The SP series thermal dispersion flow switch is a solidstate flow switch with no moving parts. It can be used for monitoring flow/no-flow conditions of a very wide range of liquids. The SP thermal dispersion flow switch can be provided with solidstate or relay output. They are relatively compact and can be applied in a range of pipe sizes. Available in a variety of process connection sizes, choices of lengths, and materials of construction to meet a wide range of application requirements. It is also available for general purpose and explosionproof environments.
Principle of operation:
The thermal dispersion flow switch is based on the principle of heat transfer. It consists of two temperature sensors. One temperature sensor is the reference and measures the temperature of the fluid where the thermal dispersion flow switch probe is immersed. The second temperature sensor is heated using constant power. This creates a temperature difference between the two temperature sensors. As the flow rate of the fluid increases there is a cooling effect due to the fluid moving past the heated sensor. The more flow, the more the cooling. A reduction in temperature difference between the two temperature sensors indicates that the flow rate exceeds a user adjustable set point. When the flow rate drops, there is less cooling, which causes an increase in the temperature difference.
Aplus Finetek offers the SP Series, a line of thermal dispersion flow switch products for liquid applications.
- No moving parts, solidstate performance and reliability
- 1~59″ per second (150cm/s) measuring range for water; 1~118″ (300cm/s) range in oil
- 304SS, 316SS, PVDF and polypropylene wetted parts
- Maximum operating pressure up to 1,450psi (100bar)
- Choice of NPN/PNP, N.O. or N.C. relay, or SPDT relay output
- Standard and custom extended insertion lengths
- Standard or high temperature, explosionproof units available
- LED indication of flow status
- Marine certified unit available
Applications and use include:
- Detect positive flow to control downstream process
- Ensure machinery safe operation with detection of coolant flow
- Food processing
- Many others
One specific application for the thermal dispersion flow switch is featured in the picture. A diesel engine for marine use with an SP series installed within the seawater cooling inlet. The flow switch ensures a positive flow of cooling water to allow the engine to operate.
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