RE: [PipingDesign] Sloped headers

From: <Richard>
Date: Tue Jan 15 2008 - 03:10:00 EST

Hi Mandar,
Thank you. I appreciate your explanation. I have always worked to three definitions to your one: "Trunnions", as I previously described. "Dummy legs" (horizontal piece of pipe welded onto an elbow), and "Base Ell Supports", such as those used at a control valve station and as you say a vertical piece of pipe welded "downwards". It is interesting and important to recognize that, while we all do the same work, we differ in our vernacular.

I agree that a base support, or vertical trunnion would work for convenient elevation change, however this approach mandates that a plate be incorporated into the design on the piperack TOS that is of adequate size to accommodate the thermal growth. While I personally have not seen base supports used in a rack, I'm still inclined to agree with Ravi's checker. Not because it's unconventional to me but because shoes meet the requirement without adding a plate.

Plus, using Ravi's 120m distance and a conservative slope of 1:500. The first base support is going to have to be 315mm high and work down to 75mm to give the fabricator some meat to work with. A shoe has a horizontal length to vertical height ratio of 3:1 (300mm long x 100mm high). Assuming a NPS 6 base support this ratio is 0.53:1 at the highest support down to 2.24:1 at the lowest. Regardless of the NPS pipe size for the base support, it'll never be as favourable a ratio as a shoe, and I predict a higher likelihood of binding with the base support design over the shoe design.

It's an opinion, and we all learn from sharing.

One last thing. I have never heard of a client opposing base ells or dummy legs on elbow. What is the reason for this?

Best wishes, and thanks for the fast response, Richard B.
Calgary, Canada

  -----Original Message-----
From: [] On Behalf Of
Sent: January 14, 2008 11:19 PM
Subject: RE: [PipingDesign] Sloped headers

A trunion can be defined as a dummy pipe welded to a pipe for supporting purpose (i.e. without puncturing the main pipe). This trunion can be on verticle pipe (One that you have explained) or it can be on a horizontal pipe (Downwards)
The trunion on horizontal pipe (Downwards) supports the pipe from below. Additional supporting arrangement can be added to the trunion like guides,
anchor, adjustable supports etc...

Advantage of using trunion on sloping horizontal pipe is that the trunion
length can be varied as per the slope, but the supporting beam elevation (On which the trunion rests) can be same. If the line size is too big a finite element analysis may be necessary to
determine if the trunion can take the load (Normally the support standards
are prepared taking this in to consideration)

Trunions are very commonly used to support the control valve stations. Trunions can be either welded to the pipe or to the elbow (Although some clients do not prefer trunion on elbow)

Have a nice day.
Motivation will almost always beat mere talent.

Richard Beale
<r_beale@shaw. <> ca>
Sent by: To
PipingDesign@yaho PipingDesign@ <> cc

15-01-2008 09:15 RE: [PipingDesign] Sloped headers

Please respond to

Hi Mandar,
I just read your post on this subject. By now you've seen my post. I am still puzzled as to how trunnions would apply in a sloped line, whereas you're seeing something I don't. Can you help me in this? If my definition of a trunnion matches yours, how does this apply to a slopped line? If my definition of a trunnion differs, then in what respects, and specifically in regard to the use in a sloped line.

Many thanks,
Richard B.
Calgary, Canada

-----Original Message-----
From: PipingDesign@ <> [mailto:PipingDesign@
On Behalf Of mapte@technip. <> com Sent: January 14, 2008 9:51 PM
To: PipingDesign@ <>
Subject: Re: [PipingDesign] Sloped headers

There is nothing fundamentaly wrong in using trunions for sloped lines. Some companies use trunions of a certain maximum length (e.g. 400mm). If your trunion lengths are within the support standard allowable lengths, it's OK.
If the line runs on shoes/saddles, the supporting structure elevation has
to change after every few supports.

However some clients (Operators) do not prefer pipe sections in supports due to difficulties in monitoring their corrosion. Check if this is applicable to your project.

Have a nice day.
Motivation will almost always beat mere talent.

ravi patel

com> To
Sent by: PipingDesign@ <>
PipingDesign@yaho cc
[PipingDesign] Sloped headers
14-01-2008 20:47

Please respond to

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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[Non-text portions of this message have been removed] Received on Tue Jan 15 03:10:00 2008

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