Welding on a live pipe 1

[God1knows]

Hi,
Has anyone got any good reference material in relation to how to assess if it is safe / or able to weld a collar onto a live water line? Am looking at welding a 20mm collar onto a 300NB water line, materials are: Collar = A516 Gr 60, pipe is A106 Gr B. Pressure in line is 6600KPag, with demin water flowing through it at

I'm interested in finding the basic process how this is assessed and the details involved. Are there any rule of thumb guidelines etc

Dave

 

[austsa]

Do a search for "in service welding".
Not easy, but definitely possible (if there is sufficient wall thickness on your pipe).

 

[bimr]

In nuclear power plants, welding often must be performed on piping systems that contain water. This occurs when the system cannot be isolated due to the piping configuration, plant operating requirements or the failure of a component in the system.

Obttain a copy of this paper:

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6167334

http://www.touchoilandgas.com/welding-procedure-development-repair-a46-1.html

 

[stanweld]

What is the diameter and wall thickness of the pipe - especially at the weld location?

 

[MiketheEngineer]

Be careful --- if you superheat the water - you can easily get a "steam" explosion. Did that to myself working on a 1/2'' water line that I thought was dry!!

 

[TGS4]

See ASME PCC-2, Article 2.10 "In-Service Welding Onto Carbon Steel Pressure Components or Pipelines". There are a large number of considerations, including Welder Performance Qualification...

 

[magzx12r]

Just a few comments:
1) Determine minimum thickness of pipe required for pressure containment of water - Internal pressure hoop stress calc
2) Add 0.1 inches for weld penetration factor and 0.04 inches safety factor to the minimum thickness calculated in step 1.
3) Take UT thickness measurements at the weld area to make sure actual thickness of pipe is greater than required thickness calculated in step 2.
4) Check welding procedures to ensure temperature of pipe with water flowing through it is not too low for welding.
5) Establish flow of water through the pipe prior to welding. There are min and max recommended rates for liquid flow during welding.
6) A qualified welder needs to do the work to reduce chances of burn through.
7) Have a contigency plan in place in case the welder does burn through the pipe.