Solution

The static pressure of a liquid refers to the pressure measured by a sensor on a fluid.

In the field of centrifugal pump technology, the pressure of a centrifugal pump refers to the static pressure. According to EN12723, the pressure of a fluid (pb and PD) can be expressed as absolute pressure, while other pressures can be expressed as gauge pressure (e.g., the pressure calculated relative to the local atmospheric pressure at the time). In the vacuum industry, gauge pressure refers to the measured relative pressure value of the gas, expressed as a negative number.

How to calculate the static pressure of a liquid:

1. The pressure at the inlet section of a single-stage single-suction centrifugal pump (Ps). The pressure is calculated starting from the pressure at that elevation (zs).

2. The pressure at the outlet section of a centrifugal pump (Pd). The pressure is calculated starting from the pressure at that elevation (zd).

3. The pressure at the pressure gauge of the inlet section of a centrifugal pump (Psm). The pressure of the pressure gauge in a liquid-filled measuring pipeline.

Liquid-filled measuring line:  Ps=psm+pg zs ,m

ρ—Density of the liquid in the measuring pipeline

g—Gravitational acceleration

zs,m—Difference in height between the pressure gauge center at the inlet section of the centrifugal pump and the measurement point

Pressure gauge pressure in a gas-filled measuring pipeline:

Ps = Psm

Equal to the pressure inside the pressure gauge at the outlet section of the centrifugal pump (Pdm)

Pressure at the inlet section of the centrifugal pump (p). The pressure calculated starting from the pressure at the inlet section (Aa) at that elevation (za) (Ae).

Pressure at the outlet section of the centrifugal pump (pa). The pressure calculated starting from the pressure at the outlet section (Aa) at that elevation (za).

Atmospheric pressure at the installation site of the centrifugal pump (PD).

Saturation vapor pressure of the fluid (PD). Refers to the absolute pressure at which the fluid evaporates at the temperature of the inlet section of the centrifugal pump.