Right, agreed i also had the same observations and firstly i scrutized with that interpretations (IX-04-03), please see below for my reply.
INTERPRETATION: IX-04-03 SUBJECT: QW-407.1, POSTWELD HEAT TREATMENTDATE ISSUED: SEPTEMBER 15, 2003FILE NO: 03-1212 QUESTION (1): MAY A PROCEDURE QUALIFICATION RECORD SUBJECT TO THE VARIABLE QW-407.1(A) WHICH QUALIFIED P-NO.8 TO P-NO.8 WITH NO PWHT SUPPORT A WPS WITH PWHT? REPLY (1): QW-407.1 (A) DOES NOT APPLY TO P-NO.8 MATERIALS. SEE QW-407.1(B).QUESTION (2): WOULD APPLICATION OF CONTROLLED AND MONITORED HEAT TO THE WELD AND SURROUNDING AREA FOR THE CORRECTION OF DISTORTION IN P-NO. 8 MATERIALS BE CONSIDERED A PWHT OPERATION? REPLY (2): SEE QW-407.1(B).
THE BALL HAS BEEN THROWN AWAY WISELY BECAUSE OF BELOW FOLLOWING REASONS.
1) IX-04-03 INTERPRETATIONS ARE FOR P8 MATERIALS NOT FOR P1.
2) IT SPECIFIES CORRECTION OF DISTORTION NOT WELDING OPERATIONS.
3) IF STILL P NO 1, THEN BOTH ARE DIFFERENT OPERATIONS AS PER DEFINITIONS.
(a) POST WELD HEAT TREATMENT: ANY HEAT TREATMENT SUBSEQUENT TO WELDING. (b) POST WELD HYDROGEN BAKE OUT: HOLDING A COMPLETED OR PARTIALLY COMPLETED WELD AT ELEVATED TEMPERATURE BELOW 800°F (425°C) FOR THE PURPOSE OF ALLOWING HYDROGEN DIFFUSION FROM THE WELD.
4) POST HEATING IS A POST HEATING IT NEVER CAN BE A PRE HEATING, BUT A PREHEAT MAINTENANCE.
(a) PREHEATING: THE APPLICATION OF HEAT TO THE BASE MATERIAL IMMEDIATELY BEFORE OR DURING A FORMING, WELDING, OR CUTTING PROCESS. SEE PARA. 330.
(b) PARA 330 PREHEATING 330.1 GENERAL PREHEATING IS USED, ALONG WITH HEAT TREATMENT, TO MINIMIZE THE DETRIMENTAL EFFECTS OF HIGH TEMPERATURE AND SEVERE THERMAL GRADIENTS INHERENT IN WELDING. PREHEATING AND THE TEMPERATURES TO BE USED SHALL BE SPECIFIED IN THE ENGINEERING DESIGN. THE REQUIREMENTS HEREIN APPLY TO ALL TYPES OF WELDING, INCLUDING TACK WELDS, REPAIR WELDS, AND SEAL WELDS ON THREADED JOINTS.
5) (A) POST-HEATING REFERS TO THE MAINTENANCE OF PREHEAT AFTER THE WELD HAS BEEN COMPLETED, TO ALLOW INCREASED RATES OF HYDROGEN EVOLUTION FROM THE WELD TO OCCUR. THE POST-HEAT TEMPERATURE MAY BE THE SAME AS, OR GREATER THAN, THE ORIGINAL PREHEAT TEMPERATURE SPECIFIED. POST-HEATING IS DIFFERENT TO POST WELD HEAT TREATMENT. POST-HEAT IS NOT USUALLY MANDATORY IN STANDARDS, BUT CAN BE SPECIFIED BY CLIENTS. THERE IS SOME GUIDANCE (APPROXIMATE TEMPERATURE AND LENGTH OF TIME REQUIRED) IN STANDARDS. BUT THIS IS NON-SPECIFIC AND FURTHER ADVICE MAY NEED TO BE TAKEN. A POST-HEAT REQUIREMENT IN A WELD PROCEDURE USUALLY IMPLIES THE NEED FOR PREHEAT. POST-HEAT REQUIRES FULL CONTROL OVER TIME AND TEMPERATURE, TO BE EFFECTIVE IN THE REMOVAL OF HYDROGEN FROM THE WELD, AND CONTROLLED TECHNIQUES INCORPORATING THERMOCOUPLES ARE PREFERABLE. HYDROGEN BAKE-OUT IS A TECHNIQUE CLOSELY RELATED TO POST-HEAT.
POST-HEAT IS A FABRICATION HYDROGEN EVOLUTION PROCESS. HYDROGEN BAKE-OUT IS USUALLY DONE DURING REPAIR OR MODIFICATION OF A COMPONENT WHICH HAS SEEN SERVICE IN A HYDROGEN ENVIRONMENT, TO REDUCE THE HYDROGEN THAT HAS BEEN INTRODUCED IN SERVICE, BEFORE ATTEMPTING TO WELD THE COMPONENT. HYDROGEN RELEASE IS A TERM OFTEN USED TO REFER TO BOTH OR EITHER OF THESE PROCESSES. BS EN 1011-2: ANNEX C PROCEDURE CAN BE ENSURED IF REQUIRED BY CLIENT AND API 577 MANDATES PREHEAT MAINTENANCE IN WPS.
HENCE IT IS NOT CONSIDERED AS A PWHT AS PER ABOVE AND BOTH ARE DIFFERENT OPERATIONS.
Thanks.
Regards,
Mohamed Muneeb Mahaboob
CSWIP 3.2-89247/2
IRCA-9001:2015 LA
ASNT-NDT-L2-RTFI-RT-UT-MT-PT.
SAP#:70021650 APs:JAPID, QCS & QCI.
''If you know any art by any means then SCULPT IT - no matter how cheap or useless it is - JUST SCULPT IT, you will never know when experts will be on demand''
Hi1. Post heating does not fall under PWHT category, It is like preheating / inter pass maintenance temperature. Max Post heating temperature shall be 250 – 300°C2. Post heating time and temperature range requirements based your P.No shall be provided by client since it is not part of ASME Sec –IX essential requirements3. After completion of welding then post-heating is done, the weld shall be allowed to cool down to below 100°C before starting of actual PWHT ( for P22 & P91)4. If post heat is applied in PQR, equivalent post heat shall be applied also in the production weld alsoAs per TWIPost-heat is a fabrication hydrogen evolution process. Hydrogen bake-out is usually done during repair or modification of a component which has seen service in a hydrogen environment, to reduce the hydrogen that has been introduced in service, before attempting to weld the component
Thanks and Regards
Rameshkannan Devaraj
"What you have learned is a mere handful; What you haven't learned is the size of the world – Avvaiyar"
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Regards,Mohamed Muneeb MahaboobCSWIP 3.2-89247/2IRCA-9001:2015 LAASNT-NDT-L2-RTFI-RT-UT-MT-PT.SAP#:70021650 APs:JAPID, QCS & QCI.''If you know any art by any means then SCULPT IT - no matter how cheap or useless it is - JUST SCULPT IT, you will never know when experts will be on demand''
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