Gas-Ballast Control; Construction - Edwards RV3 Instruction Manual

1.4.2

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').

1.5

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.
© Edwards Limited 2018. All rights reserved.
Edwards and the Edwards logo are trade marks of Edwards Limited.
A652–01–880 Issue Y
Page 5