6
Effective sealing of the inlet to the discharge is accomplished through the use of very small operating
clearances. The resulting absence of moving contact eliminates the need for any internal lubrication.
Clearances between the rotors during rotation are maintained by a pair of accurately machined helical
timing gears, mounted on the two shafts extended outside the air chamber. The intermeshing rotary lobes
are designed to rotate and trap air or gas between each rotor and the housing. As the rotor lobes rotate
past the edge of the suction port, the trapped air or gas is essentially at suction pressure and temperature.
Since the booster is a constant volume device, the trapped air remains at suction pressure until the leading
rotor lobe opens into the discharge port. The close clearances between the rotors inhibit back slippage of
the trapped volume from between the rotors and the trapped volume is forced into the discharge piping.
Compression occurs not internal to the booster, but by the amount of restriction, either downstream of the
booster discharge port, or upstream of the booster inlet port.
Figure 1 illustrates that the air
moves not between the rotors but
between the rotors and the side
of the housing. Also, the machine
is bi-directional, meaning that the
direction of rotation of the booster
can make either side the inlet or
discharge. See also the Flow
Direction by Rotation section
below.
No attempt should ever be made
to control capacity by means of
a throttle valve in the intake or
discharge piping. This will increase the power load on the drive system, increase operating temperatures,
and can overload and/or seriously damage the booster. Likewise, if a possibility exists that ow to the
booster inlet may be cut off during normal operation of a process, then an adequate vacuum relief valve
must be installed near the booster. A pressure type relief valve in the discharge line near the booster is also
strongly recommended for protection against cutoff or blocking in this line. Check valves should also be
used on every booster when more than one booster is connected to a discharge line. This is for both safety
and operating conditions.
Vacuum boosters must be protected by cut-in switches or with bypass valving to limit differential pressure
across the booster.
In a direct coupled arrangement, a variable speed motor or transmission is required, or excess air or gas
may be blown off through a manually controlled unloading valve and silencer. Gas units can use bypasses,
but some applications may require additional cooling. If there is a large volume of high pressure air or gas
downstream of the booster, a check valve in the piping downstream of the booster will protect the booster
from overspeeding in a backward direction upon shutdown.
Consult your Tuthill Vacuum & Blower Systems sales professional if questions arise.
DANGER
As with any equipment with rotating elements, the booster will over time
become a source of media leaks and a source of ignition. It is the user’s
responsibility to assure that proper installation, operation and maintenance
is performed to assure that the booster does not become a hazard.
FLOW BY DIRECTION AND ROTATION
WARNING
Refer to diagrams in this manual for proper rotation and orientation in inlet
and discharge.
Figure 1 - Illustration of general operation principle
INLET INLET INLET
DISCHARGE DISCHARGE DISCHARGE
