Q. What is Mock-up Testing?

Tube to all tubesheet weld tests shall be provided as described below.

Mock-up of 10 tubes about 305 mm (12") long are welded to a portion of a tubesheet, using the same welding procedure, cut and polish for macro test. The mock-up tube and tubesheet materials and thicknesses must be identical to the actual design and supplied materials.

Perform hardness on macro surfaces on weld, HAZ and parent materials of tubesheet and tube. Hardness not to exceed BHN 200.

A tensile pull-test of the tube and tubesheet of the mock-up must be performed to establish UTS of the failed parts. If the tube fails before the strength weld failure, UTS of the tube shall be the minimum specified value for the material of the tube. But if the weld fails, the UTS shall be a minimum specified value of UTS of the material of the tube or tubesheet, whichever is larger. Three tensile tests shall be performed, each shall be compared to the UTS of the tube or tubesheet material as described above. All three tubes for tensile pull test shall only be welded to tubesheet and not rolled.

For the production weld, after 10 tubes have been rolled lightly (if rolling is used) and the root pass welding is completed, soap suds or halogen leak tests shall be performed on each tube well. If welding is sound, no further tubewelds need be leak tested.

Repeated welding failures and repairs shall be subject to Purchaser's review and acceptance.