GB/T 35974.3-2018Plastics and plastic lining pressure vessels—Part 3:Design (English PDF)

3.1 Pressure Diameter Product of Plastics Vessel

In terms of plastics vessels (lining vessels are not restricted here) designed in accordance with this Part, PD value (pressure diameter product) shall be not more than 150 MPa·mm.

4.1 Minimum Thickness

The minimum thickness of the shell of plastics vessel after processing and forming, excluding the reserved thickness, shall be not less than 4 mm.

4.2 Internal Pressure Cylinder Design

4.2.1 Symbols and abbreviations

Di---internal diameter of cylinder shell or head, expressed in (mm);

Do---external diameter of cylinder shell or head, expressed in (mm); pc---calculating pressure, expressed in (MPa); delta---calculating thickness of shell, expressed in (mm); deltae---effective thickness, expressed in (mm); sigma1t---calculating stress of materials at design temperature, expressed in (MPa); [sigma]1t---allowable stress of materials at design temperature, expressed in (MPa); phi---welded joint coefficient.

4.2.2 Basic requirements

4.2.2.1 Formulas in this Part are applicable to the calculation of single-layer cylinder. In terms of cylinders which are molded in the method of winding, if the winded layers are already welded, they may be considered as single-layer cylinders.

4.2.2.2 Pipes shall be preferably selected in cylinder design.

4.2.2.3 Cylinder wall thickness of plastics vessels shall take an equivalent value as head thickness. In addition, the larger value in their calculation results shall be taken as the wall thickness of the entire plastics vessel.

4.2.3 Cylinder wall thickness

Determine cylinder wall thickness through hoop stress. In addition, when Do/Di <= 1.1 is satisfied, calculate in accordance with Formula (2) or Formula (3).

When Do/Di > 1.1, cylinder's axial stress shall be calculated in accordance with Formula (9). sigma1t shall be not more than [sigma]1t phi.

When Do/Di > 1.1, cylinder's hoop stress shall be calculated in accordance with Formula (10). sigma1t shall be not more than [sigma]1t phi.

4.3 Head Design

4.3.1 Symbols and abbreviations

Dc---internal diameter of conical shell calculation, expressed in (mm); Di---internal diameter of cylinder shell or head, expressed in (mm);

DiL---internal diameter of larger end of conical head, expressed in (mm);

Dis---internal diameter of smaller end of conical head, expressed in (mm); hi---inner surface depth of ellipsoidal head, expressed in (mm); K---shape factor of ellipsoidal head; M---shape factor of dished head; pc---calculating pressure, expressed in (MPa);

Ri---inner radius of equivalent spherical shell of dished head, expressed in (mm); r---inner radius of the arc of conical shell larger end transition zone, or inner radius of the corner of dished head transition zone, expressed in (mm); rs---inner radius of the arc of conical shell smaller end transition zone, expressed in (mm); alpha---semi-vertical angle of conical shell, expressed in (°);

delta---calculating thickness of ellipsoidal shaped or dished head, expressed in (mm); deltac---calculating thickness of conical shell, expressed in (mm);

deltar---calculating thickness of conical shell folding edge transition section, expressed in […]

4.4.2 Basic requirements

The selection of Flange structural type shall guarantee airtightness. Loose Flange structural type should be selected.

Sealing elements shall adopt an entire gasket or O-shaped gasket. […]

4.5.1 Symbols and abbreviations

A---reinforced cross-sectional area needed for opening weakening, expressed in (mm2); Ae---reinforcement area, expressed in (mm2);

A1---shell's effective thickness minus surplus area excluding calculating thickness, expressed in (mm2);

A2---connecting pipe's effective thickness minus surplus area excluding calculating thickness, expressed in (mm2); A3---cross-sectional area of welding materials, expressed in (mm2); A4---additional reinforcement area within effective reinforcement range, expressed in (mm2); B---effective width of reinforcement, expressed in (mm); C2---reserved thickness, expressed in (mm);

Di---internal diameter of cylinder, expressed in (mm); d---mid-diameter of connecting pipe, expressed in (mm); do---external diameter of connecting pipe, expressed in (mm); dop---opening diameter, expressed in (mm); h1---effective reinforcement height of outreached connecting pipe, expressed in (mm); delta---calculating thickness of shell's opening, expressed in (mm); deltae---effective thickness of shell's opening, expressed in (mm); deltan---nominal thickness of shell's opening, expressed in (mm); deltant---nominal thickness of connecting pipe, expressed in (mm); deltaet---effective thickness of connecting pipe, expressed in (mm); deltat---calculating thickness of connecting pipe, expressed in (mm).

4.5.2 Basic requirements

4.5.2.1 Principle

This stipulation is applicable to the opening and its reinforcement calculation of plastics vessel. The method of opening and reinforcement calculation shall comply with area equalization method.

4.5.2.2 Application scope of area equalization method

Area equalization method is applicable to shell's round opening under the effect of pressure. The scope of application is as follows:

a) When cylinder's internal diameter Di <= 1,000 mm, opening's maximum diameter dop <= Di/3. When cylinder's internal diameter Di > 1,000 mm, opening's maximum diameter dop <= Di/3; in addition, dop <= 450 mm;

b) The maximum diameter of convex head opening dop <= Di/3;

c) The maximum diameter of conical head opening dop <= Di/3; Di is conical shell's internal diameter in the center of the opening;

d) The spacing (spacing on curved surface shall be calculated by arc length) of two opening centers on the shell shall be not less than the sum of the diameter of the two openings;

e) In terms of opening on ellipsoidal head, opening range shall not exceed 80% of the diameter of the ellipsoidal head center;

f) In terms of opening on dished head, opening range shall not exceed the spherical part of the dished head.

4.5.2.3 Welded joints near openings

Openings on the vessel shall avoid vessel's welded joints. When openings are close to vessel's welded joints, it shall be guaranteed that welded joints shall not manifest any excessive defects within the 2dop range of opening center.

4.5.3 Reinforcement structural type and reinforcement material

4.5.3.1 Reinforcement ring

Please refer to Table 3 for the welded structure of reinforcement ring, connecting pipe and shell. […]