RE: Dimensioned Isometrics

From: <ed>
Date: Thu Apr 14 2005 - 10:17:00 EDT


Dear Everybody,

In the past week I have read all kinds of dissertations about dimensioned isometrics.
I suppose there are many uses for piping isometrics, but I can only speak from my own experience.
We are a Design and Build Company and we fabricate 90% of our piping in our shop which are shipped
and installed in automotive plants all over the USA. Our Company prided itself as a Modular Build
outfit, meaning all we have to do in the field is to connect our shop fabricated/engineered assemblies.
Only 10% of the job is left for the field personnel to think about, mostly threaded runs (2" and smaller)
and some miscellaneous field cuts. This is how we do piping isometrics :

1.) Our Engineering Group make the piping layout, sections and detail drawings. It's important that these

     layout and sectional drawings are to scale and up-to-date.

2.) From these layout drawings we prepare our fabrication/isometric drawings. These are not scaled drawings,

     so it is important that they be dimensioned. In the olden days, they call these spool pieces, in our shop

     we call these fabrication assemblies.

3.) Each fabrication drawing is made from an 11" X 17" sheet and the size of the assemblies we make are usually limited

     by these size. It's Fabrication Drawings are tagged(for easy reference) and it's one would have the following:

  1. Fabrication Drawing No.
  2. Piping System the Fab is for.
  3. The piping material specification
  4. The dimensioned piping isometric assembly. Dimensions are usually center to center, end to end of assemblies. In these drawing, pipe sizes, fittings and connectors are noted. Very important to note that all straight pipes are tagged which would bring us to the Bill of Materials (BOM). Once in a while, if we do not have good information on equipment location, we provide Field Weld (FW) on our piping assembly.
  5. The Bill of Materials is what I call the heart of the fabrication drawing. These BOM should contain the following :

        (1) Each and every component description as to size, quantity, full technical description/specification.

        (2) The tagged straight pipes with corresponding size, quantity, length of cut, ends of cut( BE, PE, etc)

            and full technical description/specification. In cases of field welds, we usually allow extra length

            on the pipe to be cut to suit at the job site.

     Note : The Fabrication Drawing is arranged so that all these different components are clearly readable by the shop

            fabricators, keeping in mind that the lighting in the shop is not as good as the office, plus the eyesight

            of welders deteriorate rapidly in time.

4.) After the normal routine of Iso Quality Control Checking, these Fabrication Drawings is released to the Fabrication

     Shop. These is how the Fab Drawings are utilized :

  1. From the BOM, materials will be gathered and ordered.
  2. All pipes will be cut according to specified lengths and ends on BOM.
  3. The welder/fitter will make all welds and assemble piping according to piping isometrics, with special attention to checking specified assembly dimensions on isometrics to finished assembly.

5.) End of Book

Hope this helps,

ed

-----Original Message-----
From: Dacharaju Krishnamohan Rao [mailto:dk_rao@qp.com.qa] Sent: Wednesday, April 13, 2005 11:53 PM To: <a href="/group/PipingDesign/post?postID=zZvpfxGlLvmzypjuCi_dHsW8PFXjjDzdwXdLqxe_Xjreb5cqmiPc1W-BUEizGBzZe00-r7rAUt4UB1fHClX1eaIX2A">PipingDesign@yahoogroups.com</a> Subject: Re: [PipingDesign] Dimensioned Isometrics

Mr Paul,
I agree with you that isos are made to fit to field.I was talking about about "Field Welds Location" verification by Field staff and not dimensions.

With best regards,

D.K.M.Rao.

Paul Bowers <pbowers@pipingdesign.com> 04/14/2005 02:14 AM
Please respond to
<a href="/group/PipingDesign/post?postID=zZvpfxGlLvmzypjuCi_dHsW8PFXjjDzdwXdLqxe_Xjreb5cqmiPc1W-BUEizGBzZe00-r7rAUt4UB1fHClX1eaIX2A">PipingDesign@yahoogroups.com</a>

To
<a href="/group/PipingDesign/post?postID=zZvpfxGlLvmzypjuCi_dHsW8PFXjjDzdwXdLqxe_Xjreb5cqmiPc1W-BUEizGBzZe00-r7rAUt4UB1fHClX1eaIX2A">PipingDesign@yahoogroups.com</a> cc

Subject
Re: [PipingDesign] Dimensioned Isometrics

Dacharaju Krishnamohan Rao wrote:

> In addition to the information as indicated by Mr Adolphus, the FIELD
WELD
> locations are also shown by some of the consultants in Engineering
phase

> which are usually verified (changed if required) by the field
peronnel.

No way. All piping isos are perfect and fit exactly in the field as drawn. Seriously, though...

Also, mark numbers for individual spools, field trim allowance, correct valve handwheel orientation, correct pressure seal direction for valve seats, high point vents and low point drains, consistent north arrow, heat tracing, notes relating to instrumentation design standards, orientation for HP/LP connections on orifice plate installations, flow direction, X-Y reference to a nearby structural column, instrumentation bubbles, related P&ID/model/piping GA reference, control valve default state, etc.

Paul



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