GB/T 35990-2018Metal bellows expansion joints for pressure piping (English PDF)

3.1 Bellows

A flexible element consisting of one or more corrugations and straight edges.

3.2 Convolution

A basic flexible unit that constitutes a bellows.

3.3 End tangent

A straight section of the bellows without corrugations at the end.

3.4 Collar

Used only to strengthen the barrel or ring of the straight section.

3.5 Assisting collar

Hing the loop of the straight section for easy soldering.

3.6 Reinforcing member

Suitable for reinforcing U-shaped and omega-shaped bellows, including reinforcing ferrules, reinforcing rings and equalizing rings. The ferrule is used to strengthen the straight section and A trough or ring of troughs. The reinforcing ring and the equalizing ring are devices for reinforcing the bellows or peaks of the bellows, and the equalizing ring also has a total equivalent of the single wave. The function of the axial displacement range.

3.7 Pressure thrust

The static axial thrust of the bellows due to pressure.

3.8 Neutral position

The bellows is in a position where the displacement is zero.

3.9 Integral molded bellows

Bellows without a circumferential weld.

4.1 Qualification

For expansion joints within the scope of the Catalogue of Special Equipment, the manufacturing unit and personnel shall have the following qualifications.

a) The manufacturing unit shall establish an applicable quality assurance system in accordance with the provisions of TSGZ0004 and obtain the "Special Equipment Manufacturing License";

b) The welding personnel shall hold the special equipment operator certificate of the corresponding project in accordance with the provisions of TSGZ6002;

c) Non-destructive testing personnel shall obtain corresponding non-destructive testing personnel in accordance with the relevant provisions of the national special equipment non-destructive testing personnel assessment. qualifications.

4.2 Duties

4.2.1 Responsibilities of the user or system designer

The user or system designer shall submit the design conditions in writing to the expansion joint design unit and be responsible for their completeness and accuracy.

4.2.2 Expansion unit design unit (department) duties

4.2.2.1 The design unit (department) shall be responsible for the completeness and correctness of the design documents.

4.2.2.2 The design documentation for the expansion joint shall include at least the design calculations and design drawings and, if necessary, installation instructions.

4.2.2.3 The design shall take into account all failure modes that may occur during the use of the expansion joint, and take corresponding measures to prevent failure, if necessary, to The user issues a risk assessment report.

4.2.2.4 The design unit (department) shall save all design documents during the design life of the expansion joint.

4.2.3 Manufacturing unit responsibilities

4.2.3.1 The manufacturing unit shall strictly implement relevant regulations, safety technical specifications and corresponding standards, and manufacture, inspect and accept according to the design drawings. Expansion joint.

4.2.3.2 The manufacturing unit shall be manufactured according to the design drawings, and the design documents shall be changed by the original design unit (department), and the manufacturing unit shall Modifications of the original design and substitution of materials for pressure-bearing components (see A, B in 5.2.1) shall be obtained in advance by the original design unit (department). Approved.

4.2.3.3 When each batch of expansion joints is shipped from the factory, the manufacturer shall provide the following technical documents and materials to the user at least.

a) as-built drawings;

b) If material substitution, non-destructive testing method change, processing size change, etc. occur during manufacturing, the manufacturing unit shall follow the design unit book. The requirements for the approval document are clearly marked on the as-built drawings, with the signature of the person modified and the date of modification;

c) The factory documents specified in this standard, including the certificate of conformity, the certificate of product quality and the instructions for installation and use.

5.1 Expansion section classification

5.1.1 Classification according to whether it can withstand pressure thrust

According to whether the expansion joint itself can withstand the pressure thrust, the expansion joint is divided into two types. unconstrained type and constrained type. For common structural types, see Table 1.

a) Unconstrained type. an expansion joint that cannot withstand pressure thrust itself, called an unconstrained expansion joint.

b) Constrained type. an expansion joint that can withstand pressure thrust, called a constrained expansion joint.

5.1.2 Classification according to absorption displacement type

According to the type of absorption displacement of the expansion joint, the expansion joint is divided into four types. axial type, angular type, transverse type and universal type. Common structural types See Table 1.

a) Axial type. mainly used to absorb axial displacement. Can be designed to be unconstrained or constrained.

b) Angular type. Constrained expansion joint. Used to absorb angular displacement. When setting the hinge, it is used to absorb the single plane angular displacement; When the universal ring is placed, it is used to absorb multi-plane angular displacement.

c) Lateral type. Constrained expansion joint. Used to absorb lateral displacement. When two tie rods are provided in the expansion joint, it can be used to absorb perpendicular to The two tie rods form a planar angular displacement; the expansion joints with double or double universal joints can also be used to absorb angular displacement.

d) Universal type. used to absorb displacement in multiple directions. Can be designed to be unconstrained or constrained.

5.2 Component classification of expansion joints

5.2.1 Pressure components

5.2.1.1 Main pressure components (A)

The components that make up the pressure boundary (including the ferrule and the reinforcement) will cause a sudden burst of pressure, as shown in Figure 1.

5.2.1.2 Non-main pressure components (B)

The components that are subjected to pressure thrust are shown in Figure 1.

5.2.2 Non-pressure components

5.2.2.1 Parts connected to main pressure components and non-main pressure components (C)

Components soldered directly to A or B, see Figure 1.

5.2.2.2 Other components (D)

For components other than A, B or C components, see Figure 1.

5.3 Welding joint classification

Typical expansion joint welded joints are divided into four categories. W1~W7, as shown in Figure 2.

---W1 Pressure pipe, ferrule and reinforcement longitudinal butt joint;

---W2 bellows longitudinal butt joint;

---W3 Pressure-bearing pipe type circumferential butt joint, pressure ring type splicing butt joint;

---W4 Welded joint of bellows and connecting piece (plug welded butt joint, lap joint, end welded butt joint);

---W5 Weld joints between pressure-bearing components (A and A, A and B) except W3 and W4;

---W6 is connected to the welded joint between the non-main pressure components (B and B);

---W7 Welded joints for non-pressure components (C and D).

7.1 General provisions

7.1.1 The material selection should take into account the mechanical properties, chemical properties, physical properties and process properties of the material, and the functions and working conditions to be achieved. Compatible with the expected manufacturing technology.

7.1.2 Components connected to pressure-bearing components shall not affect the use of pressure-bearing components connected to them, in particular The components of the welded joint should also take into account the weldability of the material.

7.1.3 The quality, specifications and markings of the materials used for the pressure-bearing components of the expansion joints shall comply with the requirements of the corresponding material standards.

a) When the expansion joint manufacturing unit obtains the material for the expansion joint pressure component from the material manufacturing unit, the material manufacturing unit shall guarantee the quality, and Meet the following requirements.

1) Provide the material quality certificate (original) according to the corresponding standards, the content of the material quality certificate shall be complete and clear, and Covered with the quality inspection certificate of the material manufacturing unit;

2) Make clear signs on the obvious parts of the material in accordance with the relevant standards.

b) When the expansion joint manufacturing unit obtains the material for the expansion joint pressure component from the non-material manufacturing unit, it shall obtain the material manufacturing unit The original certificate of the quality certificate or the copy of the official seal and the manager's seal of the supplier of the capping material; the expansion unit manufacturing unit Responsible for the authenticity and consistency of the materials obtained for expansion joints and the quality certificate of materials.

7.1.4 The expansion joint manufacturing unit shall accept the materials according to the material quality certificate.

7.2 Bellows

7.2.1 The materials selected shall be sufficiently resistant to corrosion by all corrosive media that may be encountered during the life of the system. Usually ripple The tube is made of a material that is more resistant to corrosion than other components in the system.

7.2.2 The materials selected shall meet the requirements of the bellows forming and welding process.

7.2.3 When the bellows is a multi-layer structure, each layer of material is allowed to be different, but the material should not exceed two.

7.2.4 See Appendix A for commonly used bellows materials.

7.3 Other pressure components

7.3.1 The material selected for contact with the medium shall be the same as or the lower than the material of the pipe in the pipe in which the expansion joint is installed. Material, when welding with the pipe should have good welding performance, commonly used materials see GB/T 20801.2-2006.

7.3.2 Materials for non-main pressure components shall be considered for safety and reliability under loads such as pressure and thrust. Appendix A.

8.1 Design conditions

8.1.1 Precautions

The user or system designer shall provide design conditions at least in accordance with Table 2, and shall be aware of the following.

a) The type of pipeline support, the location, and the extent to which the displacement is to be absorbed shall be considered in accordance with the provisions of Chapter 4 of GB/T 35979-2018. To determine the type, displacement and stiffness of the most suitable expansion joint to meet the force requirements of the piping and equipment. should Avoid twisting the bellows. When the twisting is unavoidable, the specific requirements of the torque should be made.

b) The material of the bellows should be compatible with the medium, the external environment and the working temperature, and consider the possible corrosion (special attention to stress) corrosion). The materials selected should also be able to accommodate the chemicals used in water treatment or cleaning of the pipeline. When there is a heat insulation layer, absolutely Corrosive substances that permeate through the hot layer may also cause corrosion.

c) If the flow rate of the medium causes resonance of the bellows or erosion of the corrugations, the liner shall be provided in accordance with B.5.

d) The maximum working pressure, design pressure and test pressure should be given and determined according to the actual situation, and should not be arbitrarily increased. According to excessive pressure Force design will excessively increase the thickness of the bellows, but will reduce the fatigue life of the bellows and increase the expansion joints for the piping system. Use force.

e) The maximum working temperature and the minimum operating temperature should be specified according to the actual situation. Temperature may change greatly during pipeline construction Where it is necessary, pre-displacement may be required when installing the expansion joint.

f) The displacement value should be specified according to the actual situation. Using too high safety factor will increase the flexibility of the expansion joint and reduce the expansion joint in the pressure state. Stability under. The displacement to be absorbed by the expansion joint includes the amount of expansion and contraction of the pipe, the equipment connected to the expansion joint, the fixing bracket, etc. Displacement of the device, as well as possible deviations during installation (should avoid installation deviations of the expansion joints beyond the design allowable values). If the displacement is cyclic, the expected fatigue life should also be specified.

g) For media that will accumulate or solidify, measures should be taken to prevent it from stagnation and damaging the expansion joints or pipelines within the corrugations.

h) The liner should generally be placed in the direction of the flow of the medium. To avoid the flow medium being blocked in the back of the liner, it should be stated It is necessary to open a drain hole or a purge nozzle on the liner. When backflow may occur, a thickened liner shall be specified. Prevent the inner liner from buckling.

i) If the bellows is subjected to external mechanical vibrations (for example, vibrations generated by reciprocating or pulsating machinery), the vibration of the vibration should be stated. Amplitude and frequency. Design expansion joints to avoid bellows resonance to eliminate the possibility of sudden fatigue damage. Possible at the scene Modifications must also be made to the expansion joint or other components of the system.