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Pressure vessels in Hydrogen service

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PressuresOn

PressuresOn

Mechanical
Feb 1, 2011
15
Hi all,

I am commencing a review of some new pressure vessels to be manufactured later this year. The vessels separate gas containing a high percentage of Hydrogen but not H2S.

In terms of ASME, I am advised that this is not lethal service. However, I am also mindful of some client specifications that direct me to consider additional NDT, Post Weld Heat treatment etc.

Could anyone provide some guidance to a paper, specification or code section that will specifically help me with Hydrogen service. Most of the articles and sections I read talk about H2S service and this is confusing matters for me.

ASME VIII Div 1 design code, 35 barg service at about 150 deg C. Carbon Steel throughout.

Thank you

Brian
 
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Hi,

In some areas HS2 could be considered as lethal service. But, the most important is that material that you will use to fabricate vessel, shall be HIC according NACE specification (NACE-0284). For example SA-516-60 or SA-516-70 or whatever, shall be specified as HIC, material certificate shall be an additional info about all tests according NACE-0284.

Regards
 
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Depending on the severity of service, SOHIC - stress oriented - may become a problem. Thus the PWHT.

If it was my vessel, I would negotiate a MUCH more stringent slag/porosity allowance than VIII Div. 1. Also would RT/UT 100% of shell & head buttwelds, looking for slag/porosity. Slag pockets allow Hydrogen to collect, become H2, and react into CH4. Now there will be cracking during thermal cycles.

The VIII allowance is for mechanical strength only, so additional HIC/SOHIC engineering is on you.
 
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One good reference for issues with high temperature, and hydrogen services is "Damage Mechanisms and Life Assessment of High Temperature Components"

There are also more precise API Codes that explain the issues with these services.

In the petroleum industry the H2S interacts with water (wet H2S service) which produces free hydrogen as single atoms (monatomic hydrogen) that can penetrate the walls of the vessel and cause damage inside the wall.

The risks are less with diatomic hydrogen (H2) because it is harder for H2 to wiggle its way into the wall.

One easy suggestion is to avoid slip-on flanges in the vessel designs.
 
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API 571 will give you an indication of the damage mechanisms that may be experienced and their mitigation methods, including materials requirements.

API RP 941 will give you some added comfort regarding your design conditions.

Steve Jones
Materials & Corrosion Engineer

 
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Use HIC plate per Nace
UT head and shell plates
100% RT all butt welds
Nozzles to be self reinforced, no pads.
UT nozzle attachment welds
All attachment welds, pressure & non-pressure, full penetration
MT all attachment welds, pressure and nonpressure
PWHT the vessel

Wish I could give you specific papers, this is what we do for hydrogen service.
 
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