Glossary and index of fluid power principles and components S

SAE
Society of Automotive Engineers

SAE 4 BOLT PORT, CODE 61
A system for flange and surface mounting configurations that are used to attach pipes, tubes or hoses to a component or manifold. Normally rated at 3000 psig. See SAE 4 BOLT PORT, CODE 62.

SAE 4 BOLT PORT, CODE 62
A system of flange and surface mounting configurations that are used to attach pipes, tubes or hoses to a component or manifold. Nominally rated at 6000 psig, although larger sizes are only See SAE 4 BOLT PORT, CODE 61.

SAE PORT
A threaded hole and stud system that may be used to attach fittings to a component or manifold. Sealed with an o-ring or gasket.

SAFETY FACTOR
The ratio of burst pressure to rated pressure under specific static pressure and temperature conditions. See BURST PRESSURE.

SCRAPER RING
A metal or synthetic ring that is fitted to the shaft of a cylinder to remove particles from the shaft so to prevent them from entering the cylinder seal chamber.

SEAL
See O-RING and GASKET.

SENSITIVITY
The minimum input signal required to produce a specified output signal.

SEQUENCE
-The order of a series of operations or movements. -To divert flow to accomplish a subsequent operation or movement

SEQUENCE VALVE
A valve that is normally closed or normally open and changes to the opposite state when pilot pressure is applied to its spring chamber at a preset pressure level. Normally used to initiate a secondary set of operations in a system, based on application of the pilot signal.

SERIAL DATA TRANSMISSION
A form of digital data transmission in which the data bits of a binary word are processed or transmitted one at a time. Slower than parallel data transmission, but does not require separate circuitry for each bit.

SERRATIONS
Bumps, barbs, corrugations, or other features increasing the holding power of the device.

SERVO CONTROL
A term used to describe the type of electronic system used for finite, analog control of a function. See SOLENOID CONTROL.

SERVO VALVE
A valve that uses a torque motor type coil to control a small stream of fluid. Direction of the fluid stream is used to position a large spool. Therefore a low level power signal may provide precise spool position. Normally, the spool had mechanical feedback of spool position to the torque motor, creating a closed loop spool position system.

SHANK
The portion of a fitting inserted into the bore of a hose.

SHUTTLE VALVE
A valve that has three ports and a common ball or spool check valve. When flow is applied at either of the two inlet ports, the third or output port receives flow from the higher pressure inlet port.

SKIVE
The removal of a short length of cover and/or tube to permit the attachment of a fitting directly over the hose reinforcement.

SILENCER
See MUFFLER.

SILT
Fine particles of debris. Normally found in chambers with little or no circulation, such as at the bottom of a reservoir or tank. See SLUDGE.

SLIP
Internal leakage of hydraulic fluid.

SLUDGE
Partially hardened silt. See SILT.

SOCKET
The external member or portion of a hose fitting, commonly used in describing screw-together reusable fittings.

SOLENOID
A coil of metallic wire, usually copper, wound around a bobbin. Used to magnetize the bobbin and produce linear motion of a companion spool when electricity is applied.

SPIRAL
A method of applying reinforcement in which there is no interlacing between individual strands of reinforcement; coiling around an axis in a series of planes, helical.

SPOOL
A term loosely applied to almost any moving cylindrically shaped part of a hydraulic component which moves to direct flow through the component.

SPRING GUARD
A helically wound component applied internally or externally to a hose assembly, used to strain relief, abrasion resistance, or collapse resistance.

STABILITY
Ability of a system to maintain control when subject to severe outside disturbances.

STANDARD
A document, or an object for physical comparison, for defining product characteristics, products, or processes, prepared by a consensus of a properly constituted group of those substantially affected and having the qualifications to prepare the standard for use.

STATIC BEHAVIOR
Describes how a control system, or an individual unit, carries on under fixed conditions (As contrasted to dynamic behavior which refers to behavior under changing conditions).

STATIC CONDUCTIVE
Having the capability of furnishing a path for a flow of static electricity.

STEP CHANGE
The change from one value to another in a single step.

STATIC HEAD
A measurement of pressure that is present when no fluid flow exists in a passage. The static head is normally expressed in feet of water.

STRAINER
A series of wire or fabric meshes which are bonded together by caps or perforated cylinders and are fitted into hydraulic system passages to strain particles from fluid passed through the passage.

STROKE
-The length of travel of a piston or plunger. -To change the displacement of a variable displacement pump or motor.

SUBPLATE
A metal base to which a specific valve may be attached using a specified bolt kit.

SUCTION LINE
A passage that leads from a reservoir or tank to the inlet port of a pump.

SUPERCHARGE
To replenish a hydraulic system above atmospheric pressure.

SUMP
A reservoir.

SURGE
An increase in pressure that occurs for a specified short period of time over the normal expected working pressure.

SWAGE
The method of fitting attachment incorporating a set of die halves designed to progressively reduce the collar or ferrule diameter to the required finish dimension by mechanically forcing the fitting into the mating die.

SWASH PLATE
A stationary canted plate in an axial type-piston pump which causes the pistons to reciprocate as the cylinder barrel rotates.

SWELLING
An increase in the volume or linear dimension of a specimen immersed in liquid or exposed to a vapor.

SWITCH
A digital device which closes or opens a discrete set of contacts at a pre-set condition.

SWIVEL JOINT
A connector or fitting that is equipped with seals or o-rings allowing partial rotation while passing a fluid path through a sealed internal passage.

SYNCHRO
A rotary electromagnetic device generally used as an AC feedback signal generator which indicates position. It can also be used as a reference signal generator.

SYNTHETIC FLUID
A hydraulic oil (fluid) that is made from a synthetic base. A fluid, manufactured to specified characteristics. Normally will not support combustion if heated to a specific temperature.

SYSTEM PRESSURE
See OPERATING PRESSURE.