EBARA A70W Instruction Manual page 65

(V)
The following interlocks are available as customer-specified options on A Series pumps for
toxic/flammable/pyrophoric applications:
Exhaust Purge (Dilution) Nitrogen Flow Low
A flow switch trips when nitrogen supply to the exhaust line drops below the field-adjustable
set point, opening the motor starter relay(s) and shutting down the pump. Restoration of
sufficient nitrogen flow permits restarting the pump. Users must determine appropriate flow
setting based on process gas types and amounts found in the pump exhaust stream.
Cabinet Exhaust Pressure High (Cabinet Exhaust Flow Low)
A "spool piece" mounted on the cabinet exhaust port and connected to the user's exhaust
system provides a mounting point and sense tap for a differential pressure switch, which
detects vacuum level in the exhaust line. If the pressure differential between the exhaust
vacuum and atmosphere (inside the pump enclosure) drops below the level required to
maintain sufficient exhaust flow, the normally-closed contacts in the pressure switch break,
opening the motor starter relay(s) and shutting down the pump. Because vacuum pumps
typically operate unattended, the interlock does not provide visual and audible alarms.
Restoration of differential pressure, and thereby cabinet exhaust flow, permits restarting the
pump. The spool also provides an auxiliary port (¼" tube) for connection of a vacuum
gauge/manometer or insertion of a hot-wire anemometer to measure exhaust parameters.
Additional Sensor (Optional)
Liquid Leak Detector: While not a safety interlock, a leak detector installed in the pump
serves the function of providing protection for personnel and equipment. A controller
senses resistance between two conductive elements in the base of the pump. The
presence of moisture reduces this resistance below a set point, and the controller ports a
signal to the pump CPU, stopping the pump.
Optional Features Note
Cabinet Exhaust Flow Sensor and Liquid Leak Sensor: Strict compliance with SEMI S2-93A
(and S2-0200) requires a cabinet exhaust flow interlock and a leak detector. Most
customers find incorporating these features, as needed, into facilities sensors is more
economical than including the capability with each individual pump. See Appendix 3.
EBARA Corporation