Thermal Flow Switch/Sensor

The Thermal Flow Switch And Sensor is a highly efficient and automatic control device used for monitoring and regulating the flow of liquids or gases in various industrial applications. Made of durable stainless steel material, this product can withstand extreme temperatures ranging from -20 to 80C Celsius. The product comes in an attractive orange color, making it easy to identify and install in pipelines. With a voltage of 24 V DC Volt, the Thermal Flow Switch And Sensor provides accurate and reliable flow control and measurement. Its advanced technology ensures precision and consistency in flow detection, making it an ideal choice for critical industrial processes. This product is easy to install and requires minimal maintenance, making it a cost-effective solution for your flow control needs.

Key Features

No Moving Parts

• Solid-state design ensures low maintenance and long service life

High Sensitivity

• Detects very low flow rates of liquids and gases accurately

Fast Response Time

• Provides instant switching output for flow / no-flow conditions

Wide Application Range

• Suitable for liquids, gases, and air flow monitoring

Compact & Robust Design

• Small size with rugged stainless steel housing for industrial environments

Adjustable Set Point

• Flow threshold can be easily configured as per process requirement

Temperature Compensation

• Maintains accuracy even with temperature variations

LED / Digital Indication

• Visual indication for flow status and switching output

High Reliability

• Works reliably in harsh conditions like vibration and pressure changes

Wide Operating Range

• Suitable for high pressure and temperature applications

Easy Installation

• Threaded or flanged mounting options available

Low Pressure Drop

• Minimal obstruction to flow compared to mechanical switches

Working Principle

A thermal flow switch works on the principle of heat transfer using the concept of convective cooling.

Basic Concept
It typically consists of:
Heated sensor (heater element)
Temperature sensor (RTD / thermistor)
The device continuously measures how much heat is carried away by the flowing fluid.
Step-by-Step Working
Heating Phase
o The sensor probe contains a heating element which is electrically heated to a constant temperature above the fluid temperature.
Reference Measurement
o A temperature sensor measures the actual temperature of the heated element.
No Flow Condition
o When there is no flow, heat remains around the sensor.
o The temperature of the sensor stays high and stable.
Flow Condition
o When fluid (liquid/gas) starts flowing:
It absorbs heat from the sensor.
This causes a drop in temperature of the heated element.
Heat Loss Detection
o The system measures the difference between heated and reference temperature.
o The rate of heat loss is directly proportional to flow velocity.
Switching Action
o When flow reaches a preset value:
The electronics trigger a switch output (ON/OFF).
o Used for: Flow/no-flow detection
Pump protection
Dry run prevention
Measurement Principle Types
1. Constant Power Method
o Heater is supplied with constant power.
o Temperature drop indicates flow rate.
2. Constant Temperature Difference (ΔT) Method
o Maintains constant temperature difference between sensors.
o Power required to maintain ΔT is proportional to flow.

Industrial Applications

Cooling Water Systems

• Monitoring flow in cooling lines of compressors, furnaces, and heat exchangers
• Prevents overheating and equipment damage

Pump Protection (Dry Run Protection)

• Detects no-flow condition in pipelines
• Automatically protects pumps from dry running

HVAC Systems

• Used in air ducts and chilled water lines
• Ensures proper air and water circulation

Lubrication Systems

• Monitors flow of lubricating oil in machinery
• Protects bearings and rotating equipment from failure

Chemical Processing Plants

• Flow detection of chemicals, solvents, and acids
• Ensures safe and controlled process operation

Water & Wastewater Treatment

• Detects flow in filtration units, pipelines, and dosing systems
• Ensures proper system functioning

Food & Beverage Industry

• Used for flow monitoring of milk, beverages, and process liquids
• Suitable due to hygienic and no moving parts design

Pharmaceutical Industry

• Ensures accurate flow in clean and sterile processes
• Used in purified water and CIP systems

Compressed Air Systems

• Detects flow in air pipelines
• Helps in energy saving and leak detection

Boiler & Steam Systems

• Monitors flow of feed water and steam lines
• Ensures safe boiler operation

Semiconductor & Electronics Industry

• Used for cooling water and ultra-pure fluids
• Ensures high precision process control

Fire Protection Systems

• Detects water flow in sprinkler systems
• Triggers alarms during fire conditions

Technical Specifications

Parameter	Specification
Measurement Principle	Thermal dispersion (heat transfer)
Measured Medium	Liquids / Gases / Air
Switching Output	4–20mA / PNP / NPN / Relay
Output Type	NO / NC selectable
Response Time	1 – 10 seconds
Accuracy	±1 to ±10% of set point
Repeatability	±1%
Operating Temperature	-20°C to +80°C (up to 120°C on request)
Process Pressure	Up to 100 bar (depending on model)
Power Supply	12–30 V DC / 24 V DC
Current Consumption	< 100 mA
CONSTRUCTION & FEATURES
Process Connection	Threaded (G 1/2”, G 1”, NPT) / Flanged
Wetted Material	Stainless Steel (SS304 / SS316)
Housing Material	SS / Aluminum / Plastic
Protection Class	IP65 / IP67
Indication	LED status indication
Set Point Adjustment	Potentiometer / Digital display
Mounting Position	Any (recommended horizontal for liquids)
Temperature Compensation	Yes
Certification (Optional)	CE / ATEX / ISO
Application	Flow / No-flow detection

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