What is a flow switch, in other words, a flow switch is used in industrial systems (heating, cooling, fire, etc.)
It is used for monitoring and controlling flow rates. The Flow Switch, whose contacts are in the open position when there is a flow in the industrial system, provides the security of the system by warning a system in the process or activating an action by closing its contacts and switching this information to the closed position as soon as the contacts detect the flow of the fluid. These actions can be given as examples, such as ensuring the operation of the pump after detecting the water flow, and opening the springs in the fire systems. Actions such as enabling the opening of the strings can be given as an example.
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Flow Switch Working Principle
It is possible to encounter flow switches in different shapes. The common working principle in all flow switches is that when the flow rate reaches the set point of the switch, it closes its contact and transmits the signal passing over it to an equipment or system. It could be a pump, alarm, etc.
The contact of the flow switch is open until it detects the flow rate, and it closes the contact when the flow rate reaches the set point.
Some of the flow switches can be produced in an adjustable way for adjustment according to the flow rate.
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What Are the Types of Flow Switches?
What are Paddle Flow Switches?
Pallet Flow Switches are designed with a hinged or spring-loaded pallet that provides direct contact with the fluid. During the flow, the current and voltage values that the contacts can carry are specified in the user manual of the flow switches from the position of the pallet, depending on the flow rate. By pushing forward, it closes the open contact and carries the signal over the contact.
What are Piston Type Flow Switches?
They are designed in such a way that a free-floating magnetic piston responds to flow.
What are Solid State Flow Switches?
Solid state flow switches are designed to operate on the principle of thermal heat transfer based on the flow rate of the 2 temperature sensors.
How to Assemble Pallet Type Flow Switch?
Before installation, care should be taken not to exceed the maximum pressure value specified in the user manual of the flow switch of the pipeline pressure. Crawler Type Flow switches (switches) must be mounted above horizontal pipes. They can also work in vertical pipelines. Connection can be NPT or BSP thread, size 1/2 , 3/4 or 1 inch.
Flow switches should be mounted on the pipe to process equipment such as pumps or valves, keeping the distances in accordance with the dimensions in figure 1.
It is not recommended to put flow switches at the pump inlet. It should be placed at the pump outlet. While mounting the flow switches, a pallet with a length suitable for the pipe diameter should be used. Pallets of different lengths are shipped by the manufacturer alongside the product and the flow switches.
Pallet Type Flow Switch Electrical Connection
Flow switches usually have 2 options as output signal. One of them is normally open contact (NO), the other NO+NC, SPDT can be optionally available. The voltage and maximum current values for which normally open reed contacts and NO+NC or SPDT outputs can be used should be checked from the manufacturer’s manuals.
Repair and Maintenance of Crawler Type Flow Switches
After the flow switches are installed, their tightness should be checked. Depending on the period of use, the pollution and corrosion on the pallets and the joints, which prevent sensitivity and movement, should be removed and cleaned by authorized persons by emptying the line and taking the occupational safety measures determined in your country. Necessary spare parts must be obtained from the manufacturer. Work on the electrical connections of the flow switches should be carried out by specialists, taking into account the electrical safety regulations in your country.