About the double screw bundle
What the double screw bundle does on a fire line, and how to specify it.
The bundle, explained
A double screw bundle clamps the pipe with two rods working through a central member. It will hold a run horizontally or vertically, which is why it shows up on both the straight pipe work and the risers. The two-rod arrangement keeps the pipe centered and resists it rocking side to side at the support.
With rubber, or without, and why it matters
There are two configurations. With the EPDM rubber strip, the bundle isolates vibration and noise, and keeps the clamp from bearing hard on the pipe. Without it, the bundle is the all-steel version. The temperature rating follows the rubber: the rubber version is rated to -20 to 110 degrees C, and the no-rubber version is rated to 343 degrees C. Choose the version for the location, and say so in the order.
Material and finish
Carbon steel, electro-galvanized, with the EPDM strip added where specified. The finish matches the rest of the hanger range so the support does not corrode ahead of the pipe it holds.
Ordering it right
Send the line with the rest of the assembly rather than as a single part. State the size against the pipe outside diameter it serves, the finish, and the count. Pair it with the matching threaded rod, nuts, washers and anchors from the same range, and flag whether the design needs the fire-rated, FM/UL marked version, so the support arrives with the pipe instead of chasing it later.
