The Pilot Operated Regulator is
a versatile device that can be used to advantage in
many ways. The pilot operated regulator may be
referred to as the slave, relay, flow amplifier,
booster and other terms often related to how it is
being used in an application. It reacts to the
pilot signal pressure and opens the main valve until
internal pressure balances pilot pressure and the
valve spring closes the valve.
Balance of opposing forces or pressures is the
fundamental dynamic with regulators. Balancing the
internal parts will reduce inaccuracy caused by
resultant force. A diaphragm or piston is most often
the device that separates the forces with one
pressure on either side and moves away from the
higher force. In a conventional adjustable regulator
an adjustable spring force is opposed by the
internal fluid pressure. With a pilot operated
regulator both forces come from opposing fluids,
liquid or gas.
Both diaphragms and pistons have fans who prefer one
or the other for a number of reasons. I prefer
diaphragms.
- Diaphragms flex easily with little friction or
mass to reflect the difference in force accurately.
- Diaphragms have no seals to wear, swell, drag,
stick or take a set.
- Diaphragms provide a more positive seal or
separation of the opposing media.
Myth debunking: When Christopher Columbus was a cub
scout someone argued that pistons were better
because diaphragms form a cone shape when extended
and the result is a smaller area. By the time I
thought that through he was gone. Cone shaped or
any shape, area is area.
Applications for Pilot Operated Regulators are only
limited by the imagination.
- A pilot operated regulator in the main air
supply, over head, can be controlled with a
conveniently located adjustable pilot regulator.
- A pilot operated regulator in the cootie room or
amid dangerous equipment may be piloted from a safe
remote location.
- Any of several selected outlet pressures can be
called on demand with a series of solenoid valves
connected to the pilot port.
- A feed back pilot may monitor the pressure past
restrictions, at the critical pressure position, and
pilot the slave regulator.
- Hazardous or explosion potential area.
- Some of my favorite Pilot Operated Regulators
have high relief flow with minimum hysterisis.
These allow excellent counter balance control. An
operator might lift a counsel TV set with one hand
using a pressure assist.
- With speed controls on the ported exhaust a
piano might be lowered at a slow controlled rate or stopped in mid
air with one hand.
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- Smooth start valves prevent shock and awe when air is first
applied. With a “tank” circuit (needle valve and volume) in the
pilot line a pilot operated regulator can replace the conventional
regulator and a smooth start valve. The regulator as smooth start
does not depend upon a closed system to build up secondary pressure.
It can be used with air bearings and other system that have too much
flow for a conventional smooth start.
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A pilot operated regulator can keep liquid and gas at the same
pressure for spray and mix applications.
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A pilot operated regulator with an adjustable spring as well can
be set to keep pressure B at any specific pressure (10 PSIG for
example) above pressure A. With no pilot pressure adjust the
spring to produce a 10 PSIG out put. Now connect pressure “A” to
the pilot port. If the pressure at “A” is 70 PSIG the outlet
pressure at “B” will be 80 PSIG.
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With Current to Pressure (I/P) and Voltage to Pressure (E/P)
electronically controlled regulators to pilot a “slave”
regulator 1500 or more SCFM may be controlled with precision.
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With a pressure intensifier to increase the pilot signal
pressure high flow with increased pressure may be produced by a
low flow signal at a reduced pressure.
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For extremely long air lines it would be possible to over size
the air line and/or place a reservoir at the point of use then
apply a greater pressure than required to a pilot operated
regulator at point of use. Pilot lines are static and
subsequently do not have appreciable pressure drop. A parallel
pilot line or electronic regulator at the point of use would
provide high flow with good regulation.
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Do you have more to add?
Why aren’t pilot operated regulators use more frequently? It is just
a hunch but pilot operated regulators may not be considered in
favor of more common and conventional products. Add pilot operated
regulators to your list of possible solutions.
Pressure Balance: May we take a short detour to deal with this
earth science certainty that is determined by work and gravity?
The balance seen when a high wire walker crosses a cable is
another topic. We are concerned with the balance of forces from
gravity or potential energy resulting from work done (i.e.
compressed gas, compressed springs) acting against each other.
For lack of a diagram please use your imagination. A 4 inch
diameter pipe or tube that is closed at both ends has a ˝”
diameter hole bored through both sides. A close fitting ˝”
diameter rod, 6 inches long is inserted through the 4” tube with
approximately an inch projecting outward on either side. If 100
PSIG (gas or liquid) is pumped into the closed 4” diameter pipe
what would the result of the ˝” diameter rod be? What would
happen to the rod?
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