Fabrication Parts – Riser Clamps in Revit (Problems & Solutions)

I run into a number of people who have had problems with Riser Clamps and Revit Fabrication Parts. I have as well. Here’s how you can work around them…fairly easily.

Problem #1 – Clamp Will Not Attach to Vertical Riser

The first problem I see is with Riser Clamps not attaching to vertical pipe. I’ve seen some creative workarounds. From just placing a clamp in space and moving it to near where it should be to using a modified form of a Grooved Coupling pattern. The following video shows what that would look like if you have this issue.

The fix for this issue is fairly simple. First, make sure you’re using Pattern Number (CID) 838. This is the original Hanger pattern that will allow you to make just about any hanger. Secondly, ensure that you select the ‘Slide‘ option on the pattern.

This is the ONLY Hanger option that will work for vertically oriented pipe.

Once you use the proper option, you can observe that a Riser Clamp will attach to the vertical pipe. This can be seen in the following video.

The second Riser Clamp’s configuration uses the ‘Slide’ option. This allows us to attach it to vertical pipe. This sets us up well for the next issue….oversizing.

Issue #2 – Oversized Riser Clamps

The second issue is that if you set your Insulation Specification’s material to Oversize Hangers, the Riser Clamp will also oversize. This isn’t something you do with a Riser Clamp. Many of us have brought this issue to Autodesk on several occasions, yet they seem to struggle with understanding of our need for an option in this pattern to “ignore” oversize.

Luckily, with a little added work and user intervention, we can work around this. To resolve the issue, create a secondary Riser Insulation Specification with a material that does not oversize hangers.

To do this, you’ll need a duplicate of your Insulation Material. In the image below, we configure the insulation on the right not to oversize for systems where we do not require thermal pipe inserts.

Once you have a secondary Insulation material, you can create the Insulation Specification for the Riser.

Now, all you need to do is override the Insulation Specification on the Riser (vertical pipe) before placing the Riser Clamp. You can see this in the following video.

You can see how the vertical pipe get’s a pipe sized Clamp, where as the horizontal pipe will still oversize because we didn’t change it’s insulation specification.

I’d like to thank Kevin Allen and William Tucker of Comfort Systems USA for pointing out this embarrassingly simple workaround for Insulation Specification that seemed to escaped me.

Adjusting Liner Lengths on Elbow Throats & Heels in CAMduct

Any sheet metal shop that CNC cuts their liner has likely configured their database to make seam adjustments in the liner developments. These settings are typically global and tell CAMduct to remove the Liner thickness from the Male or Female part of the development.

Another common setting is the compression adjustment in the Insulation Materials. These are all fairly common and self explanatory for most people looking to configure these settings.

Length Adjustments on Radius Elbows

What’s a little less obvious is how to adjust the throat and heel lengths on a radius elbow. If the liner is developed based on metal size, the throat is typically too short and the heel a little long. This is due to the bending allowance of thicker materials. While acoustic liner has a little give but when using something like armorflex for liner, it’s a little more rigid and these lengths can cause issues.

To better understand the Throat and Heel of a radius elbow, we can look at the Top view (cheek). The following image shows the Throat and Heel pointed to with arrows. You’re looking at these parts on their edge.

Prepare Your Fittings

To configure the calculation used for the liner on these parts, you first need to change an option on your ITM. The following image is for a radius elbow (CID 4). Here you’ll want to change the “Insulation Parts” Option to “Wraps Inside“. If you leave this set to the default “Same”, the adjustments made later will have no effect.

Configure Material Adjustments

To make adjustments to the liner calculation, you’ll go to the Insulation Materials and click the “Insulation Developments” button.

This will bring up a dialog where you can make changes to how the liner gets developed on the throats and heels. The various settings are as follows…

Metal Side

Throat & Heel Liner Developed to the same length as the metal fitting.

Air Side

Throat & Heel Lengths Developed Based on the AIR side of the liner thickness.


Throat & Heel length developed based on the middle of the liner thickness.

Value (Between 0.0 and 1.0)

Value is between 0 and 1 as a percentage of the liner thickness calculated from the metal side.

0 = Same as “Metal Side”
0.5 = Same as “Middle”
1.0 = Same as “Air Side”

Not All Fittings Supported

Not all fittings support the “Insulation Parts” option. You can run one of the Library export scripts that dumps all the OPTIONS to a CSV file and sort in Excel to look for the CID’s in your library that support “Insulation Parts”. Scripts can be found here.