Is H2 stable or unstable for PED? 1

[FPPE]

Hi,

For PED law, is H2 a stable or an unstable gas?
We have a piping with design pressure of 56 barg and ND 50, which falls in II category if H2 is considered as stable, or in III cat. if H2 is considered as an unstable gas.

Thank you in advance

 

[DriveMeNuts]

I assume you mean Hydrogen gas?

Try searching for 'unstable' in this document.
[URL unfurl="true"]https://ec.europa.eu/docsroom/documents/41641/attachments/1/translations/en/renditions/native[/url]

An unstable gas typically decomposes over time, causing an increase in internal pressure while doing so, or even combustion.
Pure Hydrogen gas safely contained in a vessel doesn't do this.

 

[XL83NL]

Not unstable. Ethylene oxide is an example of an unstable gas. H2 clearly isn’t.

Huub
- You never get what you expect, you only get what you inspect.

 

[CuMo]

The PED Classification term you're probably looking for is Group 1 Dangerous or Group 2 Other (Not contained in Group 1) rather than Stable or Unstable.

See if this classification tool can help you. It's free to use:

https://play.google.com/store/apps/...-UK-INS-FY24-Compliance-PED-App-referral-link

https://www.lrqa.com/en-gb/pressure...mpacttab_3c3b5444-e07d-4bf4-a276-2b5a30e6b358

This is the regulation that deals with the classification of the substances:

https://eur-lex.europa.eu/eli/reg/2008/1272/oj

Hydrogen is flammable so I would use the higher Risk Category.

if still in doubt - ask your local Notified Body for advice.