I am in debate on if we need a PP stamp to install Air preheater coil tank that has a MAWP 50 PSIG @ 300* F. The only welding that will be done is on the fittings and none on the tank.

It may be a jurisdiction requirement or a customer specification. The "PP" stamp is mostly uses for Power Piping to and from a Section I Power Boiler. I would check with the jurisdiction of were this is going to be installed.

ireuel,

Please be a little more precise.
Only Boiler External Piping need be PP stamped only as per Section I & B31.1 if local jurisdiction has adopted both codes as a construction codes.
Not the complete piping from boiler need be PP stamped as you did note in your message, only BEP needs.
BEP is the piping upto and including the required valve(s) by PG-58 of Section I, this piping is shown by solid lines with solid dot in the figures PG-58.3.1(a), Fig. PG-58.3.1(b), Fig. PG-58.3.1(c), Fig. PG-58.3.2, Fig. 58.3.3.

The piping beyond BEP is known as NBEP (Non-Boiler External Piping), the code for NBEP shall be decided by Client, Local jurisdiction.

Hope it helps.

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402