IFPS CFPS key terms

Principle stating that pressure applied to a confined, static fluid is transmitted undiminished to every point in the fluid and to the walls of the container. It underlies force multiplication in hydraulic cylinders.

Force per unit area exerted by a fluid on its surroundings, expressed in psi, bar, or MPa. In fluid power it is the key variable controlling actuator force and is measured by gauges or transducers.

Volume of fluid passing a point per unit time, typically gallons per minute or liters per minute. Flow rate determines actuator speed, while pressure determines force.

Relationship stating that for steady flow of an incompressible fluid, flow rate equals area times velocity at any section. A smaller flow area therefore produces higher fluid velocity.

Statement that in steady, ideal flow, an increase in fluid velocity is accompanied by a decrease in pressure or elevation energy. It explains pressure drops at restrictions and venturi effects.

Result of Pascal's Law in which a small force on a small piston creates a larger force on a larger piston, because pressure is equal but the larger area produces greater output force.

Rate at which a cylinder rod or motor shaft moves, governed by fluid flow rate entering the actuator divided by its effective area or displacement. Pressure does not set speed in a properly supplied circuit.

Difference in pressure between two points in a circuit, caused by resistance to flow in conductors, fittings, and valves. It represents energy lost as heat and reduces available actuator force.

A deliberate restriction in a flow path, used to limit flow or create a pressure differential. Orifice behavior follows a square-root relationship between flow and differential pressure.

Measure of a fluid's resistance to shear or internal flow. Higher viscosity improves sealing but increases resistance and heat; it changes strongly with temperature, affecting hydraulic performance.

Number describing how little a fluid's viscosity changes with temperature. A high viscosity index means viscosity stays more stable as the fluid warms or cools.

Liquid medium that transmits power, lubricates moving parts, and carries away heat in a hydraulic system. Mineral oil, synthetic, water-based, and fire-resistant types are selected for the application.

Tank that stores hydraulic fluid, allows contaminants and air to settle out, dissipates heat, and provides a mounting point for pumps and accessories. Baffles separate return fluid from pump intake.

Removal of solid particles and contaminants from hydraulic fluid using filters or strainers to protect pumps, valves, and actuators. Rated by micron size and beta ratio.

Practices and devices that keep hydraulic fluid clean, including filter selection, breathers, seals, and cleanliness targets such as ISO particle counts. Contamination is a leading cause of failures.

Pump that traps a fixed volume of fluid per revolution and delivers it regardless of system pressure, within limits. Gear, vane, and piston designs are common in hydraulics.

Volume of fluid delivered by a pump per revolution or cycle, expressed in cubic inches or cubic centimeters per revolution. Displacement times speed gives theoretical flow.

Pressure-limiting valve that opens to divert pump flow to tank when system pressure reaches a set value, protecting components from overpressure. It is a safety device, not a normal flow regulator.

Valve that starts, stops, and reverses fluid flow by routing it among ports. Described by number of positions and ways, such as a four-way, three-position valve.

Configuration of flow paths in the center position of a directional valve, such as open center, closed center, or tandem center. It determines pump unloading and actuator behavior at rest.

Valve that regulates the rate of fluid flow to control actuator speed, often using a needle or orifice. Pressure compensation keeps flow constant despite load changes.

Mechanism that adjusts a valve or pump to maintain a set pressure or constant flow as load changes. It allows a pressure-compensated pump to reduce output at high pressure.

Variable-displacement pump that automatically reduces displacement as system pressure approaches its setting, delivering only the flow demanded. It saves energy and reduces heat versus fixed pumps.

Device storing pressurized fluid or gas to supply flow during demand peaks, absorb shock, or hold pressure. Common types are bladder, diaphragm, and piston; gas precharge must be respected.

Linear actuator with a piston and rod that converts fluid pressure and flow into force and linear motion. Bore, rod diameter, and stroke define force and speed.

Rotary actuator that converts hydraulic flow and pressure into torque and rotation. Its displacement and the supplied flow determine speed, while pressure determines torque.

Elastomeric or polymer component that prevents internal and external leakage between moving or static parts. Seal type must match pressure, speed, and fluid compatibility.

Machine that draws in air and compresses it to a higher pressure for storage and distribution in a pneumatic system. Positive displacement and dynamic types are used.

Storage tank in a compressed-air system that smooths pressure fluctuations, stores air for peak demand, and allows some moisture and oil to condense out.

Device that removes water vapor from compressed air to prevent condensation, corrosion, and freezing in lines and tools. Refrigerated and desiccant types are common.

Temperature at which moisture in compressed air begins to condense at a given pressure. It is a key specification for dryer performance and air quality.

Combined filter, regulator, and lubricator assembly conditioning compressed air at the point of use. It removes particles and water, sets pressure, and adds lubricant if needed.

Valve that maintains a reduced, stable downstream pressure from a higher supply pressure despite flow changes. In pneumatics it is often part of an FRL unit.

Pneumatic directional control valve with five ports and two positions, commonly used to extend and retract a double-acting cylinder. It pressurizes one cylinder port while exhausting the other.

Pneumatic or hydraulic cylinder that produces force in both directions by applying pressure alternately to each side of the piston. It requires a valve that can supply and exhaust both ports.

Electromagnetic actuator that moves a valve spool or poppet when its coil is energized. Rated by voltage, current, duty cycle, and whether it is AC or DC.

Valve operated by one or more solenoids, allowing electrical control of fluid flow. May be direct-acting or pilot-operated, and may include spring return or detent.

Valve whose spool position, and therefore flow or pressure, varies continuously with an electrical command signal. It enables smooth speed and force control in electrohydraulic systems.

High-performance electrohydraulic valve that uses feedback to position its spool precisely in response to a small electrical signal, providing fast, accurate control of flow or pressure.

Control scheme in which a sensor feeds back actual output to the controller, which compares it with the command and corrects error. Used for precise position, speed, or pressure regulation.

Device that converts one form of energy to another, such as a pressure sensor producing an electrical signal or a solenoid converting current to force. It provides feedback or actuation in controls.

Graphical programming language for programmable logic controllers that arranges contacts, coils, and function blocks in rungs resembling relay logic. Widely used to sequence fluid power circuits.

Industrial computer that executes a stored program to read inputs and drive outputs, sequencing valves, pumps, and safety interlocks in automated fluid power systems.