304 / 304L stainless steel 1

[viki100]

Dear Friends,
Is the hydrogen content H2 of 2.5 [mol %] in the helium-nitrogen stream dangerous to stainless steel 304 / 304L, seamless piping 1/2 - 1 1/2 '' SCH40S, pressure working ca. 20 barg, temperature range +20 / -165 degC?
Regards,
VIKI

 

[cap1a79]

As the service temperature is just between 20 C and -165 C, the use of SS 304 will be O.K.
Refer to below.

1) HTHA (High temperature hydrogen attack)
Generally, when hydrogen (as H2) is to be an critical issue, temperature should be more than 200 C. (Even for this case, SS 304 is not susceptible to high temperature hydrogen attack while CS & low alloy steel might be.)
Reference from API 571 & 941 nelson curve

2) HE (Hydrogen embrittlement)
Not applicable for SS. This mechanism is mostly for CS and LAS(Low alloy steel)
SS is resistant to HE. (from API 571)

3. Hydrogen stress cracking
Likewise, this mechanism is not applicable if there is no HF. (from API 571)



Reference from API 941 & API 571



Lee SiHyoung,
WorleyParsons Oman Engineering,