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How differential pressure switch works for filter

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Differential Pressure Switches, some people call it as Differential Pressure Controller, Some People call it as Pressure Differential Switch, some people call it as Differential Pressure Flow Switch.  This is a very useful device in the automatic Backwash or backwashing system.

The Backwash system could be the process of thoroughly cleaning a swimming pool's filter by a method of reversing the flow of water to flush out contaminants. Back-flushing filters also could be self-cleaning systems where a cleaning of the filter elements with the filtrate is generated by flow reversal. Depending on the type, a distinction is made between manual (hand-operated) and automatic back-flushing filters This way, you don't have to clean the filter manually, and it usually takes just a few minutes. Continue the process until the water runs clear through the waste line.
auto backwash filter

[The Differential Pressure Switches in the automatic Backwash Filter system]


If you want to meet the above function of auto back-flushing, you have to install a differential pressure switches in your filter, to detect the differential pressure between inlet and outlet.

Differential Pressure Switches is installed across the filter in order to identify filter dirty condition by the pressure difference so, Differential Pressure Switches positive tube must be installed before the filter or say positive side(when dirty particles get into the filter, pressure will increase here) and negative tube to be installed after the filter say negative side and pressure range selected as 50Kpa for Differential Pressure Switches.

1. Initially when a fluid at the off condition, before the filter and after filter will be same pressure, so there is no differential pressure across before and after the filter. here pressure differential pressure or PD is zero.

PD=0 Kpa and lesser than 50Kpa(set point)

so here still NC and C remain the same.
GE-511A Differential Pressure Switches with Brass Body

GE-511A Differential Pressure Switches

GE-511A Brass body is Pressure Differential Switch with adjustable setpoint. The adjustable differen...


2. When the Pump starts to run, let us say on the negative side is 100Kpa and the positive side is 105Kpa, where the Pressure difference across the fan of the positive and negative side is

PD=105-100Kpa.

PD=5Kpa still lesser than 50Kpa(set point).

so here still NC and C remain the same.

3. Immediately when the dirty particles get into the pipe and it’s filtered by the filter, let say pressure difference before the filter and after the filter will be little high let say 120Kpa in positive side and 90Kpa in the negative side so

PD=120Kpa-90Kpa

PD=30pa still lesser than 50Kpapa(set point).

so here still NC and C remain same or say the filter is still clean and reporting to the BMS PLC PLC

This signal will be connected to BMS PLC PLC controllers or any other control circuit to perform the required operation.
GE-511C Differential Pressure Switches with stainless steel body

GE-511C Differential Pressure Switches stainless steel body

GE-511C differential pressure switches adopt stainless steel material, dirt resistant, sterile, sani...


4. After Pump running a long time, when more dirty particles get into the pipe and it’s filtered by the filter, let say pressure difference before the filter and after the filter will be high let say 150Kpa in positive side and 80Kpa in the negative side so

PD=150Kpa-80Kpa

PD=70Kpa is greater than 50Kpa( set point).

So here Differential Pressure Switches triggers NC to NO and C.

This signal will be connected to BMS PLC controllers and report as dirty signal for filter or any other control circuit to perform the required operation.


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