Hi jtseng123,
Here are the snapshots of various API documents related to Amine service:-
RP-582-Material carbon steel-all thickness-anime service- Holding Temperature-1150 to 1200 Deg C- Holding Rate 1 hr/in.-Nominal Holding Temperature

1hr minimum).
API RECOMMENDED PRACTICE 945-Avoiding Environmental Cracking in Amine Units:- An effective procedure consists of heating to 593--649 deg C(1100 -1200 deg F) and holding in this temperature range for 1 hour per 25 mm (1 in.) of metal thickness, or fraction thereof, with a 1-hour minimum holding time.
Usually API RP-945 is mandatory document in addition to ASME code, by today's technical requirements for construction of new anime plant equipment.
RP-582 applies to welding requirements only.It does not mandate additional design requirements as API-RP-945 does for design, fabrication of new anime equipments.
The PWHT temperature range adopted by the fabricator is closer to the PWHT Temp of API-RP-945. Please check if the nominal holding time(1Hr minimum) was followed or not. If done so then technically it should be fine.
Also please check if RP-945 is a requirement of the contract.If not done, you do so retrospectively also, or else you may have have problems later in post commissioning operations and weld repairs. The reason being simple, the repair contractor may follow the ASME Sec VIII guidelines and walk away.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means.