GB/T 20801.6-2020 English PDF (GBT20801.6-2020)

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GB/T 20801.6-2020: Pressure piping code - Industrial piping - Part 6: Safeguarding
GB/T 20801.6-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 23.040
J 74
Replacing GB/T 20801.6-2006
Pressure piping code - Industrial piping - Part 6:
Safeguarding
ISSUED ON: NOVEMBER 19, 2020
IMPLEMENTED ON: JUNE 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 6 
4 Safety relief device ... 11 
5 Flame arrester ... 19 
6 Other safety protection devices ... 20 
7 Safety protection ... 21 
Appendix A (Informative) Safety protection layer analysis ... 25 
Appendix B (Informative) Calculation of safety relief device ... 27 
Appendix C (Informative) Selection of safety relief device ... 39 
Appendix D (Informative) Types and selection of flame arresters ... 42 
Appendix E (Informative) MESG and explosion group of combustible gas and
vapour ... 46 
References ... 49 
Pressure piping code - Industrial piping - Part 6:
Safeguarding
1 Scope
This Part of GB/T 20801 specifies the basic requirements for safety protection
devices, such as safety relief devices, flame arresters, fire emergency block
valves and mechanical interlocking devices, of the pressure piping system, and
safety protection.
For other safety protection requirements, which are not specified in this Part,
refer to other parts of GB/T 20801 and the provisions of relevant national
regulations, standards and specifications.
This Part applies to the safety protection of pressure piping systems that are
defined by the scope of GB/T 20801.1.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB 12158, General guideline for preventing electrostatic accidents
GB/T 12242, Performance test code - Pressure relief devices
GB/T 15605, Guide for pressure venting of dust explosions
GB/T 15706, Safety of machinery - General principles for design - Risk
assessment and risk reduction
GB/T 20801.1-2020, Pressure piping code - Industrial piping - Part 1:
General
GB/T 20801.2-2020, Pressure piping code - Industrial piping - Part 2:
Materials
GB/T 20801.3-2020, Pressure piping code - Industrial piping - Part 3: Design
and calculation
GB/T 20801.4-2020, Pressure piping code - Industrial piping - Part 4:
Fabrication and assembly
GB/T 20801.5-2020, Pressure piping code - Industrial piping - Part 5:
Inspection and testing
GB 31571, Emission standard of pollutants for petroleum chemistry industry
GB 50016, Code for fire protection design of buildings
GB 50057, Code for design protection of structures against lightning
GB 50160, Fire Prevention Code of Petrochemical Enterprise Design
GB 50984, Code for plant layout design of petrochemical enterprises
TSG ZF001, Safety Technical Supervision Regulations for Safety Valves
TSG ZF003, Safety Technical Supervision Regulations for Bursting Disc
Devices
ISO 16852, Flame arresters - Performance requirements, test methods and
limits for use
ISO 23251, Petroleum, petrochemical and natural gas industries - Pressure-
relieving and depressuring systems
NFPA 68, Standard on explosion protection by deflagration venting
PD CEN/TR 16793, Guide for the selection, application and use of flame
arresters
3 Terms and definitions
Terms and definitions determined by GB/T 20801.1-2020, GB/T 20801.2-2020,
GB/T 20801.3-2020, GB/T 20801.4-2020, GB/T 20801.5-2020, and the
following ones are applicable to this document.
3.1
Safety protection device
The mechanical (physical) protection devices that function in the event of failure
of automatic control instruments and manual intervention according to the
analysis of the safety protection layer (see Appendix A).
Note: The safety protection devices, including safety relief devices, flame
arresters, fire emergency block valves and mechanical interlocking
devices, are the last barrier to prevent accidents or reduce accident
losses.
The block valve that can be automatically closed under fire conditions when
there is no manual intervention or external power (electricity, gas, liquid) supply;
it has the properties of fire resistance, anti-static, high sealing and impact
resistance.
4 Safety relief device
4.1 General provisions
4.1.1 The safety relief device shall prevent overpressure accidents in any part
of the independent pressure system. Designers should use various process
hazard assessment (PHA) methods to study all possible overpressure
conditions in the specific process. When identifying various overpressure
conditions, the following guidelines shall be followed:
a) Any single event is credible;
b) Two related events occurring in sequence are credible;
c) Two or more unrelated independent events occurring at the same time are
not credible.
4.1.2 Automatic control instruments and alarm interlocking devices shall not
replace safety relief devices as the system's overpressure protection facilities.
When emissions are not allowed or safety relief devices cannot be installed, all
overpressure conditions can be evaluated and analyzed through process
hazard sources, and a system design method, i.e., intrinsic safety design or
high integrity protection system (HIPS), can be used to eliminate the cause of
system overpressure or perform system overpressure protection.
4.1.3 Equipment or piping systems that meet the following conditions shall be
equipped with safety relief devices:
a) Equipment and piping systems where the design pressure is less than the
pressure of the external pressure source, and the outlet may be shut off
or blocked;
b) The outlet piping system of positive displacement pumps and positive
displacement compressors whose outlets may be shut off;
c) The distillation tower overhead gas-phase piping system of overpressure
caused by the interruption of cooling water or reflux and excessive heat
input from the reboiler;
d) Equipment and piping systems where non-condensable gas accumulates
to generate overpressure;
e) The upstream piping system of the block valve or the regulating valve in
the outlet piping of the heating furnace;
f) The piping system that produces thermal expansion or gasification due to
ambient temperature, sunlight radiation or heat tracing after the block
valves at both ends are closed;
g) The piping system on the upstream of the block valve at the reactor outlet
where the cooling or stirring fails, the catalyzed impurities enter, and the
reaction inhibitor is interrupted, which causes the exothermic reaction to
run out of control;
h) The vapour outlet piping system of the condensing vapour turbine;
i) The outlet piping system of gas generating equipment such as vapour
generators;
j) The outlet piping system of low boiling point liquid (such as liquefied gas)
containers;
k) The outlet piping system on the low-pressure side of the heat exchanger
where overpressure may be caused due to pipe rupture or leakage;
l) The outlet piping system of the air cooler tube pass where the fan failure
causes the cooling load to drop;
m) The outlet piping system of equipment and containers that may be
exposed to external fire....