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Exchanger Tubesheet Drilling Acceptance And Rejection Criteria

tubesheet drilling

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#1 Atttyub194

Atttyub194

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Posted 04 August 2018 - 10:35 AM

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 any one 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 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

ASME 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 this 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 . 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

#2 Pilesar

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Posted 04 August 2018 - 12:38 PM

Heat exchanger purchase is a transaction between buyer and seller. If the seller does not deliver what both parties agreed would be provided, the buyer is not obligated to complete the purchase. The manufacturer's poor quality control caused this issue and they cannot force the buyer to accept terms other than found in the contract.

  TEMA provides standards that buyers and sellers often refer to when agreeing to a purchasing contract. That purchasing contract can only be legally amended with the agreement of both parties, preferably outside of a courtroom. If it is indeed a 'common issue' for this manufacturer to not be able to drill precise holes, then the manufacturer should specify in future contracts the standards they are willing to commit to. Perhaps something like 'Manufacturer will deliver exchanger to TEMA standards except we may plug up to 10% of tubesheet holes if we make them too large.' As long as both parties understand and agree to what they are buying and selling, it is no one else's business.

  If the problem is only with tubesheet holes, as a buyer, I might require the tubes be seal welded to the tubesheet with appropriate quality control. Or if the exchanger were generously oversized, I might accept plugging a few holes and a substantial cost discount. Or I might insist the exchanger be provided to meet the specifications of the purchase order.



#3 Bobby Strain

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Posted 04 August 2018 - 02:28 PM

Is this a repair issue?

 

Bobby






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