MKS 640A/641A - Gas Pressure and Control; Pressure Limits; Installing the Unit

Chapter Two: Installation Gas Pressure and Control
15
Gas Pressure and Control
Pressure Limits
The control valve, enclosed in the 640 Series controller, is rated for a maximum inlet pressure of
150 psig for orifice sizes A through 4; 30 psig for orifice sizes 5 and 6. For more information
refer to
Applications with a Large Differential Pressure,
page 42.
The control valve is
not
a positive shutoff valve. Some leakage across the valve may occur.
Refer to
Appendix A: Product Specifications,
page 53, for the leak integrity specifications. If
necessary, install a separate positive shutoff valve in your system.
Caution
Take care not to expose the transducer to pressures above its full
scale range. Pressures exceeding 45 psia or twice the full scale
pressure (whichever is greater) may damage the transducer.
Installing the Unit
The 640 Series Pressure Controller can be mounted to provide either upstream or downstream
pressure control. Your application determines how to mount the unit into the pressure system.
Connect the port labeled “Controlled Pressure Port” to the system whose pressure you need to
control.
Note
MKS defines “u
p
stream” and “downstream” control b
y
the location of the
controlled volume
relative to
the 640 Series Pressure Controller.
Downstream Pressure Control
Downstream pressure control occurs when the 640 Series controller is positioned
before
the
controlled pressure volume in the gas flow path, so that the controlled volume is
downstream
of
the 640 Series controller. The gas flow enters the 640 Series controller on the valve side,
opposite the “Controlled Pressure Port.” Figure 1, page 16 shows the gas flow for downstream
control.