GB/T 35974.1-2018Plastics and plastic lining pressure vessels—Part 1: General requirements (English PDF)

1.1 Basic Scope

This Part of GB/T 35974 specifies the terms and definitions; general requirements of materials, design, fabrication, inspection and testing for plastics and plastic lining pressure vessels.

NOTE: if it is not particularly indicated, all parts of GB/T 35974 may use the following abbreviations:

---Plastics and plastic lining pressure vessels: "vessels" for short;

---Plastic pressure vessels: "plastics vessels" for short;

---Plastics vessels with plastic lining: "lining vessels" for short.

This Part is not applicable to movable vessels.

This Part is not applicable to plastics vessels, whose medium is flammable, explosive and toxic gas; moderately toxic liquid stipulated in HG/T 20660.

1.2 Materials

This Part is applicable to vessels fabricated by the following thermoplastic plastics:

a) Plastics vessels: rigid polyvinyl chloride (PVC-U), chlorinated polyvinyl chloride (PVC-C), polyethylene (PE), polypropylene (PP), Acrylonitrile-butadiene-styrene (ABS);

b) Lining vessels: rigid polyvinyl chloride (PVC-U), chlorinated polyvinyl chloride (PVC-C), polyethylene (PE), polytetrafluoroethylene (PTFE), tetrafluoroethylene/ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF).

1.3 Design Pressure

This Part is applicable to vessels of the following design pressure:

a) Plastics vessels: design pressure is 0 MPa ~ 0.25 MPa; nominal diameter is not more than 4 m;

b) Lining vessels: design pressure is 0.1 MPa ~ 2.5 MPa; gauge pressure is less than 0.1 MPa; it may be taken as a reference in implementation.

3.1 Stationary Pressure Vessel

Stationary pressure vessel refers to pressure vessel, which is installed in a fixed position.

3.8 Calculating Pressure

Calculating pressure refers to the pressure used to determine component thickness at corresponding design temperature.

NOTE: it includes additional loads, for example, liquid column static pressure.

3.9 Test Pressure

Test pressure refers to the pressure of the top of vessel during pressure resistance test or leakage test. [GB/T 26929-2011, Definition 2.3.3]

3.10 Operating Temperature; working temperature

Operation temperature/working temperature refers to the temperature of materials inside the vessel under the stipulated normal operating condition.

NOTE 1: in domestic and overseas technical documents of the pressure vessel industry, "operating temperature/working temperature" refers to the temperature of materials.

NOTE 2: in a vessel, the temperature of materials in different parts might differ; if necessary, operating temperature/working temperature of various parts needs to be respectively pointed out.

NOTE 3: sometimes operating temperature/working temperature is also known as operating temperature. [GB/T 26929-2011, Definition 2.4.1]

3.11 Required Thickness

Required thickness refers to the thickness obtained through formula calculation in design.

NOTE: when needed, required thickness of other loads shall also count. In terms of external pressure component, it refers to the minimum thickness which satisfies the requirement of stability.

5.2 Technical Requirements

5.2.1 In materials' technical requirements, there shall be one of the following items, or a combination of the following items:

a) Weather resistance;

b) Corrosion resistance;

c) Appearance;

d) Tensile yield stress;

e) Elongation at break;

f) Tensile modulus of elasticity;

g) Vicat softening temperature;

h) Charpy notched impact strength;

i) Density;

j) Longitudinal retraction rate;

k) Falling impact performance;

l) Hydrostatic strength;

m) Oxidation induction time;

n) Melt mass flow rate;

o) Bending strength;

p) Dimensional change rate;

q) Thermal shrinkage rate. […]

6.5 Design (calculating) Thickness

6.5.1 Material design (calculating) thickness of plastics vessel shall be calculated in accordance with relevant stipulations in GB/T 35974.3.

6.5.2 The minimum wall thickness of lining vessel shall comply with the stipulations in GB/T 35974.3.

6.5.3 Under the operating conditions where photoaging exists, in accordance with the designed service life, the reserved thickness shall be increased. Reserved thickness shall be calculated in accordance with Formula (1).

Where, C2---reserved thickness, expressed in (mm); y---materials' photoaging life, calculated in accordance with Appendix A, expressed in (a); delta---calculating thickness, expressed in (mm).

6.6 Plastics Vessel

6.6.1 The design of plastics vessel, such as internal pressure cylinder, head, Flange and its connection, opening reinforcement and welding structure, shall comply with the stipulations in GB/T 35974.3.

6.6.2 The support, safety and protection of plastics vessel shall comply with the stipulations in GB/T 35974.3.

6.7 Lining Vessel

6.7.1 The design of lining vessel, such as metal shell and lining, shall comply with the stipulations in GB/T 35974.3.

7.2 Processing Procedures

7.2.1 Processing procedures adopted in vessel fabrication shall pass corresponding procedure evaluation, and comply with the requirements.

7.2.2 Plastics vessel shall be fabricated in accordance with the processing procedures stipulated in GB/T 35974.4, such as: welding, rotational molding, extrusion and extrusion winding.

7.2.3 Lining vessel shall be fabricated in accordance with the processing procedures stipulated in GB/T 35974.5, such as: welding, rotational molding and winding sintering.

7.3 Inspection and Testing

7.3.1 Inspection

During vessel fabrication, the various fabrication stages shall be inspected in accordance with the items stipulated in quality plan and processing procedures.

7.3.2 Testing

7.3.2.1 After vessel fabrication is completed, vessels shall be tested.

7.3.2.2 Test items of plastics vessels are: appearance, dimension, minimum wall thickness, pressure resistance test, air tightness test and ultra-leakage detection. Indicator requirements shall comply with the stipulations in GB/T 35974.4.

7.3.2.3 Test items of lining vessels are: appearance, minimum wall thickness of lining, pressure resistance test, leakage test, electric spark test, thermal expansion and contraction test, and negative pressure resistance test. […]