Bronkhorst Mass Flow - Manual (Page 22)

BRONKHORST HIGH-TECH B.V.
4 Maintenance
4.1 General
No routine maintenance is required to be performed on the meters or controllers. Units may be flushed with
clean, dry inert gas.
In case of severe contamination it may be required to clean the laminar flow device and the valve orifice
separately.
4.2 Gas flow sensor
The gasflow sensor is constructed in such a way that for a change in range, the laminar flow element can be
removed. It is not recommended for the user to disassemble the instrument other than for removing the
laminar flow element for inspection, or range changing only. After replacing the laminar flow element it
becomes necessary to recalibrate the flow meter. When doing so proceed according to a suitable calibration
procedure. Depending on the model number laminar flow elements can be ordered separately.
4.3 Liquid flow sensor
The user cannot change the flow range of a liquid flow sensor. The sensor is an integral part of the
instrument and cannot be removed from it. For occasional cleaning the instrument may be flushed with a
cleaning fluid.
4.4 Pressure sensor
It is not recommended for the user to disassemble the pressure sensor, because the thin metal membrane is
very delicate.
4.5 Controllers
All sensor types can be combined with a control valve to be operated together as a control loop. Controller
systems are either available as separate units; a sensor and a control valve, or as an integrated unit.
If applicable maintenance procedures are described under “control valves”
4.6 Control valves
Control valves cannot be used for shut-off and/or on-off applications. Pressure surges, as may occur during
system pressurisation or deflation must be avoided.
4.6.1 Solenoid valves
These are considered to be the direct operated control and pilot valves. They may be disassembled in the
field by the user for cleaning and servicing. The parts can be cleaned with a cleaning liquid, or in an
ultrasonic bath.
To disassemble the valve proceed as follows:
a) disconnect the instrument connector (not necessary with separate valve)
b) remove the hex nut on top of the valve assembly
c) lift the cover (coil) assembly
d) unscrew the flange
e) lift valve assembly carefully from the base
f) unscrew set screw for the orifice and subsequently loosen the orifice and the orifice holder
g) remove the plunger assembly
page 22 9.17.001