The SRV orientation is critical for many reasons. Many of these are:
The ASME BPV Code, and other Codes by reference, require less than back pressure of 10% of device set pressure from the release flowrate for proper operation of reclosing relief devices such as relief valves. Backpressure from non-reclosing or non-ASME devices may be higher so an analysis is required. It’s not enough to assume the vent system need only be designed for 10% of the set pressure.…
Several programs can predict this such as HyRAM or PHAST. The inputs are critical to a safe
answer.
This is not a simple answer due to the many types of flame lengths and flame orientations due to pressure and direction. NFPA 2 recommends that vent systems should be designed so that if the safety relief valve is relieving at capacity the radiative heat felt by an individual at grade…
Vent stacks and building ventilation systems are different and should be analyzed/designed differently. NFPA 2 has different location requirements for vent stack and ventilation system outlets. There are code requirements for elevation, distances from exposures, and between exposures.
There are no specific regulatory or code requirements for vent system separation distances. These…
The vent system should be designed for the temperature at which it operates (ambient for GH2 and Cryogenic for LH2). The outlet of the vent system should be designed for a fire to ensure the mechanical integrity of the vent system.
The supports should also be designed for these temperatures and the associated expansion and contraction.
It should be ensured that moisture…
Refer to the white paper completed by the HSP for LH2. The same criteria should be applied to
a vent system. See below.
H2Tools Document Library: White_Paper-Qualified_Individuals_for_Liquid_Hydrogen
Similar qualifications for vent system design include:
Design of vent header lines is critical to the safety of the system. From a process perspective, the pipe design must be sufficient to withstand back pressure, thrust forces from the flow, and must be of a sufficient size to not create a restriction that prevents proper flow or activation of the devices. Per ASME BPV Code requirements, backpressure should be limited to no more than 10% of the…
AICHE ELA253 CHS ” Introduction to Hydrogen Safety for First Responders” is a good reference and discusses both LH2 and GH2. LH2 fires are very unusual. LH2 releases usually are GH2 so the fires at either ambient for low flow or the GH2 is a cryo temperature for high flow. Fires from LH2 tanks ignite less frequently than GH2 high-velocity releases. The colder the gas the less potential for…
At NASA Cape Canaveral, they used a natural gas line connected to the vent stack outlet with a thermal sensor to make sure the pilot was lit. They may also have had a sensor to ensure the H2 fire was lit. In cases where substantial quantities of unused hydrogen is vented and the timing and amount of the flow rate is known and controlled, flaring might be useful. NASA guidelines stipulate that…
No, in nearly all cases, a deluge system is not needed. The proper sizing of relief devices using documents such as CGA S1.3 will ensure that they are of sufficient size to address worst case scenarios. In addition, if the system has been sited per separation distances from exposures in accordance with documents such as NFPA 2, then there should not be a significant risk of fire
exposure.…
We are the leaders in the building industries and factories. We're word wide. We never give up on the challenges.