Friday, August 19, 2016

Industrial Temperature Sensor "Bends" the Rules for Process Control

Flexible temperature sensor
Flexible temperature sensor
by Moore Industries
Industrial temperature sensors (thermocouples and RTDs) all pretty much look, mount, and work the same way. Basically, you take a rigid probe and insert it into a protective well of some sort. The probe and well length is determined by the length required for immersion into the process. Convenience in mounting, inserting, and removing is almost always an afterthought and in many situations, a long rigid probe presents complications during installation or replacement. One manufacturer, Moore Industries, has found a better way.

Flexible temperature sensors are the new frontier in accurate temperature measurements and easy maintenance. They are designed to fit nearly everywhere, to be quickly cut to the correct length, and to reduce the number of spare parts a plant has to keep on hand.

Moore Industries "WORM" is a flexible sensor for thermowell temperature assemblies. It is designed to replace restrictive, rigid, straight sensor probes with a universal strategy that saves time and money.

When it comes to flexible and rigid temperature sensors, both can be inserted into thermowells or protection tubes, welded into place on boiler tubes or other objects, or clamped down for surface measurements. Both types of sensors are rugged, durable, and can measure a wide range of temperatures in industrial applications. 

Flexible temperature sensor compare
Comparison of rigid probe vs. flexible.
So, why replace rigid, straight sensors?

Rigid sensors have always posed installation and maintenance problems. It is difficult to work with rigid sensors— keeping the correct spares and replacing the sensors in “sagging” or dirty thermowells are some of the problems. When used with thermowells, a rigid sensor has to be the correct length to fit. That means a plant must keep several different lengths of spares in stock to fit every thermowell. If a thermowell sags from extreme heat or fills with debris, a replacement sensor often will not fit, and the thermowell needs to be replaced.

Replacing a rigid sensor can be difficult. Typically, a maintenance technician has to remove the enclosure cap, disconnect the wires from the transmitter or terminal block, disassemble the union, conduit and fittings attached to the transmitter and thermowell, and then move them out of the way before he or she can pull the rigid sensor out of the thermowell.

The flexible sensor was developed to ease these problems. The flexible sensor typically consists of a one inch, stainless steel sheath with an element and lead wires that are protected either with Te on or fiberglass insulation. A flexible temperature sensor, such as the WORM, slides into a thermowell or protection tube and is held in place with a spring. Advantages include easy replacement during maintenance and minimal need for spares - flexible sensor wires can be trimmed to the correct length, simplifying the need for spare parts because “one sensor size fits all.”

Five Reason to Consider Flexible Temperature Sensors:
  1. Flexible sensors help eliminate the debris problem.
  2. Wells installed horizontally have a tendency to sag with time and temperature.
  3. The “solid sheath” portion of flexible sensors is minimized.
  4. Flexible sensors gain durability in higher vibration applications.
  5. Replacing an old, straight sensor with a flexible sensor is easy and fast.
For more information on flexible temperature sensors, contact:

Arjay Automation
1178 E. Cliff Road
Burnsville, MN 55337-1577
Phone (800) 761-1749