Agilent Technologies 949-9360, Руководство пользователя

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Technical Information
Vaccum Seals
54/102 HS452, HS652 Rotary Vane Pumps User Manual / 87-900-978-01 (H)
Vaccum Seals
A special feature of this pump is the low number of gaskets that are
employed.
The seals in the circuit are obtained by means of VITON gaskets.
The careful surface finish of the various parts of the pump means
that vacuum sealing of the functional block is ensured by the film of
oil separating metal surfaces. Sealing of the rotor shaft is guaranteed
by a rotating gasket with dust-guard lip.
The suction flange and duct are sealed by mean of OR gaskets.
Gas Ballast Valve
When the pump sucks in vapors, these condense during compression
and mix with the oil, forming an emulsion (an aqueous vapor, for
example) or a solution (organic solvent vapors, for example).
A number of problems arise from this, such as the impossibility of
obtaining high vacuums, the alteration of the properties of the oil,
could cause scaling on parts of the pump.
To avoid this, during compression at the second stage, atmospheric
air is let into the pump through an adjustable valve, or “gas ballast
valve”, located at the top of the pump.
In this way, the discharge valve of the second stage opens through
the effect of the atmospheric air before the partial pressure of the
vapor reaches saturation point, thus preventing condensation from
occurring. The vapors are expelled mixed with air.