What are the types of flow switches?
September 27, 2021
The flow switch is mainly installed on-line or plug-in to monitor the water flow in the water system in the medium pipeline such as water, gas, oil and so on. When the water flow is higher or lower than a certain set point, the output alarm signal is triggered and transmitted to the unit, and the corresponding indication action can be made after the system acquires the signal. Avoid or reduce the "dry burning" of the host. There are many types of flow switches, and the common ones are as follows:
Here is the content list:
l Baffle flow switch
l Thermal flow switch
l Differential pressure flow switch
Baffle flow switch
Features:
1. The mechanical part of the baffle flow switch is safely isolated from the electronic part.
2. The baffle flow switch does not contain bellows which are easy to cause failure.
3. The electrical components of the baffle flow switch are not in direct contact with the metal parts with large temperature differences, and the problem of corrosion caused by condensate will not occur.
4. The baffle flow switch uses the imported magnetic sensitive switch as the electrical action component, which has less disconnection and reset flow.
Installation position
The installation position of the switch is generally installed in this section of the pipeline from the water pump outlet to the equipment outlet, and cannot be installed on the suction inlet of the pump, which will make the pump unable to absorb water normally and the switch can not be turned on. Special attention should be paid to this. Baffle flow switches allow horizontal (wire part on top) and vertical installation.
Thermal flow switch
Working principle：
It is designed based on the principle of temperature change of the detection head. A heating sensor and a sensible heat sensor are installed in the probe and are in contact with the medium. When measuring, the heating sensor emits constant heat. When there is no medium flow in the pipe, the heat received by the sensible heat sensor is a constant value. When there is medium flow, the heat received by the sensible heat sensor will change with the flow rate of the medium. The sensible heat sensor converts the temperature difference signal into an electrical signal, and then converts it into the corresponding contact signal or analog signal through the circuit.
Differential pressure flow switch
For the measurement of water flow, the accurate flow can be obtained by measuring the pressure drop at both ends of the valve and orifice plate, and then by checking the pressure drop and flow curve of the valve or orifice plate, and the flow rate can be obtained by the method of pressure drop. It has been widely used in HVAC's water side system and flows measuring instrument from 2003 to 2013. The application of differential pressure switch in HVAC system is mainly controlled according to the resistance and flow curve of HVAC equipment. Water-side heat exchangers in HVAC (sleeve-tube, shell-tube, tubesheet and commonly used plate heat exchangers), water filters, valves and pumps all have their performance curves of pressure drop and flow. As long as the measured pressure difference on both sides of the pressure difference switch is compared with the preset value, the flow can be accurately controlled.
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