Vibration Clamp - Hot Belting Material

[StressGuy]

Looking for some recommendations from the group on a material question.

I've got a recip compressor piping system and we're using
the fairly common stiffened strap type hold down clamps
to restrain the piping. Normally, we would use FABREEKA as
the belting material.

However, in this case, the compressor piping will see
temperatures in the range of 250°F to 300°F, and FABREEKA
is specifically limited to temperatures below 200°F, so it's
out of the game.

For most of the clamps, I am using Teflon to give some
additional dampening, and to provide some extra insurance
that the pipe will be able to slide thermally through
the hold downs. I'm calling for hard directional anchors
where I need to keep the line from moving axially.

All this is working fine, except for a few spots around
the machine itself. The pulsation study vendor has
asked for an additional directional anchor near the
machine at a point with little flexibility. Even with
modeling stiffness values for the pulsation bottle and
the restraint (had to ask my C/S engineer for a stiffness
of his concrete pedestal, that's fun) the thermal loads
on the compressor are higher than what the vendor can
handle.

The stiffness value that they have asked for is only
30,000 lbs/in, so a stiff directional anchor is not
required, but the vendor doesn't think the Teflon lining
is going to give enough grip to dampen the axial mode
shape that is the concern.

What I'm looking for is some kind of rubber/polymer based
material that is going to give a good bit of grip, but
that will also work at temperatures of 300°F w/o breaking
down like FABREEKA.

I'll be doing my own searching, but I imagine some of the
more seasoned members of the group have had to deal with
hot recip compressor piping before and can help steer
my investigation in some fruitful directions.

Thanks,
--ED Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.

 

[scotty36]

StressGuy,

I was excited to find your thread as it indirectly answers my question on another thread (see Pipe Supports Near Recip Compression). Could you please advise more about the "strap type clamp" you use? Do you design them/ fabricate them yourself or are they available in the market place? Also, when modelling, do you allow some lateral stiffness in the clamp, or do you only model the stiffness of associated steelwork?

No doubt you have found an elegant solution to your original material problem (above) by now. However, for the purposes of assisting others with this query, could I add the following.

I stumbled across a website yesterday (

http://www.esmat.net)

advertising a material called Eslin. They reckon this stuff is good to 560degC and provides technical details of the coefficient of friction. They can line the inside with PTFE for less friction.

 

[StressGuy]

The clamp type is the basic design provided by SouthWest Research Institute (SWRI) in San Antonio, Texas. They do a lot of work in Mechanical and Acoustical studies of recip compressor systems. Our companies standard strap type clamps are based on their dimensions.

Another source for an off the shelf design is Piping Technology and Products in Houston, Texas. You can find them on the web at

http://www.pipingtech.com

Check out the HD-1, HD-2, and HD-3 in their catalouge.

One of the reasons that we use the SWRI design is that the stiffness values are known. We use them in the computer models to insure the piping system's natural frequency is higher than the running speed of the compresser to avoid resonant vibration of the piping.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.