GB/T 20801.6-2020Pressure piping code - Industrial piping - Part 6: Safeguarding (English PDF)

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).

3.2 Safety relief device

The device that is started by the static pressure of the inlet or the static pressure difference between the inlet and outlet to release the fluid to prevent the pressure in the system from exceeding the predetermined safe value in the case of non-fire or fire accidents.

3.3 Safety valve

The valve that is controlled by spring action or pilot valves. When the static pressure at the inlet (static pressure difference between the inlet and outlet for ordinary valves) exceeds the set pressure, the valve opens to release the fluid to prevent the pressure in the system from exceeding the predetermined safe value. When the pressure drops to the re-seating pressure, the valve can be

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.

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.

4.1.4 The independent pressure system shall be equipped with one or more

parallel safety relief devices at appropriate locations.

4.1.5 The determination of relevant pressures of the safety relief device shall

meet the following requirements.

4.2 Determination of required relief capacity and minimum relief area.

4.2.1 Under typical overpressure conditions, the required relief capacity shall

be determined according to the criteria in Table 2.

4.3 Setting of inlet and outlet valves and piping of safety relief devices

4.3.1 Block valves should not be installed at the inlet and outlet of the safety

relief device. When it is necessary to install due to the inspection and maintenance of the safety relief device, the following requirements shall be met.

4.3.2 The inlet piping of the safety relief device shall meet the following

requirements.

4.3.3 The outlet piping of the safety relief device shall meet the following

requirements.

4.4 Selection of safety relief device

4.4.1 For the safety relief device, the relief medium, the process overpressure

conditions and the performance of the safety relief device shall be considered when selecting the appropriate form of the safety relief device. See Appendix C. The selection of the safety relief device shall comply with the relevant standards.

4.4.2 Safety relief device products shall comply with the relevant standards

such as TSG ZF001, TSG ZF003 and GB/T 12242.

5.1 Application of flame arrester

5.1.1 Flame arrestor products and applications shall comply with relevant

standards such as ISO 16852 and PD CEN/TR 16793.

5.1.2 In the process equipment, there are a large number of non-electrical

equipment and piping systems in potentially explosive environments. Flame arrestor is the main safety protection device for explosion-proof of non-electrical equipment. It has the function of preventing explosion, preventing explosion from spreading through piping, and preventing deflagration from developing into detonation. Refer to Appendix D for the types and selection of flame arresters.

5.2 Flame arrestor settings

The following equipment and piping systems shall be equipped with flame arresters.

5.3 MESG and explosion group of combustible gas and vapour

According to MESG, combustible gas and vapour are divided into 7 explosion groups, as shown in Table 3.The gap of the flame arrestor shall be smaller than the MESG of combustible gas and vapour.

6.1 Fire emergency block valve

6.1.1 Fire emergency block valves should be installed at the exit end of key

storage tanks such as large-scale, liquefied gas and acute toxicity category 1 and category 2 chemicals.

6.2 Mechanical interlocking device

6.2.1 Mechanical interlocking is a high-integrity safety protection device that

prevents major accidents caused by human error. Products shall comply with relevant standards such as GB/T 15706.

6.2.2 When operational errors in operation and maintenance may cause major

accidents, mechanical interlocking devices should be installed.

7.1 General provisions

When taking safety protection measures, the following factors shall be considered.

7.2 Safety protection in factory layout

7.2.1 The layout of equipment in the open air shall meet the following

requirements.

7.2.2 Flammable and toxic fluids shall be discharged into a closed system, and

shall not be directly discharged into sewers and the atmosphere.

7.2.3 Combustible gas whose density is greater than that of ambient air shall

be discharged into the flare system; combustible gas whose density is lower than that of ambient air can be discharged into the atmosphere if a torch is not allowed to be set up and it meets sanitary standards.

7.2.4 The vent pipe opening of the combustible gas piping and the discharge

position of the safety relief device shall meet the requirements of GB 50160,

GB 50984 and GB 31571.

7.2.5 The clearance height of overhead piping through roads, railways, sidewalks, etc., and the horizontal distance from the edge of the piping frame of the outer piping gallery to the building or other facilities shall meet the requirements of GB 50160, GB 50016 and GB 50984.The clear crossing distance between piping and high-voltage power lines shall comply with the relevant standards for overhead lines.

7.2.6 The piping located above the passages, roads and railways shall not be

installed with valves, flanges, threaded joints and compensators with fillers and other piping components that may leak.

7.2.7 No GC1 piping shall be arranged in the passable pipe trench.

7.3 Safety protection in production management

7.4 Safety protection facilities and measures

7.4.1 The fire-fighting system and sprinkler facilities shall include fire-proof

structures such as fire walls and explosion-proof walls of buildings, ventilation devices, telemetry and remote-control devices that are removed with toxic, corrosive or flammable vapors, and storage or recovery devices, facilities for emergency treatment of hazardous materials, such as torches or incinerators.

7.4.2 Protective covers shall be provided at the brittle material piping system or

flanges, joints, valve covers, instruments or sight glasses, so as to limit and reduce the hazard degree of leakage.

7.4.3 When the "water hammer" phenomenon may occur in piping filled with

liquid, or "steam hammer" may occur in piping with compressible fluid, appropriate protective measures should be taken based on the analysis results of fluid mechanics.

7.4.7 Necessary protective masks, gas masks, emergency breathing systems, special medicines, portable combustible and toxic gas detection and alarm systems and other sanitary safety equipment shall be installed. Emergency showers and eyewash shall be installed near discharge points or leaks that may cause accidental human injury.

7.4.8 For radiant fluid piping, shielding protection and automatic alarm systems

shall be provided, and special masks, gloves and protective clothing shall be equipped.

7.4.9 Electrostatic grounding measures shall be taken for all piping systems

that may generate static electricity hazards in explosion and fire hazardous locations. For example, it can be grounded through the grounding grid of equipment, piping and civil structures, and flange jumper. Other anti-static requirements shall meet the requirements of GB 12158.

7.4.10 The blind plate setting shall meet the following requirements.

7.4.11 When vapour, air, nitrogen and other public engineering piping are

connected with GC1 and GC2 piping, the following requirements shall be met.