POST HEATING IN PWHT

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NIKHIL THOMAS JOY

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Oct 26, 2020, 12:42:00 AM10/26/20
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Dear sir, Good evening

Sir, kindly please  solve my doubt related to POST HEATING IN PWHT.

1.Where we need to do post heating.

2.If I am doing pwht sudden after welding is there any need of post heating or not.

3.In any code post heating mentioned.

Please give me answer for the above mentioned question.

Chandru Sekar

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Oct 26, 2020, 5:06:35 AM10/26/20
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SA 335 grade P9- preheat given 200 degree only as per client requirement then once welding completed , preheat will be increased upto 350 for half an hour.

Rate of heating is same as pwht like 100 degree per hour.

Thanks & Regards
Chan

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Vinay Thattey

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Oct 26, 2020, 10:54:01 PM10/26/20
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Dear Joy ; In Post weld heat treatment we reheat the weld to generally below critical temperature , golf for given time . It is done to remove / reduce residual stresses and also to obtain favourable microstructure changes  .  For example when there is  risk of  of cracking after  weld , post weld treatment  can be adopted . You need to specify your application , material ,   dimensions etc . Yes post weld treatment is a requirement of code but again details of weld joint, MOC etc are required.



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Vishwas Keskar

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Oct 27, 2020, 7:45:35 AM10/27/20
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1.Where we need to do post heating. -This applicable to High Thickness (@> 50 mm ) Carbon steel  and  @25mm or greater Cr - Mo  (>/= 2.25 Cr steel )steels.

2.If I am doing pwht sudden after welding is there any need of post heating or not. - Then POST HEATING  is not required. But it is practicable ?

3.In any code post heating mentioned.- AWS D10.8-  Cr - Mo steel specifies it 

Please give me answer for the above mentioned questio

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udaya bhaskar

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Oct 28, 2020, 1:11:39 AM10/28/20
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Mr.Nikhil,
Post Heat applicable at,if you done any welding activity after PWHT.


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Kannayeram Gnanapandithan

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Oct 28, 2020, 3:55:17 AM10/28/20
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Post Heat is applicable to bake out Hydrogen before delayed PWHT. When Flux bearing welding process, like FCAW, SMAW, SAW ect  on Higher thickness ( Multiple layers) and Alloy steels to avoid Delayed Crack/ HICC

THANKS & BEST REGARDS,
KG.PANDITHAN, BE, IWE,  CSWIP 3.1,
ISO 9712 Level 2 in VT,
ASNT-Level II in PT,MT,RT & UT,
LA ISO 9001-2015,
International Welding Engineer. 
CONSULTANT-WELDING & QUALITY
Mobile no: +919940739349


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George Dilintas

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Oct 29, 2020, 1:41:27 AM10/29/20
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You question is very general.

PWHT depends on the following factors:

Thickness
Material grade
Service requirements (example: lethal service)

For some grades (Pno-15E materials) preheat maintenance is required when PWHT is not done immediately after welding

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Dr. Georgios Dilintas,
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Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis
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