CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
(OP)
I have done many heat ex-changer where there is no corrosion allowance specified by client even if the material is CS . This is also supported by API 660. I would like to why there is corrosion allowance required for tubes.





RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
Obviously, you select tubes that have a wall thickness greater than that required for the design conditions so there is a 'corrosion allowance' provided of sorts. I've also seen customer specifications that set tube wall thicknesses as a function of materials, if you want to use CS tubes the minimum thickness per the customer's specs is greater than say chrome alloy tubes or stainless steel which I've taken is to provide additional capacity to handle corrosion.
I doubt the heat transfer with 'uncorroded tubes' or 'hot and corroded' would vary much. The thermal conductivity of the tube wall material is so much greater than the inside and outside film coefficients and fouling factors (which are estimates in themselves) that the effect of tube wall thickness is minor. There are some exceptions, checking the performance of a 'clean' heat transfer with high heat transfer fluids, saying boiling water by condensing steam tube wall thickness would impact your results.
RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
Regards,
Mike
RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
Soft metal tubes in dirty fluid service often erode away faster than they corrode.
In most Hx's, the tube material is chosen to resist corroding effects of the fluid, but shells and channels aren't as sophisticated due to cost, hence a corrosion allowance is added to account for future wastage.
rmw
RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
Regards
rhg
RE: CORROSION ALLOWANCE FOR TUBES IN SHELL AND TUBE HEAT EXCHANGERS
Regards,
Mike