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When do I need to use a Thermowell?
A Thermowell is a device for physically, but not thermally, isolating a bulb or probe from the temperature media being sensed. Thermowells should be used to protect the bulb from otherwise intolerably corrosive media or excessive pressures. All electromechanical temperature switches may be used with a Thermowell when pressures exceed 300 psi, if high velocities are present and with corrosive or abrasive media. Thermowells also allow removal of the temperature switch or sensor without loss of contained media. When using a thermowell with a local mount temperature switch, two set screws are provided to secure the switch in the well allowing 360° rotation for easier electrical connection and readability. The use of a Thermowell may increase response time to temperature change. By using heat transfer material, the increase can be kept to a minimum.
When should I use a split nut, and when should I use a union connector?
When your temperature switch uses a standard thermowell, use a split nut to retain the sensor bulb in the thermowell. When your temperature switch requires an extra length thermowell, use a union connector to secure the sensor bulb to the bottom of the thermowell. It is important to secure the sensor bulb to the bottom of the thermowell to ensure metal to metal contact for optimum heat transfer. If the sensor bulb is not in contact with the bottom of the thermowell, it takes longer for the sensor bulb to respond to changes in temperature.
A union connector will also seal the process connection when no thermowell is used. Note: The union connector contains compression discs and will seal to 300 psi.
What is the difference between a local mount type and a remote bulb and capillary type?
Local mount type temperature switches are installed in the pipe or vessel. In this type of sensor, the filling fluid surrounds the bellows. A negative temperature change forces the fluid to contract - expanding the bellows to actuate the switch.
Remote bulb and capillary type temperature switches allow the switch enclosure to be placed up to 25 feet from the media. These models use a bulb and capillary sensing device which may be ordered in standard six and 12 foot lengths. Extra lengths up to 25 feet are available. Six and 12 foot sensors can be copper or stainless steel with or without protective spiral-wound armor. The 25 foot lengths are armored stainless steel only.
When do I need to use a Hermetically Sealed switch?
Barksdale Hermetically Sealed Temperature Switches were created for use in hostile environments where exposure to elements such as salt air, hydrogen sulfide and other corrosive agents and atmospheres might cause contact deterioration and switch failure. The switch elements meet the requirements for Class I, Division II hazardous areas.
I need a custom temperature switch. Can you help?
Yes. All you need to do is provide Barksdale with a full definition of your temperature switch control problem with all pertinent information, including your target price. Upon acknowledging the feasibility of the project, Barksdale will submit to you a sample or drawings. We can then get together and discuss any variations or modifications yet required. These changes will be incorporated into the design in order to transform your temperature control problem into a new custom temperature switch.