- What is the main function of a hydrogen gas pressure regulator?
- What types of hydrogen pressure regulator exist?
- What is the distinction between a regulator vs. a hydrogen pressure sensor, pressure transmitter and other pressure values?
- Which globally required certifications exist for hydrogen pressure regulators to be used in hydrogen fuel cell applications?
- Why are hydrogen pressure regulators for fuel cells so important?
- What are the key performance criteria of hydrogen pressure regulator?
- Which are the key interfaces to other components in a hydrogen system?
- Is the material used important, and if yes, why?
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What is the main function of a hydrogen gas pressure regulator?
The fuel cell requires a hydrogen pressure regulator with a range of features to provide accurate and stable control under varying operating conditions. Without the protection of a high-quality pressure regulator, pressure spikes can have potentially devastating consequences on the fuel cell.
Controlling hydrogen pressure in fuel cell systems is of key importance in the implementation and proliferation of hydrogen fuel cell technology, therefore furthering the overall achievement of global economic sustainability.
What types of hydrogen pressure regulator exist?
While functional requirements are often very specific, a general distinction between low pressure hydrogen regulator designs and the more widely used high pressure hydrogen regulator is prevalent in the industry.
But different hydrogen applications require different solutions, so a growing range of options have already been developed to keep pace with demand!
Pressure regulators can be categorised into two basic groups:
- forward-reducing hydrogen pressure regulator
- hydrogen back-pressure regulator
Forward-reducing regulators reduce high inlet pressures down to lower outlet pressures and, conversely, a back-pressure regulator is designed specifically to control inlet pressures.
Within those two categories, there are then also numerous features which differentiate hydrogen pressure regulators from one another.
Hydrogen line pressure regulators maintain a constant working pressure in the system, while piston-sensed pressure regulators convert inputs into pressure adaptations within the system.
Lightweight materials such as aluminum may be used to minimise the regulator’s weight for applications where this is crucial to performance. Two-stage regulators are helpful when extremely accurate pressure control is required. There are also circumstances where flow rates are important, for example in hydrogen refueling stations, to minimise refuelling times.
What is the distinction between a regulator vs. a hydrogen pressure sensor, pressure transmitter and other pressure values?
Pressure sensors, transmitters etc. all measure the pressure of a system – whereas a hydrogen pressure regulator is a pressure-reducing valve – therefore the main function is to step down a large inlet pressure to a usable line pressure for a fuel cell.
Which globally required certifications exist for hydrogen pressure regulators to be used in hydrogen fuel cell applications?
TPED 2010/35/EU certification is required for applications involving the transportation of pressure equipment including gas cylinders and their valves, whilst EC79 approval covers the commercial use of hydrogen pressure regulators on hydrogen fuel cell vehicles.
Why are hydrogen pressure regulators for fuel cells so important?
Without the regulator, the high-pressure hydrogen tank would release the hydrogen at pressures which would damage the fuel cell beyond repair. To go a step further, the regulator must reliably and repeatedly provide very stable outlet pressures to protect the fuel cell from pressure spikes – these can have an equally devastating consequences on the fuel cell.
What are the key performance criteria of hydrogen pressure regulator?
Fuel cells are very sensitive devices, where the pressure requirements for consumption are finite. Often the set pressure cannot vary beyond +/- 1 bar, so the hydrogen pressure regulator must be accurate enough to maintain a steady set pressure, which is the reason why balanced designs have proven successful in hydrogen applications.
Additionally, hydrogen refueling stations often have performance criteria relating to how quickly one can fuel a vehicle, for the convenience of the customer. Flow rate demands are currently 60 g/s, but future demands will be 120 g/s and even 300 g/s!
This will be achieved by new designs set to become commercially available in due time, such as the redesigned Pressure Tech RF1034 hydrogen pressure regulator. The specifications for this regulator include a CV of 0.5 to cope with the demand for quicker refueling, whilst adhering to the required standards.
Which are the key interfaces to other components in a hydrogen system?
The interfaces of hydrogen pressure regulators vary by application. Regulators such as the Pressure Tech LW351 mount directly onto a H2 bottle, while the CV414 cylinder valve is mounted in between due to the benefits for refilling and safety. Alternatively (and more commonly), the regulators will be piped up in a line using fittings which connect to our NPT, SAE, MP threads featured on these regulators. In a normal fuel cell system, the hydrogen cylinder will be upstream and a fuel cell downstream of the regulator.
Is the material used important, and if yes, why?
Yes certainly. Stainless Steel or Aluminium are used for applications below 690 bar. Aluminium would be utilised where weight is a driving factor for the customer, since it is a less dense metal. Above 690 bar, 660 Stainless Steel is the material of choice, due to the improved mechanical properties at higher pressures. Material selection is even more important for hydrogen, since metals such as 17-4 PH Stainless Steel cannot be used due to the risk of hydrogen embrittlement.
Content contributed by Pressure Tech
Pressure Tech is a UK manufacturer and was established in 2000 by owner Steve Yorke-Robinson. We are now renowned world over for the manufacture of high-quality pressure regulators. In 2017 we started work on expanding our product range into the Hydrogen Fuel Cell market with the development of our lightweight LW351 pressure regulator for UAV H2FC drones. We have since added an EC79 approved regulator for Hydrogen buses and trucks, a TPED approved cylinder valve for Hydrogen gas cylinders and a full range of pressure regulators for material handling applications, passenger vehicles and refuelling stations.
Last update: 15.1.2023