The
operation of a pressure control valve is based mainly on a balance
between pressure and a mechanical load, e.g. a spring force biased
against the oil pressure.
The valve can assume various positions between fully closed and fully
open conditions depending on the flow and pressure differential.
A pressure control valve performs the following functions:
- Limiting maximum system pressure as a safety measure
- Regulating/reducing pressure in certain portions of the circuit
- Unloading system pressure
- Assisting sequential operation of actuators in a circuit with
pressure control
- Any other pressure related function by virtue of pressure control
Pressure control valves are used to control and regulate pressure in
fluid power systems. They are often globe-shaped and designed with
flanged ends to allow for ease of maintenance. The valve is smaller than
the line in which it is attached. This design feature prevents the valve
from throttling, which would cause the seat to wear too quickly. In
hydraulic systems pressure regulators are used to unload the system and
to maintain and regulate pressure at the desired values.
Types of Pressure Control Valves
Pressure Regulators- Pressure regulators keep
the output pressure at a set value. Pressure regulators control pressure
in lines (usually adjustable) to remove fluctuations and maintain
consistent pressure.
Counter-Balance Valves- Counter-balance valves,
also called load holding valves or over-center valves, are normally
located between a directional control valve and the outlet of a
vertically mounted actuating cylinder that must support weight or be
held in position for a period of time. The counter-balance valve serves
as hydraulic resistance to the actuating cylinder.
Sequence Valves- Sequence valves control the
sequence of operation between two branches of a circuit. They enable one
unit to automatically set another unit into motion.
Uploading Valves- The main application of an
unloading valve is to unload a pump and save energy when the flow is not
required. There are both hydraulic and pneumatic applications. Pressure
control valves can handle a wide range of media including air and
gaseous materials; fuel, gas and oil; liquids, steam and hydraulic
fluids.
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