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Choosing a Pressure Gauge for Hydrogen Applications

Hydrogen is one of the fastest-growing alternative energy resources used today. Your pressure gauge is a vital component of your equipment or system. Many of these hydrogen applications have processes that can cause hydrogen ion diffusion that can damage your instruments.

When properly specified, your system will need to operate safely and to expected performance levels over the design life of the system or equipment, but only if you have the right pressure gauge for your equipment’s application.

The wrong pressure gauge can result in potential equipment damage, worker injury or out-of-specification measurements. So, how can you ensure you choose the right one for a hydrogen application?

To ensure you have the best pressure gauge for the job, there are a few things that you need to consider.

Hydrogen Explosions

Hydrogen, in sufficient concentrations and quantities, can create overpressure as a result of unignited releases of pressurized gas or an ignited cloud of released flammable gas. In both cases, the overpressure generated can be harmful, causing direct hazards from the overpressure and indirect hazards from building damage or flying debris.

Overpressure from Unignited Releases

As with any cryogenic fluid, if liquid hydrogen is warmed and vaporized into a gaseous state, it occupies significantly more space. From its liquid phase to its gas phase, hydrogen expands to about 850 times its size. Therefore, a confining vessel, pipeline, or sealed space could easily become over-pressurized during a liquid to gas phase change.

If a pressurized gas container is heated, the gas will expand even further. If the pressure exceeds the container design rating, mechanical failure will occur.

Pressure-relief devices (PRDs), such as rupture disks or relief valves, should be installed and vented to a safe location to prevent overpressure.

Overpressure from Ignited Releases

Beyond overpressure associated with the stored gas, flammable gases like hydrogen can burn. If a cloud of hydrogen gas is ignited, the rapid combustion (i.e., explosion) can create overpressure.

As with gasoline vapors at a fueling station, certain precautions must be taken to limit the number of ignition sources (such as lit cigarettes or unclassified electrical equipment) in areas where a release of hydrogen could form a hazardous cloud with sufficient concentration to create an ignited overpressure. These areas are often referred to as “exclusion zones” or “separation distances.”

Hydrogen Permeation

Hydrogen permeation refers to the penetration of hydrogen ions through the lattice structure of a particular material. This can cause concerns in pressure gauges when selecting internal wetted materials as certain materials can help reduce this problem.

One way to reduce hydrogen permeation is to use a material with a tight lattice structure such as 316L stainless steel or variants of 316 stainless steel. In addition to the lattice structure of a material, hydrogen permeation is also influenced by the pressure of an application. The higher the pressure of the application, the larger the force that is applied to the socket and bourdon tube.

This force stretches the lattice structure of the material, allowing more hydrogen ions to permeate the material. Therefore, you should use a material that not only has a tight lattice structure but is well suited to handle the pressure range of the application.

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Hydrogen Embrittlement

Embrittlement is a phenomenon that causes loss of ductility and, consequently, brittleness in a material. Highly susceptible materials include high-strength steels, titanium and aluminum alloys, and electrolytic tough pitch copper.

Hydrogen embrittlement is also known as hydrogen-induced cracking or hydrogen attack. The mechanisms can be aqueous or gaseous and involve the ingress of hydrogen into the metal, reducing its ductility and load-bearing capacity.

Because hydrogen is such a small atom, it can penetrate the metal through micro flaws in the surface. Once inside, the hydrogen atoms will recombine with others to form hydrogen molecules (H2).

These molecules will bond with other H2 molecules resulting in the bigger hydrogen mass that exerts outward pressure in the flaw. Stress below the yield stress of the susceptible material then causes subsequent cracking and catastrophic brittle failures.

As hydrogen molecules defuse, they create hydrogen ions, which are some of the smallest ions in the world. They can pass through the lattice structure of many metals and into the metal, and then reform as hydrogen molecules.

The absorbed hydrogen molecules create pressure and stress from within the material. This can affect the ductility and strength of the material, ultimately leading to the material cracking.

Make sure you have the right gauge material to prevent embrittlement from impacting the efficiency of your application.

Ashcroft Recommendations

If you want to ensure safe practices for hydrogen applications, use pressure gauges with at least 316/316L stainless steel for pressure ranges up to 20,000 psi.

Ashcroft’s 8008S pressure gauge offers 316 wetted internal materials, laser welded wetted parts, and an option for a 63 mm solid front.

Laser welding is used to reduce the possibility of contamination. Its precision allows less of a chance of deforming or damaging nearby areas to not reduce wall thickness. With some metals such as stainless steel, brittleness could result from conventional welding if the electrode used for welding contains traces of moisture.

The heat of the welding causes the water to decompose and release hydrogen that enters the metal causing it to become brittle. This can’t happen with laser welding because there is no electrode.

The solid front capability offers advanced safety features on a small, 63 mm gauge. The baffle wall feature with a rear blow-out plug diverts pressure away from the operator if the Bourdon tube should rupture, providing an additional layer of safety.

If you require a larger gauge, Ashcroft’s 1279 pressure gauge with 316 stainless steel wetted parts is also a good option for hydrogen applications. The 1279 is a high-performance 4.5-inch ASME- style Process pressure gauge with a comprehensive design for maximizing safety and reliability. It also comes with a solid front safety feature and can handle pressure gauges up to 30,000 psi.

We don’t like to pressure you, but we have more information.

Now that you know the factors to consider when choosing the right pressure gauge for hydrogen applications, you can research the best solution. Keeping these factors in mind can help ensure that you avoid problems or downtime with continuously reliable and accurate measurements.

If you want to learn more about pressure gauges, read some of our other blogs:

Feel free to contact us today to talk to one of our industry experts and get your questions answered.

And if you’d like to learn more about hydrogen applications, download our eBook:

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About Eric Deoliveira, Product Marketing Leader

Eric Deoliveira is a Product Marketing Leader at Ashcroft, Inc. He is currently responsible for pressure gauges, sanitary gauges, high-purity gauges, diaphragm seals and isolation rings. He’s been with Ashcroft since 2015 and spent 3 years as a Product Support Engineer for Mechanical Temperature before transitioning into the Product Manager role. Eric enjoys coming up with solutions for customer problems and introducing new products to satisfy the needs of the market. When not working on his products, he is out golfing in the summer and skiing in the winter.