NO6625 TUBE AND NO6625 TUBES - PWHT OF TTJ WELDING

[Vishwas Keskar Welding Manager WELDING]

Dear Experts 

Equipment fabrication - Heat Exchanger fabrication - as per ASME SEC VIII DIV 1 - Tube sheet -SB 564 N06625 -66mm thk x 666 mm OD 

Heat exchanger Tubes - SB-444 N06625- 2.108mm X 19.05mmOD 

Welding -Tube to Tube sheet welding 

Joint configuration - Groove and fillet - (2mm X 45 Deg V with 2 mm fillet). Welding Process - GTAW 

Filler Metal - ERNiCrMo3 

PWHT is required for Tube to tube sheet welds  due to Process reasons.

Query - WPS is to be qualified with PWHT - 

1.What would be PWHT Holding temperature and holding time for the above Tube to tube sheet welds? Advice on recommended Heating and cooling rate for PWHT . 

2. What are the cares that needs to be taken to avoid scaling ? 

3. What would be the advice for sequence for Tube expansion ? (Tube Expansion shall be before PWHT OR after PWHT ) .Technical Expert Answer with details -

Any specific care that to be taken while doing PWHT ( to avoid distortion, to avoid scaling  etc )

Thanks 

Vishwas -IWE