Tubesheet Drilling Acceptance and Rejection Criteria and Method of Repair 1

[Attyub194]

Dear All
TEMA do not specify the criteria and is silent on repair procedure if the drilled holes in new tube sheet exceed the limits specified in TEMA RCB 7.21

Please suggest that incase the drilled holes are more than the limits specified in TEMA what would be the remedy if the drilled holes exceeding the maximum limits specified in TEMA and exceeds 10% of the tube count and on the other hand if the drilled holes are more than the limits specified in TEMA what would be the remedy if the drilled holes exceeding the maximum limits specified in TEMA and is less than 10% of the tube count

As per my own understanding, ASSME VIII is also silent for specifying the criteria of acceptance or rejection of newly drilled tube sheet if the drilled hole dia are exceeding the TEMA limits

Could some one share the experience what normally exchanger manufacturer do in this case or what are the general practice adopted by Tubesheet drilling companies.

This is common issue and there are normally results in long debates between Purchaser and Manufacturer and finally it is a compromise due to cost and time involved.

Also, NBIC is silent on the acceptance and rejection criteria as well as on repair procedure and the cost of new tube sheet is a major factor. Such acceptance / rejection criteria is even not available in API standards

Normally, in such cases third party inspectors recommend to plug the tube sheet holes, provided the thermal performance is acceptable to purchaser

Could any suggest any solution or info which could lead to simplicity and suggest a repair procedure acceptable in light of code and standard with reference.


Best regards

Ahmed Attyub

 

[metengr]

The reason the Code is silent on this is because this is a nonconformance related to manufacturing and should be addressed under your Quality Program. The issue is can you recover from this nonconformance by engineering analysis or scrap it and purchase new.