RE: [Man.Distr]RE: Impressed vibration

Many thanks for your answer. I fully understand the implication of what I doing. I do not have a direct responsibility to this issue. However I have been asked to advise on the course of action to be adopted. The client will review my proposal and take appropriate measures.

In fact a purge vent line has already snapped but fortunately it was after the block valve so there was no leakage. I did not witness the vibration when it happened. I am more than glad, I did not. From what has been told and from the damage that has been done it can be inferred that there is a vibration of significant magnitude. Also this vibration is related to the flow rate.

This incident happened after operations went in for the higher flow rate. But it was soon brought down to the lower level after this incident. It is currently operating without vibration. Shim plates and guide angles were placed under the ineffective supports. This has arrested the vibration. There is no noticeable vibration to the eye or by feel now. Operations do not intend to go to the higher flow rates until they receive the go ahead.

My advice has been to do a vibration monitoring study by the equipment condition monitoring team with controlled increase in the flow rates by operations.

Please have a look at the attachments that I am sending to you off-list.

Merry Christmas,

Sajit

-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com] Sent: Wednesday, December 24, 2003 8:16 PM To: ?
Subject: [Man.Distr]RE: [PipingDesign] Impressed vibration

>The 24" piping joins the 48" pipeline from the side at the center. Will
>this be a reason for the vibration.

Things vibrate because they're subject to cyclic loading. You need to find the source of the loading before you can fix the problem. I'm assuming that you really do have vibration that causes movement somewhere and not just a noise that rises and falls. If you do have such movement, you're going to end up with a fatigue failure before long, so you might want to stand back a mile or so--too close and it could really spoil your whole afternoon. A ruptured LNG line is serious damn business.

So your first problem is to find out what's making the pulsing loads and fix that. Don't worry about the rated capacity--the rating has nothing to do with rogue vibration response, so it's irrelevant. And don't just strap the pipe down--you're only removing a symptom, not curing the patient.

I'd suggest that you get someone in there who knows both LNG systems and vibration before you have to take the plant down to fix it. Or before the plant takes itself down.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)

[Non-text portions of this message have been removed] Received on Thu Dec 25 02:28:00 2003