valve corrosion rate calculation 2

[skengg]

Hello,
i want to know that how we add thickness for corrosion allowance in valve. from where i can get data of material deterioration rate/per year as per according to sevice fluid medium.

 

[MJCronin]

skengg,

First, we must recognize that the corrosion allowance for piping, fittings, valves etc. etc. are only a guess that was developed by the piping/chemical engineers who designed those systems.

Second, it is probably reasonable to assume that the corrosion allowance that was selected for the adjoining piping system could be used for the valves in the same system. This assumes, of course, that the valve body material is the same as the piping material

Third, recognize that ALL piping systems have a service life. Piping systems are not designed to last forever, despite what any MBA may tell you. Some systems have lifetimes of ten, twenty or forty years. Common sense, skengg, would tell you that the corrosion allowance of a mixed-acid carbon steel system would be much greater than a stainless steel piping system transporting pure water.

Fourth, corrosion allowances for piping system design have been discussed many. many times before on these fora. Go back and read them ...

Then tell us your question

You must be specific about your fluid service

MJCronin
Sr. Process Engineer

 

[skengg]

thanku MJCronin for valuable information. i understand what you are saying. so i need to study corrosion allowance for piping system and implement according to it on valves & fitting system.
thanks.

 

[bcd]

Design criteria for pipe and valves are completely different. Valves are mechanical instruments that require tightly controlled machined tolerances to function properly. Allowable stresses in valves are limited to avoid creep as even small distortions to the valve body over time can cause leaks or prevent operation. Also, corrosion of the valve can prevent sealing and operation. That being said, it is not uncommon for pipe designers to transfer the corrosion allowance for their pipe to the valves in their specifications. Rather than argue, many valve manufacturers just say the requested corrosion allowance is built into the valve wall thickness or have designed their valves with extra thick walls to provide the typically requested corrosion allowance from their customers.

 

[bcd]

And sorry, forgot to answer the main question. NACE publishes corrosion rate information for various media and metals.