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High corrosion allowance for valve shell wall thickness

High corrosion allowance for valve shell wall thickness

High corrosion allowance for valve shell wall thickness

(OP)
Dear good members,
If the required corrosion allowance for a piping class is very high, which might be 4.5mm or 6mm, should this be conisdered for valve shell wall thickness?

My opinions are as follows;

1. Unless client's specification requires this high corrosion allowance to be added to valve shell wall thickness, we do not have to do it.

2. Comparing ASME B16.34 with other codes (API, BS, etc.) and also considering manufacturer's own tolerance, those high corrosion allowance might be covered.

I need your opinion....

Thanks in advance....

RE: High corrosion allowance for valve shell wall thickness

onrush,
Please review the excerpt from the ASME B16.34 set below, in regard of the issue of corrosion allowance;-

Material Selection
5.2.1 Service Conditions. Criteria for the selection of
materials are not within the scope of this Standard. The possibility of material deterioration in service and the need for periodic inspections is the responsibility of the user. Carbide phase conversion to graphite, oxidation of ferritic materials, decrease in ductility of carbon steels
at low temperatures even in applications above -10°C (20°F), and susceptibility to intergranular corrosion of austenitic materials or grain boundary attack of nickelbase alloys are among those items requiring attention by the user. A discussion of precautionary considerations can be found in ASME B31.3, Appendix F; ASME Boiler and Pressure Vessel Code, Section II, Part D, Appendix 6, and ASME Boiler and Pressure Vessel Code, Section III, Division 1, Appendix W.

This should answer your questions / opinions;- first is correct and second is assumption only.
cheers,
gr2vessels

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