Weling on internally coated pipeline

[shaff]

To construct additional Fuel supply - Hard stands for Aircrafts in a newly built airport, we need to take tapping from existing underground pipeline (20” API 5LB Sch40 pipe, internally coated). Tapping is done by a Weldolet 20”X6” on the pipe. Client mechanical engineer says that they will run jet fuel inside pipeline while welding to cool the line and prevent damage to the internal coating. My knowledge says you cannot weld on an internally coated pipe.
Here are the doubts I put forward,
1. Is it possible to weld on an internally coated pipe? What if during purging we do the welding?
2. Are there any specifications which lay down the procedure for welding on internally coated pipe?

 

[Ron]

Use a mechanical tapping saddle instead of welding.