2-5 ANTI-SUCK BACK MECHANISM
When the pump is intentionally turned off or if there is a power failure, the anti-suck back mechanism seals the
intake tube
(1)
and vents the pumping chamber. The pump starts easier when the pumping chamber is vented.
The
sealing of the intake tube (1) prevents pump fluid from surging back into the vacuum line and maintains the
vacuum
in
the vessel or system.
The primary components of the anti-suck back mechanism are the
centrifugal switch (39), the lever
(41)
with spring
(42) and
seal (43), the air inlet tube (69), and the piston (68) with valve disk (67) (see Figure
2-1).
The centrifugal switch (39) is attached to the shaft. When the pump is turned off, the shaft rotation slows, causing
the
centrifugal switch (39) to push against the lever (41). As a result, the lever (41) opens the air inlet tube
(69)
(see Figure 2-1). Air at atmospheric pressure rushes through the open tube (69) and into the high vacuum stage
pump
cylinder (55), thus venting the pump. This air also forces the brass piston (68) and attached valve disk (67)
to
seal the pump intake tube
(1).
When the pump is started again, the shaft rotation causes the centrifugal switch (39) to pull away from the lever
(41). A spring (42) pushes the lever
in
the opposite direction, causing the seal (43) attached to the lever to close
the air inlet tube (69). The suction of the pump draws the valve disk (67) and attached piston (68) away from the
opening
in
the intake tube
(1)
allowing the pump to further evacuate the vessel or system.
On
AC
pump models, the anti-suckback mechanism is modified to avoid exposing the pumping module
to
atmospheric air and to avoid the possibility of h!izardous process gas escaping from the pump during shutdown.
The
centrifugal switch and lever assembly
are
removed
and
a solenoid valve with tubing
is
added
so
that the module
is vented with gas from the oil casing during shutdown.
SECTION 3
PREPARING AND INSTALLING THE PUMP
3-1
RECEIVING
NOTE:
The Leybold packing list is attached to the outside of one of the shipping containers.
3-1-1
Reporting Shipping Damage
Leybold makes every effort to ensure that your order is packed properly. However, rough or careless
handling
in
transit occasionally results
in
shipping damage.
In
such cases, the carrier is responsible for the damages.
Unpack the pump and check for shipping damage
as
follows:
1.
Inspect the outside of the shipping container for shipping damage. If you will be making a damage claim,
save the shipping container and packing materials.
2.
Unpack the pump.
3.
Carefully inspect the pump for damage.
4.
If you find any damage, proceed as follows:
a.
Save the shipping container, packing material, and parts for inspection.
b.
Notify the carrier that made the delivery within
15
days of delivery
in
accordance with Interstate
Commerce regulations.
c. File a claim with the carrier.
d. Contact the
Leybold Order Services Department to make arrangements for replaCing
the damaged part.
3-1-2
Reporting Shipping Shortage
If you did not receive all the goods that you ordered, do the following:
1.
Check the number of pieces listed
in
the upper right section of the packing
list
If the number
of
pieces
listed is greater than the number of shipping containers received, contact the carrier concerning the missing
. y
piece.
2.
Check the packing list to see
if
the missing item is back ordered.
3.
Carefully check the packing material and container to ensure that you did not overlook the missing item.
4.
If you cannot find the item, contact our Order Services Department.
8
TRIVAC
"A"
Manual,
Edition L
..
.
..
"
';]
.+'
,
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