Flow Requred for Hot Tapping 1

[khardy]

Welding a 4" WOL on a std wt 10" live fuel line. The fuel is gasoline. This line runs from a tank farm some miles away to a port. We are sure the line is completely purged of all air. It would be very difficult to have any flow during the operation.

Must there be a minimum flow to weld the WOL on? API-2201 is a little vague. Elsewhere I have read that you can do this with no flow on a case by case basis.

My thoughts are to weld one pass at a time. The far end of the mainline at the tank farm is open to the tank which is vented - so over pressure due to thermal expansion is not an issue.

 

[BigInch]

Minimum flow should be enough to carry off any added heat.
Empty the tank and fill it during the hot tap.
Let your contractor worry about these things.

you must get smarter than the software you're using.

 

[khardy]

There is no where to empty the tank unless I rent something to put at the dock end.

 

[BigInch]

If there is nowhere to empty the tank, it's too hard for me to understand why you filled it.

Why not rent something to put at the beginning of the pipeline, pump it from the tank at hot tapping minimum flow rate to there. The hot tap won't care which way the flow goes.

you must get smarter than the software you're using.

 

[saplanti]

There is only pressure limitation during the hot tapping. The sealing system of hot tap valve is weakening the metal around.
Talk to the hot tap valve supplier for their limitation on the pressure for the hot tapping operation.

Hope it helps.

 

[Duwe6]

If it was mine, I would open all valves between the O'let and the tank, and [as usual for Hot Taps] slowly weld on the O'let, using E7018 3/32". Probably would have the welder keep the root and hotpass beads short - only burn about half of the rod, then let everything cool. Getting a decent flow will be impractical, UNLESS you could time the welding with the loadout of gasoline. In that case, just weld it up and try to get done before the loadout stops.

 

[ash9144]

You need to put some thought into what you are doing with this hot tap. Hot tapping is a dangerous operation. Time your tank fill/empty to accommodate the tapping. You could also use a nitrogen purge to give the cooling flow. Maybe fill that section of piping with water to eliminate the flammability.