It depends on the facility and risk assessment, but generally multiple pressure and temperatures to one vent stack is not the best practice unless all are similar in pressure and temperature, and the streams have compatible composition and flow rate. Care must also be taken to prevent reverse flow and misdirected flow between portions of the system. Additionally, one vent stack can become a…

Requirements for local jurisdictions vary, so the AHJ should be consulted, but NFPA 2:2023, Hydrogen Technologies Code, Chapter 13 has requirements for installation of hydrogen generators up to 100 kg H2/h. Section 13.3.1 General says permitted water electrolysis systems are to be listed to ISO 22734:2019, Hydrogen Generators Using Water Electrolysis - Industrial, Commercial, and Residential…

Cylinders are required to be tested periodically to verify structural integrity. The most common test method is hydrotesting, which means water is the most likely impurity that solidified in the inlets. Drying the tanks is normally a requirement after performing a hydrotest. In the USA, CFR 49 CFR § 180.209 applies: https://www.law.…

The end use of hydrogen usually drives the cleaning for initial construction. 

1. When the hydrogen is used for combustion and many industrial applications, normal care during construction and leak testing is usually adequate.
2. When the hydrogen needs to be very pure, as is the case for PEM fuel cell applications, more…

Catalytic recombiners are effective at preventing flammable hydrogen mixtures and also sometimes useful to monitor hydrogen concentrations through heat evolution when an oxidizer is present. Careful considerations must be made when integrating these elements into a design, so that they do not become a source ignition (and/or flame arrestors prevent propagation of a flame front) and the…

Typically, the inner vessel material used is 304 SS and the outer vessel is a combination of 304 SS and carbon steel depending on location. 316 SS or 316L material can be used, but due to higher cost and lower strength, are typically only used for higher purity systems. Nearly all tanks manufactured today use various forms of vacuum jacketed multilayer insulation for best performance. Older…

The most common means to warm liquid or cold gaseous hydrogen is the use of ambient air vaporizers using ambient atmospheric. Other means can be through the use of electric heat or process waste heat.  

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,…

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…

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…