Mechanical pressure switch principle and features

The mechanical pressure switch is a purely mechanical deformation that causes the micro switch to act. When the pressure increases, the different sensing pressure components (diaphragms, bellows, pistons) will be deformed, and will move upwards. Through mechanical structures such as railing springs, the uppermost micro-switch will finally be activated to output electrical signals.

UE 120 series pressure switches can provide different pressure, differential pressure, vacuum and temperature ranges, and can also provide different connection methods, various materials and pressure sensing element types. It is precisely because of this flexible selection method that the 120 series UE pressure switches can be widely used in various places, such as chemical, petrochemical, oil refining, oil fields, drilling platforms, oil pipelines, and various industrial processes such as pharmaceuticals.

Working principle of mechanical pressure switch

Mechanical pressure switches in a compact design ensure safe pressure monitoring in pumps, compressors and mobile work machinery. Regardless of the application, these pressure switches work on the principle of a preloaded spring and use a diaphragm or piston as the pressure measuring element.

Under this working principle, two forces act:

Process pressure

The measuring element of the pressure switch responds to the process pressure value. Therefore, the meter is designed in two ways. At lower process pressures, mechanical pressure switches use a diaphragm (because of the larger surface area to absorb the pressure), while at higher pressures, mechanical pressure switches use a piston with a smaller surface area.

Preload spring force

Adjust the spring force by adjusting the screw of the pressure switch. The further the screw is screwed in, the greater the spring force the measuring element has to overcome and the switching point value increases accordingly. The spring geometry is designed according to the desired switching range. According to the functional principle of mechanical pressure switches, the switching point is defined by the spring preload. It sets the switch point of the switch when the pressure increases and the reset point of the switch when the pressure decreases.

Features of mechanical hydraulic pressure switch

 1. The mechanical pressure switch is a switch with pure mechanical action, with simple internal structure and easy installation and maintenance.

   2. The output of the mechanical pressure switch is a switch signal, and one action point or two action points can be set, namely the upper limit and the lower limit. When the pressure reaches the upper limit, the switch will output an alarm signal. When the pressure is lower than the lower limit, the switch will Another signal is output, which causes the device to switch on automatically. The action point of the mechanical pressure switch can be adjusted according to the user's needs.

   3. The mechanical life of the mechanical pressure switch is long, the stability is good, the response time is short, and the sensitivity is good.

   4. The work of the mechanical pressure switch does not require power supply, and it only needs to be connected to the equipment for pressure control and output switch signal.

Debugging method of air pressure switch

1. The right adjustment screw on the top of the mechanical pressure switch is to directly adjust the upper limit switching value;

   2. The left adjustment screw on the top of the mechanical pressure switch is to adjust the pressure difference of the switch;

   3. Their relationship is: upper limit switching value - switch differential pressure = lower limit switching value, when the user wants to adjust the lower limit switching value, he needs to adjust the right screw and left screw on the scale.

How to set the control pressure switch range?

When choosing a setting range, the user must consider the maximum system pressure that the pressure switch will withstand. For example, for WIKA compact instruments, PSM01 and PSM02 (adjustable hysteresis) are available in 6 MPa (diaphragm) and 35 MPa (piston).

The switching point setting range of the pressure switch is smaller than the overload safety limit of the pressure switch. This means that pressure peaks can be absorbed. This is important, for example, for no-load operation protection of pumps. In this case, the system pressure may be many times higher than the switching point value of the pressure switch. Therefore, the piston-type PSM01 and PSM02 pressure switches have a switching range of up to 32 MPa. The diaphragm version of both models can switch pressures up to 1.6 MPa. The relatively small range is due to the particularly sensitive measuring element, which guarantees high repeatability. Therefore, larger switching values and overpressure ranges will require stronger diaphragms at the expense of repeatability.