Operating Principle; Single-Stage Vane Pump; Two-Stage Vane Pump; Oil - Alcatel 1004 A Instruction Manual

II. OPERATING PRINCIPLE

2,1 SINGLE-STAGE VANE PUMP

The functional part of a vane pump is composed
- a hollow cylindrical stator with an inlet and an exhaust va l ves;
- a rotor driven rotationally Inside the stator (and off center with res-
pect to It) to permit pumping
- two vanes sliding in the rotor, forced against the stator bycentrlfu­
gal force and springs.
The pumping cycle Is as follows
• Intake : As the vane ,passes in front of Inlet orifice an
increasing space ls formed into which the gas
from the chamber to be evacuated expands.
When the second vane passes, the space is
closed.
• transfer :
The gas trapped In the space between the two
vanes Is transferred to the exhaust orifice as the
rotor rotates .
• compression : The space communicates with the exhaust, which
is fitted with a valve
open the valve.
• exhaust :
The gas Is expelled into the oil casing When the
pressure Is sufficient to open the
lnta�e
campres,lan

2.2 TWO-STAGE VANE PUMP

To improve the backing pressure and displacement at low pressure ,
two stages are connected In series. The second is similar to the first
both structurally and operationally. The gases drawn in by first stage
(LP low pressure), are transferred to second s·tage (HP high­
pressure) and discharged through the high p r essure dischatge
valve.
low•preesure stage
')1
of
:
,
: the gas ls compressed until
valve.
t.ro.nsler
high-pressure alege

2.3 OIL

Oil has several Important functions In the pump
- It lubrica1es mechanical components (bearings, shaft seals, rotor,
vanes, etc.) ;
- It makes moving parts relatively tight by limiting Internal leakage
- It carrles·away the heat produced by the compressed gases.
ALCATEL has selected various types of oil fo r Its pump ; they are lis­
ted In § 3.3.2.

2.4 ANTI-SUCKBACK SYSTEM AND LUBRICATION

If the power supply should fail or the pump stops, an anti-suckback
device prevents air or oil in the pump for being drawn back into the
chamber Ming evacuated
- by flush-mounted 0-rings between the surfaces of the functional
elements (stators, flanges, frame. etc.) ;
- by spring-loaded check valves placed in the exhaust orifices ;
- by a system for automatically blocking the lubrication oil Injection
channel, which also supplies oil to the pump. The operating principle
Is as follows (see diagram 2)
• when the pump is rotating the oll exerts a resistive torque on the oil
Impeller cam wheel, preventing the cam from rotating. The
city of the cam causes lever (1) to move and
seat (Q), so that all flows In through the orifice (2) .
• oil flowrate Is controlled by an oil jet (50) mounted in the valve­
.
seat (36) (see general drawing).
·
• w tien the pump is stopped, the olf Impeller cam recenters because
of its weight and the force of the spring
valve drop back Into its seat, preventing all from entering.

2.5 GAS BALLAST

When condensable vapors are being pumped , in the
phase gas Is compressed beyond Its saturated pressure and can
condense, Impairing pump performance.
The gas ballast allows a quantity of air to be injected into the second
stage of the pump during "compression", to reduce the partia l pres­
sure of the pumped gas below its saturated vapor pressure and thus
prevent condensation. In a single-stage pump the air Is injected Into
the main stage.
At the end of "compression", the pressute In the discharge chambe r
Is g r eater than atmospheric. An antl-suckback system (ball and
spr i ng) prevents gas and oil from being discharged Into the environ­
ment (see diagram below).
The saturated vapor pressure of a gas Is higher when ltls hot when It
is cold ; therefore, the pump must reach operating temperature
before pumping condensable vapors.
Using the gas ballast increases the urtfmate pressure of the pump as
well as the tempetature.
Air
Comprenlon
·
eccentri­
valve· (3) to rise from Its
: the lever returns, letting the
"compression"
---
----
-
Ball
& spring
;