Piping Iso diagrams 2

[grunt58]

Piping Iso diagrams are from the center of the pipe, correct? See attached sample.

 

[danschwind]

I dunno if there is any standard prohibiting you of occasionally using the pipe's wall as reference when pertinent. I've used it in the past when it was pertinent to convey the information I was trying to highlight to the builders and IMO, conveying correct information is the ultimate goal of any technical drawing.

Not sure what you want us to see in the sample, except to make me happy that I use metric.

Daniel
Rio de Janeiro - Brazil

 

[grunt58]

Looking to see if others assume the sample drawings dimensions are from the centerline? There is nothing indicating that they are from the pipe wall. Alternately there is nothing indicating they are from the centerline. I understand not having the whole drawing doesn't help.

 

[danschwind]

Yes, the sample's dimensions are from the centerline.

I understood your original question wrong (could be that you failed a little to really explain your issue at first). But yes, Iso's are from the centerline except where indicated.

Daniel
Rio de Janeiro - Brazil

 

[RVAmeche]

Centerline is typically implied. If measurements are not from centerline, they should be clearly called out as such.

 

[LittleInch]

Yes, normallly centreline. But that is an odd sample. Appears to be a pipe stab into another pipe at an angle or some sort of weird mitre joint, given that the other end appears to be an elbow of unkown angle. Very odd.



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[grunt58]

Yes, it is odd. We are being asked to replace the angled "stabbing" section and the main pipe section. They are saying the dimensions are from where the pipes meet. No one here agrees with their thought. It's always interesting telling the customer they are wrong and can't read a drawing.

 

[LittleInch]

Well it's not very well detailed (to say the least....) but given the poor amount of information on the drawing they could be right given that this is a "stab in" It really should be called out as a detail so that it was clear but for me the key point is that they dimension it (very precisely!) to the weld ( the dot) where is the weld? - On the surface.

So for me in this very specific case it is the outside of the connecting pipe but it's a sh1te drawing and doesn't list many of the key design points. It should have it's own detail.

Do you have a photo? An angled off centre stab in?? WOW

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[danschwind]

Dunno if it is possible for your particular application in this case, but I would try to specify most of this spool with field welds to allow adjustments during installation.

Daniel
Rio de Janeiro - Brazil

 

[grunt58]

Picture attached.

 

[LittleInch]

Oh holy shit.

So not only is the pipe on an angle and rotated away from the centreline but the whole thing is rotated off the vertical up in location as well!!! Now that isn't int he ISO as far as I can see.

This must be pretty low pressure / low temperature given the lack of reinforcement around the weld.

Was the original pipe spool extended into the pipe like that? Possibly the only real way to make such a weird connection. Are you planning on cutting it off?

It looks like the rotation of the header pipe connection then gets the branch pipe in parallel to the main header pipe.

I think it could have been done a LOT better.

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Also: If you get a response it's polite to respond to it.

 

[danschwind]

"Oh holy shit" was my reaction as well.

I never saw a pipe extending into the other like this. Is this work finished?

Daniel
Rio de Janeiro - Brazil

 

[grunt58]

We are to extend the pipe into the larger pipe. We are going to fabricate in a verticle orientation. When installed it can be rotated into place. The small flange is a lap joint so it can be rotated to line up with the existing holes.

 

[LittleInch]

But that drawing is not what the iso or the picture show.

The branch pipe is rotated away from the header centre line by 35 degrees.

Now your drawing may in fact work with the lap joint flange able to rotate but you need to mkae sure there's nothing in the way as the pipe joint will need to be rotated further around.

This has all the hall marks of a late addition / site bodge up / fit up to me. I can't actually believe anyone actually designed it this way!

This is some weird connection.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[grunt58]

I don't follow you. We just rotated the pipe 35deg as that is how it will get fabricated. I'm not going to ask our shop to figure out how to rotate it to an orientation they can work with when I can just rotate the CAD model. We laid it out in 3D as the Iso drawing shows hitting all our dimensions and angles. We just then rotated it to a vertical orientation on the fabrication drawing.

Also, this is in a corrosive environment so it is a replaceable section. The material is very expensive. I'm not saying it couldn't or shouldn't have been simplified geometry so it can be fabricated and replaced easier.

 

[LittleInch]

Don't get me wrong, I think it will work, but it doesn't match the iso.

Your drawing above doesn't show the rotation away from the centre line, but maybe that's in the instruction to the shop.

what do you mean by "rotated the pipe 35 degrees". Which pipe and 35 degrees from what?

If you figure it out in 3D for the connection then I think a simple 30 degree stab in and elbow rotated the appropriate amount to match the end point connection flange. Then you need to work out some new dimensions.

But that pipe extending into the pipe is very odd...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[grunt58]

My apologies we rotated it 45deg to vertical. This way our shop can focus on hitting the 45deg stab and the dimensions shown. We reference the installation orientation for inspection.

 

[LittleInch]

No problem. That original iso was something weird though.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MJCronin]

The strange in-line component you describe does not belong on a "piping iso drawing" ..!!

In the same manner that you can fabricate and certify a pressure vessel from piping components, that vessel should not be dimensioned and detailed on a piping isometric drawing !

Make a seperate detailed drawing of your bizzare "whatever" and refer to this drawing on the adjoining piping isometric drawings

MJCronin
Sr. Process Engineer

 

[saplanti]

Are you sure it is a stab-in pipe which is extended to the centre of main? You'd better get confirmation on that, otherwise you may need to cut internal part at site. Sometime this kind of drawings may be misleading without details.