BOC Edwards EO2K, Инструкция по эксплуатации

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EO2K, EO4K and EO6K Diffusion Pumps
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Issue G 2 Aug 06
1.2 Description
The EO series of pumps are compact, high-performance diffusion pumps. The pumps provide clean
pumping and minimum pump-down times, even when high-vapour loads are pumped. Three models of
pumps are available.
The EO2K, EO4K and EO6K pumps have a vacuum-brazed stainless steel body and a precision machined
aluminium interior. The component parts of these pumps are shown in Figures 1 to 4.
The body of the EO pump has a top-flange, a main body tube and a condenser assembly. All EO pumps
are available as water-cooled pumps. These pumps are cooled by water which flows through a stainless
steel cooling-coil wound around the main body and vacuum brazed to provide maximum cooling
efficiency. The condenser has a pre-formed stainless steel cooling-coil wound around it for optimum
cooling.
The EO2K pump is also available as an air-cooled pump. Refer to Figure 2. On the air-cooled EO2K
pump, the backing condenser has cooling-fins (2) and a cooling-jacket (1) is attached to the pump-body’
air is blown over the fins of the cooling-jacket by an integral electric cooling-fan (6).
The interior assembly has three fully-fractionating jet-stages and an ejector-stage. Above the top jet-stage
is a detachable jet-cap with a guard-ring. A plate heater inside the base of the pump heats the pump fluid
to generate the required vapour. A radiation shield is attached to the underside of the heater.
The electrical supply cables from the heater are brought out to a terminal-box at the bottom of the pump
for ease of connection to your electrical supply.
1.3 Principle of operation
The arrows in Figures 1 to 4 show the flow of vapour through the pumps. Pump fluid is heated in the
boiler to produce a vapour which passes up through the interior of the jet assembly and emerges from
the jets as high-velocity vapour streams. The vapour streams condense on the cooled pump-body wall
and drain into the boiler at the bottom of the pump for recirculation.
A portion of system gas which arrives at the pump-inlet is trapped in the vapour stream from the first-
stage jet. The gases are compressed and transferred to the next stage. This process is repeated through
the pump jet-stages until the gases are removed by the backing-pump through the cooled backing-
condenser.
The guard-ring above the top-jet is designed to minimise any back-streaming of pump fluid vapour by
trapping and condensing it on the cooled surface of the guard-ring.
The fractionating feature of the EO pump design provides a means of purging the fluid charge of
undesirable light fractions and foreign matter and the process helps significantly towards the attainment
of a low ultimate vacuum. The ejector-jet also purges the fluid of any contaminants as it returns to the
boiler and at the same time ensures a high critical backing pressure, even when you use low vapour
pressure fluids.
1.4 Performance
The ultimate vacuum depends on the fluid used in the pump, the leak tightness of the system, outgassing
from surfaces and the use of cold traps.
The performance values given in Section 2.2 are likely values which can be achieved with a clean system.