Sensors Care in Extreme Environments

Sensors: ‘Normal’ vs. ‘Extreme’ Environments

Winter maintenance and snow melting systems are designed for “normal” environmental conditions. Sensors and controls for these applications are made the same way. Normally, ETI sensors detect typical amounts of snow, ice and freezing rain. Normally, ETI controls manage systems where safe dry surfaces and free-flowing gutters or pipes are important. Generally speaking, product installation and application expectations are for optimal operation under normal (that is, “typical”) climate conditions.

Actual environments are never typical. Sensors, controllers and systems work within given operational ranges. These ranges for ETI sensors allow for some extreme weather or environmental conditions. Further, these products may remain the best solutions technologically and economically for any given, even extreme, application. While specific examples are beyond the scope of a blog post, some applications share characteristics under extreme environments.

Additional care and installation/maintenance procedures will be required of any exposed device in extreme environments, even ETI moisture or temperature sensors. Consider those conditions which

• corrode a sensor grid, such as
  • Acid Rain
  • Sea/Salt Water
    • Pooled (temporary condition)
    • Submerged
    • Mist or Fog (“sea fog,” “salt fog” or “brine fog”)
• or coat a sensor grid with a non-conductive residue build-up, such as
  • Oil Spray
    • Drilling operations
    • Refineries
  • Dust

Extreme Sensor Sealing

Here are a few things to keep in mind if your situation runs to the extreme. As with any procedure, be certain to confirm with local code officials that the suggestions offered here will work for your specific situation.

First of all, ETI pavement-mounted snow and ice sensors, such as the SIT-6E, or deicing controllers, like the HSC-4 or HSC-5, are made from brass and resistant to corrosion from salt spray and acid rain. They may be cleaned with the use of a non-metallic scrub pad. Sensors in these environments should be placed on a periodic maintenance schedule for cleaning and inspection.

Pavement sensors subject to salt water or water pooling require extra care to seal the pavement cup and sensor.

If the sensor has wire splices in the pavement cup under these conditions, the silicone wire nuts may prove ineffective if the cup is not sealed well. In these cases, it is best to use a waterproof butt splice which is then wrapped with fusion tape and coated with a sealant and bonding compound intended for use as a moisture and corrosion resistant outer seal (like 3M’s Scotchkote™ Electrical Coating FD).  Depending on conditions, consider a second layer of fusion tape and sealant/bonding compound.  When the wires are spliced in this manner they should have no issues with water penetration.

Grid and Bear It

Sensing actual environmental conditions, the grid on an ETI sensor requires added attention in extreme applications.

In an acid rain environment, the moisture grid of an aerial sensor, like the venerable CIT-1, or gutter sensor, like ETI’s GIT-1, should be inspected routinely for corrosion. Acid rain and salt sprays can corrode a grid completely off its surface pad, rendering the sensor useless and a candidate for replacement. Routine inspection can help a sensor to operate optimally in these extreme conditions for years.

In exceptionally dusty or oily environments—perhaps oil extraction or refinery operations—routine cleaning of all sensors is recommended since dust and oil can become barriers to moisture contacting the sensors.  To remove oily films, a heavy duty scrub sponge or pad with tough fibers and/or abrasives, like Scotch Brite pads, or paper towels with rubbing alcohol can be used.