Bronkhorst EX-FLOW Mass Flow - Manual (Page 11)

BRONKHORST HIGH-TECH B.V.
1.6 Control valve
1.6.1 Introduction
Control valves are not designed to provide positive shut-off, although some models have excellent
capabilities for this purpose.
It is recommended to install a separate shut-off valve in the line if so required. Also pressure surges, as may
occur during system pressurisation must be avoided. The following models can be distinguished:
Solenoid valve
This is considered to be the standard (direct operated) control valve. In general it
is a normally closed solenoid valve. The plunger is lifted by the force of the
magnetic field of the coil. The orifice under the plunger is removable for optimising
the orifice diameter. Also a normally opened solenoid valve is available.
Vary-P valve
For process conditions where up- and downstream pressure vary much,
a special type of valve, VARY-P has been designed. This valve consists
of two valves, a solenoid operated control valve and a fixed adjusted
pressure compensation valve.
Pilot operated valve
For high flow rates the pilot operated valve has been designed. A
solenoid driven control valve controls the pressure difference
across a piston, which lifts the main plunger.
flowcontrol
valve
pressure
compensating
valve
flowcontrol
valve
P1
pilot valve pressure
compensating
valve
P2
flowcontrol valve
9.17.028 page 11