Air ûcooled heat exchangers for general refinery services

[0707]

API 661 “ Air –cooled heat exchangers for general refinery services”-1997 states in paragraph 11.2.3: All tubes not strength welded to the tube sheet shall be expanded and seal welded.
Does any one know why?
Is it acceptable to have the tubes just expanded? Or the seal weld is mandatory?
When there is a big temperature differential between tube inlet and tube outlet should the inlet header box be independent from the outlet header box?
An answer from the forum would be appreciated,
Regards
Luis Marques

 

[ijzer]

First of all your API is old.Par.11.2.3 is not the standard API requirement. Par11 and further are only applicable if specified by the Custemer e.g. for high pressure , critical service application .In the new API 2003 it is similar but under par. 12.
Normal API requirements for tube to tubesheet connections are:
strength welded or rolled or seal welded as per par 9.3 (new API).

 

[0707]

Tank you for the approach
My understanding is that tubes should be strength welded to tube sheet only if specified by the purchaser. In high pressure Vacuum Hydrobon service I don’t think it would be necessary to have tubes strength welded to tube sheet. Normal expanded tubes to tube sheet would be enough in a Vacuum Hydrobon service.

For high temperature differences between inlet and outlets should be accommodated in a split header design that allows for thermal expansion. Normally two header boxes suffice one on top of each other.

Regards

Luis Marques