2 1/4Cr-1 Mo in high pressure service

[jtseng123]

Dear all,
Couple of simple questions:

1. For 2 1/4 Cr-1Mo in high pressure hydrogen service, more than 2000 psig, but design temp below 500F, shall API RP 934-A still be followed ?
2. Can external support clips for ladder/platform/pipe be welded to such thick wall vessel with fillet welds only ?

 

[metengr]

Replies;
(1) No, based on API 941 Introduction.

(2) Yes, with proper precautions followed for sizing of welds, preheat and interpass temperature.

 

[davefitz]

I had thought that vanandium modified 2.25Cr-1Mo-V was now universally used in hydrogen service, but with fabrication issues.
<

http://www.dillinger.de/imperia/md/...fied_crmo_steel_plates_in_pv_fabrication.pdf>

"Whom the gods would destroy, they first make mad "

 

[weldstan]

1. It can be used. API RP 934-A was produced to reflect leading Industry requirements used in the design and fabrication of Hydrocracker Reactors which had wall thickness generally greater than 6". API has generally been adding Recommended Practices to reflect the Exxon/Chevron/Shell and previous oil companies' (Unocal/ARCO) welding requirements.
2. It depends. If nascent hydrogen is present, attachment welds must be full penetration. Nascent hydrogen will penetrate to the unfused areas, building pressure therein and finally causing the welds to crack. Classic hydrogen blistering.