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GB/T 35974.4-2018 (GB/T35974.4-2018)

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GB/T 35974.4-2018: PDF in English (GBT 35974.4-2018)
GB/T 35974.4-2018
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.120; 83.140
G 94
Plastics and Plastic Lining Pressure Vessels -
Part 4: Fabrication, Inspection and Testing for Plastic
Pressure Vessels
塑料及其衬里制压力容器
ISSUED ON: FEBRUARY 6, 2018
IMPLEMENTED ON: SEPTEMBER 1, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Fabrication ... 4 
4 Technical Requirements ... 10 
5 Inspection ... 11 
6 Exit-factory Requirements ... 14 
Plastics and Plastic Lining Pressure Vessels - Part 4:
Fabrication, Inspection and Testing for Plastic
Pressure Vessels
1 Scope
This Part of GB/T 35974 specifies the fabrication, technical requirements, testing and
exit-factory requirements of plastic pressure vessels.
2 Normative References
The following documents are indispensable to the application of this Standard. In terms
of references with a specified date, only versions with a specified date are applicable
to this Standard. In terms of references without a specified date, the latest version
(including all the modifications) is applicable to this Standard.
GB/T 150.4 Pressure Vessels - Part 4: Fabrication, Inspection and Testing, and
Acceptance
GB/T 33488.3 Test Method of Pressure Equipment of Thermoplastics Welded for
Chemicals - Part 3: Radiographic Examination
GB/T 33488.4 Test Method of Pressure Equipment of Thermoplastics Welded for
Chemicals - Part 4: Ultrasonic Examination
GB/T 35974.2 Plastics and Plastic Lining Pressure Vessels - Part 2: Materials
GB/T 35974.3 Plastics and Plastic Lining Pressure Vessels - Part 3: Design
HG/T 4280 Welding Procedure Qualification for Plastics
HG/T 4281 Welding Procedure Specification for Plastics
JB/T 4711 Coating and Packing for Pressure Vessels Transport
3 Fabrication
3.1 General Requirements
3.1.1 Plastics vessels shall be fabricated in accordance with the processing procedure
stipulated in this Part.
in GB/T 35974.2 and design documents.
3.2.2 Acceptance check
3.2.2.1 Items
Acceptance check items of materials are: quality certificate, appearance, dimensions
and performance indexes.
3.2.2.2 Quality certificate
Materials shall have an exit-factory quality certificate. Items and indexes in the quality
certificate shall comply with the stipulations in GB/T 35974.2.
3.2.2.3 Appearance
Materials’ appearance shall receive full inspection. The indexes shall comply with the
stipulations in GB/T 35974.2.
3.2.2.4 Dimensions
Materials’ main dimensions shall receive 100% inspection. The indexes shall comply
with the stipulations in GB/T 35974.2.
3.2.2.5 Performance indexes
Main materials’ performance indexes shall comply with the stipulations in GB/T
35974.2.
3.2.3 Material re-inspection
3.2.3.1 Under one of the following circumstances, materials’ performance indexes shall
be re-inspected in accordance with GB/T 35974.2 and design requirements:
a) When there are doubts about the performance indexes in the quality certificate;
b) When re-inspection is requested in design documents.
3.2.3.2 Material re-inspection shall receive sampling inspection of the performance
indexes. The sampling range shall cover every exit-factory batch of the materials.
Sampling inspection items shall at least include the content in Table 2. Materials shall
be qualified in all the inspection items, then, they may be used in the fabrication of
plastics vessels.
Table 2 -- Re-inspection Items and Requirements
Fabrication
Procedures
Material
Status Inspection Items Requirements
Welding Pipes PVC-U, PVC-C, ABS: density, Vicat softening Comply with the
Initiate the rotating mechanism, so that the mold starts to rotate. Set up the speed ratio
to make sure that during the heating process, materials can be evenly attached to the
mold. Heat the rotating mold. The setting of heating temperature and time shall satisfy
the requirements of the processing procedures. The highest air heating temperature in
the mold shall be not lower than 180 °C.
3.3.2.1.3 Cooling
Cool down the mold that is already heated. During the cooling process, the mold shall
maintain the rotatory state. One of the following cooling modes, or a combination of
several cooling modes may be adopted for cooling: natural cooling, water mist cooling
or water spray cooling. During the cooling process, the difference between the air
temperature in the mold and the external surface temperature of the mold is requested
not to exceed 40 °C. When the external surface temperature of the shell decreases to
50 °C ~ 80 °C, stop the rotation of the shell.
3.3.2.1.4 Demolding and post-processing
After the cooling is completed, disassemble the plastics vessel. Adopt vibration method
to eliminate the internal stress of the plastics vessel.
3.3.2.2 Procedure evaluation
Procedure evaluation shall at least include the items listed in Table 1. The various item
indexes shall comply with the designed value and the stipulations in GB/T 35974.2.
3.3.3 Extrusion
3.3.3.1 Methods
3.3.3.1.1 Plasticization
Extrusion plasticization shall adopt the following methods:
a) Dry extrusion: through in-cylinder heating and heat generation by mechanical
screw’s rotary shearing, plastics that enter the extruder’s cylinder would reach
the plastics melt temperature. In accordance with the differences of materials,
determine corresponding procedure parameters, such as plasticization
temperature and shear torque force.
b) Wet extrusion: adopt an organic solvent to soften and dissolve plastics. In
accordance with the solvent’s technical parameters, determine procedure
parameters, such as the matching ratio and plasticization time.
3.3.3.1.2 Molding
In accordance with plastics vessel’s shape and dimensions, design a molding mold.
Under mechanical pressure, plasticized plastics enter the mold, fill up the mold cavity.
3.3.3.1.3 Cooling
Adopt the following methods for cooling, so that after cooling, the plastics vessel would
reach relatively stable structure and dimensions:
a) Dry extrusion: adopt one of the following cooling modes, or a combination of
several cooling modes: natural cooling, water mist cooling or water spray
cooling;
b) Wet extrusion: adopt cooling modes like natural curing and heating curing.
3.3.3.1.4 Demolding and post-processing
When plastics vessel’s structure and dimensions become relatively stable in the mold,
disassemble the mold; take out the plastics vessel. In addition, cut off or remove
redundant edges.
3.3.3.2 Procedure evaluation
Procedure evaluation shall at least include the items listed in Table 1. The various item
indexes shall comply with the designed value and the stipulations in GB/T 35974.2.
3.3.4 Extrusion winding
3.3.4.1 Methods
Extrusion winding molding shall be conducted in accordance with the following three
procedures:
a) Cylinder’s extrusion winding molding: select the specifications of mold;
determine the number of winding layers and the length of cylinder. After the
cooling, demold it; make the head flat. It is requested that there shall be no gap
among the layers. The minimum wall thickness shall be not less than the
nominal thickness.
b) Bottom cover (head) installation: hemispherical, ellipsoidal and conical head
may adopt integral injection molding or plate thermo-compression molding. In
the thermo-compression of the head flap plate and top plate butt joint, welded
joints are merely allowed to be in radial and circumferential direction. In
accordance with the drawings, properly handle the grooves of the cylinder’s
joints; adopt extrusion welding equipment for welding.
c) Accessory installation: in the welding of connecting pipe’s Flange and cylinder
body, in accordance with the size of the connecting pipe, select an appropriate
welding mode. Flange bolt holes shall be symmetrically distributed on both
sides of the cylinder’s axis and in mid-span distribution. When there are any
special requirements, they shall be indicated in the drawings.
b) When there are relatively significant changes in structure, materials and
procedures that might influence product performance;
c) When there are significant differences between the result of exit-factory
inspection and the previous type inspection.
5.2.4 Determination
5.2.4.1 Determination of exit-factory inspection
When the result of exit-factory inspection complies with the requirements, products
shall be determined as qualified. If products fail to comply with one or more
requirements, they shall be determined as disqualified. Disqualified products may be
returned for re-fabrication. One re-fabrication is allowed on welded joints. Two re-
fabrications are allowed on other parts. After the re-fabrication, products shall be re-
inspected. If products are still disqualified in the re-inspection, they shall be determined
as disqualified. If there is re-fabrication, the time, the parts and the situation of the re-
fabrication shall be recorded in the quality certificate.
5.2.4.2 Determination of type inspection
When the result of type inspection complies with the requirements stipulated in Table
5, products shall be determined as qualified in type inspection. If products fail to comply
with one or more requirements, they shall be determined as disqualified in type
inspection.
6 Exit-factory Requirements
6.1 Exit-factory Information
6.1.1 Fabrication organizations shall provide exit-factory information to vessels’
purchaser. When there are special requirements towards the usage of vessels, they
shall also provide an instruction manual.
6.1.2 Exit-factory information shall at least include the following content:
a) Vessels’ original design drawings and general completion drawings;
b) Vessels’ documentary quality certificates (including product certificate, product
data sheet and quality certificate);
c) Vessels’ characteristics (including design pressure, maximum allowable
operating pressure, test pressure, design temperature and operating medium);
d) Vessels’ instruction manual.
6.2 Vessel Nameplate
......
 
(Above excerpt was released on 2019-04-27, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT35974.4-2018