Cladding and Liner Process Requirement

[StrugglingEngineer]

I recently stepped into designing of pressure vessels for an Oil and Gas Refinery, and was going through codes and engineering practices but was unable to find process requirements for Clad Vessels?
Is there any set of values of H2S mole percent, Sour Service, or minimum corrosion rate for which internal lining or cladding is required for a vessel?
Literature is available for HOW to Clad a vessel but I could not find WHEN to Clad a vessel.

Help a Struggling Design Engineer.

 

[r6155]

Example: required thickness SS316 =30 mm, you can choose 27 mm carbon steel + 3 mm clad SS316. Depends of design conditions.

Regards

 

[EdStainless]

Usually clad is chosen when the issues with CS get too difficult. If the risk of pitting of cracking is too great or if the projected corrosion rates are too high then you look to clad.
Some real limits apply to different clad methods (roll bond, explosive weld, weld overlay), and also how the vessel will be fabricated (weld joints), and what alloy will be used for clad (SS, Ni, ?).

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P.E. Metallurgy, consulting work welcomed

 

A word to the wise:
Leave more than 1/8" depth (the typical thickness of bonded cladding) for the welded back cladding. Your draftsman may argue.

With conventional welding processes 1/8" is not sufficient room to develop full corrosion resistance at the finished weld surface.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[StrugglingEngineer]

I agree with all those points and I appreciate help of everyone, it surely is sources to increase my checklist but I still couldn't find the Base line of Specifically Process Related Requirements.

Will be grateful if someone from process or a metallurgist will help.

 

[weldstan]

The Engineers' corrosion metallurgists and the Owner's corrosion metallurgists decide when the process service requires corrosion resistant alloys and whether corrosion resistant alloy cladding may be used.

 

weldstan,

Alternatively, the large EPC, who don't retain fulltime welding or metallurgical engineering help, impose their material choices on the Owner, whose own welding and/or metallurgical engineers are ignored. Then the EPC will then go and have expensive CRA materials welded at some back alley fab shop. Because, low cost.

But there's a silver lining to all this: lots of corrosion failures for me to investigate 15 years later.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[weldstan]

ironic metallurgist
In my first employment with an EPC firm almost 50 years ago, we had exceptionaly experienced corrosion metallurgists and the Owners had the same. And we collaborated together well. We also placed corrosion resistant alloy work with experienced fabricators. When Purchasing began to rule in the mid '80's, that began to change dramatically and I was often required to resolve manufacturing issues.

During thw past 20 years prior to my retirement, I worked for a construction firm and must admit that some of the materials choises made by others were hard to fathom. In some cases corrosion faiures occured whithin weeks - not years. In many cases alloy selection was done by subcontracted third party metallurgical firms - not by the Owner or the EP companies and I must admit some of the selections were incredibly wrong.

 

[SJones]

The process of determining whether a CRA clad vessel is required is called materials selection. There can be a multitude of considerations to juggle in order to arrive at the decision to go for cladding; far too many to go through on a forum such as this.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

weldstan,

EPCs today are not much more than general contractors, using hired guns where they need them (which cuts into their profits).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."