Description
11
GA01301_002_C1 - 07/2018 - © Leybold
The gas ballast valve is opened (position I) and closed (position 0) by turning
the gas ballast knob (7/5) on the front.
The gas ballast facility of the TRIVAC BCS pump has been prepared for con-
necting 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-lubrication
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.
The oil pump is fitted in the front end plate on the coupling side of the pump
module. The oil suction line is placed low, resulting in a large usable oil reser-
voir.
The oil is separated from the gas in the TRIVAC BCS in two steps as descri-
bed above. First, small droplets are coalesced into large drops in the internal
demister (2/11) fitted above the exhaust valve (2/10). Then, the large drops
fall into the oil reservoir as the exhaust gas is diverted by the inner walls of
the oil case. Thus a low loss of oil is obtained. This and the large usable oil
reservoir ensure long intervals between oil changes even at high intake pres-
sures.
The vacuum is maintained by the TRIVAC BCS through an integrated hydro-
pneumatic anti-suckback valve (2/3) which is controlled via the oil pressure.
During operation of the TRIVAC BCS the control piston (4/3) remains sealed
against a spring (4/2) by the oil pressure. The valve disk (4/6) of the anti-
suckback valve is held at the lower position by its own weight (valve open).
When the pump stops (because it has been switched off or because of a fai-
lure), the oil pressure drops and the spring (4/2) presses the control piston
(4/3) up. Thus a connection is provided between the oil case or the oil reser-
voir (4/1) and the piston (4/4) of the anti-suckback valve.
Due to the pressure difference between the oil case and the intake port the
oil presses the piston (4/4) up and the valve plate (4/6) against the valve seat
(4/5). The quantity of oil in the oil reservoir (4/1) prevents the entry of air into
the intake port (2/1) at the beginning of this process.
After the oil has flowed out from the reservoir and when the valve plate rests
on the valve seat, air follows in, which vents the pump chamber and forces
the valve disc (4/6) against its seat. This effectively prevents backstreaming of
oil or oil vapours. The anti-suckback valve (2/3) operates independently of the
operating mode of the pump, i.e. also with gas ballast.
All aluminium surfaces of the TRIVAC BCS are surface protected and thus
particularly capable of resisting aggressive chemicals. A thermocouple has
been incorporated in the pump which is used in connection with the optional
electrical monitoring facility. The thermocouple may be accessed through the
built-in connector (7/8).
Via a second oil fill opening, an exhaust line may be connected for venting
the oil case when using the inert gas purging facility.
