Repairing S&T HX Channel Pass Plate 1

[Krausen]

I have a task to repair an existing pass plate on an existing S&T HX channel (~5'-6" diameter channel, pass plate is 1/2"-thk, carbon steel) during an upcoming outage due to knife-edging expected on the pass plate edge where it bolts up to the existing tubesheet. The service for this channel is cooling water. The current plan is to demo a section of the existing knife-edge pass plate out & weld in a new 1/2"-thk plate section in its place. We'd be welding back to the existing channel cylinder & existing pass plate in this case. Curious if forum thinks this is the best repair strategy, or would just building up the existing knife-edge pass plate with a machinable Belzona metal repair paste-grade type product be a better overall strategy?

 

[ShabsRBI]

Normally in this kind of situation, we weld build up the part partition plate, which has suffered knife edging and machine it to get the required thickness on the edge. By this way welding to channel is avoided. In most case the pass partition plate will have a tapered thickness on the edge. Possibly for 1/2 inch (12mm) thick partition plate the tapered thickness will be 8-10mm.

 

[r6155]

Pass Partition plate must be 5/8". See TEMA 11 edit

 

[ShabsRBI]

Hi @r6155
I have old edition of TEMA and don't have latest edition of TEMA edition 11. It seems that TEMA Ed-11 has standardised the pass partition plate thickness as 5/8" , where as in old editions minimum thickness was based on Nominal size of Channel. Partition plate thickness used to vary from 3/8"(9.5mm), 1/2" (12.7mm) and 5/8"(15.9mm). If you can share the information from latest edition that will be helpful.

 

[r6155]

@ ShabsRBI
Note that OP said diameter 5'-6" = 66"
hence the thickness is 5/8" in your Table RCB-9-131, same as Table RCB -9.1.3.1 in the 11th edit

Regards

 

[ShabsRBI]

This means that pass partition plate being used for 5'-6" Channel is not conforming to TEMA requirements. Does this require replacement or shall be considered for continued service as it has worked well in the given situation?

 

[Christine74]

TEMA standards are intended for new equipment, not for repairs of existing equipment.


-Christine

 

[Trestala]

is not conforming to TEMA requirements.

Regarding the thickness, the requirement in RCB-9.1.3. is that you either use the thickness in the table, or the thickness as calculated per formula in RCB-9.1.3.2. That is clearly indicated on your snaphot provided above. If it is less than 5/8", you can still use your 1/2" plate if it can still hold the pressure drop across the plate based on the formula.

 

[r6155]

@ Christine74
You are confused

B.1 PLANNING REPAIRS AND ALTERATIONS
Repairs or alterations to heat exchangers may be required or desired for many reasons, including damaged or leaking pressure containing components, changes in service, or modifications to nozzles, supports, or exchanger configurations. In some cases, the most cost-effective option may be to replace the unit or component entirely In deciding whether to repair or replace a damaged exchanger or component, the following should be considered:


@ Trestala
You are wrong.
RCB-9.1.3 PASS PARTITION PLATES
RCB-9.1.3.1 MINIMUM THICKNESS.
The thickness of pass partitions shall not be less than the greater of that shown in Table RCB9.1.3.1 or calculated in Paragraph RCB-9.1.3.2. Pass partition plates may be tapered or step machined to gasket width at the contact surface

Regards

 

[Christine74]

Please ignore r6155's comments. I suspect that he suffers from Advanced Senile Dementia, which would explain the hostile behavior and the irrelevant citation above. Furthermore he's never demonstrated any knowledge whatsoever of heat exchangers in his previous posts here.

TEMA standards are for new equipment. It has never covered repair methodology or repair requirements.


-Christine

 

[r6155]

TEMA
PREFACE
Eleventh Edition- 2023
The Eleventh Edition of the TEMA Standards was prepared by the Technical Committee of the Tubular Exchanger Manufacturers Association. Sections have been added to provide direction concerning the design of one pass floating heads and Type-D high pressure channel closures. The Eleventh Edition introduces an Exchanger Type Selection Guide which discusses the benefits and disadvantages of various types of exchangers and a section on Inspection which has information concerning nondestructive examination techniques and recommendations for their use for shell and tube heat exchangers. This edition includes new appendices for Repairs and Alterations of Heat Exchangers; for Clad and Overlay Construction; and for Installation, Operation, and Maintenance of Shell and Tube Heat Exchangers. TEMA has modified the Heat Exchanger Specification Sheet to better define the design requirements necessary to specify a heat exchanger. This Standard has been revised to include weld calculations for vertical support lugs, a clarification to the mitigation of erosion of the tube ends due to certain tube side flows, and a more detailed discussion concerning tube to tubesheet joints.

REPAIRS AND ALTERATIONS APPENDIX B
NON-MANDATORY APPENDIX B - REPAIRS AND ALTERATIONS OF HEAT EXCHANGERS

 

[EdStainless]

It is common to see people update a HX at time of repairs.
For PP Plates I have usually seen people do as Shabs suggested and weld repair the edges of the old ones and then put in new ones.
How long has this been in service?
Are you getting reasonable life?

 

[Christine74]

REPAIRS AND ALTERATIONS APPENDIX B
NON-MANDATORY APPENDIX B - REPAIRS AND ALTERATIONS OF HEAT EXCHANGERS

You can ALL CAPS "shout" all you want but the fact that TEMA now has a separate Appendix (and a non-mandatory at that) covering Repairs proves that the TEMA standards were never intended for new equipment. Table RCB-9.131 is not located inside Appendix B so it would not apply to this repair.


-Christine

 

[r6155]

CAPS are in the TEMA.