RADIAL BEARINGS: Bearings designed to carry loads applied in a plant perpendicular to the axis of the shaft and used to prevent movement in a radial direction.

RADIAL THRUST BEARINGS: Bearings designed to carry a combination of radial and thrust loads. The loads are applied both radially and axially with a resultant angular component.

RADIANT HEAT: Heat transferred without physical contact between the emitting region and the receiving region.

RADIUS: A straight line from the center of a circle or sphere to its circumference or surface.

RAM TYPE CYLINDER: A fluidic actuating cylinder in which the cross-sectional area of the piston rod is more than one-half the cross-sectional area of the movable piston-like element. The piston used is also referred to as a PLUNGER.

RATE ACTION: That action of a control system component whose output is proportional to the rate of change in its input for slowly changing signals and proportional to the input for rapidly changing signals.

RATIO: The value obtained by dividing one number by another, indicating their relative proportions.

RAW WATER: Untreated water used for cooling.

REACH ROD: A length of pipe or bar stock used as extension on valve stems.

RECEIVER: (1) A container in which compressed gas is stored to supply pneumatic power. (2) A reservoir for pressure refrigerant.

RECEIVER INDICATOR: Pressure-sensitive instrument indicating the loading pressure signals in percentage.

RECIPROCATING: Moving back and forth, as a piston reciprocating in a cylinder.

REDUCER: (1) Any coupling or fitting that connects a large opening to a smaller pipe or hose. (2) A device that reduces pressure in a fluid (gas or liquid) system.

REDUCING STATION: An assembly con-sisting of a reducing valve, isolation valves, and bypass valves for the reducer.

REDUCING VALVES: Automatic valves that provide a steady pressure lower than the supply pressure.

REDUCTION GEAR: An arrangement of shafts and gears such that the number of revolutions of the output shaft is less than that of the input shaft-generally used between a prime mover and the propeller shaft.

REEFER: (1) A provision cargo ship or a refrigerated compartment. (2) An authorized abbreviation for refrigerator.

REFRIGERANT 12 (R-12): A gas used in air conditioning and refrigeration systems. One of a series of fluorocarbon refrigerants.

REFRIGERATION TON: Unit of measure for the amount of heat removed, equal to 12,000 Btu per hour.

REGULATOR (gas): An instrument that controls the flow of gases from compressed gas cylinders.

RELATIVE HUMIDITY: The ratio of the weight of water vapor in a quantity of air to the weight of water vapor which that quantity of air would hold if saturated at the existing temperature. Usually expressed as a percentage; for example, if air is holding half the moisture it is capable of holding at the existing temperature, the relative humidity is 50%.

RELAY: A magnetically operated switch that makes and breaks the flow of current in a circuit.

RELIEF VALVE: A pressure control valve used to limit system pressure.

REMOTE OPERATING GEAR: Flexible cables or shafts attached to valve wheels so the valves can be operated from another compartment.

RESERVOIR: A container which serves primarily as a supply source of the liquid for a hydraulic system.

RESISTANCE: The oppositon to the flow of current caused by the nature and physical dimensions of a conductor.

RESPONSE TIME: The time lag between a signal input and the resulting change of output.

RESTRICTION: A reduced cross-sectional area in a line or passage which reduces the rate of flow.

RETURN LINE: A line used for returning fluid to the reservoir or atmosphere.

RHEOSTAT: A variable resistor. Similar in function and construction to a potentiometer.

RISER: A vertical pipe leading off a large one; for example, a firemain line.

ROCKER ARM: Part of the valve actuating mechanism of a reciprocating engine.

ROOT: The surface of the thread corre-sponding to the minor diameter of an external thread and the major diameter of an internal thread.

ROOT VALVE: A valve located where a branch line comes off the main line.

ROTOR: The rotating element of a motor, pump, or turbine.

RUDDER STOCK: A vertical shaft that has a rudder attached to its lower end and a yoke, quadrant, or tiller fitted to its upper portion by which it may be turned.

RUDDER STOPS: Fittings attached to the ship structure or to shoulders on the rudder post to limit the swing of the rudder.

SAFETY VALVE: An automatic, quick opening and closing valve that has a reset pressure lower than the lift pressure.

SALINE/SALINITY: (1) Constituting, or characteristic of, salt. (2) Relative salt content of water.

SALINOMETER: A hydrometer that mea-sures the concentration of salt in a solution.

SATURATED AIR: Air that attains the maximum amount of moisture it can hold at a specified temperature.

SATURATED STEAM: Steam at the satura-tion temperature.

SATURATION PRESSURE: The pressure corresponding to the saturation temperature.

SATURATION TEMPERATURE: The temperature at which a liquid boils under a given pressure. For a given pressure there is a corresponding saturation temperature.

SAY BOLT VISCOSIMETER: An instrument that determines the fluidity or viscosity (resistance to flow) of an oil.

SCALE: Undesirable deposit, mostly calcium sulfate, which forms in the tubes of boilers.

SCAVENGING AIR: Increased amount of air available as a result of blower action used to fill an engine cylinder with a fresh charge of air and, during the process, to aid in clearing the cylinder of the gases of combustion.

SCHEMATIC DIAGRAM: A diagram using graphic symbols to show how a circuit functions electrically.

SCREW: See PROPELLER.

SEA CHEST: An arrangement for supplying seawater to engines, condensers, and pumps and for discharging waste water from the ship to the sea. It is a cast fitting or a built-up structure located below the waterline of the vessel and having means for attachment of the piping. Suction sea chests are fitted with strainers or gratings.

SEA COCK, SEA CONNECTION: A sea valve secured to the plating of the vessel below the waterline for use in flooding tanks, magazines, and so forth, to supply water to pumps and for similar purposes.

SEAWATER: The water in the sea. Seawater is an aqueous solution of various minerals and salts (chlorides). In suspension also, but not dissolved in the water, may be various types of vegetable and animal growths, including, in many cases, bacteria and organisms harmful or actually dangerous to health.

SECTION: A view showing internal features as if the viewed object had been cut or sectioned.

SEDIMENT: An accumulation of matter that settles to the bottom of a liquid.

SENSIBLE HEAT: Heat that is given off or absorbed by a substance without changing its state.

SENSING POINT: (1) The physical and/or functional point in a system at which a signal may be detected and monitored or may cause some automatic operation to result. (2) Where parameters are determined.

SENSITIVITY: The change in speed required before the governor will make a corrective movement.

SENSOR: A component that senses physical variables and produces a signal to be observed or to actuate other elements in a control system. Temperature, sound, pressure and position sensors are examples.

SENTINEL VALVE: A relief valve designed to emit an audible sound; does not have substantial pressure-relieving capacity.

SEPARATOR: A trap for removing oil and water from compressed gas before it can collect in the lines or interfere with the efficient operation of pneumatic systems.

SERVICE TANKS: Tanks in which fluids for use in the service systems are stored. Also DAY TANK.

SERVO: A device used to convert a small movement into a greater movement or force.

SET POINT: The level or value at which a controlled variable is to be maintained.

SETSCREW: A machine screw with a slotted, allen, or square head used to hold a part in place.

SHAFT ALLEY: A watertight passage, housing the propeller shafting from the engine room to the bulkhead at which the stern tube commences.

SHAFT/SHAFTING: The cylindrical forging, solid or tubular, used for transmission of rotary motion from the source of power, the engine, to the propellers.

SHIM: A thin layer of metal or other material used to true up a machine or inserted in bearings to permit adjustment after wear of the bearing.

SHIPS PLANS: A set of drawings of allsignificant construction features and equipment of a ship, as needed to operate and maintain the ship. Also called ONBOARD PLANS.

SHORE WATER: A broad term for clas-sifying water originating from a source ashore.

SHUTOFF VALVE: A valve which operates fully open or fully closed.

SIMPLEX PUMP: A pump that has only one liquid cylinder.

SLEEVE: A casing fitted over a line or shaft for protection against wear or corrosion.

SOLENOID: An electromagnetic coil that contains a movable plunger.

SOLID COUPLING: A device that joins two shafts rigidly.

SOUNDING PIPE OR SOUNDING TUBE: A vertical pipe in an oil or water tank, used to guide a sounding device during measurement of the depth of liquid in the tank.

SPECIFIC GRAVITY: The ratio of the weight of a given volume of any substance to the weight of an equal volume of distilled water. Since the distilled water weighs approximately 62.4 pounds per cubic foot, any substance which weighs less than this has a specific gravity of less than one and will float on water. Any substance of greater weight per cubic foot has a specific gravity of more than one and will sink. Specific gravity of gases is based in a like manner on the weight of air.

SPECIFIC HEAT: The amount of heat required to raise the temperature of 1 pound of a substance 1F. All substances are compared to water, which has a specific heat of 1 Btu/lb/F.

SPEED DROOP: A progressive drop in speed as load is picked up by the prime mover from no load to full load without manually changing the speed setting.

SPEED-LIMITING GOVERNOR: A device for limiting the speed of a prime mover.

SPEED-REGULATING GOVERNOR: A device that maintains a constant speed on an engine that is operating under varying load conditions.

SPLIT PLANT: A method of operating propulsion plants so that they are divided into two or more separate and complete units.

SPRING BEARINGS: Bearings positioned at varying intervals along a propulsion shaft to help keep it in alignment and to support its weight.

STABILITY: The ability of a governor to correct a speed disturbance with a minimum of corrective motions.

STANDBY EQUIPMENT: Two auxiliaries that perform one function. When one auxiliary is running, the standby is so connected that it may be started if the first fails.

STATOR: The stationary element of a motor or generator.

STEAM: Vapor of water; invisible, odor-less, tasteless, and usually under greater than atmospheric pressure.

STEERING ENGINE: The machinery that turns the rudder.

STEERING GEAR: A term applied to the steering wheels, leads, steering engine, and fittings by which the rudder is turned.

STEP-TOOTHED LABYRINTH: Labyrinth type packing having each alternate tooth ring installed on the shaft and running in close proximity to the fixed packing ring.

STERN TUBE: (1) The bearing supporting the propeller shaft where it emerges from the ship. (2) A watertight enclosure for the propeller shaft.

STERN TUBE FLUSHING WATER: Water circulated through the stern tube from in-board to prevent accumulation of debris in the stern tube while the ship is at rest or backing down.

STUFFING BOX: A device to prevent leakage between a moving and a fixed part.

SUMP: A container, compartment, or reservoir used as a drain or receptacle for engine oil.

SUPERCHARGE: To supply a charge of air at a pressure higher than that of the surrounding atmosphere.

SUPERCHARGER: A device for increasing the volume of the air charge of an internal-combustion engine.

SUPERHEAT: Amount of heat applied to vapor to raise its temperature above the saturation temperature, while maintaining constant pressure.

SUPPLY AIR: Compressed air required for the proper operation of pneumatic control components.

SURGING: A rhythmic variation of speed of an engine, which can be eliminated by blocking the fuel supply manually or with load limit, and which will not reappear when returned to governor control unless the speed adjustment is changed or the load changes.

SWING CHECK VALVE: A valve that has a guide-mounted disk swung from the top by a horizontal pin. A liquid exerting pressure against the disk will cause it to open, allowing a flow. Pressure exerted in the opposite direction will close the valve, ensuring only one direction of flow.

SWITCHBOARD: A panel or group of panels with automatic protective devices, used to distribute the electrical power throughout the ship.

SYNCHRONIZE: (1) To make two or more events or operations occur at the proper time with respect to each other. (2) To adjust two engines to run at the same speed.

SYNTHRON SEAL: A rubber strip seal installed on the shaft to prevent seawater from leaking into the ship along the shaft.