GB/T 12777-2019General specification for metal bellows expansion joints (English PDF)

4.1 Classification

4.1.1 Classification of expansion joints Expansion joints are divided into three types according to working conditions, see Table 1.

4.1.2 Type classification of expansion joints Expansion joints can be divided into two types. unconstrained and constrained according to whether they can constrain the pressure and thrust. Commonly used expansion joints are divided into 15 types according to the structural form Type, see Table 2.

4.1.3 Classification of expansion joints

4.1.3.1 Components of expansion joints The expansion joint is composed of bellows and structural parts. The structural parts are divided into pressure parts, stressed parts and non-pressure (force) parts.

4.1.3.2 Bellows (P0) The failure of components (including strengthening ring, equalizing ring and strengthening ring) that play the role of displacement compensation will lead to the loss of the function of the expansion joint, see Figure 16.

4.1.3.3 Pressure parts (P1) The failure of components directly in contact with the pressurized medium will cause the pressure to be released suddenly, see Figure 16.

4.1.3.4 Force parts (P2) The failure of components that bear the pressure and thrust of the bellows (such as hinge plates, tie rods, etc.) will cause the loss of the restraint function of the expansion joint, see Figure 16.

4.1.3.5 Non-compression (force) parts (P3, P4) Non-compression (force) parts are divided into P3 and P4 (see Figure 16).

a) Parts connected with pressure parts or stress parts (P3);

b) Components other than P3 components (P4).

a) Single axial type

b) External pressure axial type

c) Single hinge type

d) Double lever type a If it is a reinforced collar, it is P0.

4.1.4 Classification of welded joints

4.1.4.1 The welded joints of bellows, pressure parts, and stress parts in expansion joints are divided into the following four categories (see Figure 17).

a) Corrugated pipe longitudinal butt joints (including strengthening ring, equalizing ring and strengthening collar), compression tube section (including connecting pipe and end pipe) longitudinally aligned All longitudinal tailor-welded joints and end ring-type tailor-welded joints are classified as Class A welded joints;

b) The circumferential joint of the bellows and the pressure cylinder section and the circumferential butt joint of the pressure cylinder section are all Type B welded joints;

c) Flat flanges, end plates, end rings, vertical plates, etc. are connected to the pressure cylinder section, and the reinforcement collar, end balance ring and the pressure cylinder section are connected Lap joints are all Type C welded joints;

d) The joints between the pressure cylinder section and the head, the joints between the detection tube and the straight side section of the corrugated pipe, are all D-type welded joints.

4.1.4.2 Other welded joints are Class E welded joints, see Figure 17.

4.1.5 Type classification of bellows The type and code of the bellows in the expansion joint are shown in Table 3.

4.1.6 Classification of end connection types The connection type and code of the end of the expansion joint and the pipeline or equipment are shown in Table 4.

4.2 Model and marking

4.2.1 Model representation method Expansion joint model representation method is as follows: Expansion joint type code (see Table 2). Bellows type code (see Table 3); Type code of the end of the expansion joint (see Table 4); The value of 10 times the design pressure, in megapascals (MPa); The value of the nominal size. the round pipe is the nominal diameter, and the unit is millimeters (mm); Rectangular pipe is long side × short side, the unit is millimeter (mm); The value of the design displacement in millimeters (mm) or degrees (°);

Note. For expansion joints with combined displacements (codes FZ, FZB, WP, FJP, FWP, etc.), the design displacement represents the design axial displacement and the design transverse position respectively. When the displacement is moved, the axial displacement is in the front and the lateral displacement is in the back. The displacements are connected with a "/".

5.1 Bellows

5.1.1 The material of the bellows should be selected according to the working conditions such as working medium, external environment and working temperature. Commonly used bellows materials are shown in Table 5.

5.1.2 Different materials can be used for each layer of the multi-layer corrugated pipe.

5.1.3 Refer to GB/T 20801.2, GB/T 24511, NB/T 47008, NB/T 47010 for commonly used materials for strengthening ring or equalizing ring.

5.2 Pressure parts The material used for pressure parts such as the middle end pipe and flange of the expansion joint should be the same as or better than that of the pipe in the pipeline where the expansion joint is installed. Commonly used pressure parts materials see GB/T 20801.2, GB/T 24511, NB/T 47008, NB/T 47010.

5.3 Force parts The tension rods, hinge plates, universal rings, pin shafts and their connecting accessories in the expansion joints should be used in accordance with the pressure and thrust of the bellows. Selection of working conditions.

5.4 Allowable stress

5.4.1 The allowable stress shall comply with the relevant material standards.

5.4.2 When the design temperature is lower than 20°C, the allowable stress of 20°C shall be taken.

5.4.3 The allowable stress at the design temperature of multi-layer bellows with different material combinations is calculated according to formula (1).

5.5 Material inspection Use the method of checking the material designation, appearance quality and quality certificate to carry out material inspection, and the results should meet the requirements of 5.1,

6.1 Round bellows

6.1.1 The limit deviation of the wave height and wave distance of the U-shaped bellows should be implemented in accordance with Table 6, and the limit deviation of the corrugated length should be implemented in accordance with Table 7.

6.1.2 The consistency requirements of the wave height in the same U-shaped corrugated pipe shall be implemented in accordance with Table 8.

6.1.4 The limit deviation of the radius of curvature of the peak and valley of the U-shaped bellows shall be ±15% of the nominal radius of curvature of the ripple, and the peak, valley and wave side The transition between the walls should be smooth.

6.1.5 The limit deviation of the average corrugation radius of the Omega-shaped bellows should be ±15% of the nominal average radius of the corrugation, and the roundness of the Omega-shaped corrugated section The difference should be ±20% of the nominal average radius of the corrugation.

6.1.6 The perpendicularity tolerance of both ends of the bellows facing the axis of the bellows should be 1% of the outer diameter of the straight side section of the bellows, and not more than 3mm. Straight edge For corrugated pipes with a section outer diameter not greater than.200mm, the coaxiality tolerance between the axis of the two ends of the bellows and the axis of the bellows shall be phi2mm; straight side section For bellows with an outer diameter greater than.200mm, the coaxiality tolerance between the two ends of the bellows and the axis of the bellows should be 1%. The outer diameter is not greater than phi5mm.

6.2 Rectangular bellows

6.2.1 The requirements of corrugated pipe wave height, wave distance and corrugation length shall be in accordance with the provisions in 6.1.1.

6.2.2 The standard tolerance level of the side length and diagonal of the bellows shall be IT17 level in Table 1 of GB/T 1800.1-2009, and its limit deviation It is ±IT17/2, and not more than 8mm.

6.3 Pressure cylinder section

6.3.1 The size of the rolled circular pressure cylinder section shall meet the requirements of

5.4 in GB 50235-2010.

6.3.2 See Figure 18 for the butt groove of the end pipe welded connection end connected to the pipeline or equipment. When the wall thickness of the end pipe is greater than the wall thickness of the connected pipe, press The requirements of 7.4.3a) in GB/T 20801.4-2006 are thinned.

a) End pipe wall thickness<=20mm

b) End pipe wall thickness >20mm Figure

7.1 Design conditions

7.1.1 The system design unit or user should provide the design conditions of expansion joints in accordance with Table 11 or Table

12.The design pressure and design Measure temperature, design displacement and design fatigue life. The torsion of the bellows should be avoided. When the torsion of the circular bellows is unavoidable, it should be Torque on expansion joints.

7.1.2 The design pressure of the expansion joint should not be lower than the maximum working pressure given in Table 11 or Table 12, and should not be higher than

1.1 of the maximum working pressure. Times. When determining the design pressure, the piping test pressure should be taken into account.

7.1.3 When the expansion joint bears internal pressure and external pressure at the same time, or operates under vacuum conditions, the design pressure should take into account the The maximum internal and external pressure difference that can occur.

7.1.4 For expansion joints without internal heat insulation structure, the design temperature of the bellows should be based on the working temperature; for expansion joints with heat insulation structure, the bellows The design temperature of the tube should be determined according to heat transfer analysis calculations, tests or with reference to the actual temperature measured under the operating conditions of similar devices.

7.1.5 When determining the design temperature, various conditions including the low temperature conditions of the atmospheric environment expected during the operation of the expansion joint should be taken into account.

7.1.6 Refer to Appendix C C.2.3 for the determination of the design temperature of the expansion joint structure.

7.4 Structural parts Refer to Appendix C for the design of structural parts such as pressure parts and stress parts in expansion joints.

7.5 Guide tube

7.5.1 The design of the expansion joint diversion tube is shown in Appendix A, A.5.

7.5.2 When the temperature of the working medium is higher than the upper limit of the allowable temperature of the bellows material, it should be in the annular space between the diversion tube and the bellows Fill with heat-insulating material compatible with the temperature and characteristics of the working medium. The heat-insulating material should be reliably fixed to the diversion tube or end pipe.

7.5.3 When the working medium contains dust, a dust-proof device should be installed at the open end of the diversion tube, and the dust-proof device should be reliably fixed with the diversion tube or end pipe. And the open end of the guide tube should not be upward.

7.5.4 When the working medium is liquid or steam and flows upward, the deflector should be provided with a drain hole.

7.6 Shipping fixtures

7.6.1 Expansion joints should be provided with shipping fixtures to keep the expansion joints at the correct length during transportation and installation. After the expansion joint is installed The shipping fasteners should be removed or loosened before the system pressure test. When pre-shifting is required during installation, the shipping fasteners should be removed before pre-shifting.

7.6.2 When the mass of the expansion joint is greater than.200kg, a lifting device should be installed.

7.7 Protective cover The design of the expansion joint protective cover is shown in Appendix A, A.6.

7.8 Expansion joint The connection type of the straight side section of the bellows and the pressure cylinder section (flange) in the expansion joint should adopt an insert or outer sleeve structure.

8.1 Material mark transplantation

8.1.1 The materials of bellows (P0), pressure parts (P1) and stress parts (P2) shall have traceable marks. In the manufacturing process, if the original logo is When cut...