Outdoor pressure transducers/tubing freezing

Hello all, I'm looking for ideas to keep transducers and tubing in un-insullated outdoor enclosures from freezing. We have some of the plug in wraps that never get unplugged so the elements fail. Pipe insullation isn't working. Just looking for some examples of what some of you do.
And..24vdc output cards are maxed out at all the sites, I could hard wire 120vac.
Thanks for any input.

I have seen incandescent light bulbs put inside enclosures. It becomes a problem($$)if they have to be explosion proof though.

I worked in the Chicago area many years ago and I distinctly remember how fun it was to deal with that. Anyway we pumped anti freeze in the tubing around the xmitters. Glycol I think. Alcohol may work. You will have to install some valves so you can isolate the xmitter. similar to a double block and bleed. Also if you move the xmitter above the process piping so the tubing is also above, that might help to keep water out. The system I was working was a fractionator(distillation tower). The process piping was hot or warm but minute amounts of water in the process would find its way into the tubing. We took a hydraulic hand pump and pumped anti freeze into the tubing from the xmitter.

Check this out. I have never used it should be worth a phone call.

http://www.ashcroft.com/tech/upload/TR-PI-23.pdf

http://www.prlog.org/11167668-freez...ransducers-survive-frozen-pressure-media.html

I found this using Google search with the search words "pressure transducers is freezing".

You might want to check out the search because there were many pages to look through.

I have used a variety of products in the past. In my last job I stuck with Chromalox products. They seemed to have a good survival rate and a wide variety of styles of products to keep the panel and tubing from freezing up.


note: I am not affiliated with Chromalox in any way.

Heat trace cable is heater element in the form of a cable.
There are two styles:
- mineral insulated, a fairly rigid tube for higher BTU,
- flexible, a plastic cable for lower BTU. (sold at retail for keeping gutters free of ice at hardware stores)

Obviously, it requires AC power for the heat source.

Self limiting heat trace cable is temperature sensitive, no thermostate needed.

Regular heat trace cable is turned on/off through thermostat control.

Heat trace is only expected to replace the heat loss from properly installed, dry insulation. It is not intended to keep uninsulated piping/tubing from freezing.

I've seen panel heaters and thermostats in enclosure catalogs.
I've used a 100W light bulb or two with a thermostat.

Distributors sell heat trace product. Google will find them. Nelson, Tyco, Thermon are names from my past.

all cabinet supplier have heater solutions for outdoors as it'snt insulated you will need more power and bring for sure a 120vac line to put 100-200w depending of the panel size

I assume your problem is actually two parts
1. Tubing and transmitters freezing in cold weather
2. Tubing between the cabinet and monitored location freezing

ASSUMING pneumatic system - you need to correct the problem at the source ie water in your compressed air. You need an instrumentation air dryer - I would prefer a refrigeration type myself. Arrangle lines to drain to a low point collection point with drain valve.

IF liquid and assuming water
The easiest may be glycol antifreeze IF it does not foul up your system. For Fresno this may be the cure. You may have to correct for density change of water glycol mix.

I would think Fresno the problem is same as Seattle - only for one or two periods of just 3 to 5 days. We are just now finishing one of our "artic" situations.

A light bulb or two in the cabinet may be the solution for short term problem or a hair dryer.

For external tubing heat trace that is compatible with tubing to avoid melting tubing. Insulation on top of that of course.

Dan Bentler