Re: [MW:32051] In -service welding on HP Gas line, prior to Hot Tapping. Need immediate suggestions.

Yes, we doing nitrogen purging. Thanks for your details with the experiment. 

Best Regards,

Venkat G

On Fri, 12 Mar 2021 at 2:20 PM, Sudhakar Kuppuswamy <sudhakarceng@gmail.com> wrote:

Hi,

As you have mentioned in your email already , it is always recommended to carry out Hot-TAP welding with a certain amount of minimum flow. 

In this case, the run pipe thickness is 15 mm. So,the risk is really low. Just recently, we qualified a HOT-PQR with 7.9 mm thickness and while buttering pass the maximum inside temperature on run pipe found is 350 Deg C .

I suggest you the following ,

Discuss with the process safety engineering team and seek advise on the maximum allowable inside temperature that is acceptable while welding(1st pass I.e buttering and 2nd pass mainly) 

They ll advise based on flash and fire point and internal pressure built up due to gas expansion and so on.

Also, check  the feasibility for nitrogen purging  the line during welding. 

Regards,

Sudhakar K 

On Wed, 10 Mar 2021 at 7:10 AM Venkatachalam Govindan <vinisaa@gmail.com> wrote:

Dear Respected ones, 

We are planning a hot tapping on the HP gas line, which is 30" dia, and thickness 15mm, and carbon steel material. 

Around 15-meter length, where both the ends are closed by check valves. 

The line is isolated, we want to weld a 2" dia ventilate on the 30" pipe.

There is no flow is possible. We have to complete this work at any cost, the client says. Is this okay for you? it can be safe? 

Due to 15mm thickness, we are planning to do by 2.5mm, E 7018 electrode by the lower current. 

Please advise, any vapor cloud will be an issue inside the pipe? or we can do it because thick ness is high?  or shall we ask for at least a minimum flow so the vapor cloud will not be there. 

Looking sincerely your support friends. 

For your information, we regularly do such hot tapping works, at 800PSI pressure, but, with the flow. 04m/s. 

--

Venkatachalam Govindan

QHSE Lead | Auditor | Trainer

(API U Trainer | IRCA Lead Auditor | Exemplar Global MS Specialist |CQI Practitioner)

Mobile +965-97604989

www.cgic.co.in E: info@cgic.co.in

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Regards,

Sudhakar K CEng MWeldI,IWE.

Welding & Metallurgical Engineer,

Email: sudhakarceng@gmail.com.

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