In the 649 Pressure Controller, the Baratron® Pressure Transducer measures absolute pressure. Full Scale ranges of 10, 100, or 1000 Torr are available. Each 649 can control pressure from Full Scale to less than 2% of Full Scale. Prudent design suggests choosing the lowest possible Full Scale for the application, taking into consideration the overpressure to which the sensor may be exposed (both normal and accidental).
Please Note: This procedure is provided as a reference guide to sizing the orifice for most typical applications. To assure proper orifice size selection for the specific application conditions, particularly those where the procedure results in an orifice selection near the limit lines in the graph, please contact MKS Applications Engineers for assistance in selecting the proper valve orifice.
The flow through any orifice depends on the size of the orifice, the inlet and outlet pressures, and gas density. To simplify 649 Pressure Controller orifice selection, use the following procedure:
The flow meter is simply sized.
Type 649 Control Valves should not be used for positive shutoff. Where positive shutoff is required, a separate valve should be installed.
When selecting the location of an external shutoff valve, consideration should be given to the maximum pressure rating of the internal transducer and to the possibility that leakage across the internal valve over time can build up and result in a sudden surge of gas.
This information subject to change without notice.