You did not say if the tie-ins are above or below ground. Burried flanges is not prefered, but it could be done by using ceramic coated stud bolts and nuts and FBE coated flanges and welds.
Leaks from below ground flange gaskets are hard to monitor and detect early and very likely it will happen on of the 11 tie-ins.
I have been involved with many tie in 12" to 30", we typically maintain constant air flow from the upstream and downstream vents toward the tie-in point with continuos LEL monitoring.
For best in class operations, you can use the Pipe freeze plugging method see http://www.pipefreezing.com/ for more information.
Pipe Freezing
Pipe freeze plugging is a simple, cost-effective method to perform pipe maintenance or line modification without shutting down your plant process. Using liquid nitrogen, Freeze Service, Inc., a division of T.D. Williamson, Inc., can isolate the problem area in the line with SOLID freeze plugs of the fluid within the line. This allows the job to be done with very little draindown or refill, no loss of expensive process fluids, and in many cases, no system downtime. Once the work is completed, the plugs are thawed and the line is back in operation. Standard freeze plugs range in size from 1/2" to 48" OD.
Successful pipe freezing is accomplished by establishing solid freeze plugs and maintaining them during the duration of the project. Freeze Service's freeze plugs are constantly monitored and designed to withstand up to 8,000 psig line pressure or 225,000 pounds force. Independent laboratory tests have documented that no physical change in the structural matrix of the pipe occurs due to the controlled freezing process.
melvin_magbanua <melvin_magbanua@yahoo.com> wrote:
I would like to solicit your opinion and advice gentlemen regarding
our tie-in joints (11 joints) in our upcoming pipeline
repair/replacement (ASTM
A106 PIPE Std thickness) activities for our crude oil transmission
line 16" and 10", both are 50 km long, 50 yr old lines.
Can we use a flange joint for the tie-ins instead of welded joints? I proposed flange joints since we can not insert pipeline balloons or Pipe plugs during tie-in if we don't have a flange connection.
My question is. if flange connection acceptable for line like this?
The line will be drained before it will be handed over to the contractor but for sure, flammable gases would still be emitted by the remaining sludge inside the line.
One incident similar to this tie-in in Kuwait National Petroleum Company âKNPC which they are going to do a tie-in welding in a 30" line about 1.5km long between isolating valves, at the beginning teh LEL readings was zero, but after sometime when during tie-in welding was goin on, the flammable fumes emitted by the remaining sludge inside the pipe was ignited and the welder was thrown 6 meters away due to the explosion and was hospitalized due to 3rd degree burns.
It was a good lesson learned and don't want it to happen in our tiein project. Please I need your input gentlemen so I can consider it in our scope of work (constructability issue and safety will be considered).
[Non-text portions of this message have been removed] Received on Wed Jan 24 19:57:00 2007
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