Cirrus SP101013.111 – 10 October 2012
MKS Instruments UK Ltd., Spectra Products
20
Exhaust Purge IN/OUT
You may want to connect the Cirrus to a nitrogen purge system, or vent the exhaust gas to an
extractor system. You may have been advised whether we feel for your particular application nitrogen
purging is necessary, desirable or absolutely vital.
Optional:
The Cirrus includes the facility to purge the turbo pump bearings and vent the vacuum
chamber with nitrogen. This feature is usually used when the unit is likely to be exposed to corrosive
and/or toxic gases.
Flushing the pump exhaust
Connect a dry nitrogen supply at a pressure of 1 - 2 p.s.i. above atmospheric pressure to the IN port to
improve detection levels.
Connect a second pipe to the port labeled OUT to exhaust the dry nitrogen safely. The exhaust
nitrogen may now contain corrosive/toxic gases.
Exhaust the pump only
Even if you are not using nitrogen purge you MUST connect the Cirrus to an exhaust system.
Blank off the port marked IN and use only the OUT to exhaust the pump.
The standard configuration of Cirrus does not use rotary pumps, so there will be no hydrocarbon
vapors emitted by the vacuum pumping.
However, options are available that may use external rotary pumps. These should always be vented
into an exhaust system.
It is important that the pumps exhaust gases are ALWAYS vented safely. Even if they are
not toxic or corrosive, they may cause asphyxiation.
Never block, or obstruct any pump exhaust, as this may cause dangerous internal
pressure buildup.
