FFWs on Isometrics

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9 years 2 weeks ago #8895 by mtvalla
FFWs on Isometrics was created by mtvalla
Hi all,

Am I losing my mind with this one ?......I'm used to having the extra allowance shown alongside the design dimension, i.e. if the design dimension is 575 with a FFW, then I expect to see the actual dimension on the isometric as 575+150 or 575 (+150).....however, it would appear the way I'm used to having it, is not how it's done in North America.....

.....instead it's simply 575 with a cumbersome note added to the notes part....seems long winded to me, especially when the 575+150 can be automatically generated by isogen

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9 years 2 weeks ago #8896 by Jop
Replied by Jop on topic FFWs on Isometrics
Another way of doing this is to include instructions for the added length in the Shop Fabrication Purchase Order in the form of a Specification or Mandatory Technical Notes.

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9 years 4 days ago - 9 years 4 days ago #8915 by 11echo
Replied by 11echo on topic FFWs on Isometrics
The basic concept here is that the "correct" dimension is not exactly known, so an additional length is added to the overall length of the pipe and the welders in the field will make the final determination during fit up. It is best to keep this effort as simple as possible (your drawing will pass thru a lot of hands before it gets to the field, and a lot of those people are not high on the pay scale ... ;) )!
What we normally do in my part of the world is just give the one dimension (in the scenario indicated here it would be 725) and then add the documentation "FFW" underneath that dimension, so two things will happen, when the spool is shop fabricated it will automatically be made to the 725 dimension (welders in the shop are only interested in a length they have to make ...not why), and once it's in the field the welders will see the FFW notation and know that that spool will be too long and they'll have to measure and cut the excess off that leg of the spool for finally fit up. You could put a note on the Iso-drawing indicating that "an additional 150 is added to spool lengths for "field fit up" (FFW)". However most experienced welders will know what's going on once they see the FFW notation ... they don't really care how much extra has been added, and they'll do what they have too to make the connection ...simple as that.
Last edit: 9 years 4 days ago by 11echo.

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9 years 2 days ago #8916 by Garzabla1
Replied by Garzabla1 on topic FFWs on Isometrics
The point is that your model is built to the correct dimensions and the additional 150mm is required because of the uncertainty that a particular connecting component will not be where the model shows it.
The designer will place an FFW at this point
Isogen will therefore generate the dimension without the additional 150 and indicate FFW.
In my world I do not allow ANY manipulation of an Iso.dwg after it is generated.
FFW will be defined as "150mm longer than the dimension shown" in the fabrication spec.
The following user(s) said Thank You: RobbC

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9 years 2 days ago #8917 by Jop
Replied by Jop on topic FFWs on Isometrics
Good comment Garzabla1 B)

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9 years 2 days ago #8918 by 11echo
Replied by 11echo on topic FFWs on Isometrics
Garzabla1

...Isogen will therefore generate the dimension without the additional 150 and indicate FFW.
In my world I do not allow ANY manipulation of an Iso.dwg after it is generated.


…So you pass the confusion & difficulty on down the line to the “lower bidding fab shop”, where the real brainy people work, because the wages are lower, to fabricate your spool pieces, and hope they read and intrepid your notes correctly, to calculate the “correct dimension” for fabrication!??
So what is the present day definition of a good piping designer? One that generates and document piping systems in a "monkey see, monkey do environment" only according to the limitations of his 3D piping program? …OR designers that can see beyond the fancy 3D program down to the construction people and try to make piping drawings that are really easy to read and understand to help eliminate possible confusion and construction errors? Draw your own conclusions! ;)

(10+1 ...10+1) @ JOPTsk –Tsk! ... :huh:

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