There is a huge pressure difference between rupture disks and safety valves

First, it’s necessary to understand the functions of the two of them. If the difference isn’t significant, it’s possible that both will launch at the same time:D. The rupture disc can be considered a one-time-use item

Why are the burst disc and safety valve connected in series, with the burst disc in front and the safety valve behind, and why is the set pressure of the safety valve lower than the designed burst pressure of the burst disc? For what reason? What is the reason for this design? Please reply, thank you

Installing a safety valve in this way is completely pointless; if the pressure of the rupture disc exceeds the designed pressure, it still constitutes an unsuitable installation method.

If the design pressure is 2930 kPa or higher, then this arrangement is acceptable; however, the safety valve is unnecessary； If the design pressure is below 2930 kPa, then this installation is not acceptable ； If the design pressure is 2068 kPa or higher, this arrangement is not acceptable; a parallel configuration, on the other hand, is feasible.

The numerical deviation between the safety valve and the burst disc is 1.1 times, meeting the maximum requirement for parallel safety valves.

Blowout disc: It uses a bursting element that breaks under high pressure to release gas. It has good sealing performance and will not leak when the container is operating normally ； The rupture speed of the burst disc is high, so the pressure relief reaction is rapid ； After the pressure relief action is completed, the blasting element can no longer be used, and the container must be forced to stop operating once it experiences overpressure. Blasting elements are under high stress for extended periods, making them prone to premature failure due to fatigue; as a result, their lifespan is short and they need to be replaced regularly. Safety valve: It reduces the excessive pressure inside by automatically opening to release gas. It only releases the pressure in the vessel that is above the specified level; once the pressure inside the vessel drops to the normal operating level, it shuts off automatically, thus preventing waste and production disruptions that would occur if all the gas had to be released. The sealing performance is relatively poor (compared to rupture discs); even safety valves that meet the specifications may still experience slight leakage under normal operating pressure ； Due to the inertia of springs and similar components, there is a delay in the opening of the valve, resulting in a slow pressure relief response. This format is commonly used in applications where high sealing and corrosion resistance are required, as well as in situations with sticky media. The rupture disc serves to protect the safety valve, while the safety valve allows the container to continue operating; this also helps to reduce losses of process material resulting from the rupture of the rupture disc. At this point, the calibrated burst pressure of the rupture disc is the same as the set pressure of the safety valve.

It seems that the rupture disc is used to protect the pipelines or equipment at the front end, while the safety valve is used to protect the collection equipment or pipelines in case of a rupture (the equipment on the PI(F) branch)

Generally, the burst pressure of a bursting disc should be the same as the set pressure of a safety valve

The purpose of series connection is that the rupture disc, placed in front of the safety valve, serves to protect it by preventing impurities in the fluid flowing through the pipeline from accumulating or crystallizing in front of the safety valve, thereby ensuring that the safety valve can activate in a timely manner and fulfill its protective function； After pressure release is complete, the safety valve can return to its original position; this will not happen if only a burst disc is installed ； Regarding pressure issues, in my opinion, the premature release of pressure by the burst disc means that the set pressure of the safety valve is not reached, and thus it fails to serve its purpose of protecting the safety valve ；

If the design pressure is greater than 2930 kPa, the rupture disc will burst when overpressure occurs, after which the safety valve activates; once the pressure returns to the operating level, the safety valve closes. That makes sense. The main reasons for installing a rupture disc in front of the safety valve are: 1. To protect the safety valve from corrosive substances (since safety valves are more expensive than rupture discs), and 2. To provide dual protection.