Design of safety valves

It’s unclear whether it refers to manufacturing a safety valve or selecting one – I don’t know what to ask

GB 12241—89 (General requirements for safety valves > Key points for the installation and design of safety valves): 1. Safety valves installed on equipment or pipelines should generally be installed vertically; however, in cases where they are located in liquid pipelines, heat exchangers, containers, etc., and where pressure may increase due to thermal expansion after the valve is closed, they can be installed horizontally. 2. The safety valve should be installed as close as possible to the equipment or pipeline it is meant to protect. If an installation at close range is not possible, the pressure drop in the pipeline between the outlet of the equipment to be protected and the inlet of the safety valve must not exceed 3% of the valve’s set pressure value. 3. Safety valves should not be installed at the dead ends of long horizontal pipes, to prevent the accumulation of solid or liquid materials at those ends, which could affect the proper functioning of the safety valve. 4. The safety valve should be installed in a location that is easy to maintain and adjust, with sufficient working space around it. 5. For large-diameter safety valves, consideration should be given to the possibility of lifting them after removal when arranging them; lifting rods should be provided if necessary. 6. Long-radius elbows should be used for the inlet pipeline of the safety valve. 7. The design of the outlet pipeline for safety valves should take into account that the back pressure should not exceed a certain percentage of the valve’s set pressure; for example, for ordinary spring-loaded safety valves, the back pressure should not exceed 10% of the valve’s set pressure. 8. The outlet pipe of the safety valve connected to a closed system should be angled at 45 degrees in the direction of flow of the medium, attached to the top of the pressure relief main, in order to prevent condensate in the main from flowing back into the branch pipes and to reduce the back pressure on the safety valve. 9. The outlet pipe of the safety valve must not form a \"bag shape\"; when the outlet pipe is long, it is advisable to provide a certain slope (except in dry gas systems). 10. When the safety valve discharge pipe vents to the atmosphere, its outlet must not face equipment, platforms, ladders, cables, etc. 11. The discharge pipe of the wet gas pressure relief system should have a \"pouch-like\" accumulation area, and the installation height of the safety valve should be higher than that of the pressure relief system. If the outlet of the safety valve is below the pressure relief main or the discharge pipe, and it is necessary to raise it to connect to the main pipe, a demister should be installed at a location at the lower point that is easily accessible. When a shut-off valve is installed on the outlet pipe of the safety valve, a single-plate gate valve should be used and sealed with lead; the valve stem should be installed horizontally to prevent the valve plate from sliding down in case the pin connecting the valve stem to the valve plate corrodes or loosens. When a safety valve is equipped with a bypass valve, this valve should be sealed with lead

Detailed calculation procedures are provided in Annex 5 of the pressure vessel regulations (design calculations for safety valves and rupture discs) and Appendix B of GB150 (overpressure relief devices).