Vertical Information | Total Control

Valve Sizing

Valve sizing on a control valve is very important. The sizing graphs below are designed to assist in the selection of the correct valve size. When sizing a control valve the valve will control at a optimum between 20% and 80% capacity where 20% is the minimum flow and the 80% the maximum flow rate. This will prevent the valve from operating too close to the seat or from losing control during high flow.

Pressure Drop Chart

Valve Size	50 mm	80 mm	100mm	150 mm	200 mm	250 mm	300 mm	350 mm	400 mm
Minimum Flow	3.5 m³/h	7 m³/h2	12 m³/h	26 m³/h	48 m³/h	70 m³/h	90 m³/h	121 m³/h	149 m³/h
Normal Flow	47 m³/h	108 m³/h	180 m³/h	411 m³/h	710 m³/h	1120 m³/h	1365 m³/h	1945 m³/h	2500 m³/h
Maximum Flow	62 m³/h	130 m³/h	224 m³/h	520 m³/h	900 m³/h	1585 m³/h	1960 m³/h	2394 m³/h	3186 m³/h

Normal flow @ 6m/s
Maximum flow @ 7.6m/s

System Sizing

Another important factor to remember is that control valves can be installed in a parallel system (to increase flow range) or series system (to increase pressure range).

Parallel Systems

If there is a large flow rate range, it is advised to make use of a parallel valve installation system. A quick reference for a bypass valve is:

Flow rate	Main valve size	Bypass valve size
<3.6 - 47 m³/h	50 mm	12 mm
<7.2 - 108 m³/h	80 mm	25 mm
<12 - 180 m³/h	100 mm	50 mm
<26 - 411 m³/h	150 mm	50 mm
<48 - 701 m³/h	200 mm	80 mm
<70 - 1120 m³/h	250 mm	80 mm
<90 - 1585 m³/h	300 mm	100 mm
<121 - 1945 m³/h	350 mm	100 mm
<149 - 2500 m³/h	400 mm	150 mm

Series system

When the pressure reduction ratio through a control valve exceeds 5:1, it is recommended to have two valves in series installed. The pressure reduction will then be done in two stages.