Is it necessary to install a check valve on the pipeline leading into the torch main pipe?
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Do all pipes leading into the torch main pipe need check valves? Under what circumstances is it necessary to add it? Under what circumstances can it be omitted? I earnestly ask all the experts for their guidance!
The devices and systems I have worked on did not have such features; the reason is that the back pressure in the system’s piping is very stable, so it’s impossible for pressure to rise above the discharge pressure of the device
I’ve never heard of check valves; it is recommended to consult the standard SH3009 on the design of fuel gas systems and flammable gas emission systems in petrochemical enterprises
SH3009, I’ve checked it – indeed, there are no requirements. Some of the factory PID units have them, while some do not have check valves. Are there any regulations regarding this?
What device’s torch line? Generally, the backpressure of the flare is designed to ensure overall balance across the plant; however, it is possible that a newly built facility may have an excessively high emission pressure, in which case a separate flare is usually installed. I’m not quite sure what the purpose of a check valve is Is it to prevent an increase in the back pressure of this device when other devices release pressure? But even with a check valve, the back pressure in the flare header is still high; why can’t this device discharge? It might not be appropriate to use a check valve, and such valves also don’t require annual inspection. What if they get rusted shut and can’t be opened? That would be a serious problem Please, the original poster, share the details; I’m very interested.
Almost none of the devices I’ve seen are equipped with check valves. If additional devices are added, it is likely in situations where two sets of devices share one flare system; the high-pressure device has a large amount of gas to be released, while the other device operates at low pressure. In such cases, installing check valves can prevent backflow. Previously, the gas separation unit and the catalytic unit shared a single flare line; when the gas separation unit was depressurized, gas leaked into the catalytic unit, causing overpressure and nearly leading to an accident. Later, they went their separate ways without a check valve being installed
A check valve must be installed when the nitrogen pipeline is connected to the flare header to prevent process gases from entering the nitrogen network. No check valve is required to connect process gas to the flare line
Basically, it doesn’t need to be added. But you need to decide based on the process diagrams and PID diagrams; if they are available, then you need to take those into consideration when doing the piping work. There is also a lot of expertise involved in the design phase.
First of all, thank you all for your enthusiastic remarks! Regarding the question raised by Haiyou from the sixth floor, I carefully examined the PID diagrams and found that check valves are present in all cases except those after the PSV and control valves. For clarification, this device was designed by a South Korean company, complies with ASME standards, and has only one flare. The designer explained that this is to prevent backflow of the medium caused by the release of other devices, which could affect the operation of this unit. Personally, I think: it makes some sense ； Yet there are no standards to follow. Please feel free to share your thoughts!
Basically, it doesn’t need to be added. Except for the requirements regarding PID.