GA01300_0902 - 04/2006 - © by Leybold Vacuum
7
Description
The pump module consists of assembly parts which are pin-fitted so as to
allow easy disassembly and reassembly. The pump module can be easily
removed without special tools.
Those of standard design are
not
suitable for pumping greater
than atmospheric concentrations of oxygen.
Before pumping oxygen (or other highly reactive gases) at con-
centrations exceeding the concentration in the atmosphere
(> 21 % for oxygen) it will be necessary to use a special pump.
Such a pump will have to be modified and de-greased, and an
inert special lubricant (like PFPE) must be used.
1.1
Design and Function
The rotor (2/7), mounted eccentrically in the pump housing (2/6), has two
radially sliding vanes (2/5) which divide the pump chamber into several
compartments. The volume of each compartment changes periodically
with the rotation of the rotor.
As a result, gas is sucked in at the intake port (2/1). The gas passes
through the dirt trap sieve (2/2), flows past the open anti-suckback valve
(2/3) and then enters the pump chamber. In the pump chamber, the gas is
passed on and compressed, after the inlet aperture is closed by the vane.
The oil injected into the pump chamber is used for sealing and lubricating.
The slap noise of the oil in the pump which usually occurs when attaining
the ultimate pressure is prevented by admitting a very small amount of air
into the pump chamber.
The compressed gas in the pump chamber is ejected through the exhaust
valve (2/10). The oil entrained in the gas is coarsely trapped in the internal
demister (2/11); there the oil is also freed of mechanical impurities. The TRI-
VAC BCS PFPE pumps do not have an internal demister. The gas leaves
the TRIVAC BCS-PFPE through the exhaust port.
During compression, a controlled amount of air – the so-called gas ballast
– can be allowed to enter the pump chamber by opening the gas ballast
valve. The gas ballast stops condensation of vapours in the pump cham-
ber up to the limit of the water vapour tolerance as specified in the techni-
cal data for the pump.
The gas ballast valve is opened (position I) and closed (position 0) by tur-
ning the gas ballast knob (7/5) on the front.
The gas ballast facility of the TRIVAC BCS pump has been prepared for
connecting the inert gas system IGS.
To enable the TRIVAC BCS to be used at intake pressures as high as 1,000
mbar, a special lubricating system was developed featuring force-lubricati-
on of the sliding bearings.
An oil pump (3/6) pumps the oil from the oil reservoir (3/5) into a pressure-
lubrication system which supplies oil to all bearing points (3/2). From there
the oil enters the pump chamber area (3/4) of the vacuum pump.
Warning
Operating principle
Oil filter
Operation with gas ballast
Lubrication system
