial number of the group of studs TOz determined by the formula

The value of the coefficient y z depending on the type of the sealing ring, the number of groups of studs in the flange connection and the serial number of the group, is determined according to appendices 10 and 11. For flange connections with an octagonal sealing ring and a flat gasket, the coefficient y z is taken equal to 1. 4.2. Coefficient of unloading of studs in bypass-equalizing tightening mode. The value of the unloading factor of the studs for the first bypass is determined similarly to paragraph 4.1. In subsequent walks, the value of the unloading factor for each group of pins is taken equal to the value of the unloading factor for the last group of the first bypass. 4.3. Coefficient of unloading of studs when using pre-torque. In the case when the loading device has a mechanism for tightening nuts with torque control, the value of the optimal torque with the stud pulled out is determined by the formula

, (16)

Where Kh= 10 10 (10 5). In this case, the value of the coefficient of unloading of the studs Kz(clause 4.1) is specified by the formula

The value of the unloading factor Kz (M) is used in section 2 when determining the current loading forces of the studs when using devices with a nut tightening mechanism.

5. COEFFICIENTS OF AXIAL COMPLIANCE OF ELEMENTS OF FLANGED JOINTS

5.1. Coefficient of axial compliance of studs

5.1.1. The coefficient of axial compliance of one stud under load is determined by the formula

. (18)

Coefficient of axial compliance of the estimated length of the stud lst determined by the formula

The coefficient of specific axial compliance of the effective length of the stud c is selected for the corresponding standard size of the stud from Appendix 6. The effective length of the stud shaft lst is determined by the formula

. (20)

The total coefficient of axial compliance of the thread of the stud-nut and stud-socket connections with the corresponding load on one stud is determined in accordance with Appendix 9. The values of the total coefficient of axial compliance of the thread at load values \u200b\u200bbetween two consecutive table values \u200b\u200bspecified in the appendices are determined using a linear interpolation. The load equal to the tightening force of one stud at the end of the tightening process is determined by the formula

5.1.2. The coefficient of axial compliance of a group of studs is determined by the formula

. (22)

5.2. Coefficients of axial compliance of sealing rings of flange connections of pressure vessels

5.2.1. Coefficient of axial compliance of the two-cone ring The coefficient of axial compliance of the two-cone free ring is selected for the corresponding standard size of the ring from Appendix 7. The coefficient of axial compliance of the two-cone ring pressed against the stop of the cover is selected for the corresponding standard size of the ring from Appendix 7. Stud group number Zy, at which the two-cone ring approaches the stop of the cover and, at the same time, the value of its axial compliance changes, is determined by the formula

Final force per group of studs at the end of the tightening process Qn, determined in accordance with Section 2. The total force in the studs Qat, at which the inner surface of the ring approaches the lid stop, is determined by the formula

When calculating the current forces according to the formula (1) of section 2, up to the serial number of the tightened group of studs Z = Zat should be used in expression (5) values , and when Z > Zat- values. 5.2.2. The value of the coefficient of axial compliance of the triangular ring (delta) l from choose rings for the corresponding size from Appendix 7. 5.2.3. The value of the coefficient of axial compliance of the coupling flange of the pressure vessel body - octagonal ring - cover l ov choose rings for the corresponding standard size from appendix 8. 5.2.4. The value of the coefficient of axial compliance of the flat gasket l op determined by the formula

Where K 1 = 10 6 (10 2). Flat lay area Fop determined by the formula

. (26)

ANNEX 1

Reference

BASIC TERMS

1. Tightening mode - the sequence of loading the flange connection studs with current forces (current torques) of a certain value. 2. Current force - loading force of the next group of studs. 3. Current torque - the moment corresponding to the current loading force of one stud of the next group. 4. Stud group - the number of studs loaded simultaneously during the tightening process. 5. One-way tightening mode - a mode in which the required amount of tightening force for the connection studs is achieved with a single application of the corresponding current force (current moment) to each stud (group of studs). 6. Bypass-equalizing tightening mode - a mode in which the required value of the tightening force of the connection studs is achieved in several bypasses by applying current forces (current moments) to each group of studs corresponding to their bypass. 7. Permissible load - force, the value of which is determined by the strength of the mounting section of the stud thread or the power of the loading device. 8. Coefficient of stud unloading - a coefficient that takes into account the reduction in force in the studs when the load is transferred to the nut after the load of the loading device is removed and is numerically equal to the ratio of the magnitude of the force applied to the stud to the magnitude of the residual force in the stud. 9. Tightening torque - the moment that is applied to the nut with a stretched stud in order to reduce the value of the unloading factor. 10. Mounting section of the stud thread - the threaded part of the stud used to secure the thrust of the loading device.

APPENDIX 2

Mandatory

SYMBOLS

Qh- tightening force of all bolt studs, MN (kgf); - tightening force of one stud, MN (kgf); Q h is the final force per one group of studs at the end of the tightening process, MN (kgf); Q z is the current loading force of the next group of studs in a single-pass tightening mode, MN (kgf); - current loading force of one stud of the next group, MN (kgf); Q z (m) - current loading force of the next group of studs for the corresponding bypass in the bypass-equalizing tightening mode, MN (kgf); - current loading force of one stud of the next group, MN (kgf); [ Q] - permissible load on one stud, MN (kgf); [ Q] - permissible load on a group of studs, MN (kgf); Q well- working force of the loading device, MN (kgf); M z - current torque for tightening one stud of the corresponding group, MN m (kgf m); M Kr.opt - optimal torque for tightening nuts, MN m (kgf m); coefficient of axial compliance of the two-cone ring: l - free, mm/MN (mm/kgf); l - pressed against the cover stop, mm/MN (mm/kgf); l - coefficient of axial compliance of an octagonal ring, mm/MN (mm/kgf); l ot is the coefficient of axial compliance of the triangular section ring (delta), mm/MN (mm/kgf); l - coefficient of axial compliance of the flat gasket, mm/MN (mm/kgf); l w - coefficient of axial compliance of a group of studs, mm/MN (mm/kgf); - coefficient of axial compliance of one stud, mm/MN (mm/kgf); - coefficient of axial compliance of the threaded connection stud-nut and stud-socket (total), mm/MN (mm/kgf); - coefficient of axial compliance of one stud, on the length l st mm/MN (mm/kgf); c - coefficient of specific axial compliance of the stud, on the length l st mm/MN mm (mm/kgf mm); - yield strength of the stud material at 20 °C, MPa (kgf/cm2); - modulus of elasticity of the flat gasket material at 20 °C, MPa (kgf/cm2); Fw- cross-sectional area of the smooth part of the stud, mm 2; Fop- flat gasket area, mm 2; b is the taper angle of the sealing surfaces (the angle between the axis of rotation of the part and the generatrix of the sealing surface), deg; lst- estimated length of the stud, mm; Hshb- washer height, mm; Hkr- cover thickness, mm; hzaz- gap between the end face of the lid and the flange of the vessel body, mm; d Or- radial clearance between the inner surface of the obturator and the cover stop, mm; d 2 - average thread diameter, mm; h- height of the flat gasket, mm; D- inner diameter of the vessel or neck, mm; D 1 , D 2 - diametrical dimensions of the flat gasket; DG- diameter of the outer groove of the nut, mm; dshb- washer inner diameter, mm; dR- diameter of the threaded part of the stud, mm; dO- diameter of the central hole in the stud, mm; DT- conditional friction diameter of the end surface of the nut, mm; P- stud thread pitch, mm; m- the number of studs in the flange connection; i- the number of simultaneously operating hydraulic jacks; n- the number of groups of studs in the flange connection; Z- serial number of the group of hairpins; Zat- number of the group of studs at which the obturator changes its compliance; M- number of bypasses; N- serial number of bypass; Kz 1 is the unloading factor of the studs in the one-way tightening mode for the corresponding group; Kz 2 - coefficient of unloading of the studs in the bypass-equalizing tightening mode; Kz(M) the stud unloading factor for the relevant group (assuming the nuts are tightened with torque); K 1 , K 2 , K 3 - coefficient of proportionality for converting values into units of SI systems and (ISS); a - coefficient of relative compliance of the sealing ring (gasket); a With- coefficient of relative compliance of a free two-cone sealing ring; a at- coefficient of relative compliance of the two-cone sealing ring pressed against the stop; f 1 , f 2 - coefficient of friction in the thread and on the supporting surface of the nut; y z- coefficient.

APPENDIX 3

Mandatory

SYMBOLS OF THE MAIN DIMENSIONS OF THE ELEMENTS OF THE FLANGED CONNECTION OF VESSELS AND HIGH PRESSURE APPARATUS

1 - vessel body, 2 - cover, 3 - two-cone ring, 4 - stud, 5 - nut, 6 - washer

APPENDIX 4 SCHEMES FOR REPLACEMENT OF LOADING DEVICES WITH AXIAL DRAWING OF STUDS

APPENDIX 5 WRENCH REPLACEMENT SCHEMES AT TORQUE TIGHTENING OF STUDS

Tightening with one torque wrench

1 - 1 - stud group number

Tightening with two keys

APPENDIX 6

Mandatory

COEFFICIENT OF THE SPECIFIC AXIAL COMPLIANCE OF THE STUD ROD

table 2

Thread diameter dR, mm	Specific axial compliance of the stud shaft c × 10 mm/MN (10 6 mm/kgf mm)

APPENDIX 7

Mandatory

O-RING AXIAL COMPLIANCE COEFFICIENT

Table 3

Internal diameter of the vessel or neck, mm	Compliance of a two-cone ring		Compliance of the ring of triangular section l from, mm / MN (10 5 mm / kgf)
Internal diameter of the vessel or neck, mm	free, mm / MN (10 5 mm / kgf)	located on the stop, mm / MN (10 5 mm / kgf)

APPENDIX 8

Mandatory

AXIAL COMPLIANCE COEFFICIENT OF SEAL ASSEMBLY WITH OCTAGONAL RING

Table 4

Internal diameter of the apparatus or neck, mm	Pressure, MPa (kgf / cm 2)	Seal assembly compliance l ov, mm / MN (10 5 mm / kgf) depending on the size of the section corresponding to the mechanical properties of the material of the sealing ring
Internal diameter of the apparatus or neck, mm	Pressure, MPa (kgf / cm 2)	230 MPa (2300 kgf/cm 2) £ £ 300 MPa (3000 kgf/cm 2)	³ 300 MPa (3000 kgf / cm 2)

APPENDIX 9

Mandatory

TOTAL COEFFICIENT OF AXIAL FLEXIBILITY OF THREADED CONNECTIONS STUD-NUT AND STUD-SOCKET

Table 5

Thread diameter, mm, dR
Thread diameter, mm, dR	5 × 10 -2 M H (5 × 10 3 kgf)	10 × 10 -2 MN (10 × 10 3 kgf)	15 × 10 -2 MN (15 × 10 3 kgf)	20 × 10 -2 MN (20 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	25 × 10 -2 M H (25 × 10 3 kgf)	30 × 10 -2 M H (30 × 10 3 kgf)	40 × 10 -2 M H (40 × 10 3 kgf)	50 × 10 -2 M H (50 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	60 × 10 -2 M H (60 × 10 3 kgf)	80 × 10 -2 M H (80 × 10 3 kgf)	100 × 10 -2 M H (100 × 10 3 kgf)	120 × 10 -2 M H (120 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	140 × 10 -2 M H (140 × 10 3 kgf)	160 × 10 -2 M H (160 × 10 3 kgf)	180 × 10 -2 M H (180 × 10 3 kgf)	200 × 10 -2 M H (200 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	250 × 10 -2 M H (250 × 10 3 kgf)	300 × 10 -2 M H (300 × 10 3 kgf)	350 × 10 -2 M H (350 × 10 3 kgf)	400 × 10 -2 M H (400 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	450 × 10 -2 M H (450 × 10 3 kgf)	500 × 10 -2 M H (500 × 10 3 kgf)	600 × 10 -2 M H (600 × 10 3 kgf)	700 × 10 -2 M H (700 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	800 × 10 -2 M H (800 × 10 3 kgf)	900 × 10 -2 M H (900 × 10 3 kgf)	1000 × 10 -2 M H (1000 × 10 3 kgf)	1100 × 10 -2 M H (1100 × 10 3 kgf)

Continuation of the table. 5

Thread diameter, mm, dR	The total coefficient of axial compliance of the thread mm / MH (10 5 mm / kgf) depending on the load, MN (kgf)
Thread diameter, mm, dR	1200 × 10 -2 M H (1200 × 10 3 kgf)	1300 × 10 -2 M H (1300 × 10 3 kgf)	1400 × 10 -2 M H (1400 × 10 3 kgf)	1500 × 10 -2 M H (1500 × 10 3 kgf)

APPENDIX 10

Mandatory

DEPENDENCE OF THE COEFFICIENT Y z ON THE NUMBER OF GROUP AND THE SERIAL NUMBER OF THE GROUP FOR A FLANGED CONNECTION WITH A DOUBLE CONE RING

APPENDIX 11

Mandatory

DEPENDENCE OF THE COEFFICIENT Y z ON THE NUMBER OF GROUPS AND THE ORDER NUMBER OF THE GROUP FOR A FLANGED CONNECTION WITH A TRIANGULAR SECTION O-RING (DELTA)

APPENDIX 12

Reference

EXAMPLE OF CALCULATION OF A SINGLE-BYPASS MODE OF TIGHTENING THE STUDS OF A FLANGED CONNECTION WITH A TWO-CONE RING

1. Initial data The inner diameter of the vessel is 1000 mm. Design pressure - 70 MPa. Copper gasket - scm= 100 MPa. Average seal diameter - D to= 1044.9 mm. Double cone ring dimensions: h1= 85 mm; h2= 42 mm. Number of pins - m= 12. Stud thread diameter - d p M140×6. Stud neck diameter - d= 131 mm. Cover height - H cr= 280 mm. Washer height - H shb= 38 mm. Gap between cover and flange - h zaz= 10 mm. 2. The total tightening force of all studs is determined in accordance with RD 26-01-168 by the formula:

MH 7.2. We determine, according to Appendix 7, the axial compliance of the two-cone ring, respectively, free and pressed against the stop:

7.3. Total force in studs Qat, at which the inner surface of the two-cone ring approaches the cover stop, is determined by the formula:

MN,

Where d Or= 1.07 mm - the average gap between the two-cone ring and the cover stop for a seal diameter of 1000 mm is selected in accordance with OST 26-01-86. 7.4. The values of the relative compliance of the sealing ring free a With and located on the lid stop a at will be equal:

7.5. Group number Zat at which the two-conical ring approaches the stop of the lid and, at the same time, the value of its axial compliance changes, is determined by the formula

Therefore, when tightening the studs of the first group, the obturator approaches the cylindrical stop of the lid and the value of its axial compliance changes. Thus, when calculating the current loading forces of the studs of groups 1 to 6, the value mm/MN should be used. 8. Unloading factor 8.1. According to clause 4.1, the maximum value of the stud unloading factor for a flange connection with a two-cone ring is equal to K n= 1.5. 8.2. Stud unload factor for each group. According to Appendix 10, we determine for each serial number of the group the coefficient y z and according to the formula Kz=y z × K n determine the unloading coefficient for each group of studs: Z = 1 K 1 = 0.8 × 1.5 = 1.20; Z = 2 K 2 = 0.9 × 1.5 = 1.35; Z = 3 K 3 = 0.96 × 1.5 = 1.44; Z = 4 K 4 = 0.986 × 1.5 = 1.48; Z = 5 TO 5 = 0.996 × 1.5 = 1.49; Z = 6 K 6 = 1 x 1.5 = 1.5. 9. Determine the current loading forces for each group of studs using the formula:

INFORMATION DATA

1. APPROVED by the Ministry of Chemical and Petroleum Engineering, UkrNIIkhimmash 2. PERFORMERS Viryukin V.P. (theme leader), Pogodin V.K., Ph.D. tech. Sciences 3. The term of the first inspection in 1992. The frequency of inspection is 5 years 4. Instead of RD RTM 26-01-122-79 5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

1. General Provisions. 1 2. Calculation of modes when tightening studs using the axial drawing method. 1 2.1. Sequence of calculation of tightening modes. 1 2.2. Calculation of tightening modes. 2 2.3. Stud tightening sequence. 3 3. Calculation of modes when tightening the studs with torque .. 4 3.1. Calculation of tightening modes. 4 3.2. Stud tightening sequence. 4 4. Coefficient of unloading of studs. 5 5. Coefficients of axial compliance of elements of flange connections. 6 5.1. Coefficient of axial compliance of studs. 6 5.2. Coefficients of axial compliance of sealing rings of flange connections of pressure vessels. 6 Appendix 1 Basic terms. 7 Appendix 2 Symbols. 8 Appendix 3 Symbols of the main dimensions of the elements of the flange connection of vessels and high-pressure apparatus. 9 Appendix 4 Schemes of rearrangement of loading devices during axial drawing of studs. 9 Appendix 5 Schemes for changing the key when tightening the studs. 10 Appendix 6 Coefficient of specific axial compliance of the stud rod. 11 Appendix 7 Coefficient of axial compliance of sealing rings. 11 Appendix 8 Coefficient of axial compliance of an octagonal seal assembly. 11 Appendix 9 Total coefficient of axial compliance of threaded connections stud-nut and stud-socket. 12 Appendix 10 Dependence of the Y z factor on the number of groups and group number for a flange connection with a double cone ring. 15 Appendix 11 Dependence of the Y z factor on the number of groups and the group number for a flange connection with a triangular seal ring 15 Appendix 12 Calculation example of one-by-pass tightening mode for flange connection studs with a two-cone ring.. 16 Information data. 18

REGISTRATION SHEET OF CHANGES RD 26-01-122-89

EXPLANATORY NOTE

To the draft guiding document “Flange connections of vessels and apparatuses for pressure over 10 to 100 MPa (over 100 to 1000 kgf / cm 2). Method for calculating the tightening modes of studs. (Final version submitted for approval).

1. BASIS FOR THE DEVELOPMENT OF THE GUIDANCE DOCUMENT

Industry standardization plan for 1988, the institute's thematic plan for 1988, topic code 7965-68-21. The draft guidance document complies with the terms of reference for its development, approved by UkrNIIkhimmash on March 17, 1988.

2. GOALS AND OBJECTIVES OF THE DEVELOPMENT OF THE GUIDANCE DOCUMENT

The purpose of this work is to revise RD RTM 26-01-122-79 “Flange connections of vessels and apparatus for pressures over 9.81 to 98.1 MPa (over 100 to 1000 kgf / cm 2). The Method for Calculating Stud Tightening Modes” with the introduction of additions and changes that have arisen during its operation, as well as the results of recent research work. The development of a guidance document will make it possible to solve the problem of increasing the reliability of high-pressure vessels and apparatuses operating in the mineral fertilizer industry and other industries. The revision of the guidance document will ensure that it is in line with the current global scientific and technical level and the requirements of current standards.

3. CHARACTERISTICS OF THE OBJECT OF STANDARDIZATION

The object of standardization is a method for calculating the tightening modes of the studs of flanged joints of vessels and apparatuses operating under pressures above 9.81 to 98.1 Pa. The guidance document is being developed to replace the current RD RTM 26-01-122-79. Recently, GOST 26303-84 (ST SEV 4350-83) “High-pressure vessels and apparatuses. Hairpins. Strength Calculation Methods”, the regulatory documents OST 26-01-86-78 and OST 26-01-87-78, respectively, were revised into documents OST 26-01-86-88 “Stationary metal seals for vessels and apparatus for pressures over 10 to 100 MPa (over 100 to 1000 kgf / cm 2). Types. Design and dimensions. Technical requirements. Acceptance rules. Methods of control” and RD 26-01-168-88 “Stationary metal seals for vessels and apparatuses for pressure over 10 to 100 MPa (over 100 to 1000 kgf/cm2). Method of calculation for strength and density”, which come into effect from 01.01.89. Also revised OST 26-1360-75 into the collection OST 26-01-136-81 ¸ OST 26-01-144-81 "Fastening products for vessels and apparatus for pressure over 9.81 to 98.1 MPa (over 100 to 1000 kgf / cm 2). Types. Design and dimensions. General technical requirements”, which was put into effect on July 1, 1982. The content of the revised guidance document had to be brought into line with the newly enacted regulatory documents. In addition, during the period of operation of the governing document RD RTM 26-01-122-79, considerable experience has been gained in calculating the tightening modes for studs and using these modes in the operation of flanged joints of high-pressure vessels and apparatus, which allowed interested organizations to make some comments and suggestions for improvement calculation methods. As a result, the revised guidance document takes into account the comments and suggestions of organizations, changes in newly introduced standards and the results of research work to clarify the values of the coefficients of axial compliance of sealing rings and threaded connections of the stud-nut and stud-threaded socket flange of the vessel or apparatus housing (topic 84-09).

4. SCIENTIFIC AND TECHNICAL LEVEL OF THE GUIDANCE DOCUMENT

The guiding document has been developed using the results of theoretical and experimental studies, as well as the experience of using RD RTM 26-01-122-79 and is made at the modern scientific and technical level.

5. TECHNICAL AND ECONOMIC EFFICIENCY FROM THE IMPLEMENTATION OF THE GUIDANCE DOCUMENT

The technical and economic efficiency of the introduction of the guidance document is due to the refinement of the values of the coefficients of axial compliance of the elements of the valves of high-pressure vessels, which allows for a better process of tightening the studs (ensuring a given tightening force with its uniform distribution over all the studs of the valve), and therefore increasing the reliability of the seals of the vessels and high pressure equipment.

6. IMPLEMENTATION, IMPLEMENTATION OF THE GUIDANCE DOCUMENT (DURATION) AND VERIFICATION OF THE GUIDANCE DOCUMENT

The expected date for the introduction of the guidance document into force, taking into account the time for its publication and provision of it to interested organizations and enterprises, is planned from 01.01.90. Based on the experience of using the standards, it has been established that the limited period of validity of the regulatory document of 5 years is the most optimal. During this period, new standards may be developed or old referenced standards may be replaced, as well as new solutions to issues may arise, etc. The verification of the guidance document is carried out in accordance with the established procedure, the estimated date of the first verification is 1993.

7. RELATIONSHIP WITH OTHER REGULATIONS AND TECHNICAL DOCUMENTS

The governing document is interconnected with GOST 26303-84, OST 26-01-138-81 - OST 26-01-144-81, OST 26-01-86-88, RD 26-01-168-88, RD RTM 26-01 -122-79, which should be canceled as a result of the approval and implementation of the developed guidance document.

The first draft of the guiding document was sent for review to 26 organizations and enterprises of the Ministry of Chemical and Petroleum Engineering and Related Industries. 20 reviews were received: 5 from enterprises and organizations of the MHNM and 15 from organizations and enterprises of related industries. 7 reviews with comments and suggestions were received, 2 of them were from MHNM (UkrNIIKhimmash and Uralkhimmash) and 5 from organizations of other related industries. The vast majority of comments and proposals were accepted during the development of the final version of the guidance document. Some comments are clarified. Compiled a summary of reviews. There are no fundamental disagreements on comments and proposals.

9. INFORMATION ABOUT APPROVAL

The final version of the draft guiding document, according to the terms of reference, was agreed with NIIkhimmash, GIAP, the USSR Ministry of Mineral Fertilizers, UkrNIIkhimmash, Gosgortekhnadzor of the USSR. Due to the fact that there are no fundamental disagreements on the document (most of the comments and proposals were accepted), there was no need to hold a conciliation meeting.

10. SOURCES OF INFORMATION

The following technical materials were used in the development of the guidance document: GOST 26303-84 (ST SEV 4350-83) “Vessels and pressure vessels. Hairpins. Strength calculation methods”; OST 26-01-138-81 ¸ OST 26-01-144-81 “Fastening products for vessels and apparatuses for pressure over 9.81 to 98.1 MPa (over 100 to 1000 kgf / cm 2). Types. Design and dimensions. General technical requirements”; OST 26-01-86-88 “Stationary metal seals for vessels and apparatuses for pressure over 10 to 100 MPa (over 100 to 1000 kgf / cm 2). Types. Design and dimensions. Technical requirements. Acceptance rules. Control methods"; RD 26-01-168-88 “Stationary metal seals for vessels and apparatus for pressures over 10 to 100 MPa (over 100 to 1000 kgf / cm 2) . Method of calculation for strength and density”; RD RTM 26-01-122-79 “Flange connections of vessels and apparatuses for pressure over 9.81 to 98.1 MPa (over 100 to 1000 kgf / cm 2). Method for calculating the tightening modes of studs”; Reports of IrkutskNIIkhimmash on the topic 0154-78-20 “Guiding technical material. Closures for vessels and apparatuses for pressure over 100 to 1000 kgf/cm 2 . Method for calculating the tightening modes of studs”; Reports of IrkutskNIIkhimmash on the topic 0154-84-09 "Conducting research to determine the deformation characteristics of valve parts and developing recommendations for the revision of RD RTM 26-01-122-79", 1985 Article "Refining the unloading factor when tightening threaded connections", Rumyantsev O .Z., Sold by V.D. and others. "Bulletin of mechanical engineering". Moscow, 1974. Deputy Director for Research V.I. Livshits Head of the Standardization Department V.I. Korolev Head of Strength Department A.K. Drevin Head of Laboratory V.K. Pogodin Leader of the theme, researcher V.P. Viryukin

The tightness of the flange connection is achieved by proper installation of the gasket, ensuring the necessary tightening torque for the bolts, and the distribution of the total tension from the tightening must be uniform over the entire flange area.

With the correct tightening torque of the bolt, it becomes possible to realize its elastic properties. The bolt should behave like a spring when tightened, this allows it to fully perform its task.

torque wrench

A torque wrench is a generic name for a hand-held screwdriving tool and is used to accurately tighten nuts or bolts.

The following tools are used to tighten bolted joints:

Manual key
Pneumatic Impact Wrench
ring key
Hydraulic Torque Wrench
Torque wrench with adjustable torque limit
Hydraulic Bolt Tensioner

Loss of Torque (Loose Torque)

Loss of torque is possible in any type of bolted connection. The combined effect of bolt settling and creep is approximately 10% of total tightening in the first 24 hours after installation, gasket misalignment, system vibration, thermal expansion and elastic interaction when bolts are tightened also contribute to torque loss.

When the torque loss reaches its limit, the internal pressure exceeds the compressive force holding the gasket in place and causes the gasket to leak or rupture.

A key factor in reducing the impact of these effects is the correct installation of the gasket. Accurate flange assembly, parallel gasket installation, secured with a minimum of four bolts using the correct tightening torque, assuming the correct mounting sequence, increases the possibility of reducing operating costs and increasing safety.

Choosing the right gasket thickness is also important. If the gasket is thicker than necessary, this can cause the gasket to slip, and this increases the chance of losing torque. A 1.6mm thick gasket is recommended for ASME faceted flanges. A thinner gasket will take on a greater load, and, therefore, the internal pressure will increase.

Friction Reducing Lubricant

Lubrication reduces friction during bolt tightening, reduces bolt installation problems and increases bolt life. Changing the coefficient of friction affects the level of preload achieved at a given torque. A high level of friction results in less preload torque.

The coefficient of friction provided by the lubricants used must be calculated as accurately as possible, as this will help to set the desired torque value.

Lubrication must be applied to both surfaces of both the nut being screwed and the thread.

Flange tightening sequence

First you need to tighten the first bolt, then go to 180 ° and tighten the second bolt, then go ¼ turn in a circle (90 °) and tighten the third bolt, go to the bolt opposite - the fourth - and tighten. Continue the sequence until they are all twisted in a circle.

When using a flange with four bolt holes, the bolts are tightened "crosswise".

Method for Calculating Torques for Bolted Flange Connections Part II

A measure of the load required to stretch a bolt is the yield strength. By acting within it, we allow the bolt to return to its original length. Overloading the bolt can overshoot the yield strength and actually reduce the loads acting on the gasket due to additional stresses generated inside the flange joint. In this case, continuing to tighten the bolts does not necessarily increase the load on the gasket. Most likely, instead of preventing leakage, the bolt may fail.

A bolt can lose its compressive function if it is not stretched enough and the system loosens following its tightening. It is recommended to load the bolt at 50-60% of its yield strength in order for it to stretch sufficiently. In some cases, however, this value can be reduced, in particular if the load could damage the gasket or bend it.

Bolts are made from a variety of materials, each with a different yield strength. Proper bolt selection is critical to the effectiveness of the assembled flange joint.

So, we have a torque wrench to measure torque and a formula that allows us to calculate this moment based on the required gasket compression force. The question is, how hard do you have to compress the gasket to ensure a tight seal?

The force exerting pressure on the gasket consists of several components:

The first component is to compress and hold the gasket in place. The load generated by the bolt compresses the gasket and it takes the shape of the flange face. The hydrostatic pressure that occurs inside the vessel or pipeline, on the contrary, tends to squeeze the gasket out of the connection weld flanges. The compression of the gasket must be sufficient to hold it in place while compensating for internal pressure. It also requires some residual load to hold the gasket in place after the pressure is released.

The force required to create a tight seal depends on the type or shape of the gasket, the fluid in the system, and the temperature and pressure. ASME standards list the main factors that affect a gasket, but it's always best to get advice from the gasket manufacturer.

The equation for determining the minimum force on the gasket is as follows:

Wm2 = (π b G)

The first combination of parameters is the effective area of the pad based on its width b and the load diameter G, which reflects the backlash of the pad. Deriving numerical values for all gasket types and compression configurations is beyond the scope of this article. However, this data can be found in the documentation for the boilers or pressure vessels.

It should be noted that some manufacturers use a more conservative approach, in particular, they propose to equate the gasket area to the sealing surface as much as possible. However, the above formula allows you to calculate the minimum loads.

To get the final compression Wm2, it is necessary to multiply all this by the coefficient of laying y. The larger the coefficient y, the more effort is required to “settle” the gasket.

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Flange connections and fasteners. Overview, general information. Flange connection. Flange connection.

FLANGED CONNECTIONS AND FASTENERS. Overview, general information.

Flange connections, consist of:

Actually flange;
a set of fasteners (studs, nuts, washers);
gaskets (paronite, fluoroplastic, from thermally expanded graphite, steel, etc.).

Flange connection is convenient for installation and is in great demand. There are a large number of aspects of the selection of flange connections, with questions about which you should only contact specialists.

What is a flange and what is it for?
Flange - a part of the pipeline, designed for mounting its individual parts, as well as for connecting equipment to the pipeline.

Areas of use
The flange is used in the installation of pipelines and equipment in almost all industries. The variety of materials from which flanges are made today makes it possible to use these products as pipeline fittings under almost any environmental conditions (temperature, humidity, etc.) and in accordance with the environment passing through the pipeline (including aggressive ones) .

Distinctive features and characteristics of flanges

There are certain characteristics of flanges:

1. Constructive.
The basis of this group of characteristics is the design of the flange. On the territory of the Russian Federation and the CIS countries, three flange standards are most widely used:

GOST 12820-80 — flat welded steel flange.
GOST 12821-80 - steel butt-welded flange.
GOST 12822-80 - loose steel flange on the welded ring.

Flanges according to the three most common standards mentioned above are designed to connect pipe fittings and equipment.
Due to the design features, the mounting conditions for these flanges are different.

Flange steel flat welded. During installation, the flange is “put on” on the pipe and welded with two welds around the circumference of the pipe.

Butt-welded steel flange. The installation of such a flange, compared to a flat welded flange, provides for only one connecting weld (in this case, it is necessary to butt the end of the pipe and the “collar” of the flange), which simplifies work and reduces time costs.

Steel Loose Flange on Weld Ring consists of two parts - a flange and a ring. In this case, of course, the flange and the ring must be of the same nominal diameter and pressure. Compared to the above-mentioned flanges, such flanges differ in ease of installation, since only the ring is welded to the pipe, and the flange itself remains free, which ensures easy mating of the bolt holes of the free flange with the bolt holes of the valve or equipment flange without turning the pipe. They are often used when installing pipeline fittings and equipment in hard-to-reach places or when frequently repairing (checking) flange connections (for example, in the chemical industry).

In addition, it is positive that when selecting free flanges for a stainless steel pipe, in order to save money, it is allowed to use a stainless steel ring, and a carbon steel flange (Table 1).

Flange type	Environment settings		Material Grade
Flange type	Conditional pressure Ru, kg / cm 2	Temperature K (°C)	Flange
Steel flat welded GOST 12820-80	from 1 to 25	-30 to 300
		-70 to 300	09G2S according to GOST 19281-89, 10G2 according to GOST 4543-71
		-30 to 300	Steel 20, 25 according to GOST 1050-88
		-40 to 300	15XM according to GOST 4543-71
		-40 to 300	12X18H9T according to GOST 7769-82
Steel weld butt GOST 12821-80	1 to 25	-30 to 300	St3sp not lower than the 2nd category according to GOST 535-88
	from 1 to 100	-40 to 425	Steel 20, 25 according to GOST 1050-88
	from 1 to 200	-30 to 450	Steel 20, 25 according to GOST 1050-88
		-40 to 450	15XM according to GOST 4543-71
		-40 to 300	5X18N12S4TYu (type) GOST 5632-72
		-70 to 300	5X18N12S4TYu (type) GOST 5632-72
		-70 to 350	09G2S according to GOST 19281-89 10G2 according to GOST 4543-71
		-40 to 400	06HN28MDT (type EI-945) according to GOST 5632-72
		-70 to 400	06HN28MDT (type EI-945) according to GOST 5632-72
		-40 to 450	12X18R9T 10X17H13M3T (type EI-432) according to GOST 5632-72
		-40 to 510	15X5M according to GOST 5632-72
		-80 to 600	12Х18Н9Т according to GOST 5632-72
		-253 to 600	10X17H13M3T (type EI-432) according to GOST 5632-72
	from 1 to 25	-30 to 300	St3sp not lower than the 2nd category according to GOST 535-88

In addition to these three standards, special attention should be given to flanges manufactured according to customer drawings. (non-standard flanges). Unlike the first three flanges mentioned above, this design is not permanent and can change depending on the expectations and requirements of the client. These flanges are customized and serve to meet any customer needs.

Flanges manufactured according to foreign standards, differ from Russian constructively. Among imported flanges, the most widespread in Russia are flanges made according to German DIN standards (the standard is accepted throughout Europe) and American ANSI.

Distinctive characteristics of flanges
constructive		Technological
Nominal diameter DN
Nominal pressure Ru
Version 1 to 9
Row 1 or 2
Round (square)
Material	Art. 20
	Art. 09G2S
	Art. 15X5M
	Art. 08X18H10T (12X18H10T)
	Other
Design	Steel flat welded flanges GOST 12820-80
	Butt-welded steel flanges GOST 12821-80
	Steel free on the welded ring GOST 12822-80
	foreign standard
	non-standard
	Flanges according to other Russian standards

To flanges according to other Russian standards include such as: steel threaded flanges, flanges of vessels and apparatuses, insulating flanges for underwater pipelines. They differ from those mentioned above in terms of design and applications.

Also, design features include (using the example of the three most common GOSTs):

Conditional pass. Designated as Du and measured in mm.
conditional pressure. It is designated as Ru and is measured in kgf / cm 2.
Execution from 1 to 9. Defines the type of surface under the gasket.
Material(represented by Russian steel grades).

2. Technological.

These characteristics are associated with the peculiarities of production (from what blanks and by what technologies the flange is made).

Round and square flanges. Currently, a small number of gate valves, valves, etc., pipeline fittings are produced, which have a square flange as a connecting unit. Therefore, in accordance with GOST 12815-80, up to a conditional pressure of Ru 4 MPa (40 kgf / cm 2), both round and square flanges are provided by design. When ordering square flanges, it must be remembered that there is a direct dependence of the flange diameter on the conditional pressure: the higher the pressure, the smaller the diameter of the flange can be produced (Table 2).

Ru, kg / cm 2	1,0; 2,5; 6,0	10,0; 16,0	25,0; 40,0
DN, mm	10, 15, 20, 25, 32, 40, 50, 65, 80, 100	10, 15, 20, 25, 32, 40, 50, 65, 80	10, 15, 20, 25, 32, 40, 50

Conditional pass. Features of its designation

It should be noted right away that the conditional passage is not the outer diameter of the pipe, but denotes the passage (section) through which the medium flows through the flange connection. One of the features of steel flat welded flanges and steel loose flanges on a welded ring for nominal bore diameters DN 100.125 and 150 mm is that three of their designs are possible for different outer diameters of the pipe.

Therefore, when ordering these flanges for DN 100, 125 or 150 mm, it is necessary to indicate the letter corresponding to the required pipe diameter. If the letter is not indicated in the application (specification) for these standard sizes of flanges, then the flanges are manufactured for the following pipe diameters: 100A, 125A, 150B (Table 3).

The next feature of flanges with nominal diameter Du> 200 mm is that due to the different accuracy classes of pipes and flanges, the boring of the inner diameter of the flat, free and ring flanges is allowed according to the actual outer diameter of the pipe with a gap per side of not more than 2.5 mm, i.e., over the entire inner diameter flange and ring no more than 5.0 mm. In other words, pipe manufacturing may deviate from the ideal circle shape, so the pipe may not match the inner diameter of the flange, which in turn makes it difficult to connect the pipe and flange.

ranks

If the design features of the connecting dimensions (row 1 or 2) are not specified when ordering, then the flange is manufactured by default in accordance with row 2. The structural difference between the flanges of row 1 and the flanges of row 2 is a different number of holes in it for mounting bolts (studs) and their diameters.

For example, a flange for DN 300 mm and PN 63 kgf / cm 2 row 1 has a mounting hole diameter of 36 mm, and row 2-39 mm. Similarly, the flange for DN 80 mm and PN 10 kgf / cm 2 row 1 has a mounting hole diameter of 18 mm with a total of 8 pcs., And row 2, respectively - 18 mm and 4 pcs. Therefore, this feature must be taken into account when ordering flanges as counterparts for stop valves.

Pressure

Another important design feature of all products that make up the flange connection is the conditional pressure that the connection can withstand. The pressure values depend on the geometric dimensions of the flange and the design of the sealing surface. A steel flat welded flange (GOST 12820-80) and a free steel flange on a welded ring (GOST 12822-80) can withstand pressure up to 25 kgf / cm 2, but a steel welded flange (GOST 12821-80) can withstand pressure up to 200 kgf /cm 2 .

At the same time, a feature of this indicator is that it can be expressed in various units of measurement: kgf / cm 2, Pa, MPa, atm, bar. The unit of measurement in the production and designation of flanges is kgf / cm 2. To avoid confusion, always specify the pressure unit when ordering products.

Flange versions

In accordance with the requirements of GOST, there are nine versions of the flange surface (Fig. 2), and for a free flange, various versions are possible only for the weld ring. Therefore, when selecting mating flanges of pipeline fittings, in addition to the nominal diameter and pressure, it is necessary to indicate the design of the sealing surface.

Execution 1. It is used at conditional pressure not higher than 63 kgf/cm 2 . For pipelines transporting substances A and B of technological facilities of category I explosive, it is not allowed to use flange connections with design I of the sealing surface, except for the cases of using spirally wound gaskets with a restrictive ring.

In this case, there is the following scheme for joining flanges according to versions:

Execution 1 (with a connecting ledge) with execution 1;
Execution 2 (with a ledge) with execution 3 (with a depression);
Execution 4 (with a thorn) with execution 5 (with a groove);
Version 6 (for lens gasket) with version 6;
Version 7 (for oval gasket) with version 7;
Execution 8 (with a stud) with execution 9 (with a groove) with the obligatory use of a fluoroplastic gasket.

Material Grades

The final distinguishing design characteristic of the flange is the material used. Flanges can be made of carbon and alloy steels, as well as stainless steels. Currently, a large number of steel grades are used for the manufacture of flanges, the most widely used of which are Art.20, ST.09G2S, Art.15X5M and Art.12X18H10T.

Steel grades are selected taking into account the use of flanges for a given operating temperature, nominal pressure and transported medium in the pipeline. The requirements for the steel grade of the flange, depending on the operating pressure and medium temperature, are given in GOST 12816-80 (Table 1).

fasteners- these are parts for the fixed connection of parts of machines and structures. These usually include connection details: bolts, screws, studs, nuts, screws, capercaillie, cotter pins, washers, rivets, pins and much more.

Fasteners are usually divided into two main groups:

1. general industrial- fasteners used in almost all industries and the national economy, which do not have narrow specialized characteristics.

2. Special fasteners- characterized by a highly specialized field of application (for example, automobile, railway, etc.).

Such products are characterized by a clear focus on application in a specific area or even products (mechanisms, products, etc.), due to special characteristics.

Flange fasteners- designed to connect pipeline parts.
Flange fasteners include: bolt, stud, nut, washer.

These parts are defined as follows:

Bolt- a fastener for detachable connection of parts of machines and structures in the form of a rod with a thread at one end and a six- or four-sided head at the other.
screw- a part of a threaded connection or screw gear having a threaded hole. A fastening nut in a threaded connection is screwed onto the end of a bolt or stud or onto a threaded section of a shaft, an axis to secure against axial movement of the parts sitting on them - rolling bearings, pulleys, etc.
Washer- a part placed under a nut or screw head. General purpose washers are used to increase the area of support if the supporting surface is made of soft material or uneven, and also if the screw hole is oblong or of increased diameter. Oblique and spherical washers are used to eliminate misalignment of the nut or screw head when tightening. A quick-release washer is used in fixtures to save time on removing a machined part and installing a new one. A sealing washer made of soft material is placed under the head of the screw plug to ensure the tightness of the connection. The spring washer reduces the risk of self-loosening of screws or nuts due to the elastic forces of the compressed washer. The locking (locking) washer, by bending its parts, eliminates the possibility of turning the nut or screw relative to the supporting part or shaft. End washers prevent axial movement along the shaft of parts that are fixed or rotate on the shaft.
Hairpin- fastener, which is a metal rod with threads at both ends. The end of the stud is screwed into one of the parts to be joined, and the other part is pressed against the first when the nut is screwed onto the other end of the stud. It is also possible to connect parts with a stud, on the ends of which nuts are screwed. There are a large number of regulatory documents that formulate technical requirements for fasteners. For example, the requirements for fasteners used in flanged connections are set out in GOST 20700-75. These requirements are determined by operating conditions: operating pressure, medium characteristics, etc. The design and dimensions of fasteners are regulated in GOST 9064-75,9065-75, 9066-75.

Basic parameters of flange fasteners

Operating pressure

This is the pressure with which a liquid (gas, steam, etc.) is transported through the system. Therefore, the higher the working pressure in the system, the higher the strength characteristics it is necessary to choose fasteners. In turn, the necessary strength characteristics of fasteners are ensured by the correct choice of material, heat treatment modes, etc. Thus, in the temperature range from -40 to + 400 ° C, and at pressures up to 100 kgf / cm from steel 35, while an increase in pressure up to 200 kgf / cm 2 requires the use of fasteners from steel 20X13.

Working temperature

One of the most important parameters is the operating temperature. Based on the temperature of the medium that will be transported through the pipeline, as well as taking into account the external environment, the steel grade from which the fasteners will be made also depends. Each steel grade has a certain range of operating temperatures at which the fastener can provide strength and reliability of the connection.

For example, at the same nominal pressure at a temperature not lower than -30 °C, it is recommended to use studs made of steel 35, while at an expected operating temperature of up to -70 °C, fasteners made of cold-resistant steel grades, for example, 09G2S, should be used. or 10G2.

Working environment

There are certain characteristics of the working environment: temperature, chemical properties (composition - aggressive, non-aggressive).

In accordance with the indicators listed above, flange fasteners should be selected. For aggressive environments, fasteners are selected that can withstand the negative destructive influence of this environment. These steel grades include 20X13, 14X17H2, 12X18H9T and others.

Type and/or version

Most GOSTs provide for the possibility of manufacturing products that are similar in general appearance and purpose, but have certain differences, which are denoted by the concept of "type" and "performance".

For example, GOST 22042-76, which applies to studs for parts with smooth holes, provides for the possibility of manufacturing studs that differ in the diameter of the smooth part.

For execution 1, the diameter of the smooth part is equal to the nominal diameter of the thread. For execution 2, the diameter of the smooth part is approximately equal to the average diameter of the thread.

Thread diameter

All threaded fasteners have an internal (nuts) and an external (studs and bolts) thread diameter. Depending on the purpose and the normative document according to which the products are manufactured, the thread can be metric and inch. Metric thread pitch is measured in millimeters, and inch thread pitch is measured in inches.

Example: M12 is a metric thread with a nominal diameter of 12 mm; 3/4" is an inch thread with a nominal diameter of 3/4".

thread pitch is the distance between two adjacent thread ends.

Depending on the purpose of the fastener, most regulatory documents provide for the possibility of manufacturing fasteners with different thread pitches (coarse or fine thread pitch). As a rule, a large thread pitch is the main one and is not indicated when ordering a product.
In some cases, the thread pitch may be different from that recommended by regulatory documents.

Example: bolt M12×1.25 - bolt with metric thread, nominal diameter 12 mm and fine thread pitch 1.25 mm.

Turnkey size equal to the diameter of the inscribed circle.
As a rule, one turnkey value is provided for each nominal thread diameter.

Example: For a nut with a nominal thread diameter of 16 mm, a spanner dimension S of 24 mm is required.

Bolt length- the length, which is indicated in the product designation when ordering, in most cases is not an overall characteristic. Preferably, the length of the bolt indicated in the product designation is equal to the length of the bolt shaft, i.e. the height of the bolt head is not taken into account.

Example: for a bolt M12x120 - the length of the bolt shaft is 120 mm, while the total overall length is 7.5 mm longer by the height of the bolt head, i.e. the total overall length is 127.5 mm. On fig. 3: l - bolt length; l+ k = total overall length of the bolt.

Stud length

For most studs, the length l given when ordering is the overall overall length of the stud. However, some regulatory documents do not provide for the entire length of the stud in the designation of the studs.

Example: GOST 22032-76, which applies to studs with a screw-in end of length d v, provides for the designation of the length of the stud, not including the length of the screw-in end. l is the length of the pin, b is the length of the screwed end (Fig. 4).

Version 1

Tolerance field thread indicates the accuracy of the thread.
The larger the value of the tolerance field, the greater the deviation of the thread parameters from the nominal ones.
For most fasteners, the thread tolerance field for external threads is 6d, for internal threads 6H.

Threaded end length- the length of the part of the bolt or stud intended for screwing the nut.

Coating

If it is necessary to protect the fastener from the negative effects of the environment, it is possible to apply various protective coatings (zinc, chromium, nickel, etc.) to its surface, which must also be specified when ordering.

Quality groups

Depending on the purpose of fasteners and the working conditions of fasteners, five quality groups of finished products have been established (Table 1, GOST 20700-75).

According to GOST 20700-75, steels for fasteners are divided into the following categories:

category I - carbon steels with technical requirements for general-purpose products of normal accuracy with a nominal thread diameter of up to 48 mm, product operating temperature up to 200 ° C;
category II - carbon steels used for bolts, studs, plugs, clamps and nuts of increased accuracy with a nominal thread diameter of up to 48 mm and washers of all sizes with a working temperature of the product up to 300 ° C. Carbon steels of ordinary quality according to GOST 380-71;
category III - high-quality carbon steels in improved condition, used for bolts, studs, plugs, clamps and nuts of all sizes with a working temperature of up to 425 ° C in cases where the tempering temperature is at least 100 ° C higher than this temperature;
category IV - heat-resistant, heat-resistant, alloy steels in a heat-treated state, used for fasteners of all sizes with a working temperature not exceeding the temperature of the environment that meets all the norms and rules of design and safe operation accepted in the industry ("Rules for the design and safe operation of steam pipelines and hot water", "Rules for the design and safe operation of pressure vessels", "Rules for the design and safe operation of steam pipelines and hot water boilers").

How to choose the right fastener for you

Flange fasteners are selected in accordance with the following documents: GOST 20700-75; GOST 12816-80; GOST 9064-70; GOST 9066-75; PB 10-115-96; PB-03-75-94; OST 26-2043-91; OST 26-2037-96; OST 26-2038-96; OST 26-2039-96; OST 26-2040-96; OST 26-2041-96 and other regulatory documents governing the use of fasteners depending on their purpose.

In order to choose the right fasteners, it is necessary to remember that they will be equipped with a specific flange connection, therefore, it is necessary to take into account the following parameters:

operating pressure
working temperature
working medium (gas, water, steam, oil, etc.)
external environment

In addition to the above parameters, the choice of fasteners is also influenced by the steel grade from which the flange is made. The most commonly used grades of flange steel are considered and recommendations are given on options for completing them with flange fasteners.

Note 1. There are certain restrictions on the choice of fastener type for flange connection. With pressure up to 25 kgf/cm 2 you can order both a bolt and a stud. At a pressure of more than 25 kgf / cm 2, according to GOST 12816-80, the use of bolts is not allowed.

Note 2. For flange connections, there are a large number of recommended grades of material for assembly. If desired, you can order a stud and a nut both from the same steel grade, and from different ones. When manufacturing a fastening pair nut-stud from the same steel grade, the hardness of the nut should be 20 units less than that of the stud. This is due to the fact that if excessive pressure occurs in the system, the stud is likely to be damaged, while the nut will not be damaged. In this case, it will be more difficult to identify the problem. If the stud is made by thread rolling, then GOST 20700-75 allows the manufacture of a pair of material with the same hardness.

Below we consider options for completing flanges made of the most popular steel grades with fasteners.

For flange connections for pressures not exceeding 100 kgf / cm 2, a stud made of steel 35 and a nut made of steel 20 are usually used.

Such fasteners are typical for communications of various buildings and structures.

At operating pressures up to 160 kgf / cm 2, for example, in systems where water is supplied at high pressure (during the construction of mines, etc.), GOST 20700-75 recommends using steel grade 35X, but according to the same GOST: “By agreement between the consumer and the manufacturer, it is allowed to manufacture fasteners from other steel grades that ensure the production of products in accordance with the requirements of this standard”, therefore, it is permissible to use studs and nuts from steel 10G2 - steel that is not inferior to the performance characteristics of steel 35X. At the same time, there is a significant difference in the cost of these two steel grades. Steel grade 10G2 is 20% cheaper than steel grade 35X.

Steel 20X13 is one of the most common steel grades for completing flange connections, and therefore, it is almost always available from the manufacturer. Fasteners made of this steel grade make it possible to cover a wide range of pressure and temperature indicators. Therefore, for pressures up to 200 kgf / cm 2, fasteners made of steel 20X13 can be used.

For flanges made of steel grade 09G2S, it is recommended to use fasteners made of steel grade 14X17N2, but at the same time, if the system provides for a pressure of only up to 160 kgf / cm 2, it is recommended to use fasteners made of steel grade 10G2, which does not contradict regulatory and technical documents and is recommended by Rostekhnadzor. At a cost, 10G2 is much cheaper than 14X17H2.

Flanges made of steel 12X18H10T are completed with fasteners made of steel 20X13, when operating in the temperature range from -40 to + 450 °C.

If it is required to ensure operation at temperatures from -80 to +600 ° C, then it is necessary to use fasteners made of steel grade 12X18H1 OT.

Steel grade 10Kh17N13MZT belongs to the category of corrosion-resistant steel grades. Such a flange is completed with a pair of stud-nut made of steel 10X17 H13MZT.
This steel grade has found wide application in food and chemical industry systems.

Article rating:

When installing pipelines, welding is most often used to connect individual elements. But sometimes it is necessary to make the connection collapsible or to dock elements made of different materials. In this case, a flanged pipe connection can be used. Let's see how it is done.

Flange connections are used when installing large diameter pipelines, since the flanges used for joining parts are quite bulky and heavy. There are several types of flange connections, but they are all made in accordance with the requirements of GOST. Let's figure out which options for connecting with flanges are used most often.

general description

To connect two pipes, flanges are used, which are a flat ring (the flange can also have a different shape, for example, a square frame). In the center of the part there is a hole into which the end of the pipe is inserted.

Along the contour of the "frame" there is an even number of mounting holes designed to install fasteners. For fastening, bolts or studs with nuts can be used.

When using flanges, the joints are detachable. In order for the connection to be tight, sealing gaskets are installed. Flanges are used for joining pipes to each other, as well as when connecting a pipe to a tank that has an inlet pipe to which a flange is welded.

Manufacturing materials and types

To perform the connection of metal pipes, flanges made of the following materials can be used:

Gray cast iron. Parts are made by casting. It is allowed to use these parts at an operating pressure range of up to 16 MPa. The temperature of the transported medium must be in the range from -15 to +300.

Cast iron is malleable. Parts are made by casting. It is allowed to use for the installation of pipelines with a working pressure of up to 4 MPa, but the working temperature range is wider - from -30 to +400.
Steel. Cast steel flanges can be used to connect pipes of different materials. The maximum working pressure is up to 20 MPa, the temperature range is very wide - from -250 to +600 degrees.
Steel. Welded flanges are used to assemble pipelines operating at low pressure - up to 2.5 MPa.

Advice! For the manufacture of flanges, different types of steel are used - alloyed, carbon, stainless.

Relatively recently, flanges made of polymeric material began to be used. Polypropylene parts are used on plastic pipelines operating without pressure (or with low pressure). Depending on the purpose, two types of flanges are distinguished:

Checkpoints. They are used to connect the pipe to other parts of the pipeline.
Deaf. Installed in dead-end branches of the highway.

Principle

To connect pipes with flanges, it is necessary that fasteners are installed at the ends of both connected parts. Moreover, these parts must be identical, otherwise it will be impossible to make a hermetic connection of the parts.

Advice! Flanges installed at the ends of the parts to be welded are called reciprocal.

The flange is attached to the end of the pipe in one of two ways:

on the thread (applicable only for non-pressure pipelines);
by welding.

After both mating flanges are installed, they are connected and pulled together with fasteners.

Advice! A stud, unlike a bolt, does not have a head. The thread is cut on the stud on both sides. Thanks to this, when making the connection, it is possible to tighten the flanges from both sides by screwing the nuts on both sides of the stud.

Choice

Like any other fittings used to assemble pipelines, flanges are available in different sizes. Let's figure out what characteristics you need to pay attention to.

Conditional passage

This is a very important feature. The nominal diameter of the flange is, in fact, the inner diameter of the pipe on which this part is installed. This parameter is denoted by the letter Du, measured in mm. For welded flanges, along with the size of the conditional passage, a Latin letter is indicated, the letter indicates the outer diameter of the pipe.

Row

Parts that have the same conditional passage are not always the same. Another important parameter is rowing. Model differences:

in the difference between the center distances of the mounting holes;
mounting hole diameter.

Operating pressure

When choosing fittings, it is very important to pay attention to such an indicator as the working pressure in the pipeline. This indicator is determined by the maximum possible pressure at which the pipeline can function without leakage at the places of collapsible connections. Conditional pressure indicators depend on the following parameters:

geometric dimensions of parts;
material of manufacture;
the presence and material of the gasket.

Working temperature

This indicator is no less important, since if the maximum values \u200b\u200bare exceeded, a leak may form at the flange joints. The parameters of working pressure and working temperature depend on each other, therefore these indicators are indicated in special tables in the accompanying documentation for the product.

Gasket selection

Gaskets must be used to seal the connection. It is especially important to correctly calculate the degree of sealing when operating a pipeline under pressure. The choice of material for the manufacture of gaskets depends on the operating conditions and the properties of the transported medium. Most often used:

Rubber. Depending on the properties of the medium, a material is selected that is resistant to acids and alkalis, oil and petroleum products, and temperature.
Paronite. General purpose or oil resistant material can be applied.
Fluoroplast.
Asbestos cardboard.

The gasket is cut to the shape of the flange, its thickness depends on the selected material.

How is the connection made?

The most important moment of installation is the tightening of the flange connection. It is important to achieve maximum sealing of the joint.

Preparatory stage

First of all, you need to inspect the surfaces of the flanges to be joined, they should not have noticeable defects in the form of potholes and scratches. There must be no signs of corrosion.

Advice! It is necessary to inspect for defects not only the flanges themselves, but also the fasteners - bolts (studs) and nuts.

When disassembling and reassembling, it is not recommended to install the old gasket. In extreme cases, it is permissible to install 2-3 used gaskets, provided that they do not have obvious damage.

How is tightening done?

To ensure uniform tightening, it is necessary to tighten the bolts in a certain sequence. It is recommended to work like this:

the first bolt (any) is slightly screwed on;
the second tighten (also slightly) the bolt located opposite the first;
the third bolt, which should be slightly tightened, is located at an angle of about 90 degrees with respect to the first and second;
the fourth bolt to work with is opposite the third.

Thus, if a flange with four holes is used, then the bolts are tightened according to the “crosswise” principle. If a part with six holes is used, then the first four bolts are tightened in the same way, then they work with the fifth bolt located between the first and third, and the last bolt is tightened between the second and fourth.

Having completed this stage, they begin to gradually tighten the bolts in the same sequence. To ensure a tight connection, the bolts must be tightened with a certain force.

If you overdo it, you can break the thread, and if the tightening is uneven, then tightness will not be achieved. To ensure uniform tightening force, special devices are used:

torque wrench - manual or hydraulic;
pneumatic wrench;
hydraulic tensioner.

After starting the pipeline during the first day of operation, loosening of the tightening within 10% is possible. Therefore, on the second day after starting the system, it is necessary to additionally tighten the connections.

So, flanges can be used to create a collapsible pipeline connection. Despite the relative ease of flange connections, installation work should only be carried out by specialists. Especially if the connections are made on pipelines for the transport of hazardous media (e.g. flue gas). Performance of work on pipelines operating under pressure, the implementation of flange connections is carried out under the supervision of engineers.