Gauge damper (snubber) - A device employing a fixed or variable restrictor inserted in the pipeline to a pressure gage, to prevent damage to the gage mechanism caused by rapid fluctuations of fluid pressure.

Gauge protector - A device inserted in the pipeline to a pressure gage and arranged to isolate the pressure gage from the fluid pressure if this exceeds a predetermined limit. The device can usually be adjusted to suit the range of the pressure gage.

Gauge, bourdon tube - A pressure gage in which the sensing element is a curved tube that tends to straighten out when subjected to internal fluid pressure.

Gauge, diaphragm - A gage in which the sensing element is relatively thin and its inner portion is free to deflect with respect to its periphery.

Gauge, instrument - An instrument or device for measuring, indicating, or comparing a physical characteristic.

Gauge, pressure - A gage which indicates the pressure in the system to which it is connected.

Head - The height of a column or body of fluid above a given point expressed in linear units. Head is often used to indicate gage pressure. Pressure is equal to the height times the density of the fluid.

Head, cylinder - The cylinder end closure which covers the differential area between the bore area and the piston rod area.

Head, friction - The pressure required to overcome the friction at the interior surface of a conductor and between fluid particles in motion. It varies with flow, size, type and condition of conductors and fittings, and the fluid characteristics.

Head, pressure - The pressure due to the height of a column or body of fluid.

Head, static - The height of a column or body of fluid above a given point.

Heat exchanger - A device which transfers heat through a conducting wall from one fluid to another. (Typically to cool a system.)

Heater - A device which transfers heat through a conducting wall from one fluid to another. (Typically to warm up a system.)

Hose, wire braided - Hose consisting of a flexible material reinforced with woven wire braid.

Hose - A flexible line or conductor whose nominal size is its inside diameter.

Hydraulic amplifier - A fluid device which enables one or more inputs to control a source of fluid power and thus is capable of delivering at its output an enlarged reproduction of the essential characteristics of the input. Hydraulic amplifiers may utilize sliding spools, nozzle-flappers, jet pipes, etc.

Hydraulic motor - A device which converts hydraulic fluid power into mechanical force and motion. It usually provides rotary mechanical motion.

Hydraulic motor efficiency, hydromechanical - Ratio of the effective torque to the derived torque.

Hydraulic motor efficiency, overall - Ratio of the output power to the effective hydraulic power.

Hydraulic motor efficiency, volumetric - Ratio of the derived output flow to the effective input flow.

Hydraulic motor, fixed displacement - A hydraulic motor in which the displacement per unit of output motion cannot be varied.

Hydraulic motor, flow, input - Flow rate crossing the transverse plane of the inlet port.

Hydraulic motor, gear, external - A motor having two or more external gears.

Hydraulic motor, gear, internal - A motor with an internal gear in engagement with one or more external gears.

Hydraulic motor, gear - A motor in which two or more gears act in arrangement as working members.

Hydraulic motor, vane - A motor in which the fluid under pressure acting on a set of radial vanes causes rotation of an internal member.

Hydraulic stepping motor - A hydraulic motor which follows the commands of a stepped input signal to achieve positional accuracy.

Hydraulics - Engineering science pertaining to liquid pressure and flow.

Hydrodynamics - The engineering science which governs the movement of liquids and the forces opposing that movement.

Hydrokinetics - Engineering science pertaining to the energy of liquid flow and pressure.

Hydropneumatics - Pertaining to the combination of hydraulic and pneumatic fluid power.

Hydrostatic transmission - Combination of one or more hydraulic pumps and motors forming a unit.

Hydrostatics - Engineering science pertaining to the energy of liquids at rest.