General information

Useful calculation data

ISO 9001

P

2

Example

11.5.7

P

2

Cert. No. LRQ 0963008

Note: = Kv √ P

1

,

Water

Valve Sizing Chart

= Water flow (m

3

/ h), P

1

= Pressure drop across the valve (bar),

This chart assumes no cavitation after the control valve.

TI-GCM-09

CM Issue 1

Kv = Flow coefficient (m

3

/ h bar).

P

1

How to use the chart

Note: the chart below is used for the following example only. A

complete chart is shown overleaf.

Example:

The heat exchanger has a MTHW demand of

The full-load pressure drop P

1

* Established from 'Valve authority' (see below).

Go to the selection chart below:

- Draw a horizontal line from 10 m

3

/ h

= 10 m

3

/ h

= 50 kPa *

- Run a vertical line from 50 kPa until it crosses 10 m

3

/ h line.

- Kv is given at this crossing point i.e. Kv  14

Refer to the Kv values given on the appropiate Technical Information

Sheet for each valve type.

SA (self-acting), EL (electronic) and PN (pneumatic) controls should

be sized on maximum Kv value.

Valve authority - Two-port valve

P

1

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P

2

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Valve authority

The ratio of pressure drop across the valve when fully open to that

across the complete circuit is termed the 'Valve authority' (N) and

Valve authority - Three-port mixing valve

P

1

Valve authority - Three-port diverting valve

is expressed as:

N =

Where: N =

P

1

=

P

2

=

P

1

P

1

+ P

2

Valve authority

Pressure drop across the fully open valve

Pressure drop across the remainder of the circuit

The diagrams opposite illustrate P

1

and P

2

more fully.

Valve authority is a means of selecting a valve size on a water

system with due regard to economic viability and good control.

When selecting a valve size, the valve authority should be between

0.2 and 0.5 (and preferably 0.5). This will ensure that each small

valve movement will influence some authority over the flow whilst

not excessively increasing pumping power costs.

Valve authority will always relate to the circuit which has a varying

flowrate.

Local regulations may restrict the use of this product to below the conditions quoted.

In the interests of development and improvement of the product, we reserve the right to change the specification without notice.

© Copyright 2006

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