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Shell & tube HX - TEMA R minimum tube wall thickness

Shell & tube HX - TEMA R minimum tube wall thickness

Shell & tube HX - TEMA R minimum tube wall thickness

(OP)
Hello Everybody ,

i am new to the design of HX and i would like to ask something. We have an occasion of a S/T HX per TEMA R, minimum thickness as per API 660 is 2,11mm. the corrosion and errosion allowances i add them to the above value or i add them to the calculated value of 1,7mm?

thank you in advance
Kpap

RE: Shell & tube HX - TEMA R minimum tube wall thickness

The tube wall thickness is determined by sum of minimum code thickness plus corrosion/erosion allowance, if applicable. There are additional recommendation for the minimum wall thickness as specified by API 660 or by TEMA. Generally, TEMA is less restrictive, advising that there are other tube diameters and gages available.
I'm not sure where did you get the 1.7 mm calculated thickness, but if it is a code calculation, you need to add the allowances to it and select the next standard thickness available for the tube diameter you are using.
Cheers,
gr2vessels

RE: Shell & tube HX - TEMA R minimum tube wall thickness

Corrosion allowance is generally not considered for tubes, please refer to TEMA RCB 1.517. Higher tube thickness will severly affect heat transfer. If corrosion is a real concern, tubes in corrosion resistant alloy to be considered.

Similar requirement is specfied in API 661 for air cooled heat exchangers. I am however failed to locate any such requirement in API 660 and ASME Sec VIII.

Just to add on to previous query, how do we confirm compliance to ASME Sec VIII or API 660 requirements when both shell and tube sides are required with corrosion allowance and CS tubes are provided without any corrosion allowance?

Cheers
Sanj

RE: Shell & tube HX - TEMA R minimum tube wall thickness

Tubes are not required to have included corrosion allowance for general service. However, there are very corrosive services when the Client specification overrides the TEMA and includes a corrosion allowance. If that's the case, refer to my previous reply.
gr2vessels

RE: Shell & tube HX - TEMA R minimum tube wall thickness

gr2vessels;
It is not recommended to use very thick tubes to account for corrosion allowance in corrosive services. In case of corrosive services, better to use tubes in CRA construction.

Most of the client specs I have come across, require to report excess tube thickness available over pressure required thickness which can be considered as allowance for corrosion.

wink
Sanj

RE: Shell & tube HX - TEMA R minimum tube wall thickness

kpap, tube (and other) minimum thickness specfied in TEMA, API 660, etc. are pretty generally taken to be new, nominal thicknesses. As gr2vessels says, "you need to add the allowances to it and select the next standard thickness available for the tube diameter you are using."

Then compare the selected thickness to the required minimum.

sanshu1111. API 660, 7.6.1.2. Also note that deviation is allowed by agreement with the buyer. This is common in TEMA as well.

Regards,

Mike


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