Hi,
Advise would be to go for local PWHT encompassing the entire circumference of the larger pipe as per the above sketch. Recommended practice AWS-D-10.10 is accepted by all ASME codes for local PWHT.
Please see the extract from AWS D-10.10(clause 6.6.4) with respect to the placement of heating bands, and thermocouples. The contour, size of the components being heated are different, hence there’s every possibility that the smaller nozzle will get overheated, while the larger dia pipe may experience under heating.
Hence using heating band as per attached sketch and guidelines mentioned below would be advisable. Fig-15(D-10.10) may be referred for No of Thermocouples to be place at various locations.
Note clause 6.6.4 of D 10.10 as mentioned earlier by Mr Bathula is also clarified.
Hope this would clarify the query for all.
Thanks.
Pradip Goswami, P.Eng,IWE
Independent Welding & Metallurgical Engineering Specialist & Consultant.
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
6.6.4 Butt Welds Joining Branch Connections or Attachments to Piping.
For welds joining branch connections or attachments to pipe, 360-degree band PWHT practices, as illustrated above is recommended. This has been adapted from the requirements in BS 2633.
For branch connections, it is likely that the heaters fitted to the weld will not contour to the shape without leaving larger than normal gaps between the heaters. In such instances, it is good practice to attach additional monitoring thermocouples in the expected cold spots created by these gaps and heat the control thermocouples to the higher end of the soak range such that the cold spots achieve the desired temperature.
It is good practice to use separate control zones on both the pipe and branch connections.
Where small branch connections, 1/2 to 1-1/2 in. (12.7 to 38.1 mm) diameter, are welded to larger pipe sections, it may be desirable to heat the entire region as shown in the above figure using heaters with control thermocouples on the larger pipe and monitoring thermocouples on the smaller branch connection.
The reasoning for this is that the amount of energy required to heat the branch is small in comparison with that required to heat the pipe.
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Hareesh K V
Sent: Friday, March 18, 2016 3:03 AM
To: materials-welding
Subject: Re: [MW:24544] PWHT of branch connections.//B31.3
Dear Sir,
Thank you for the replies.
The temperature gradient along the main pipe (Header) are managed by the coils and wool. why not it be considered with the same theory around the branch. That is the basis of my doubt.
We are following the code requirements. It is because of my academic interest I raised this question.
Coiling of a 60" dia (for example) pipe for a branch weld of 3/4" dia, logically is not explainable.
Thanking you
Hareesh K V
+91-8547859202
On Mar 18, 2016 12:21 PM, "Prakash Gotimukul" <gprakash31@gmail.com> wrote:
>
> Codes are written after careful consideration. So it is good to argue but better to follow the code. If there is any other code with other options, that needs discussion. More over the thicker side is considered as main line and thinner side as branch line.
>
> Rgds
> Prakash Gotimukul
> ASME AIS, Technical Manager ASME/ISO/PED
> gprakash31@gmail.com.
> Tel: +9714 2778511 Mob:+97152 979 5678
>
> On Fri, Mar 18, 2016 at 10:42 AM, Raghuram Bathula <raghurambathula@gmail.com> wrote:
>>
>> that is the reason controlling theromocouples and monitoring thermocouples are recommended in D10.10 (amount of energy required to heat the branch small compared to run pipe), similar recommendations are provided in WRC 452.
>> concern could be distortion or induced stresses due to circular or spot heating
>>
>> On 18 March 2016 at 10:02, Hareesh K V <hareesh13h@gmail.com> wrote:
>>>
>>> Dear Sir,
>>>
>>> My doubt is, the width of the band (HB or GCB) along the length of main pipe is on the logic of diminishing temperature and its metallurgical effects. Why not it is not considered to do the pwht of the branch in the vicinity area of branch/RF pad only by the same logic of HB and GCB near the weld area of RF pad/branch.( This will reduce the consumption of power, coiling time etc.)
>>>
>>> Thanking you
>>>
>>> Hareesh K V
>>>
>>> On Mar 18, 2016 9:52 AM, "Raghuram Bathula" <raghurambathula@gmail.com> wrote:
>>>>
>>>> Dear Hareesh
>>>>
>>>> Yes, it is. guidance for placement of thermocouples can be reffered to para 6.6.4 of AWS D10.10
>>>> control thermocouples on larger pipe and monitoring thermocouples on smaller branch connection
>>>>
>>>>
>>>> On 18 March 2016 at 06:03, Hareesh K V <hareesh13h@gmail.com> wrote:
>>>>>
>>>>> Dear Sir,
>>>>>
>>>>> As per ASME B31.3, for branch connections, PWHT is to be done for the entire circumference of main pipe. Is there any exceptions/code interpretations for that, in Carbon steel material or Alloy steel material (SA335 Gr P9,95)?
>>>>>
>>>>> For example: A 3/4" branch is done on the main pipe of 60" dia. As per the code requirement, the entire 60" dia is to be wrapped with coil and PWHT is to be done.
>>>>>
>>>>> Thanks in advance.
>>>>>
>>>>> Regards,
>>>>>
>>>>> Hareesh K V
>>>>> +91-8547859202
>>>>>
>>>>>
>>>> --
>>
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