Typical corrosion allowances.
Typical corrosion allowances.
(OP)
Piping designer, based on service corrosivity, adds corrosion allowances to the calculated pipe thickness. In a new oil refinery construction project, which would be typical corrosion allowances?
Is there any rule to be followed?
Thanks
Luis





RE: Typical corrosion allowances.
http://virtualpipeline.spaces.msn.com
RE: Typical corrosion allowances.
From Chapter 20 of Norman P. Lieberman's Troubleshooting Refinery Processes (Penwell), which I recommend reading:
According to this criterion, for a CS pipe carrying high-sulfur diesel at 260oC with an original wall thickness of ¼ in. or 250 mils (mil = 1/1000 inch), a uniform loss of 10 mil/year would be OK. This rate can be known from previous (published) experience or measured with coupons, probes or suitable instruments. It means the corrosion allowance would be 12.5 years × 10 mil/year = 125 mils = 0.125 in.
There are many different causes and types of corrosion in a petroleum refinery. Each involves a different material wastage rate (not always wall thinning) which depends on the corroding environment (chemistry, hydraulics, temperature, pressure, etc.), the selected metallurgy, and even welding and other preliminary procedures.
RE: Typical corrosion allowances.
high-sulfur diesel at 260ÂșC is a good place to start.
http://virtualpipeline.spaces.msn.com
RE: Typical corrosion allowances.
From my search on this subject I suppose that there is no rule or recommended practice and the things are a little bit established ad hoc empirical based on licensors experience.
I think that actually in a new refinery construction a RBI approach should be made to define expectable corrosion rates then based on those expectable corrosion rates designer should add corrosion allowances with the following criteria: high corrosion rates high corrosion allowance, medium corrosion rates medium corrosion allowance, low corrosion rates low corrosion allowances.
Thanks for you sharing
Luis
RE: Typical corrosion allowances.
BigInch, thanks. A big hand on your being elected TMW by the community.
Luis, creo que sus conclusiones son muy razonables.