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flange and outlet flange connections. Oil filler, oil drainage and external evacuation
connections are provided on the hydrokinetic drive/gearbox.
The timing gears on all of the EH1200, EH2600 and EH4200 model pumps are lubricated
by oil inside the gear cover. An oil filler connection is provided. The oil level can be
inspected through a sight glass installed to the gear cover.
2.2.3 Principle of operation
The pump is shown in
EH1200FX, EH2600 and EH4200 pump
through the hydrokinetic drive. The 1:1 gears inside the hydrokinetic drive/gearbox drive
the second rotor in the opposite direction inside the stator housing. A small, accurately
gauged clearance is maintained between the rotors and between each rotor and the
stator wall. This clearance allows the pump to operate at high speed without mechanical
wear and without the need for lubrication inside the swept volume.
2.2.4 Hydrokinetic drive
The hydrokinetic drive consists of a fluid coupling which connects the electric motor
shaft to the rotor. This system is configured so that when the gas load is high, the
rotational speed of the rotors is reduced. As the gas load decreases, the rotors
accelerate to full speed. This allows continuous operation of the pump over the vacuum
range without the risk of overloading the motor and removes the need for bypass valves
and associated pipelines.
The fluid coupling is viscosity sensitive. The two versions of the pump (for hydrocarbon
and PFPE oils) have fluid coupling drives which are specifically designed for the type of
oil used in the pump.
2.3 Chemical and ATEX compliant EH pumps
2.3.1 Flameproof motors
For all EH250C, EH250T4, EH500C, EH500T4...T3, EH1200C, EH1200T4, EH2600C,
EH2600T3, EH2600T4, EH4200C, EH4200T3 and EH4200T4:
▪
Pumps suitable for 50 Hz operation are installed with a flameproof motor
approved to Ex db, Ex db IIB, Temperature Class T4.
▪
Pumps suitable for 60 Hz operation are installed with a flameproof motor
approved to CSA, Division 1 area, Gas Class I Group C & D, and Dust Class II Group F
& G, Temperature Class T3C.
▪
If the pump is operated in a IIC external environment, fit a IIC motor to the EH
mechanical booster.
2.3.2 ATEX directive (2014/34/EU): Europe only
ATEX compliant EH pumps with an internal T3 or T4 temperature classification (refer to
Temperature classification
system only if the pumps are configured and used in accordance with the requirements
of this manual. For ATEX compliant systems using an EH booster pump in combination
with an EDP dry pump, the requirements of the ATEX Instruction Manual (see
'Associated publications') must also be met.
A30151880_AA
A30151880_AA - Introduction
Figure: EH250FX and EH500FX pump variants
variants. The motor shaft drives one of the rotors
on page 14) may be used in an ATEX-compliant vacuum
Page 12
or
Figure:
11/2020 - ©Edwards Limited
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