Hydrocarbon Processing - October 2021 - 86

Valves, Pumps and Turbomachinery
thrust necessary to move the internal
piston and compress the air in the compression
volume. The compression volume
is calculated depending on the ratio
at which the pressure is to be amplified.
For example, a 2:1 amplifier that will duplicate
the inlet pressure will have a larger
area than one with a 3:1 or 4:1 ratio. Once
the piston reaches the end of the stroke,
the movement starts in the other direction.
The booster will continue this cyclic
motion until the pressure given by the
ratio-either 2:1, 3:1 or 4:1-is reached.
How do boosters work when used
as part of valve automation failure
systems? The inlet of the booster is connected
to the main air line and the outlet
to a storage tank. When pressure enters
the booster, the booster increases the
pressure according to its design ratio. For
example, with a 4:1 booster and an inlet
pressure of 60 psig, there will be a 240psig
output to the tank. The tank then
stores the air at a pressure of 240 psig.
In normal operation, the regular plant
air pressure supply can be used to operate
the valve. If there is a failure on this main
supply, the pressurized air in the tank is
used to operate the valve.
Because the booster enables the air in
the tank to be stored at a higher pressure,
the size of the tank and the actuator can
be significantly reduced.
FIG. 3. Air tank size reduction comparison.
A practical example. A 20-in. valve,
which needs a thrust of 18,000 lb of force
to operate, requires a 24-in.-diameter ac14th
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December 1-2, 2021
The Woodlands Waterway Marriott
The Woodlands, Texas
tuator, with an available regular air plant
supply of 60 psig. For a failure system
with air stored at 60 psig, an 800-gal tank
is needed to have enough energy to stroke
the valve two times (one full cycle). If a
4:1 pressure booster is added, the pressure
is boosted to 240 psig, with a final intank
pressure after the failure of 100 psig.
Therefore, the valve actuator can be sized
to 100 psig and not 60 psig. By doing this,
the diameter of the actuator can be reduced
to 16 in, reducing the volume of air
required and resulting in a reduction from
an 800-gal tank to a 60-gal tank (FIG. 3).
This example illustrates that the use
of pneumatic pressure boosters results
in more efficient storage of the energy
or valve automation systems for failure
actions.
MARIA AGUIRRE is the General Sales Manager-
Latin America for Cowan Dynamics. She has more
than 10 yr of expertise in the selection and design
of valve automation solutions. Ms. Aguirre earned
a master's degree in engineering from Concordia
University in Montreal, Quebec, Canada, and is
licensed in Canada as a professional mechanical
engineer with the Professional Engineers and
Geoscientists of Alberta (APEGA).
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86 OCTOBER 2021 | HydrocarbonProcessing.com
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Hydrocarbon Processing - October 2021

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