Following the concerns of welding defects for in-service maintenance hot works, the Mock-up test should be performed to increase the confidence level of works.

See this: In-service and maintenance welding defects

Mock-Up Testing ; 

This comes at a Mock-up Testing for In-service welding or welding On-stream … For onstream welding, while there is fluid flowing inside the pipe or equipment The most important is the safety that is not going to burn through the weld and weld it must not happen Hydrogen cracking (HIC) according to the method used to prove that the simulated welding or the Mock-up test. 

In conducting a mock-up test, the workpiece must look like or represent the actual work in the matter including: 

(1) Type ( Material Spec.), and the thickness of the material,

(2) Pressure within the equipment or Stress that occurs, 

(3) Cooling of welding Or liquid flow within pipes or equipment Which may cause welding to cool too quickly,

(4) and a Mock-up test , it will Qualify welders (Welder) and Welding procedure to be used for In-service welding.

Take a look at the requirement in the AMSE PCC-2 Repair of Pressure Equipment and Piping, which will tell us what methods the Mock-up test will be tested. To see the complete strength of the weld (Fillet weld) as well as see if the Heat affected zone (HAZ) has a rigid structure or not. The testing methods including Bend Test, Nick Break Test, Metallography, and Hardness Test.