Bronkhorst Mass Flow - Manual (Page 23)

BRONKHORST HIGH-TECH B.V.
Clean parts and carefully re-assemble in reverse order. It is recommended to replace the O-rings prior to re-
assembly.
After having re-assembled the control valve, it is recommended to check the control characteristics of the
valve. This can best be done by using a separate variable 15 Vdc power supply source.
Proceed as follows:
- disconnect the valve leads and connect to supply source
- apply gas pressure as per working conditions
- apply power by gradually increasing voltage
- the valve should open at 7 Vdc ± 3 Vdc
- the fully opened position is reached at approx. 9 Vdc ± 1.5 Vdc.
In case the valve does not operate within the voltage levels stated, then it must be disassembled, and the
orifice must be adjusted to the proper position.
Re-assemble valve and repeat procedure if required.
4.6.2 Vary-P valve
The vary-P valve is designed to cope with extremely varying process conditions on either upstream or
downstream side of the valve or a combination of these. ∆p can vary over a wide range. The basic control
valve is a direct operated solenoid control valve.
The design has been patented.
For orifice selection and maintenance other than the pilot valve consult the factory.
4.6.3 Pilot operated valve
This control valve is an indirect control valve, consisting of a spring-loaded membrane/orifice system which is
positioned by a solenoid operated direct control (pilot valve). The two devices are integrated in one block.
Basically follow the same procedures for dis-assembly as stipulated under “Solenoid valves”
For cleaning purposes it may be required to dis-assemble further, i.e. also remove the membrane assembly.
Note:
When pressure testing a system incorporating a pilot operated control valve, a special procedure must be
followed in order to prevent damage to the valve. In such cases it is necessary to contact the factory prior to
do this.
4.6.4 Bellows valve
These valves are suited for low pressure or vacuum applications. Preferably the user should not disassemble
this model.
9.17.001 page 23