The answer could be no devices at all, just a TPRD, just a PRD, or both. It depends on the potential overpressure scenarios identified during a hazard assessment. TPRDs typically are not used on ASME pressure vessels since they are not ASME compliant devices and since system siting provides protection from engulfing fires. However, TPRDs are frequently used in portable applications for…
It depends on the service. Variables include disk design, corrosion resistance, number of cycles, and how to close the operating pressure is to the rupture disc set pressure. One approach is to ask the manufacturer for their recommendation. Typical practice for U.S. Department of Transportation vessels and discs is to replace them at the tube requalification (i.e., every 5 to 10 years in the U…
Based on the question, it’s not clear if the reference to stress corrosion cracking (SCC) has been proven or is only suspected. It can be difficult to identify the nature of the cracks (SCC vs H2 embrittlement without analysis and microscopy). In addition, the question does not mention that the cylinders contain hydrogen gas, but it’s assumed since it was submitted to the Panel.
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This is a fairly common arrangement and can be acceptable if properly designed. Some considerations:
Refineries and large petrochemical plants will frequently have flare systems for H2 and other flammable materials. One of the major purposes of these flare systems is to prevent a large unignited cloud from forming since that could result in an explosion hazard and large deflagration overpressures if there is a delayed ignition. However, these are in large facilities which have the…
As is mentioned in the question, it should always be assumed that vent stack fires will occur. The vent stack must be designed to withstand a possible deflagration and the heat from a continuous vent stack fire. The stack should also have sufficient height and be located such that thermal radiation is safe for surrounding personnel, equipment, and buildings. The codes and standards have…
It is not, but the vent stack design outlet is based on radiant heat exposure.
An annual inspection of safety devices is recommended. Testing requirements will be based on the type of device and a quantified risk analysis. Typical replacement or function testing of relief valves is between 5 and 10 years depending on the application within the industrial gas industry. Rupture discs are not tested but are frequently replaced on an interval based on manufacturer…
A pressure gauge is not usually provided, as one set of devices (safety valve and rupture disc) is always online by design. If the diverter valve connecting the two sets of relief devices is in the center position, both sets are online although depending upon the design of the diverter valve, it might not allow full flow in either direction. For the secondary stack with a rupture disc and a…
The pressure regulator controls the liquid flow from the tank to the pressure build (PB) vaporizer. As the tank pressure falls, the pressure regulator opens. When the set pressure of the regulator is reached, then the regulator closes. The pressure build circuit depends largely on the required use pressure and the system house-line pressure drop, which is driven by peak flow rate, pressure,…
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