RE: [PipingDesign] Sloped headers

From: <Richard>
Date: Mon Jan 14 2008 - 23:42:00 EST

Hi Ravi,
A trunnion is a pipe support that is comprised of two short pieces of pipe, each welded at the same centreline elevation horizontally on opposing sides of a vertical pipe (a double dummy leg arrangement, if you will). This "trunnion" rests on a structural cantilever arrangement and supports the weight of the vertical pipe. Commonly these are used as the first support on a downcomer from a tower as close to the nozzle as you can get. I'm having trouble visualizing this being used on a sloped line, and I suspect that you actually mean a base support (such as would be used at a control valve station) being used at each support on the sloped line.

If, as I suspect, you're referring to base supports then, yes, there is a problem with the design, and your checker is correct. A base support from BOP on to the top of the piperack steel support will accommodate very little growth in the line before it falls off of the support. This is why we use shoes of 300mm or more in length. Commonly a sloped line is supported on shoes and shims. The steel "T" or cantilever supports on the piperack have a common TOS for several bays and the slope is allowed for in varying shim heights from 25mm down to 0, then, when you reach the standard shoe height and no shim, you drop the TOS and start again.

If I'm off the mark here Ravi and have not answered your question, then please provide some more info that will give me a better visualization and therefore be in a better position to give an answer that you're looking for.

Best Wishes,
Richard B.
Calgary, Canada

-----Original Message-----
From: [] On Behalf Of ravi patel
Sent: January 14, 2008 9:47 AM
Subject: [PipingDesign] Sloped headers

In the current project of a petrochemical plant, one of the senior designers had run a sloped header 120 m long on trunions of varying height. he had issued the drawing 2 months ago.

Now we have a senior checker in company, who was going through the model review.
he wants it to revise the header and run it on shoes/saddle.

I just wanted to know whether anything was wrong with using trunions. Is it fundamentally wrong to run sloped headers on trunions??


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Received on Mon Jan 14 23:42:00 2008

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