Fixing Acute Angle Pipe Deflection and other Piping Errors in Revit MEP

This tip comes straight from the top, from my buddy Dave Pothier...even though he's management now, he's still a geek at heart - gotta love it...

We had a recurring couple of problems with fittings we had defined for Ductile Iron pipe. When Autodesk brought their new versions out a short while ago for the AWWA standards, we were still having some issues, so we had a chat with Dave about it.

Problem 1 - some fittings at angles like 45 degrees could not be created, and we kept getting a "line too short" error - even though you could set the angle in the family, and it would work fine. As it turns out, my techs were modeling an existing plant on a project. To keep from getting crazy plant dimensions, they did what any good CAD tech would do - they set the units to 1/2" and 1".

Then we sailed in trying to place fittings that were accurate down to 1/16" - so when these fittings would try to fit under the higher scale, they couldn't be placed. We changed the project units down to 1/32" and everything works again. Go figure...

Problem 2 - this one was a doozy, and we had a lot of back and forth about it. When we finally did a web session with Autodesk, we were explaining how mechanical joint pipe connections have to be able to flex up to 5 degrees (2.5 each way) around a fitting, since all of this work is buried underground (and gasp, dirt does move). We also had ongoing problems where we could get pipe to deflect at angles great than 90 degrees (since the fitting angles were all between 0-90) but not at acute angles (when the deflection needed to occur, since these fittings don't exist as standard). Their fittings weren't doing deflecting, but then Dave noticed how we had the pipe connector set on the fitting. Here's part of his response:

"...Select the (pipe) connectors and temporarily change the system classification from “Fitting” to “Global”

Once you do that, you can turn On the Allow Slope Adjustments check box. After turning it on, set the System Classification back to Fitting. Do that for both connectors.

Now the fitting should allow the pipe to deflect without the fitting’s angle adjusting. I’m not sure how great of an angle you can have but it should work for what you are doing. Let me know if this works for you."

Now we when make the connection, we get piping deflecting the right way:

Sometimes it's just the simplest things - but thanks again to Autodesk for helping us out, and really get the most from this great package! I'll make sure we get this into the Revit MEP lab I'm teaching at AU, so you can see how do fix this first hand.

Have a great evening! David B.

 

Do your Revit MEP Pipe Fittings Appear Funky...or Just Plain Wrong?

It's always good to start a Monday off with a mind bender...got a call from one of my techs (that is really good at Revit already, but still learning a thing or two). He had been working in a site specific project, where they were working on piping in tunnels. He got to a valve vault - laid out the piping, then cut a section - and got this for his view:

I went through all the usual tech support convolutions - checked the graphics settings, unloaded and reloaded the fittings, etc. When I got to the part of deleting the fittings and replacing them, I was using the Routing solutions tools - and started getting all kinds of errors. Then I remember something I learned a while back...

Revit accuracy is only good to about 1/256" in plan views, so if the angle of the pipes is somewhere south of this, it could potentially cause graphic errors. BAM...that was it...so here's the solution: DON'T work in a true north plan view if you've got a lot of perpendicular or parallel pipe. Create a duplicate of your overall plan, then create cropped views of key areas (in this example, a valve vault). Rotate the view, and make sure you're drawing pipe orthogonally in the view. Here's the steps:

We start with a project layout that looks like this...

Which was part of a series of steam tunnels on a site. Since the plan is based on existing sketches, or field verifications, it’s tough to get it accurate – but in our industry, we at least try to get it to close to 1” or less. 1/256” is far more accurate than we’ll ever get in the field using traditional methods.

So the valve vault shown is the area we want to work in:

Note that it’s a little skewed from a traditional plan view. If your instinct is to just start drawing the pipe, then STOP – that’s where you’ll get into trouble. In this case, the view was worked on at this angle – so when the pipe angle relative to the vault wall is measured, it comes up like this:

Even though it looks correct when “eyeballed” (which is how a lot of users did this in plain AutoCAD or Microstation), it’s enough of a variance to cause Revit to fail, and you get section views like the one at the top of this post. Notice how the graphics for the elbows is missing – it’s because of the slight angular distance variation between the section cut (which is based on the wall of the vault) and the pipe line. So how do we fix this?

Normally, piping inside of structure is parallel or perpendicular to the structure. Since it’s tough to lay pipe out at this angle, start by creating a duplicate of the overall view, and then rotating the duplicated view, so it’s orthographic.From the view control bar, select the Show Crop Region tool. Make sure it’s turned on (the light bulb is yellow). Use the ZF command to zoom out and see the entire view.

Next, pick the viewport – if it’s bigger than the area you’re working in, use the grips to stretch it down to size:

Once the viewport is the size you want, select it, and then pick the rotate tool from the Modify tab. By default, the rotate tool will be centered in the view:

Left Click on the center of the rotation, and drag it to a known point on a wall or corner:

Once it’s where you need it to be, pick the angle you want to rotate the view to first – normally, this would be 0 degrees. Pick a point to set the rotation, then pick a point along the wall, which is usually less the 90 degrees rotation:

I used a near snap to snap along a wall face, so I know I’m picking it accurately. After picking the second point, the view should look like this:

Now, when I add pipe, I can add it orthogonally, aligning it easily with the architectural components.

If your pipe and equipment is correct, but all off by the same angle, then place the objects into a group, and rotate the group – but in a lot of cases, you’ll find it’s easier to recreate the pipe layout from scratch. I tried it both ways on this particular model, and because there were little variations in the different pipe runs, it was easier and quicker to just start over, and draw it correctly. Don’t try to do piping, duct, cable tray or conduit layouts in the original overall model, but instead work in the rotated views – and you won’t have as many graphical or connection issues.

later - David B.