corrosion allowance - piping 31.3, 31.1
corrosion allowance - piping 31.3, 31.1
(OP)
I'm looking for ways to simplify piping specifications that we are developing.
The traditional corrosion allowance for CS pipe is .0625". This leads to calc wall pipe in sizes 32" to 36" (150# CS). However, we would like to keep everything in this class to a fixed wall. I've noticed that another company has allowed the corrosion allowance to drop to .047" when the calculation is "close" so that they can stick with the thinner wall and no calc wall. This spec is also 150# CS.
Any problems with letting the corrosion allance drop below .0625.? (other than the obvious lesser lifespan of the pipe). Is .0625" CA just a tradition?
The traditional corrosion allowance for CS pipe is .0625". This leads to calc wall pipe in sizes 32" to 36" (150# CS). However, we would like to keep everything in this class to a fixed wall. I've noticed that another company has allowed the corrosion allowance to drop to .047" when the calculation is "close" so that they can stick with the thinner wall and no calc wall. This spec is also 150# CS.
Any problems with letting the corrosion allance drop below .0625.? (other than the obvious lesser lifespan of the pipe). Is .0625" CA just a tradition?





RE: corrosion allowance - piping 31.3, 31.1
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: corrosion allowance - piping 31.3, 31.1
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: corrosion allowance - piping 31.3, 31.1
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: corrosion allowance - piping 31.3, 31.1
The problem with piping specs is that they always try to dumb down engineering to the level where anyone can specify piping, but then no one wants to pay for how expensive things start to get when all is taken into acount (such as CA on large pipes).
The question you should be asking is not "will 0.047 be ok" but rather as BigInch said "what is the right CA for the application". Do you even know where the 1/16 allowance came from? And by the way "thats how we have always done it" is about the most useless answer to that question (or any other). Is that allowance for uniform corrosion over the life of the pipe? Can you review the calcs to see if there is fluff in the number? Is the allowance for local corrosion (pitting)? Is it for errosion due to the medie you are moving? Did it simply come from somones rear 50 years ago (with the stench that implies)and everyone has been using it since?
I would get a firm grasp on why 1/16 is being used and then determine if it can be modified based on calculation in accordance with sound engineering principles.
Always remember, free advice is worth exactly what you pay for it!