[MW:12511] MW:12508- Requirement of No. of Thermocouples.

Mr. Vichare,

 

ASME B-31.3 does not have any specific instruction on placement of thermocouples for local PWHT of pipe spools. AWS D-10.10-1999-Recommended Practices for Local Heating of Welds in Piping and Tubing is the industry standard followed to develop local PWHT standards and guidelines.

 

Please see the recommendation of AWS D-10.10 on the recommended no of thermocouples to be placed for PWHT of such pipe spools. Further detailed instrctions are available in this standard.

 

PWHT is extremely important for B-31.3 piping as the service environment is extremely conducive to SCC, and all forms of hydrogen assisted cracking. Moreover since spools are locally PWHT-ed there are every possibilities of  mistakes.Common mistakes could be  wrong ramp rate, incorrect temperature of PWHT, improper width of the weld+BM heated to the PWHT temperature, sudden power loss during PWHT, wrong thermocouple placement, improper calibration of strip chart (recorder), damaged thermocouple ends so on & on.

 

You may please insist the PWHT contractor  to meet  all requirements of D-10.10.

 

 

Pradip Goswami,P.Eng.IWE

Welding & Metallurgical Specialist & Consultant

Ontario,Canada.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

---

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Shashank Vagal
Sent: Friday, September 23, 2011 4:36 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:12508] Requirement of No. of Thermocouples.

Dear members, In all these arguments one imp aspect remains ignored, the very purpose of a thermocpuple, TC. All the requirements given in B31.3, Shell DEP, Aramco SP etc are the minimum requirements. What we have to ensure is that all the area required to be heat treated is indeed heated and soaked as specified.  It then becomes obvious that to meet this requirement you may need some additional TCs at certain locations whereby all required area gets speicified heat treatment. Sometimes I have used 6 to 8 TCs to satisfy myself on adequacy of HT because of the job geometry. Regards, Shashank Vagal --- On Fri, 23/9/11, Ramchandra vichare <vicharerke@indiatimes.com> wrote: From: Ramchandra vichare <vicharerke@indiatimes.com> Subject: [MW:12507] Requirement of No. of Thermocouples. To: materials-welding@googlegroups.com Date: Friday, 23 September, 2011, 12:39 PM Dear Experts, With reference to the above mentioned subject , during Heat-treatment of Piping spool joints I insisit one of my vendor to used thermocouples as noted below:- Up to 4"NB = 1 no.(Bottom side) Above 4" to 8"NB= 2 nos.(top & Bottom)(say 180Deg.) 8" to 24"= 3 nos (120Deg) Above 24" =4 nos. and according to accepted Heattreatment Procedure it was alo acceptable but unfortunitaly delay in Heat treat the joint; vendor is not ready to follow Procedure due to the reseason referred above & no where written in ASME 31.3 regarding the requirement of Tharmocouples.  Reauested experts to Guide guaide me why we are placing thromocouples? I think it is control soaking anyhow;let me tell  were I will get ready reference and documentryevidence for requiremnt of Number of thermocouples? Is any effect during soaking time or any metallourgicval changes will be there if we use one thermocouple instead of above? . Pl be guaide in detail with documentry evidence. Regards, RK Vichare Mumbai-India -- To post to this group, send email to materials-welding@googlegroups.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.