# Selecting strainers

Relations:

1. Water flow ratio at the strainer at Δp = p1 – p2 = 1 bar pressure loss:

1. Pressure loss at the strainer:

Note: Select the strainer based on the nominal line diameter for flow rates up to 1 m/s.

Quantities and units:

Kvs    m3/h        – flow ratio for different strainer diameters

Q      m3/h        – flow rate

p1      bar           – absolute pressure upstream of the strainer

p2      bar           – absolute pressure downstream of the strainer

Δp     bar           – pressure drop at the strainer

ρ       kg/m3      – medium density at the strainer depending on p1 and T1

The strainer can be selected based on calculations or characteristic curves.

CALCULATION

Determine the pressure loss between the inlet and outlet port of TerFOM 80 strainer based on the following data:

Data:

Q = 10 m3/h            medium flow rate at the strainer

Procedure:

1. Determine flow ratio Kvs:

From DN15-200 strainer data sheet

Specifications / Nominal diameter DN table

– flow ratio for DN80 is Kvs = 126 m3/h

1. Determine pressure loss at the strainer:

1. Table Technical specifications specifies Kvs flow ratio for each DN nominal diameter. Kvs flow ratio specifies water flow via strainer at 1 bar pressure loss between the inlet and outlet port.
1. Use Kvs flow ratio for a specific DN nominal diameter and nominal medium flow rate to determine the pressure drop at the strainer. To simplify, the medium density ρ for water is 1000 kg/m3.

CHARACTERISTIC CURVE

Determine the pressure loss between the inlet and outlet port for TerFOM 80 strainer using the following data (example 1) from the strainer

Data:

Q = 10 m3/h            medium flow rate at the strainer

Strainer performance

Procedure:

1. Determine pressure loss at the strainer:

From the strainer characteristic curve:

– pressure loss at the strainer is Δp = 0.025 bar