20

Mechanical pressure switches

Definitions

Definitions

Pressure data

Overpressure

Pressure

over the relevant atmospheric pressure. The reference point is

atmospheric pressure.

Vacuum

Pressure

under the relevant atmospheric pressure. The reference point is

atmospheric pressure.

Absolute pressure

Overpressure relative to absolute vacuum.

Differential pressure Difference in pressure between 2 pressure measuring points.

Relative pressure

Overpressure or vacuum relative to atmospheric pressure.

Pressure data in all FEMA documents refers to relative pressure.

That is to say, it concerns pressure differentials relative to atmospheric pressure.

Overpressures have a positive sign, vacuums a negative sign.

Permissible working pressure (maximum permissible pressure)

The maximum working pressure is defined as the upper limit at which the operation, switching reliability

and water tightness are in no way impaired (for values see Product summary).

Bursting pressure (test pressure)

Type-tested products undergo a pressure test certified by TÜV affirming that the bursting pressure

reaches at least the values mentioned in the Product summary. During the pressure tests the measuring

bellows are permanently deformed, but the pressurized parts do not leak or burst. The bursting pressure

is usually a multiple of the permissible working pressure.

Setting range

Pressure range in which the cutoff pressure can be set with the setting spindle.

Pressure units

Important:

All pressure data refers to overpressures or vacuums relative to atmospheric pressure.

Overpressures have a positive sign, vacuums a negative sign.

Unit

bar

mbar

Pa

kPa

MPa

(psi) Ib/m2

1 bar

1

1000

105

100

0.1

14.5

1 mbar

0.001

1

100

0.1

10-4

0.0145

1 Pa

10-5

0.01

1

0.001

10-6

1.45 · 10-4

1 kPa

0,01

10

1000

1

0.001

0,145

1 MPa

10

104

106

1000

1

145

In FEMA documents pressures are stated in

bar or mbar.

Pressure data for a pressure

switchbased on the example

of DWR625:

Setting range: 0.5-6 bar

Perm. working pressure: 20 bar

Bursting pressure: >100 bar