HOT TAP ON 6 IN DIAMETER COMPRESSED AIR CARBON STEEL LINE

Date 03-22-2008 16:57

Is the pipe under pressure?

Hot taps are usually associated with petroleum lines that are in operation while the welding is performed. So, that is the reason for my question. You are using the term "hot tap" in a context that I'm unfamiliar with.

Best regards - Al

By thewelder (***)

Date 03-23-2008 00:32

The "hot tap" is a term most of us used when we "top" into a live lines went are working (any line), not just to reffer to a "live putroleum lines".

By Superflux (****)

Date 03-23-2008 02:38 Edited 03-23-2008 03:05

I/we've refered to it as a "Live Tap" when the product was non-petroleum. As in a "Hot Tap" on crude oil and refinery production piping, if there is no oxygen (no meaning 0%, "0" ppm of oxygen) then there is no risk of internal combustion. Ignition temperatures of any flammable substance under pressure with oxygen present, is going to be lower than the "normal" / ambient atmospheric environment that flash point charts are based on.
So, depending on the residue, % of 02 and pressure...Hmmm.... What is downstream? If it were to flash internally, could it just flare off the residue with nothing more than a small spike in pressure??? Or could you open a vent/blow down valve as a safety device?
If I were involved with such a project, I'd definately want a proceedure from a competent engineer of applicable discipline and said engineer standing right there during the operation!!! Or, have I just turned chicken in my old age?
Best to think this one through carefully.

It's been one of the biggest rushes of my career making hot taps in a refinery, knowing there is 600 degree F high pressure hydro carbon fluid only a fraction of an inch away and the slightest slip,cough, sneeze could instantly vaporize you, your co-workers and place the facility on "live CNN Breaking NEWS"!Good luck!

By Sourdough (****)

Date 04-05-2008 01:01

Nothing like welding through a 2 ft flame.......

By thomasyyz (**)

Date 03-23-2008 02:44

understand that when tapping a change in atmospheric pressure changes the ignition temperature, what I mean by that, at a higher pressure the ignition temperature is not the same as compared to regular atmospheric temperature. Do you really need to hot tap?

By Kix

Date 03-24-2008 17:40

I don't see any problem with a vent blowing down in the line somewhere. As long as the oil vapor is consistenly being burned or vented in the line their should be no threat of an explosion.

By YVAN

Date 03-24-2008 20:43

Additionnal informations about the application:

Hot tap shall be done on compressed air (90 psi), 6 inch diameter, carbon steel pipe, 1/4 inch wall thickness.

There is air flow in the line (volume not known yet)

We know API 2201.

We will measure cooling rate and control heat input.

We have done hot tap in natural gas and oil industry.

We know how to measure inside pipe temperature during welding.

Main concern is about minimum inside pipe temperature for ignition.

Thanks for helping me

Regards,

Yvan
Montréal
Canada

Thanhs for helping me with that work.

Regards

Yvan
Montréal
Canada

By Joseph P. Kane (****)

Date 03-24-2008 21:59

Don't do it!

Although most compressor lubricants are not flammable at normal pressures and temperatures associated with compressed air operations, at higher temperatures some may become vaporized and become flammable. Look at the vapor as a fuel air mixture in a diesel engine's cylinder.

By YVAN

Date 03-25-2008 00:30

Thanks for your comments.

We know it has already been done.

However we're not gone do it before making sure there is no ignition risk.

Regards,

Yvan
Montréal

By RonG

Date 03-26-2008 16:54 Edited 03-26-2008 17:23

Think in terms of Air to Fuel ratio. They need to be right for ignition.

By YVAN

Date 03-26-2008 17:52

Yes, you're right.

We know it has been done before.

But how to prove no risk.

I know that air flow will evacuate any flammable that may be produced by welding heat ( vaporized oil residue on inside surface of the pipe).

I would need some documented work.

Regards,

Yvan Lessard
Montréal
Canada

By pipeliner01 (**)

Date 03-31-2008 00:41

just a thought get in touch with TD Williamson, I heard they have a branch in Ontario- www.tdwilliamson.com
I work with an outfit where we do lots of hot tie-ins and hot work but I hear those guys are specialists in hot tapping.