Gas-Ballast Control; Construction - Edwards RV3 Instruction Manual

With the mode selector set to High Throughput mode S , pressurised oil is fed to the
high vacuum and low vacuum stages. In this mode of operation, the pump can sustain
long‑term high inlet pressures.

2.4.2 Gas-ballast control

To pump high vapour loads, gas-ballast is delivered into the pump to prevent
condensation of the vapour carried by the pumped gases.
Air can be introduced to the low vacuum stage through the gas-ballast valve.
Alternatively, an inert gas such as nitrogen can be supplied through a suitable external
valve.
The gas-ballast control has three positions:
▪ Closed (position '0')
▪ Low flow (position 'I')
▪ High flow (position 'II')

2.5 Construction

The pump-shafts and rotors are made of high-grade cast-iron. The pump-body and oil-
box are made from cast-aluminium. All surfaces of the pump which are exposed to the
pumped gases are free from copper, zinc and cadmium.
Other materials of construction include fluorocarbon elastomer, nitrile, silicon,
chemically-resistant polymers, nickel and stainless steel.
A65201880_AA
A65201880_AA - Introduction
Page 12 03/2021 - ©Edwards Limited