Ageing system

[scott minter]

Good morning,

In our hazardous classified testing area, we have poured boundary seals. The commodity is LH2. The installation was more than 10 years ago, are there any health checks or concerns as the system ages? Specifically the seal offs.

Thank you, Scott

 

[rbalex]

Assuming LH2 is liquid hydrogen. Although it is extremely flammable it is not particularly corrosive. It can cause suffocation.

Sealing compounds are pretty stable.

You should have an MSDS readily available.

 

[scott minter]

Thanks for the information. Yes, the LH2 I was referring to is liquid hydrogen. We have a flow test up coming and the question came up in a review, I have never seen anything that would indicate the need for a health check if the conduit is undamaged and in good shape.

Thank you, Scott

 

[ruxton.stanislaw]

Absolutely, there are health and safety concerns for LH2 boundary seals as the system ages, especially if it's been over 10 years since installation. Here's why:

• Material degradation: LH2 is cryogenic, meaning extremely cold. Over time, the seal materials can become brittle and lose their elasticity, increasing the risk of leaks.
• Permeability: Microscopic cracks can develop in the seals, allowing small amounts of LH2 to leak. This can lead to a buildup of gaseous hydrogen, which is a major fire and explosion hazard.
• Loss of adhesion: The bond between the seal and the surrounding structure can weaken, compromising the seal's integrity.

Here are some recommended health checks for your LH2 boundary seals:

• Visual inspection: Regularly inspect the seals for signs of damage, cracks, or deformation.
• Leak detection: Use specialised equipment to detect even small leaks of LH2 gas.
• Ultrasonic testing: This non-destructive method can identify cracks or voids within the seal material.
• Material property testing: Samples of the seal material can be tested to assess their current mechanical properties and identify any degradation.

It's crucial to consult the specific recommendations from the manufacturer of your LH2 system and the regulations set by relevant safety agencies. They will provide detailed guidance on inspection frequency, acceptable levels of degradation, and replacement procedures.

Here are some additional resources that you might find helpful:

• National Fire Protection Association (NFPA) - Hydrogen Technologies Code (NFPA 50A): https://www.nfpa.org/codes-and-standards/nfpa-2-standard-development/2
• American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) - Section IX Welding and Brazing Qualifications: https://www.asme.org/codes-standards/bpvc-standards

Remember, LH2 is a hazardous material, and any operations involving it should be conducted by trained and qualified personnel following strict safety protocols. Don't hesitate to involve a qualified inspector or your LH2 system supplier for a comprehensive assessment of your ageing seals.

 

[rbalex]

I wouldn’t count so much on AI speculation answers.

Many of the raw statements are true, but It’s unlikely the seals would be directly exposed to liquid hydrogen which vaporizes very quickly in open air. If the actual installation conditions were as your AI described, failures would have occurred well before 10 years.

 

[ruxton.stanislaw]

I wouldn’t count so much on AI speculation answers.

Many of the raw statements are true, but It’s unlikely the seals would be directly exposed to liquid hydrogen which vaporizes very quickly in open air. If the actual installation conditions were as your AI described, failures would have occurred well before 10 years.

You're absolutely right. Liquid hydrogen (LH2) has an extremely low boiling point (-253°C) and readily vaporizes in open air. In most well-designed LH2 systems, the seals wouldn't be directly exposed to the liquid itself.

Here's a more nuanced take on LH2 seals:

• Material Selection: Even with minimal direct contact, the entire system experiences the cryogenic temperatures. Standard elastomer seals become brittle and ineffective at such low temperatures.
• Suitable Seal Designs: As you mentioned, 10 years of service life suggests a well-designed system. For LH2 applications, resilient metal seals (like C-rings) or specialty polytetrafluoroethylene (PTFE) seals with spring preloads (FlexiSeals) are common choices. These can maintain sealing capabilities at cryogenic temperatures.
• Indirect Exposure Concerns: Even if not directly bathed in LH2, seals can be affected by the extreme cold. Permeation of hydrogen gas through the seal material is a potential issue. Careful material selection and design considerations mitigate this risk.

In conclusion, your real-world experience with a successful 10-year LH2 system highlights the importance of proper design and material selection for seals. While direct exposure might be unlikely, the entire system needs to be able to handle the cryogenic environment effectively.

 

[rbalex]

HAZLOC seals aren’t elastomer. So the whole basis of your AI evaluation is questionable.

 

[ruxton.stanislaw]

HAZLOC seals aren’t elastomer. So the whole basis of your AI evaluation is questionable.

This reads as requiring non-elastomer seals.

 

[rbalex]

Read Section 501.15(C) for more relevant requirements.