MKS HPS 917, Operation And Maintenance Manual

Page: 8 / 32

2 Pirani Vacuum Sensor System
Do not use te Serie 917 System's Pirani Sensor with
explosive gas mixtures or with gases that are
combustible in air.
If the control circuit fails or an exothermic catalytic reaction occurs at the
sensor wire, the wire could ignite the gas mixture.
Prevent chances of explosion when using with gases other
than air or nitrogen.
The sensor is calibrated for air/nitrogen, so the measured pressure will differ
from the true pressure of another gas. Calibrations diverge widely at higher
pressures. With no linear relationship for the gases, a gas correction factor
could lead to hazardous overpressure. Capacitance manometers and
mechanical dial gauges are best suited for higher pressures. Refer to page 18
for use with other gases.
Take precautions to avoid overpressure during
system backfill.
When backfilling, do not use the Series 917 Pirani System to read pressures
above 100 Torr. In a system which is filled with a pressurized source, install a
safety relief valve or burst disc to safely limit pressure and prevent an
explosion.
The Series 917 Pirani Controller contains lethal voltages
within the casing.
Avoid the danger of electrical shock. Disconnect the power cord before
opening the Controller case.
Turn off power to the Controller before plugging or
unplugging cables to the Sensor.
The Controller is grounded through the conductor of the power cord. Plug the
cord only into a properly grounded outlet. If the protective ground connection
is lost, all accessible conductive parts may pose a risk of electrical shock.
Prevent personnel injury by making sure that only qualified
technicians service the Series 917 Pirani System.
Safety Precautions and
Other Procedures