Blowout valves and safety valves

http://bbs.hcbbs.com/viewthread.php?tid=414857&extra=page%3D1&frombbs=1 I uploaded some technical materials here; take a look.

Safety valves are suitable for equipment handling relatively clean gases such as air and water vapor, and should not be used in equipment dealing with toxic substances； It must not be used in equipment where intense chemical reactions may occur, leading to a sudden increase in pressure. Blowout valves are suitable for containers where rapid pressure increases may occur due to chemical reactions, or where the medium is highly toxic; they are not suitable for liquefied gas storage tanks. It is also not suitable for containers with large pressure fluctuations, i.e., those that experience frequent overpressures. Safety valves equipped with rupture disks are generally used in containers holding corrosive liquefied gases, or highly toxic and rare gases. Due to the hysteresis effect of the safety valve in the device, it cannot be used in reaction vessels where the pressure rise rate is extremely high.

First, from the perspective of the protected system, some basic requirements and installation principles for selecting safety valves will be explained; that is, where safety valves should be installed and under what operating conditions they are not suitable for use. 1. Principles for installing safety valves The basic principle for installing safety valves is that they are suitable for use with clean, particle-free fluids of low viscosity. In situations where particles are present and a safety valve must still be installed, it is necessary to consider adding a filtering device before the safety valve; however, it is important to ensure that this filtering device does not affect the performance of the safety valve. In locations where a safety relief device must be installed but where safety valves are not suitable, burst discs should be used, or safety valves in series with burst discs. 2. Safety valves shall be installed on containers that fall under any of the following conditions: ① The pressurized material in the container originates from a source where no safety valve is available ； ②Containers and pipes with a design pressure lower than the pressure at the source of pressure ； ③Outlet pipes for positive displacement pumps and compressors ； ④Containers where overpressure is generated due to the accumulation of non-condensable gases ； ⑤If a shut-off valve or control valve is installed on the outlet pipeline of the heating furnace, a safety valve should be installed upstream of such valve ； ⑥Overpressure areas caused by process accidents, automatic control failures, power supply failures, and utility system failures ； ⑦The area where the liquid undergoes thermal expansion due to the closed valves at both ends ； ⑧Steam outlet pipe of the condensing turbine ； ⑨In some cases, due to leakage in the pump outlet check valve, a safety valve is installed on the pump’s inlet pipeline ； ⑩Areas with frequent overpressure and those with large temperature fluctuations. 3. Safety valves are not suitable for use in the following situations; instead, rupture disc devices should be installed: ① Situations where system pressure may rise rapidly, such as in cases of chemical explosions ； ②The discharge medium contains particles, is prone to precipitation, crystallization, and polymerization, and has a high viscosity ； ③The medium being discharged is highly corrosive, and the cost of using safety valves is too high ； ④The working pressure is either very low or very high, and in such cases it is relatively difficult to manufacture safety valves ； ⑤A larger discharge area is required ； ⑥The system temperature is low, which affects the performance of the safety valve ； 4. Safety valves and burst discs should be used in combination in the following situations: ① When the process medium is extremely valuable or highly toxic, and no leakage is allowed during operation, the safety valve and burst disc are used in series or only the burst disc is used ； ②To increase the discharge area under abnormal conditions (such as fires), its use in parallel with a burst disc must be considered.

Safety valves are used for anything that is toxic or harmful to clean production, as they allow release of contents into a sealed environment in case of abnormalities. Blown films, on the other hand, are typically used in reaction vessels or with substances that are not harmful, and they generally do not cause pollution to the environment; their use is determined primarily by the properties of the substance and safety considerations

I have not yet seen safety valves equipped with rupture disks. I only know that when our rupture disks and safety valves are installed on pressure vessels together, it provides dual protection

I. Scope of use for shrapnel: 1. The medium inside the container tends to crystallize or polymerize； 2. Chemical reactions make it difficult to control safety valves ； 3. The medium is extremely or highly hazardous, making it difficult for safety valves to meet the requirements ； 4. Ultra-high pressure, with an extremely low possibility of release. II. The rupture disc can be installed at the inlet or the outlet of the safety valve. When the pressure stabilized, neither the series-connected safety valve nor the burst disc activated ； In the event of overpressure, if the set pressure of the safety valve is lower than the burst pressure of the rupture disc, it will activate first to release pressure ； If the overpressure remains severe at this point, or if the pressure relief rate of the safety valve is insufficient, the rupture disc will activate and the pressure will drop rapidly ； If the pressure inside the container returns to normal at this point, the safety valve reseats, achieving a sealed condition. Using this time, the blast disc can be replaced online.

The explanations and calculations are provided in Appendix B of GB150-89

If the medium emitted is toxic and harmful, the two are generally used in series

The most basic function of a series-connected rupture disc is to provide isolation and protection for the safety valve; it is not about using a safety valve equipped with a rupture disc, but rather about using a rupture disc to isolate the safety valve – they are two separate products.

The description in \"Rivers Flowing Upward\" is quite detailed; let’s add a bit more: When are shrapnel not suitable? Blowout discs are not suitable for applications with frequent overpressure. When should rupture discs not be used? Places with large temperature fluctuations.