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Very often you can hear that "the gasket is leaking." This statement is not always true. In fact, the connection always leaks, and the gasket is only one of its components. It is often expected that the gasket will be able to compensate for deficiencies in flange facing and flange movement due to changes in operating temperature and pressure, vibration, etc. In many cases, gaskets are capable of this, but only if right choice their type and material, as well as following the correct installation procedure.
A) What to do and what not to do when installing gaskets
- The main and counter flanges must be of the same type and properly aligned. The total misalignment of the flanges must not exceed 0.4 mm.
- It is unacceptable to try to tighten flanges that are far apart with fasteners. In such cases it is necessary to use spacers using spacers on both sides of the spacer.
- Fasteners must be selected in such a way that their elastic limit is not exceeded when applying the required load.
- Additional tightening of bolts after the connection with a flat non-metallic gasket has been exposed elevated temperatures, is unacceptable. (The gasket may harden and additional force will cause it to break.)
- Make sure that there is no corrosion on the fastener, as this will reduce the ability of the fastener to bear the load.
- Ensure that the gasket material is within specification for the connection.
- It is necessary to make sure that there are no nicks and scratches on the working surfaces of the gasket, especially in the radial direction.
- The material should be selected so that the allowable load on the nuts is 20% higher than the allowable load on the studs or bolts. Washers of the same material as the nuts should always be used.
- If necessary, grease should be applied to the threads, but only in a uniform thin layer. When using stainless steel fasteners, make sure that the specific type of grease is acceptable.
- Fasteners and gaskets must not be reused.
- Gaskets of the minimum allowable thickness should always be used.
- When cutting gaskets for flat flanges, the bolt holes must be cut before the outer and inner diameters of the gasket are cut. If the bolt holes are close to the outside diameter of the gasket, cutting them out after the gasket has been cut out may cause the gasket to deform.
- Gaskets should be stored in a cool dry place away from sources of heat, moisture, oils and chemicals. They should also be stored flat and horizontal (i.e. not hung from hooks).
- Avoid applying grease to gaskets and flange faces.
B) Tightening the bolts of the flange connection.
The joints should be tightened evenly in three or even four passes, in a criss-cross pattern, as shown in the figure. Keep in mind that in this sequence, tightening one of the bolts may cause the other(s) to loosen, so it is recommended that all bolts be re-tightened in a circle as a last operation. Some connections need to be retightened just prior to commissioning to compensate for the relaxation of gaskets and fasteners. Also, in some cases, when using gaskets of certain types in conjunction with flanges of certain forms of the connecting surface on heat exchangers, it is necessary to additionally tighten the connection during the initial heating of the heat exchanger.
C) Troubleshooting
MALFUNCTION | POSSIBLE REASON | SOLUTION |
The leak occurred immediately when the medium was supplied to the pipeline | Underload or overload in the joint, or the load is applied unevenly | Carefully insert a new gasket. Check the alignment of the flanges, their working surfaces and tighten the bolts according to the described procedure. |
Leak occurred after a short period of use |
|
|
The leak occurred after several hours or days of operation | Chemical impact on the gasket from the medium or its mechanical destruction. | Check the chemical compatibility of the gasket material with a given concentration of media under operating conditions. Check that the gasket type is correct. |
The assembly of flange connections must be carried out taking into account the following basic requirements. Bolts and studs of pipelines operating at temperatures above 300 C must be marked before installation. Gaskets must be sized to match the sealing surfaces of the flanges.
The assembly of flange connections must be carried out taking into account the following basic requirements. Bolts and studs of pipelines operating at temperatures above 300 C must be marked before installation. Gaskets must be sized to match the flange faces.
Test plates for checking the sealing surfaces of flanges with raised and lowered flanges.| Tightening flange bolts. The assembly of flange connections is one of the most frequently performed and critical operations in the repair and installation of valves. Only products are allowed for assembly, in which the roughness and flatness of the sealing surfaces of the flanges meet the established technical requirements. Transverse risks crossing the annular sealing surface of the flange for the gasket, nicks and other defects are not allowed.
The assembly of flange connections must be carried out without adjusting operations; the bolts must enter the holes freely, without tension.
Assembly flange connection consists of installing gaskets and fixing flanges with fasteners.
The assembly of flange connections begins with putting flanges on the ends of the pipes, then Simplex rubber rings are pulled on and gaskets are installed between the ends of the pipes. Next, the convergence of the flanges and their tightening with bolts begins.
The assembly of flange connections is one of the labor-intensive operations during the installation of air ducts, for the mechanization of which electric wrenches are used.
Mobile device for fitting flanges. The assembly of flange connections consists of joining flanges, installing gaskets and tightening bolts or studs. Before installation, bolts (studs) and pipeline gaskets operating at temperatures above 200 ° C must be prographic.
The assembly of flange connections is a critical operation in the manufacture of pipeline assemblies. In order to achieve a good tightness of the flange joints and maintain it during operation, the flange joint must be correctly assembled and tightened.
The assembly of flanged joints is one of the most common and critical operations in the manufacture and installation of pipelines, since their decompression during operation necessitates shutting down the pipeline. The product passes through leaks in flange connections due to weak tightening of the flanges, distortions between the planes of the flanges, insufficient cleaning of the sealing surfaces before installing the gasket, incorrect installation of the gasket, the use of gasket material that does not correspond to the parameters of the product, defects on the sealing surfaces. Deviation from perpendicularity of the flange to the axis of the pipe (skew), measured along the outer diameter of the flange, should not exceed 0 2 mm for every 100 mm of the diameter of the pipeline designed to operate under pressure up to 1 6 MPa, 0 1 mm - under pressure 1 6 - 6 4 MPa and 0 05 mm - under pressure above 6 4 MPa. Thus, the displacement should not exceed 1 mm with a hole diameter of 12 - 18 mm, 15 mm - with a diameter of 23 - 33 mm, 2 mm - with a diameter of 40 - 52 mm. When installing flat welded flanges, the end of the pipe must be recessed into the flange.
Device KTB-1222 for pushing flange mirrors. The assembly of flange connections is carried out using a square or using the fixture shown in fig. VII-7. For joining pipes for welding, the devices shown in Fig. VII-8. An ordinary compass can be used to mark pipes at their installation site.
The assembly of flange connections on bolts or studs must be carried out freely, without the use of fitting operations.
The assembly of flange connections of plastic pipelines consists in installing gaskets between the flanges and tightening the bolts with nuts. If the ends of the pipes to be connected do not match, adjusting work is performed, consisting in cutting a piece of pipe and welding (gluing) a collar sleeve or a flanged pipe. Before welding the sleeve or branch pipe, a free flange is put on the cut end of the pipe. The exception is fluoroplastic and faolitic pipelines, in which it is impossible to form a shoulder on the part under the conditions of the installation site. In this case, it is necessary to replace the entire part, this is done by installing straight pipe sections of the required length. If the ends of the glass pipes do not match, the correction can only be made by cutting off the excess piece of pipe. If the pipe is shorter than necessary, then the gap is eliminated by inserts with a length of at least 200 mm for connections on flanges with two tension rings and at least 250 mm for connections on flanges with three tension rings.
The assembly of flange connections of pipeline elements is carried out on exposed, calibrated and reinforced supports, on which pipes, fittings or fittings are laid and pre-reinforced. Between the ends of the joined elements of the pipeline, a minimum gap is left through which it is possible to insert a lens.
Assembly of flange connections of pipelines high pressure performed subject to a number of additional requirements. Before assembly, the studs are rubbed with flake graphite or lubricated with a graphite paste composed of graphite thickly mixed with water in a ratio of 2: 1 or with glycerin. Graphite-copper grease of the following composition is also used: flake graphite-15 - 20%; copper powder-10 25%; glycerin - 60 - 70% Graphite-copper lubricant excludes the setting of the metal of the stud and nut at temperatures up to 600 C, ensures the absence of burrs on the thread when tightening the connection.
The assembly of flange connections of high-pressure pipelines is carried out in compliance with a number of additional requirements. Before assembly, the studs are rubbed with flake graphite or lubricated with a graphite paste composed of graphite thickly mixed with water in a ratio of 2: 1 or with glycerin. Graphite-copper grease of the following composition is also used: flake graphite-15 - 20%; copper powder-10 - 25%; glycerin - 60 - 70% Graphite-copper lubricant excludes the setting of the metal of the stud and nut at temperatures up to 600 C, ensures the absence of scratches on the thread when tightening the connection.
Connection of branch pipes with plugs to glass pipelines. The assembly of flange connections is carried out in the following sequence. First, flanges are installed on the pipes, having a diameter 1 mm larger than the collar cone. Then a split rubber or plastic ring is placed on the shoulder, a rubber gasket is installed between the ends and the bolted connection is assembled.
The assembly of flange connections on gaskets begins only after checking that the flanges are not skewed. To do this, the connections are first pre-assembled without installing gaskets. Flanges must approach strictly parallel to the sealing surfaces. The non-parallelism of the two flanges should not exceed twice the tolerance for deviation from perpendicularity of the flange axes to the pipe axes. The gap is checked with a feeler gauge at diametrically opposite points. It is necessary to strive to ensure that the gap around the entire circumference is the same and corresponds to the thickness of the gasket.
Permissible displacements of the edges of the circumferential welds of apparatuses. The assembly of flange connections on bolts or studs must be carried out freely without adjusting operations. Flange connections must be tightened simultaneously using diametrically opposite bolts or studs. The final tightening of flange joints assembled on mastics should be carried out after their complete assembly with a break necessary for the mastic to dry. The tightening of flange joints with gaskets made of corded asbestos and a thick layer of mastic is done in a hot state with heating of the entire apparatus with steam by 50 - 60 ° C.
It is recommended to assemble flange connections immediately with a full number of bolts or studs, so as not to return to the installation of this connection in the future. The nuts of the bolts in a flanged connection should, if possible, be on the same side.
Dimensions of welded pipe joints. The assembly of flange connections is started only after checking the absence of distortion of the flanges. To do this, the connections are first pre-assembled without installing gaskets. Flanges must approach strictly parallel to the sealing surfaces. The non-parallelism of two flanges should not exceed twice the permissible deviation from the perpendicularity of one flange to the axis of the pipe. The gap is checked with a feeler gauge at diametrically opposite points.
The assembly of flange connections, as a rule, is carried out at a positive temperature using torque wrenches with tightening tightening corresponding to the project. If the gasket is made of other materials, then the tightening force is selected empirically from the condition of ensuring strength and density.
The assembly of flange connections on gaskets is carried out only after checking for the absence of distortion between the sealing surfaces of the flanges. To do this, pre-assemble the connections without gaskets. Flanges must approach strictly parallel to their sealing surfaces. The non-parallelism of the sealing surfaces of the counter flanges should not exceed the tolerances specified in Table. V-11. In the absence of distortion, the final welding and assembly of the flange connection is carried out.
The assembly of flange connections on gaskets begins only after checking that the flanges are not skewed. To do this, the connections are first pre-assembled without installing gaskets.
The assembly of flange connections is carried out as follows: the tightening is carried out gradually, alternately (with three tie rods) or variable (crosswise - with four studs) tightening the nuts in order to avoid distortion of the connection. The studs are finally tightened with special wrenches with adjustable torque. The tightening forces of the studs must comply with the requirements of SNiP and the project.
The assembly of flange connections is carried out as follows: the tightening is carried out gradually, alternately with three tie rods and alternate (crosswise) with four studs, wrapping the nuts in order to avoid distortion of the connection. The studs are finally tightened with special wrenches with adjustable torque. The tightening forces of the studs must comply with the requirements of SNiP and the project.
Device for mounting flanges on pipes. The process of assembling a flange connection consists of installing, aligning and fastening (lining) flanges at the ends of pipes, installing a gasket and connecting two flanges with tie bolts. Before assembling the flange connection, the pipe sections to be connected are verified for the straightness of their axes. The flanges are installed in such a way that the bolt holes are symmetrically displaced relative to the main axes of the fittings, devices and the cross section of pipelines. The perpendicularity is checked with a flanged square.
Device for assembling vertical sections of pipelines. When assembling flange connections on pipelines of small diameter, there is no need for fixtures and trolleys. Flanges are tapped on a square or in a jig.
When assembling a flange connection, the bolts are tightened gradually and evenly in such a way as to avoid distortions.
When assembling flange connections, tighten the bolts evenly by screwing oppositely located nuts alternately and keeping the flanges parallel. Bolt nuts should be located on one side of the flange connection, and torque wrenches are recommended for tightening. Gaskets must be sized to match the sealing surfaces of the collar bushings. The material of gaskets is indicated by the project.
Self-aligning wedge gate valve. When assembling flange connections sealed with corrugated metal gaskets, the following conditions must be observed.
When assembling flange connections, deviations from the parallelism of the flanges are allowed for every 100 mm of nominal diameter; for pipelines of the 3rd category - 0 1 mm, 4th category - 0 2 mm. Correcting the misalignment of the flanges when they are connected by tightening bolts or studs, as well as eliminating the gap by installing wedge gaskets is not allowed.
When assembling a flange connection, it is necessary to strictly control the distance from the pipe end to the flange plane.
When assembling flange connections, the bolts are tightened alternately, screwing oppositely located nuts with a calibrated or torque wrench with a force regulated by the project.
When assembling a flange connection, to prevent distortions, the bolts are tightened gradually by alternately tightening the nuts with three bolts and alternately (crosswise) with four. The nuts are finally tightened with special wrenches with adjustable torque, while monitoring the parallelism of the flanges and pipe ends.
When assembling flange connections, the tightening of diametrically opposite nuts is done with an ordinary wrench. After tightening the studs with a wrench of normal length, it is allowed to use wrenches with levers.
When assembling flange connections, the following requirements must be observed: boring of the inner diameter of the flange for the pipe Df ZOO mm is allowed according to the actual outer diameter of the pipe with a gap on the side of not more than 2 5 mm; the internal diameters of the butt-welded flange and the pipes at the junction must match; if they do not match, a smooth transition must be made at an angle of not more than 10; when assembling flange connections, distortion is not allowed, gaskets and threaded studs must be rubbed with silver flake graphite.
When assembling flange connections with pipes and parts, a symmetrical arrangement of holes for bolts and studs relative to the vertical axis must be ensured. The offset of the holes of two adjacent flanges must not exceed half the difference between the nominal diameters of the holes and the bolt or stud being installed.
When assembling flange connections, the correct location of the bolt holes is observed; bolt heads are placed on one side. The tightening of bolts or studs is done in several steps crosswise.
The sequence of tightening the nuts of bolted connections 1 - 8 - nuts. When assembling flanged joints, the gap between the flanges should not exceed twice the tolerance for deviation from the perpendicularity of the flange axes to the axes of the pipe parts. The gap is checked with a feeler gauge.
When assembling flange connections, ensure a symmetrical arrangement of holes for bolts and studs relative to the vertical axis.
When assembling flange connections using lenses, it is necessary to inspect the latter before installation and make sure that there are no defects.
When assembling flanged joints, the alignment of the bolt holes should only be checked using crowbars or mandrels.
When assembling flange connections, it is necessary to ensure the symmetrical arrangement of holes for bolts (studs) relative to the vertical axis, using colic wrenches.
When assembling flange connections, the nuts are screwed with a normal wrench (without using a lever) with the studs tightened in a diametrically opposite order.
When assembling flange connections, the correct location of the bolt holes should be observed, the bolt heads are located on one side. The tightening of bolts or studs is done in several steps, crosswise.
When assembling flange connections, special attention must be paid to their reliable sealing.
When assembling a flange connection, first install a few lower bolts, after which a gasket is inserted into the gap, centering it when installing the remaining bolts.
When assembling flanged joints, it is of great importance to use bolts, studs and gaskets of proper quality and size.
CCCR
GUIDANCE DOCUMENT
VESSELS AND APPARATUS.
STANDARDS AND METHODS FOR CALCULATION OF STRENGTH AND TIGHTNESS OF FLANGED JOINTS
RD 26-15-88
Moscow 1990
GUIDANCE DOCUMENT
Introduction date 01.07.89
This guidance document establishes the standards and methods for calculating the strength and tightness of flanged joints of steel vessels and apparatuses operating in the chemical, petrochemical and related industries under the influence of static and repeated static loads. It is allowed to use this RD for the calculation of flanged connections of pipelines and fittings, provided that clause 1.3 is complied with. The guidance document is applicable subject to the requirements of OST 26-291.
1. GENERAL REQUIREMENTS
1.1. The terms and symbols of the physical quantities corresponding to them are given in mandatory Appendix 1. 1.2. Types of flange connections are shown in Fig. 1-4*. Refer to reference appendix 5 for application limits for flange connection types. *Drawing does not define design. 1.3. The calculation formulas of this standard are applicable whenAnd
1.4. If the number of loading cycles caused by assembly-disassembly and changes in the operating mode (pressure, temperature) is more than 1000, then after checking the strength of the flanges in section 8, it is necessary to calculate the low-cycle strength in accordance with section 9. 1.5. The operating temperature of the elements of the flange connection is determined on the basis of thermal calculations or test results. It is allowed to determine the design temperature of the elements of the flange connection according to Table. one .
Table 1
Flange type |
Isolated |
Non-isolated |
||||
t f |
t to |
t b |
t f |
t to |
t b |
|
Flat, butt-welded (Fig. 1, 2) |
t |
0,95 t |
||||
With loose rings (fig. 3) |
t |
0,81 t |
||||
Welded flanges for clamps (Fig. 4) |
t |
0,55 t |
1.6. When the apparatus is operating under conditions of several design modes for temperature and pressure, the calculation is made for conditions that ensure the strength and tightness of the flange connection in all modes.
2. ALLOWABLE VOLTAGES
2.1. Permissible stresses for the materials of bolts (studs) are determined by the formulas provided: a) if the design temperature does not exceed 380°C for bolts (studs) made of carbon steels, 420°C for low-alloy steels, 525°C for austenitic steelsB) if the design temperature of the bolts (studs) exceeds that specified in paragraph a
2.2. Factors of safety P t are given in table. 2.
table 2
Bolt material |
|||||
Working conditions |
Test conditions |
||||
tightening is not controlled |
tightening is controlled |
tightening is not controlled |
tightening is controlled |
||
carbon steels |
|||||
Austenitic steels |
For test and tightening conditions
B) for flanges according to fig. 1, 2, 3, 4, 11 in section S 0: for operating conditions and tightening
For test conditions
B) for loose flange ring: for operating conditions and tightening
For test conditions
S 0.2, s in, [ s ] 20 - are accepted in accordance with GOST 14249 or other regulatory documentation at design temperature. The design of a flange connection for test conditions is not required if the design pressure under test conditions is less than the design pressure under working conditions, multiplied by 1.35. Notes: 1. For flanges according to fig. 1 allowable stress in the section S 1 , for working conditions and tightening conditions when calculated taking into account the load from thermal deformations Q 1 can be increased up to 30%. 2. For flanges according to fig. 3 allowable stress for the free ring when calculated taking into account the load from temperature deformations Q 1 can be increased by 30%. (Changed edition, Rev. No. 1)
3. CALCULATION OF AUXILIARY VALUES
3.1. Effective gasket width, mm:b 0 = b n at b n £ 15 mm
At b n > 15 mm
For oval or octagonal gaskets
3.2. Gasket characteristics m , q girth, To, E p taken according to the table. four . 3.3. Gasket compliance, mm/N.
.
For metal and asbestos-metal gaskets
atn =0.
3.4. Compliance of bolts (studs) for flanges according to fig. 1 , 2 , 3 , 11 , mm/N
Where Lb = Lb 0 +0,28d - for the bolt Lb = Lb 0 +0,56d - for hairpin, fb- taken according to the table. 5. 3.5. Compliance of clamps for flanges according to fig. 4, mm/N
Where l h accepted according to OST 26-01-64. 3.6. Flange parameters* * In case of connection with different (materials or sizes) flanges, the calculation should be made for each flange. 3.6.1. Equivalent bushing thickness, mm
Suh=K × S 0 ,
Where K- determined by hell. 5. For flanges according to fig. 2, 3, 4
Suh = S 0 .
3.6.2. Odds
,
Where ; y 1 - determined by hell. 6. For spherical caps without beading
.
3.6.3. Angular compliance of the flange, 1/N × mm
,
Where y 2 - determined by hell. 7. For flange with spherical non-flared cover
3.7. Angular compliance of the free ring according to fig. 3, 1/N×mm,
Where yto- determined by hell. 6.3.8. Angular compliance of the flat cover, 1/N × mm,
Where ;
3.9. Angular compliance of a flange loaded with an external bending moment, 1/N × mm, for flanges according to fig. 12
;
For flange according to fig. 3
;
For free ring
;
3.10. Shoulders of moments, mm: for flanges according to fig. 1, 2, 4*
,
*For flanges according to fig. four
;
For flanges according to fig. 3
,
,
,
4. RIGIDITY COEFFICIENT OF THE FLANGED CONNECTION
4.1. Flange connection stressed by internal or external pressure and external axial force: for connection according to fig. 1, 2, 4,
Where ; for connection according to hell. four
For connections by crap. 3
For connection with cover
Where . 4.2. Flange connection loaded with an external bending moment,
Where ; for flanges according to fig. 3
.
5. LOAD CALCULATION
5.1. Resultant internal pressure, N,**
**For vacuum conditions or external pressure P< 0 5.2. Реакция прокладки в рабочих условиях, Н,
.
5.3. Load arising from thermal deformations, N*: *If a tube sheet or other part is clamped between the flanges, it is necessary to take into account the thermal deformation of this part. in the connection according to hell. 12
Where - the thickness of the upper and lower flange in the connection according to fig. 3
Where ; in the connection according to hell. four
Where ; - height of the upper lower stops in connection with the cover
,
Where ;af , ato , akr- determined according to OST 26-11-04-84; ah- determined according to Appendix 2. Notes. 1. When determining loads from temperature deformations, the design temperature of flanges, covers, bolts (studs), tube sheet, free ring should be reduced by the temperature at which the flange connection is assembled (20 ° C). 2. If a tube sheet is clamped between the flanges or additional washers are installed to reduce the loads from thermal deformations, then when determining lb 0 it is necessary to take into account their thicknesses. (Revised edition, Rev. No. 1). 5.4. Bolt load P b under installation conditions, the larger of the following values, H*, * F<0, если усилие сжимающее. При определении Р б 4 . величина Q t учитывается только при Q t <0, при a <1в расчетах принимается a =1.
;
for flanges according to fig. 1, 2, 3;
For flanges according to fig. four,
Where B 1 - taken according to the table. 5. For vacuum or external pressure conditions
R b =R b 2.
(Revised edition, Rev. No. 1). 5.5. Load increment in bolts (studs) under operating conditions, N,,
at a<1в расчетах принимается a=1.(Revised edition, Rev. No. 1).
6. CALCULATION OF BOLTS (STUDS)
6.1. Strength conditions for bolts (studs)*: *Value x >1 is allowed upon agreement with one of the authors of the standard. for flanges according to fig. 1, 2, 3;
**
**For vacuum and external pressure conditions where x =1.1+1.2; for flanges according to fig. four
;
.
Note - when checking the strength of bolts for operating conditions, taking into account the load on the bolts from the constraint of temperature deformations, the allowable stress can be increased by 30%. (Revised edition, Rev. No. 1). 6.2. See appendix 3 for recommended tightening torque (recommended).
7. CALCULATION OF GASKETS
The gasket strength condition is checked for soft gaskets.
8. CALCULATION OF FLANGES FOR STATIC STRENGTH*
8.1. Flange rotation angle when tightening,
Where M 01 =Pb × b . *In case of connection with different (by dimensions or materials) flanges, the calculation should be made for each flange. 8.2. Increasing the angle of rotation of the flange in working conditions
Where . 8.3. Meridional stress in the shell (sleeve) on the outer and inner surfaces during tightening, MPa: for flanges according to fig. 1 in section S 1:
sn = s 1; s 12 =- s 1
Where ,T- determined by hell. eight, D *= D at D ³ S 1 ,D *= D + S 0 at D <S 1 and ¦ >1 ,D *= D + S 1 at D <S 1 and ¦ =1 ; for flanges according to fig. 1 in section S 0
s 21 = ¦ × s 1 ; s 22 =- ¦ × s 1 ,
Where ¦ - is determined by hell. 9; for flanges according to fig. 2, 3, 4
s 21 =s 1 ; s 22 =-s 1 ,
Where . 8.4. Increments of meridional stresses in the shell (sleeve) on the outer and inner surfaces under operating conditions, MPa: for flanges according to fig. 1 in section S 1
D s 11 = D sn + D s one ; D s 12 = D sn + D s 1
,
;
in section S 0
D s 21 = D sn + ¦D s one ; D s 22 = D sn + ¦D s 1
;
D s 21 = D sn + D s one ; D s 2 2 = D sn + D s 1
8.5. Circumferential stresses in the shell (sleeve) on the outer and inner surfaces during tightening, MPa: for flanges according to fig. 1 in section S 1
For flanges according to fig. 1 in section S 0
D s 23 = 0.3 ¦ × s one ; D s 24 = -0.3 ¦ × s 1;
For flanges according to fig. 2, 3, 4
D s 23 = 0,3s one ; D s 24 = -0,3s 1;
8.6. Increasing circumferential stresses in the shell (sleeve) on the outer and inner surfaces under operating conditions, MPa: for flanges according to fig. 1 in section S 1
,
;
in section S about
For flanges according to fig. 2, 3, 4
8.7. Flange strength condition when calculating static strength: for flanges according to fig. 1 in section S 1
when tightening
in working conditions
For flanges according to fig. 1, 2, 3, 4 in section S about
when tightening
;
in working conditions
9. CALCULATION FOR LOW-CYCLE FATIGUE
9.1. The calculated amplitude of the reduced conditional elastic stresses during tightening is determined by the formulaWhere for flanges in hell. one ab determined by hell. 10. for flanges according to fig. 2
s 1 =0,
For flanges according to fig. 3, 4
s 1 =0,
9.2. The calculated amplitude of the reduced conditional elastic stresses under operating conditions is determined by the formula
For flanges according to fig. one
Ds 1 = ab × Ds 11 ,
For flanges according to fig. 2
s 1 =0,
For flanges according to fig. 3, 4
s 1 =0,
9.3. Checking the low-cycle strength of the flange connection is carried out in accordance with GOST 25859-83. For this, according to the stress amplitude determined from the tightening condition ( sa) according to clause 9.1, the allowable number of assemblies-dismantlings [ N ]With. According to the stress amplitude determined for operating conditions () according to clause 9.2, the permissible number of cycles of changing the operating mode is determined [ N ]R. The strength condition for a given number of loadings ( NWith , NR) will be executed if
10. CALCULATION OF A FREE RING
10.1. Rotation angle of the free ring.
10.2. Ring stress in the free ring, MPa
.
10.3. Strength condition
11. RIGIDITY REQUIREMENTS
Permissible angle of rotation for flanges according to fig. 2, 3, 4:
for operating conditions and tightening
For test conditions
For flanges according to fig. one:
for operating conditions and tightening
0.009 at D £ 2000 mm;
0.013 at D > 2000 mm;
for test conditions
0.011 at D £ 2000 mm;
0.015 at D > 2000 mm;
Table 3
Uncountable temperature, °С |
Permissible stress, MPa, for steel grades |
||||||
12X18H10T, 10X17H13M2T |
35H, 40H, 38HA, 37H12N8G8MFB, 20HN3A |
||||||
Continuation of the table. 3
Design temperature |
Permissible stress, MPa, for steel grades |
||||||
18X12VMBFR |
08X15N24V4TR |
||||||
Table 4
Gasket type and material |
Coefficient m |
Specific gasket compression pressure q life safety fundamentals, MPa |
Permissible specific pressure [ q], MPa |
Compression ratio, K |
Conditional compression modulus E n× 10 -5 , MPa |
Flat made of: rubber according to GOST 7338 with hardness according to SHORE A up to 65 units |
0.3 × 10 -4 ´ |
||||
rubber according to GOST 7338 with SHORE A hardness of more than 65 units |
0.4 × 10 -4 ´ |
||||
paronite according to GOST 481 with a thickness of not more than 2 mm | |||||
asbestos cardboard according to GOST 2850 with a thickness of 1-3 mm | |||||
fluoroplast-4 TU 6-05-810 with a thickness of 1-3 mm | |||||
aluminum grade AD according to GOST 21631 | |||||
brass brand L63 according to GOST 2208 | |||||
steel 05kp according to GOST 9045 | |||||
Flat out: | |||||
asbestos according to GOST 2850 | |||||
sheathed in aluminum | |||||
copper and brass | |||||
steel 05KP | |||||
steel type 12X18H10T | |||||
Oval or octagonal ring made of: | |||||
steel 0.5KP according to GOST 9045 or 08X13 according to GOST 5632 | |||||
steel 08X18H10T |
Table 5
Bolt diameter d, mm |
||||||||||
Bolt cross-sectional area by thread ID* f b, mm 2 | ||||||||||
clamping capacity AT n H | ||||||||||
stop height h 2 mm |
12. CALCULATION OF FLANGED CONNECTIONS WITH CONTACT FLANGES
12.1. General requirements. 12.1.1. The terms and symbols of the physical quantities corresponding to them are given in mandatory Appendix 1. 12.1.2. Types of flange connections are shown in Fig. 11. Limits of application of the specified types of flange connections are given in reference appendix 5. 12.1.3. The limits of application of the calculation formulas of this section must comply with clause 1.3. 12.1.4. The design temperature of the elements of the flange connection is set in accordance with clause 1.5. 12.2. Permissible voltages. 12.2.1. Permissible stresses for the material of the bolts are determined according to clause 2.1 with an increase of 25%. 12.2.2. Permissible stresses for the flange material when calculating the static strength are determined according to clause 2.5. 12.3. Calculation of auxiliary quantities. 12.3.1. The effective width and characteristics of the gasket are determined by paragraphs. 3.1; 3.2. 12.3.2. Compliance of the contact belts of the gasket, mm/N12.3.3. Estimated length and flexibility of bolts (studs) are determined according to clause 3.4. 12.3.4. Flange options. 12.3.4.1. The angular compliance of the flange is determined according to clause 3.6. 12.3.5. The angular compliance of the flat cover is determined according to clause 3.8. The angular compliance of the spherical non-beaded cover is determined according to clause 3.6.3. 12.3.6. Shoulder moments, mm:
;
;
.
12.3.7. Odds:
;
The drawing does not define the design
guide values h 1 , a 1 , a 2 are taken according to the table. 6:
;
;
;
;
Where For flanges according to fig. 11a
For flanges according to fig. 11b
Table 6
D |
|||
12.4.2. Loads in the connection elements arising from temperature deformations
12.4.3. The bolt load under mounting conditions is assumed to be the greater of the following values, N:
.
12.4.4. Load increment in bolts (studs) under operating conditions, N
.
12.4.5. The reaction of the contact belts of the gasket under working conditions, N:
;
.
12.4.6. The maximum bending moment is assumed to be large, N × mm:
;
Where [ s ] 20 , [s] - are accepted according to OST 26-11-04. 12.5. Calculation of bolts (studs) 12.5.1. The conditions for the strength of bolts (studs) and the amount of torque on the key are determined according to clause 6. 12.6. Gasket strength condition
.
12.7. Sealing condition
.
12.8. Flange calculation 12.8.1. Meridional stress in the shell (sleeve), MPa
,
Where is the coefficient T determined by hell. 8.12.8.2. Circumferential stress in the shell (sleeve), MPa
.
12.8.3. Shell strength condition
.
ATTACHMENT 1
Mandatory
Terms and notation
Table 7
Designation |
|
Gasket width, mm |
b n |
Clamp load capacity, N |
B 1 |
Corrosion compensation allowance, mm |
C |
Flange inner diameter, mm | |
Free ring inner diameter, mm |
Dto |
Flange outer diameter, mm |
Dn |
Free ring outer diameter, mm |
Dnk |
Bolt (stud) circle diameter, mm |
Db |
Average gasket diameter, mm |
Dcn |
Bolt outer diameter (stud), m< |
d |
The modulus of longitudinal elasticity of the material at a temperature of 20°C and calculated, MPa, is taken according to GOST 14249: | |
flange |
E 20 , E |
bolts (studs) |
E 20 b, E b |
free ring. |
E 20 to, E k |
lids |
E 20 kr, E cr |
Conditional compression modulus of the gasket material, MPa | |
External axial force (compressive with a minus sign), N |
F |
Cross-sectional area of the bolt (stud) along the inner diameter of the thread, mm 2 |
fb |
Flange thickness, free ring, mm |
h , hto |
Stop height, taken according to OST 26-01-64, mm |
h 1 |
Collar height for clamp support, mm |
h 2 |
Thickness of the cover and flange part in the sealing zone, mm |
hkr , skr |
Gasket thickness, mm |
hP |
Taper bushing length, mm |
L |
External bending moment, N × mm |
M |
Radius of a sphere of a spherical non-beaded cover, mm |
Rc |
Shoulder radius for clamp support, accepted according to OST 26-01-64, mm |
R |
Design pressure, MPa | |
The thickness of the conical bush at the junction with | |
flange |
S 1 |
shell, bushing, bottom, mm |
S 0 |
Shell, bottom, bushing thickness, mm |
S 0 |
Distance between bearing surfaces of nut and bolt head, studs, mm |
Lb 0 |
Number of bolts (studs), pcs |
n |
Design temperature, °C | |
flanges, covers |
tf |
bolts (studs) | |
free ring |
tto |
Temperature coefficient of linear expansion of the material, 1/°С | |
flange |
af |
bolts (studs) |
ab |
free ring |
ato |
lids |
akr |
Yield strength of bolts (studs) material at design temperature, MPa |
s t |
Average value of ultimate strength for 10 5 hours at design temperature, MPa |
s d × 10 5 |
Average 1% creep strength for 10 5 hours at design temperature, MPa |
s 1% × 10 5 |
Permissible stress of the material of bolts (studs) at a temperature of 20°C and design, MPa |
[s ] 20 b,[s ]b |
Yield strength of flange material, MPa |
s 0,2 |
Permissible stress of the flange material at a temperature of 20°C and design, MPa |
[s ] 20 , [s ] |
Permissible stress of the material of the free ring at design temperature, MPa |
[s ]to |
Permissible stresses for flanges in sections S 1 and S 0 |
[s ]S 1 , [s ]S 0 |
Design and allowable amplitude of conditional elastic stresses, MPa |
sa , [sa ] |
Specified and allowed number of loading cycles |
N , [N ] |
APPENDIX 2
Linear expansion coefficients
Table 8
Steel grades |
Linear expansion coefficient a × 10 6 , 1/°С depending on temperature, °С |
|||||
35 | ||||||
40 | ||||||
20X13 | ||||||
14X17H2 | ||||||
35X 40X 38 XA | ||||||
20XH3A | ||||||
30XMA | ||||||
25X1MF | ||||||
25X2M1F | ||||||
18X12VMBFR | ||||||
37X12N8G8MFB | ||||||
12X18H10T 10X17H13M2T | ||||||
45Х14Н14В2М | ||||||
XN35VT | ||||||
08Х15Н24В4 |
APPENDIX 3
Torque on wrench when tightening
APPENDIX 4
Reference
Flange Connection Calculation Example
Initial data: D= 400 mm, h= 300 mm, f= 200°С, E 20 \u003d 1.99 × 10 5 MPa; Dn= 535 mm, hP= 2 mm, P= 0.6 MPa, E= 1.81 × 10 5 MPa; Db= 495 mm, S 0 = 8 mm, M= 0.83 × 10 7 N × mm, = 2.1 × 10 5 MPa; Dcn= 445 mm, d= 20 mm, F= 15000 N, E b= 2.01 d 10 5 MPa; bP= 12 mm, n = 20, With= 2 mm, af= 12.6 × 10 -6 1/°С; ab\u003d 11.9 × 10 -6 1 / ° С Flange material - steel 20K. Bolt material - steel 35. Gasket material - PON paronite.
1. Calculation of auxiliary quantities
1.1. Effective pad width
b o= b n= 12 mm.
1.2. Characteristics of the gasket, taken according to the table. four: m = 2.5;qlife safety fundamentals= 20 MPa; To = 0,9;En= 2 × 10 3 MPa. 1.3. Gasket Compliance
1.4. Bolt Compliance
Where fb\u003d 225 mm 2 is taken according to table. 5. 1.5. Flange parameters 1.5.1. Equivalent bushing thickness
S o= S o = 8 mm.
1.5.2. Odds
y 1 \u003d 0.16 is determined by hell. 6;1.5.3. Flange Angular Compliance
Where y 2 \u003d 6.9 is determined by hell. 7. 1.6. Angular compliance of a flange loaded with an external bending moment,
1.7. Shoulders of the moment:
b = 0,5(D b -D cn) = 0.5(495 - 445) = 25 mm;
e = 0,5(Dcn - D - Suh) = 0.5(445 - 400 - 8) = 18.5 mm.
2. Rigidity factor of the flange connection
2.1. Flanged connection loaded with internal pressure and external axial force:
2.2. Flange connection loaded with external bending moment:
=
;
3. Calculation of loads
3.1. Resultant internal pressure
Qd= 0.785 × D 2 cn × P= 0.785 × 445 2 × 0.6 = 93270.0 N.
3.2. Gasket reaction under operating conditions
R n = p × Dcn × babout × m × P= 3.14 × 445 × 12 × 2.5 × 0.6 = 25151.4 N.
3.3. Load arising from temperature deformations
Under installation conditions, the greater of the following values is taken:
Pb1=0.5× p × Dcn × buh × qlife safety fundamentals\u003d 0.5 × 3.14 × 445 × 12 × 20 \u003d 167676.0 H
Pb1=0.4 × × P × fb\u003d 0.4 × 130 × 20 × 225 \u003d 234000.0 H .
3.5. Load increment in bolts under operating conditions
4. Calculation of bolts
Where taken according to the table. 3,
5. Gasket calculation
;
[q] = 130 MPa, taken according to the table. four;6. Flange calculation
6.1. Flange rotation angle when tightening:
6.2. Increment of the angle of rotation of the flange in working conditions:
6.3. Meridional stresses in the shell on the outer and inner surfaces during tightening, MPa
Where T= 1.78 - taken according to hell. eight;
s 21 = 353.6 MPa; s 22 = -353.6 MPa.
6.4. Increments of meridional stresses in the shell on the outer and inner surfaces under operating conditions:
Ds 21 = Dsn +Ds 1 = 24.3 + 104 = 128.3 MPa;
Ds 22 = Dsn -Ds 1 = 24.3 + 104 = 128.3 MPa;
6.5. Circumferential stresses in the shell on the outer inner surfaces during tightening, MPa:
s 23 = 0.3× s 1 = 0.3 × 353.6 = 106.1 MPa;
s 24 = -0.3× s 1 = -0.3 × 356.6 = -106.1 MPa.
ss 0 = 425.6 MPa< 491 МПа.
The stress state level does not exceed the allowable one.
7. Stiffness requirement
q +Dq £ ,
0,0040 + 0,0012 = 0,0052<0,013.
APPENDIX 5
Limits of application of types of flange connections
Flat flanges (Fig. 2), with a free ring (Fig. 3), with clamps (Fig. 4) are recommended for use at medium temperatures up to 300°C. Flanges with a smooth sealing surface are recommended for nominal medium pressures up to 1.6 MPa. Flanges with a protrusion-cavity sealing surface are recommended for conditional medium pressures of more than 1.6 MPa. Spike-VAZ flanges are recommended for gaskets that need to be placed in a closed space. Flanges with a sealing surface for a metal gasket of oval or octagonal cross-section are recommended for conditional medium pressures of more than 6.0 MPa. Contact flanges (Fig. 11) are recommended for nominal pressures up to 0.6 MPa and vacuum with a residual pressure of at least 5 mm Hg. (0.005 MPa rest.) at temperatures up to plus 300°C.
Flange connection parameters, mm |
Flange types |
|||
Butt welded (Fig. 1) |
Flat (dev. 2) |
Loose (dev. 3) |
Note |
|
1. Thickness of the shell (sleeve) |
S = S 0 +1,3S but not in all cases |
S 0 ³ S |
S- thickness of the shell to which the flange is welded; b taken to hell. 13 |
|
S 0 -S× 5 mm |
||||
S 1 = bS 0 |
||||
2. Taper sleeve length t |
i= 1:3 bushing slope |
|||
3. Bolt circle diameter |
Db ³ D + 2(S 1 + d + u) |
Db ³ D +2(2S 1 +d × u) |
Db >Dto +8(d+u 1) |
u= 6 mm u 1 = 8 mm |
Db |
Db = ε 1× D 0,931 |
ε 1 is taken according to the table. eleven d taken according to the table. 13 |
||
4. Flange outer diameter Dn |
Dn ³ Db +a |
a taken according to the table. 13 |
||
5. Gasket outer diameter Ds |
Ds = Db - e |
Ds £ Ds 1 |
e taken according to the table. 13 |
|
6. Average gasket diameter Dcn |
Dcn = Ds - b |
b taken according to the table. fourteen |
||
7. Number of bolts n |
t 1 is taken according to the table. 12 |
|||
8. Estimated flange thickness h |
l 1 is taken according to hell. fourteen S 0 is accepted according to clause 3.6.1 |
RU, MPa |
Diameters of bolts (studs) for devices, mm |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Bolt diameter d b |
|||||||||||||
Bolt hole diameter d |
|||||||||||||
For hexagon nuts | |||||||||||||
For hexagon nuts with reduced wrench size | |||||||||||||
For flat gaskets | |||||||||||||
For oval or octagonal gaskets |
Table 14
Gasket sizes
Gasket material |
Apparatus diameter, mm |
Gasket width, mm |
Flat non-metallic gaskets |
D£1000 |
|
1000 < D£2000 |
||
D > 2000 |
||
Flat metal gaskets |
D£1000 |
|
D > 1000 |
||
Metal-sheathed flat gaskets and serrated metal gaskets |
D£1600 |
|
D > 1600 |
||
Oval or octagonal gasket for RU³ 6.3 MPa |
D£600 |
|
600 < D£800 |
||
800 < D£1000 |
||
1000 < D£1600 |
Table continuation*
Gasket material |
Apparatus diameter, mm |
Gasket width, mm |
Gasket thickness, mm |
TRG "Graflek c) not reinforced with an abturetor |
400< D £ 600 |
||
£600D<1000 |
|||
1000 £D<1500 |
|||
£400D<600 |
|||
TRG "Graflek c) reinforced with abturetor |
£400D<600 |
||
£600D<1000 |
Appendix 6
(required)
STANDARDS AND METHODS FOR CALCULATION OF THE STRENGTH AND TIGHTNESS OF FLANGED JOINTS WITH GASKETS FROM THE THERMALLY EXPANDED GRAPHITE MATERIAL "GRAFLEX"
1. This appendix applies to the calculation of flanged joints with tongue-and-groove sealing surfaces with gaskets from TRG "GRAFLEX".2. Characteristics of gaskets from TRG "GRAFLEX" * m, q,.[q], are given in Table. Modulus of elasticity of the gasket E p = 11,1q, where is the specific pressure on the gasket during tightening, MPa.3. Stiffness factor of the flange connection a determined in accordance with clause 4.1. Due to the fact that the elastic modulus of the gasket depends on the specific pressure on the gasket ( q), then when determining a the compliance of the gasket is determined by the method of successive approximations in the following way: The specific pressure on the gasket during tightening is preliminarily determined by the formula: R b- bolt force for installation conditions, determined according to clause 5.4. When determining R b- the coefficient in the first approximation is assumed to be equal to one. Then, according to the formula E p = 11,1q the modulus of elasticity is determined and, according to clause 3.3, the compliance of the gasket. If a more than one, then it is necessary to determine the bolt force R b1, according to clause 5.4. with the resulting coefficient a and repeat the definition q and E. After that, re-determine the coefficient a. *Note. The characteristics of the gaskets are presented by NPO UNIKHIMTEK If, at a first approximation, the coefficient a is less than one, then when calculating flange connections, the coefficient a is taken equal to unity and further approximations by definition a not required.
Gasket type and material |
Coefficient m |
Specific gasket compression pressure qlife safety fundamentals, MPa |
Permissible specific pressure [ q], MPa |
Gasket TRG unreinforced with obturator | |||
Reinforced TRG gasket without obturator |
120 at t=2 mm*) 100 at t=3 mm*) |
||
Reinforced TRG gasket with obturator | |||
*) gasket thickness in free state |
INFORMATION DATA
1. DEVELOPED BY NIIkhimmash, Ukrniikhimmash, VNIIneftemash PERFORMERS: Rachkov V.I., Ph.D.; Zusmanovskaya S.I., Ph.D.; Gaponova L.P.; Smolsky K.V., Ph.D.; Zavarov V.A.; Morozov V.G.; Pertsev L.P., Doctor of Technical Sciences; Golubova T.P.; Mamontov G.V., Ph.D.; Zeyde I.E.; Wolfson B.S. 2. APPROVED AND INTRODUCED BY the approval sheet of the Main Scientific and Technical Department dated 11/29/88. 3. INSTEAD OF OST 26-373-78, OST 26-01-396-78, OST 26-01-54-77. 4. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS
Number of paragraph, subparagraph, enumeration, application |
|
GOST 481-80 | |
GOST 2208-75 | |
GOST 2850-80 | |
GOST 5632-72 | |
GOST 7338-77. | |
GOST 9045-80 | |
GOST 14249-80 |
Attachment 1 |
GOST 21631-76 | |
GOST 25859-83 | |
OST 26-01-64-83 |
Attachment 1 |
OST 26-11-04-84 |
2.5, 5.3, 12.4.6 |
OST 26-291-87 |
Introduction |
TU6-05-810-76 |
1. General requirements. one 2. Permissible stresses. 3 3. Calculation of auxiliary quantities. four 4. Rigidity factor of the flange connection. 6 5. Calculation of loads. 7 6. Calculation of bolts (studs) 8 7. Calculation of gaskets. 9 8. Calculation of flanges for static strength *. 9 9. Calculation for low-cycle fatigue. eleven 10. Calculation of the free ring. 12 11. Requirements for rigidity. 12 12. Calculation of flange connections with contacting flanges. 16 Appendix 1 Terms and designations. twenty Appendix 2 Coefficients of linear expansion. 21 Appendix 3 Wrench torque when tightening. 21 Appendix 4 An example of calculating a flange connection. 22 Appendix 5 Application limits for flange connection types. 26 Appendix 6 Norms and methods for calculating the strength and tightness of flanged joints with gaskets made of thermally expanded graphite material "Graflex". 29 |