R717 (ammonia) refrigerant storage vessel

[VPbris]

Hi,

I'm designing a storage vessel for R717 refrigerant.

Usually when I design those I specify normalized carbon steel (usually 516gr70N)and PWHT, and also recommend that if possible the addition of 0.2% of water, all that to avoid stress corrosion cracking.

All vessels I've designed for this application had a diamenter between 800-1000 mm.

Client asked me the possibility to use non-normalized steel and to avoid PWHT because there is a lack of companies on the region that can supply that. He also wants a manhole opening.

Specs given by client: Horizontal Vessel, ID-900mm , Design Pressure -250psi

I'm thinking on using a lower yield strenght material (such as SA516gr60) to help with SCC, do not know if is "enough" to protect the vessel against SCC though. Any Inputs on that?

I'l also concerned about the manhole opening on such a small diameter horizontal vessel. I see two problems, one is the high stress concentration and hard spots (which may increase the possiblity of SCC), the other is related to ergonomic issues.

Edit: Vessel is not to be stamped. Design Code is ASME BPVC VIII div 1

 

[MJCronin]

I suggest that you review the international requirements for storage of anhydrous ammonia storage vessels.

Particular attention should be given to the USA ANSI Standard K61.1

They contain recommendations for MOC that will resist stress corrosion cracking

https://www.tannerind.com/sto-anh-ammonia.html#pamphlet

https://www.tannerind.com/sto-anh-ammonia.html

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9757

A full manway is impractical for your small vessel.

ASME permits smaller inspection "hatches" installed for internal inspection.



MJCronin
Sr. Process Engineer

 

[MJCronin]

MSDS data sheets contain for R717 also contain the material requirements for the carbon steel pressure vessel metalurgy

https://pseref.com.au/MSDS/R717 (Ammonia) - (MSDS).pdf

Oh, and stay away from all brasses, bronze and aluminum fittings which will degrade rapidly in a NH3 environment

MJCronin
Sr. Process Engineer

 

[georgeverghese]

Lower design temp for NH3 vessels should be -35degC or so, so A333 or fine grain impact tested silicon killed CS will be required in all cases.

 

[oknow]

Suggest a review of the Jurisdictional Requirements be done to verify a 'Non Stamped' vessel is acceptable. In many cases the customer has no understanding of those requirements. If insured at site the rates usually are increased if the ASME Certification Mark is not indicated.

 

[chicopee]

I don't know where you are located but if you are in the USA make sure that it is a NB/ASME stamped vessel otherwise the jurisdiction and your insurance company will not approve the tank installation.

 

[oknow]

Chicopee...To clarify "your insurnce company" is the Authorized Inspection Agency".It is no longer required that the AIA be an "insurance compamy".