View Full Version : Need help with pipe fitting question

Steve Steven
10-18-2013, 09:15 PM
I have gone back to my last company as a design engineer. I am currently working on a piping drawing, and need help with a AutoCAD 2009 question.

I am working with 8" IPS thinwall pipe, 8.625" OD. I am using buttweld fittings, Navy drawing 1385880 type. These have a tangent on them ( a straight section on the end of the fitting).

Here is where I need help: I need to make a jog of 2 3/4" between a horizontal and a vertical run. I was going to put on a 90deg ell facing down, and then align two 45deg ells to get the offset I need. How do I show that with AutoCAD? I have plenty of room in the horizontal direction, so the jog in the horizontal direction is not a problem. I am not skilled with AutoCAD, but can get by with simple tasks. Anyone out there than can coach me through it, I would really appreciate it. What I am looking for is how to show the fittings on the drawing, with the offset.

The 8" 45deg ell has a 1 3/8" tangent on each end, so does the 90deg ell. I have a copy of the Navy standard as a PDF, but Photobucket won't take it. I could email it to someone if they want it.

Thanks for any help!


10-19-2013, 09:26 AM
My chart shows an end to center travel of 5" for a 8" 45 weld ell. That is a 10" travel for a two 45 offset, which is a offset of about 7".


If you slice a 45 in half, you would have about 2" travel, which would mean you would need an elbow of about 30 degrees (WAG you need to calculate what exactly... including weld joint allowance) but that should put you close. In the real world of weld fittings, we often 'section' them to what ever piece of a fitting yields the correct result.

If you used a 90 and a 45 you will find that you would need to cut a 45 down to less that a 22.5 elbow to get your offset using just those two fittings. (maybe 15 degrees?)

To find this empirically in cad you could draw a 5" line (the end to center length of the 90 ell) from a point to an adjacent line.
The distance from the end of the 5 " line to the adjacent line must be equal to or greater that a segment cut from a 45. If you use double lines to sketch this up you will see just how short the cut elbow segment can be. You need about .5" of the inside radius of the cut-down fitting.

A field calc might have been no more than a paper cutout of the end view of the 90 ell and a piece of plywood. Drive a nail though the paper pattern and swing it until you are left with a bit of 'throat' on the tight side of the fitting and trim a 90 or 45 to fit. In some cases the empirical paper solution takes less time than is required to boot the computer...

Been out of the cad world for about 5 years now, but you might find some online addons that will help. Did you check out the cad forums?? lotsa good help there as well.

retired plumber and welder... and I still love 6010

Steve Steven
10-19-2013, 09:44 AM
Thanks for your reply. You have a good experience in both the design and construction end. The problem with the solution you suggested is that the Army doesn't allow cutting fittings, as it removes the tangent. I just don't know how to show the slightly shifted view of two 45deg fittings.



10-19-2013, 11:42 AM
Sounds like you need three fittings: two 45-degree angles and a 90-degree angle

The two 45s will be welded together with the ends parallel and offset. That assembly will be welded to the horizontal pipe with assembly rotated slightly (about the axis of the horizontal pipe) to give the 2 3/4" offset. The 90 will be welded between the last 45 and the vertical pipe. Something like this.


10-19-2013, 12:45 PM
Thanks for your reply. You have a good experience in both the design and construction end. The problem with the solution you suggested is that the Army doesn't allow cutting fittings, as it removes the tangent. I just don't know how to show the slightly shifted view of two 45deg fittings.




So just to clear this up in my mind, do you plan on assembling the two 45's and them rotating them to achieve the 2.75" offset? Can't the army just spec a special fitting? :>)
Perhaps you can specify a custom bent section to be use for the offset

If you are only creating 2d drawings you could detail the 45 offset with a top (plan) view. Drawing two lines 2.75" apart, draw the 8.65" circle representing one fittings' plan view and then draw the other fitting on the other line so that the center to center distance on the 'offset", 7.07", (which would be what you can see in the plan view) which would represent the jog. This would also develop the angle of the jog's rotation. When you draw that in an elevation view all you would show would be the 2.75" 'jog'

cad sketch...plan and elevation view see:

We would typically draw this in an iso view, which in my industry was never to scale, to show the offset.

My 3D skills are woefully lacking, but I did have some experience with Quickpen, a $5k add on, but this seems to have been purchased/absorbed by Trimble... Things happen fast in the Cad world...

hope this helps...


Paul Alciatore
10-19-2013, 01:15 PM
I am not expert in either AutoCAD, pipe-fitting, or the drawings for that discipline. If I understand the question properly, I would think that the three, standard orthogonal views would show your assembly properly. You may need a note or two to express any difficult to understand parts. You can dimension the offset in those orthogonal directions, either center to center or from outside edge to outside edge, depending on which is more important.

The main problem I see is getting the proper dimensions for the rotated parts. I would get them by drawing the standard three views and rotating (copies of) each of them in a scratch area of the drawing. Perhaps put them on a separate layer so they can be saved, but not printed. You can then pick up points on the rotated drawing to get the exact dimensions for the angled objects in the standard views.

You had trouble trying to post a picture of this. You could have taken a screen shot by pressing the Print Screen button while AutoCAD was showing the drawing. Then you open Microsoft Paint or any other such program that allows you to paste in it and pasting that screen shot into the Paint drawing. Then you can crop it and finally save it as a .JPG file. Photobucket will accept this. I do this all the time and it will let you post anything you can see on your screen. You can add notes or other simple things like circles in Paint, but I find it easier to make any additional things in my CAD program where it is easier to control them.

Steve Steven
10-19-2013, 09:51 PM
That's exactly what I need to do. Ironmonger (Paul), thanks for the sketch. Just how I will show this in the section view I am not sure of yet, but I know how to do it in the plan view. I can probably just polyline it in for the section view.

Thanks guys for the help, its great to get someone else's views on something like this!


Paul A., I was able to do the screen shot and Paint thing with the fitting drawing, I don't think I need to show it at this point. Thanks for the help!


J Tiers
10-19-2013, 10:35 PM
No help for you now, assuredly, but in 3D CAD standard things such as fittings are normally available as 3D models from suppliers.

Virtually any 3D CAD will extract views in any set of angles, plus isometric, and all you have to do is to assemble the standard parts in the desired way. Then you pull the views you need. In cases where an exploded view is needed, they do that also, quickly and relatively painlessly.

I have done tons of Autocad drawings, although not with ACAD 2009, and as soon as I started working with a 3D package, I suddenly developed a total lack of interest in doing any more 2D.

Piping, and anything else 3D is just BETTER in a 3D package. And they are not hard to learn, once you grasp a few basic principles.