Glossary

Absolute Pressure - The sum of atmospheric and gauge pressure, its a pressure scale with zero point at perfect vacuum.

Absorbent Filters - It's a filter medium that entraps contaminants as well as holds them through mechanical means. .

Accumulator - These are containers where fluid is stored under pressure and include limit in loading mechanism for maintaining pressure. .

Acid Number - Its quantity of base which is expressed in milligrams of potassium hydroxide. The same is required for neutralizing acidic constituents in one gram of sample (See neutralization number). .

Adaptive Control System - It's a system that modifies control algorithm as system operating conditions change so as to achieve optimal performance. .

Adhesive Lock - Its adherence of surfaces because of weldment/fusion of asperity contact points/ junctions or through increased surface contact area because of polishing. .

Air Cleaner Fine Test Dust (ACFTD) - It's a naturally occurring material representative of contaminant which is associated with ingression-type systems. Produced from natural Arizona road dust, it is processed, packaged, and distributed worldwide and is used for filter tests, particle counter calibration and component contaminant sensitivity testing. .

Air Release Valve - It's a check type valve that has movable closing element like ball with density less than host liquid. At the time when closure element is surrounded by air, valve automatically opens and will close when it is surrounded by liquid. .

Airdraulic - It's a component that features combination of both air and oil system like an intensifier that uses air as driving medium and oil as amplified pressure medium. B Bed - It's a flat, stationary machined surface which supports bolster/dies. .

Bolster - Its removable plate serving as working surface for bed and Ram. With plate typically bolted to bed and Ram substructures, bolsters can be machined with variety of work holding features like Drilled and Tapped Holes, T-Slots, Lift Rails for Quick Die Change and others. .

Bed Cushion - It's a bed cushion and is generally needed for draw tooling. As a system that applies resistance when pushed upon, the generated resistance can be in form of dynamic or statically controlled throughout that stroke. Bed cushion features pusher pin plates that are located beneath bed bolster where these are inserted in multiple through holes. These pins are used by tooling for generating resistive force as hydraulic press raw pushes down. .

Blankholder - It's a control controlled force for holding edges of blank in deep drawing operations. Similar to die cushion. .

Bottom Stop - By Pressure: In this, the press may be designed to 'return on pressure'. The method utilizes pressure sensing device that is adjustable and is set for determining desired maximum pressure that needs to be achieved by Ram. Once pressure is achieved, Ram typically completes cycle through returning to home position or Up Limit position. .

By Position - These presses can be designed to 'return on position' with the method involving either position sensing device or limit or proximity switch which can be set to signal that desired Ram extension is achieved. .

Bed Height - It's the distance from bottom of hydraulic press structure to working height/ top of bed bolster. .

Bed Cushion - Its commonly required for draw tooling. It works as a system that applies resistance when pushed upon where the resistance can be in form of dynamic or statically controlled throughout stroke. With Bed cushions having "pusher pin plate" located just beneath bed bolster, these pins are used by tooling for generating resistive force as hydraulic press Ram pushes down. Further, the cushion can also be configured for multiple control zones for achieving on-the-fly dynamic control. .

Bench or Laboratory Hydraulic Press - It's a smaller sized hydraulic press which is suitable for works like prototyping, research and development or laboratory use. .

Basic Fluid Power Research Program BFPR - It's a research program administered by Fluid Power Research Center at OSU for consortium of companies worldwide. This helps in economically discovering, developing, verifying, and presenting designs and other technical information for serving needs of practicing engineers in he fluid power industry. .

Bernoulli's Law - This states that if no work is done on or by a flowing frictionless fluid, its energy due to pressure and velocity remains constant at all points along the streamline. That is, an increase of velocity is always accompanied by a decrease in pressure. .

Beta Ratio - Its an international standard method that is used for expressing filtration ratio/particle capture characteristics of hydraulic filter. It is ratio of number of particles greater than given size in influent fluid to number of particles greater than same size in he effluent fluid. C Cylinder - Its part of Cylinder assembly that also consists of piston, Ram, packing and seals. Here, piston diameter and oil pressure determines force (tonnage) that given presses can deliver. .

Closed Circuit - It's a conduit arrangement where pump delivery, after passing through hydraulic actuator, by-passes reservoir and returns directly to pump inlet. The closed circuit configuration is generally used for hydrostatic transmission drive systems. Here, the movement of actuator in this circuit is controlled by variable displacement pump and not through valve. .

Closed Loop - Its group of control elements that are linked together such that output is continually monitored as well as compared with inputs. Should output differ from input, resulting error signals cause corrective action in the system. .

C-Frame Hydraulic Press - Its also known as gap frame hydraulic press that has frame configuration resembling a "C." The C-frame hydraulic press is designed for having minimal footprint on shop floors. Other advantages of C-frame hydraulic press construction include increased open work area that increases accessibility. These hydraulic presses are also used for forming wide range of materials including plastics, composites and rubber. .

Capillary - It's a tube exhibiting length to diameter ratio ³ 400. In most cases tube has internal diameter in range of few thousandths of inch that causes characteristic elevation or depression of liquids. .

Cartridge Valve - It's a valve that can be removed as well as replaced easily without need of them getting fully dismantled. As these are completely bodiless, these are capable of satisfying directional, flow and pressure functions. .

Cartridge - Its a component that can be removed as well as replaced easily without being fully dismantled like a replaceable element for filter, pump or valve. .

Cavitation - It's a localized vaporous/gaseous condition where liquid stream occurs when pressure gets reduced below atmospheric and vapor pressure of liquid. In pumps, this situation occurs when suction line is restricted and resulting vacuum causes fluid to boil and surface of fluid wet component to flake and pit. .

Contamination Control - Its an engineering technology that is involved in planning, organizing and implementing all activities which are required for identifying (recognizing and describing) contaminants, analyzing (characterizing and quantifying) contaminants, excluding (restricting, isolating, and rejecting) contaminants, reducing (capturing, retaining, and removing) contaminants, establishing the tolerance of components for contaminants and also ascertaining necessary contaminants balance (between level of contamination in fluid and level of contaminant tolerance of components to yield given contaminant service life). D Dual Palm Button Controls - These are common methods of actuating hydraulic presses where both buttons are depressed at same time for bringing Ram down requiring operator to use both hands. Control circuits also include non-repeat and anti-tie down features. .

Distance Reversal Switch - These are adjustable limit switches required for setting depth of stroke at which ram reverses. .

Dwell Timer - Its an adjustable timer for setting length of dwell at bottom of stroke. The timer may be used for other functions like timing sequence of press movement. .

Dwell -Hydraulic Presses are cable of maintaining force on work for extended time periods. It is typically accomplished by using Pressure lock value/variable volume pumps that are remotely controlled for precise as well as long period of Pressure holding. .

Daylight - Its distance between bed bolster and Ram bolster when Ram is fully retracted. Its also commonly known as Open Height. .

Damping Length - Its horizontal distance between centers of incoming and outgoing flows in spool valve and is used in transient flow force analysis. Choose positive sign if fluid flows outward at metering orifice and negative sign otherwise. .

Derivative, Partial - It's a derivative taken with respect to single independent variable where all remaining independent variables are treated as constants. .

Distributed Parameter Model - It's a mathematical model that has infinite degree of freedom where variables can act over entire length of system elements. The converse is lumped model. .

Dither - Its a relatively high frequency, low amplitude periodic signal or oscillatory motion that is sometimes superimposed on servo valve input for bringing improvisation in system resolution. The dither (mechanically/hydraulically) is also applied to offset friction (static friction/silt lock), which promotes rapid and accurate response and/or improve system resolution. .

Double-acting - Its describes component like a cylinder that operates in two directions or where actuating force can be applied in either direction. E Effective Length of Rod - Its distance between load application point and cylinder resistance point. .

Efficiency, Hydraulic - The efficiency is defined as actual head that is produced by centrifugal pump to its ideal head. .

Elastance Loads - It's a load analogous to one produced by spring - when stretched, it tries to contract and vice versa as given by Hooke's law. .

Elastomer - Its elastic, rubber-like material that has elastic properties. At room temperatures, the same can be stretched to twice its original length and would snap back to original length upon release. These are used for seals, hoses as well as special enclosures. .

Electro-hydraulic - These are components that convert electric signal into hydraulic signal. .

EnBloc Manifold - These are manifold machined from solid block of metal and often containing large number of control elements that are interconnected by drilled passages. .

Equation of State - It's a mathematical expression that defines physical state of substance (gas/liquid/solid) by relating volume to pressure and to absolute temperature for given mass of substance. .

Equivalent Length - It's an expression for pressure loss of fittings and conduit interruptions in terms of equivalent length of straight conduit of specified diameter. F Frame - Its main structure of press containing cylinder(s) and working surfaces. .

Flange Connection - It's a block of metal where tubing or conduit is terminated and bolted to equipment or to companion flange to form union connection. .

Flash Point - It's the temperature at which liquid gives off sufficient flammable vapors to ignite when approached by small flame under carefully specified conditions. .

It refers to pump suction port that is pressurized by natural gravitational/elevated head of fluid. Here, the reservoir oil level is above pump inlet port or flooded by charging/booster pump. .

FMECA - "Failure Mode, Effects and Criticality Analysis" is procedure that is designed for documenting all conceivable potential failures of system/components, effect of each failure on system operation as well as identifying those that are critical to meeting operational success and personnel safety. G Gain Margin - It's the amount of control loop gain in decibels which can be increased before system reaches instability. .

Galling - Its an adhesion condition that arises from combination of materials that possess either poor bearing characteristics or are operated with improper/no lubrication. The wear mechanism also results in transfer of material from one member to other member where this causes extremely high force to move members relative to each other. Galling can also result in both members virtually locked together. Gauge Pressure - It's a pressure of system over and above atmospheric pressure where the difference between absolute pressure and atmospheric pressure. Its pressure used to calculate forces exerted in hydraulic system. .

Generated Contaminant - Its contaminant produced because of deterioration of surfaces, incompatible materials, various tribological wear mechanisms and others. A product of system activity and inactivity. .

Gland - Its the cavity of a stuffing box.

Heat Exchanger - It's a device that is attached to oil reservoir to circulate water/air to keep oil at proper operating temperatures. .

Heated Platens - These are plates having heating capabilities and can be heated using steam, electric rods, oil, water or other medium. These systems usually require thermal breaks between heated plates and hydraulic press structure. Further, heating controls can be separate/fully integrated into press control system. .

H-Frame Hydraulic Press - These are commonly known as 4 column hydraulic press and have construction style that resembles letter H. A H-frame hydraulic press can be used in multiple press applications simultaneously. These can be made available in a wide range of hydraulic press lines from 3-200 tons and serve needs of rubber, plastics, composite and printed circuit board markets. .

Horsepower - It's a standard unit of power or work where Hp is equal to 550 ft lb. of energy/work done per second, 33,000 ft lb. of work per minute, 0.746 KW, or 42.4 BTU per minute. .

Hydraulic Balance - It's a condition of equal opposed hydraulic forces that acts on an element in hydraulic component. It's a condition where opposing hydraulic forces are equal. .

Hydraulic Detent - It's a valve configuration that applies open actuator port pressure against axial control surface of spool to hold valve spool position until greater axial force is applied for shifting valve in opposite direction. .

Hydraulic Fuse - It's a hydraulic fuse designed to provide excess flow protection and automatically shuts off any line where failure (component rupture/fracture) has occurred and where hydraulic fluid spews out of system. Its analogous to electrical safety device called "fuse" where strip of metal melts and interrupts circuit when current exceeds particular amperage. These devices comprise different types of excess-flow valves and are used to block flow and not to relieve pressure as performed by hydraulic system protector. .

Hydrokinetics - Its engineering science that pertains to forces produced by liquid as result of its motion. For example centrifugal pump. .

Hydrolytic Stability - Its resistance to permanent changes in properties that are caused by chemical reaction with water. I Inertance, Hydraulic - It's a quantity related to inertial forces which are needed for accelerating or decelerating fluid in conduit or passage. It is analogous to electrical inductance. .

Inertial Load - It's the reaction force that results from acceleration of mass and is equal to product of mass and acceleration. The force always acts opposite direction to that of actuator motion. .

Inertial Load - It's a reaction force that results from acceleration of mass and is equal to product of mass and acceleration. It always acts in direction opposite to that of actuator motion.

Jack - It's a single-acting cylinder that can be pressure actuated in only one direction. K Kinetic Energy - Its energy that substance/body possesses by virtue of its mass (weight) and velocity. .

Knockout - Its a device for stripping the part from punch or die.

Lapping-in - Its polishing a surface so that valve seat obtains a smooth mating surface. .

Lap - It's a relative axial position relationship between fixed and movable flow metering edges with spool at null. Here, Lap is measured as total separation at zero flow of straight line extension of nearly straight portions of normal flow curve that are drawn separately for each polarity and are expressed as per cent of rated input parameter. .

Leakage, Center Position - It refers to amount of leakage that is associated with spool lap conditions for given clearance. .

Learning Control System - It's a system that is designed for recognizing familiar features as well as patterns of situation and then, based on its past experience/learned behavior, reacting in an optimum manner. .

Linear Actuator - It's a device that converts pressure energy into linear motion with limited stroke like a hydraulic cylinder or ram. .

Linear Equation (Function) - It's a equation of first degree that always maps as straight line. .

Linearity - It's a measure of deviation from proportional relationship in ratio of valve output to input where the degree to which normal flow curve conforms to normal flow gain line with other operational variables that are held constant. Here, when output varies in direct proportion to input, valve is considered linear. .

Load Sensing System - It's a closed-circuit system with load/pressure feedback and combines advantages of open-center system as well as constant pressure closed-center systems while avoiding their major disadvantages. .

Lumped Parameter Model - it's a mathematical model that treats all variables of system element (lumped) as if they acted at only one point in element. The converse is distributed system. M Magnetic Lock - It's a motion impediment that is produced by unshielded magnetic field which attracts and accumulates ferromagnetic particles that induce surface lockup. .

Manual Override - It means manually operating automatic control. .

Micron (or Micrometer) - Its one thousandth part of one mm, 0.0000394-in., or one-millionth of a meter and is used as a common unit used when specifying filters, sieves and screens. .

Modulus, Rubber (or Elastomer) - Its stress level at predetermined elongation, usually reported at 100% and is a good indicator of compound toughness and at given hardness, high modulus generally means good anti-extrusion as well as dynamic characteristics. .

Motor, Fixed-displacement - It's a rotary motor where displacement per revolution is not adjustable. .

Motor, Rotary - It's a motor capable of making continuous rotary motion and producing output torque proportional to displacement per revolution and pressure drop between intake and discharge ports. .

Motor, Variable-displacement - It's a rotary motor where displacement per revolution is adjustable. N Natural Frequency - It's the frequency of cycling motion of undamped second-order component. For transient-response curve, frequency of cycling which deviation would have if the response were undamped. Also frequency at which object would vibrate at zero damping. On Bode Plot of second-order system, it is frequency where extension of final slope of response curves that intersects 0-db line of amplitude ratio. .

Neutralization Number - It's a measure of acidity of fluid that is defined as milligrams of potassium hydroxide which is required to neutralize acidity in one gram of fluid. .

Newtonian Fluid - It's a liquid where viscosity is independent of shear rate of the fluid. .

Nomograph - It's a chart on which straight line can be drawn so as to intersect three scales in values satisfying an equation/ given set of conditions. .

Non-return Valve - It's a valve that normally allows flow in one direction only.

Obliteration - It's a process that produces obstructed flow path choked off by obliterates (polar materials like water, long chain polymers and silica) that become attracted to walls of flow passage. .

Omega Rating - It's a standard method for expressing tolerance/sensitivity of hydraulic component to contaminants in hydraulic fluid. The OMEGA value corresponds to Beta-Ten value of filtration system which is needed to protect pump for 1000 hours of service at rated conditions. .

Open Loop Circuit - It's a hydraulic circuit where there is no automatic feedback to control input signal. .

Operating Conditions - These are conditions like temperature and pressure numerical values which relate to any given specific application of unit. These may change during course of operations. .

Optimal Control System - It's a system where control process is manipulated according to "performance index" defined by user. .

Ordinary Differential Equation - It's a differential equation that expresses response of system in respect to single independent variable. .

O-Ring - It's a type of seal comprising of elastomer in shape of toroid or donut. Its normally mounted in groove in a manner that effectiveness of sealing increases with pressure. .

Overshoot - It's the exceeding or surpassing of target value as operating conditions change. .

Oxidation Stability - It's the ability of substance to withstand chemical reaction with oxygen/air and subsequent degradation, a factor of prime importance in high temperature operations.

Platen - It's a plate-sometimes heated-attached for moving or stationary press member. .

Pressure Reversal Switch - Its an adjustable switch for setting the pressure at which Ram reverses. .

Post Press - Its basic hydraulic press design that utilizes four corner posts for supporting and guiding press platens and bolster assembly during forming process.

Quadratic - Its another name for second order, based on form of equation that represents second order response. .

Quick Disconnect - It's a coupling that usually contains at least one check valve that can be rapidly disconnected with minimal leakage. R Rabbet Mount - It's a mounting configuration that utilize matching male and female forms (usually coaxial circular) between cylinder and the mating mounting element. .

Ram - It's a single-acting cylinder where movable element has approximately same cross-sectional area as cylinder bore. Hence, Ram has single diameter type plunger as opposed to piston and rod. The plunger in Ram-type cylinder is also called Ram. .

Ramp Input Function - Its inclined slope, a constantly increasing function, a linear intensification of magnitude. .

Ratchetting - Its stick-slip action (intermittent motion) of control system. .

Rated - It refers to manufacturer's designation of normal operating condition - the allowable, maximum, continuous, etc. .

Ratio of Specific Heats - Its ratio of amount of heat that is required to raise mass of material 1 degree in temperature to amount of heat required for raising an equal mass of reference substance 1 degree in temperature. .

Reciprocation - Its back-and-forth straight line motion or oscillation. .

Redundancy - It's the existence of more than one means for accomplishing given function. .

Regeneration - It's the recovery of energy that would ordinarily be lost. .

Regenerative Control System - It's a system where part or all of output is fed back to help drive function or is stored for driving output converter. .

Reproducibility - It's a quantitative expression of random error that is associated with testers working in different laboratories. The each obtaining single results on identical test material, using same method. That is, precision with which measurement of given quantity can be duplicated in separate facilities. .

Response Time - It's the time required for system output to reach as well as stay within specified percentage of its theoretical final value due to step input - usually equal to five time constants. .

Restrictor - It's the device having reduced fixed or variable area that creates deliberate pressure drop and resistance to normal flow of fluid. Variable types are pressure-compensated, non-compensated or pressure- and temperature-compensated. .

Reynolds Number - It's the dimensionless ratio of dynamic force due to mass flow to shear stress due to viscosity. .

Remote Power Skid - Some press applications may require that hydraulics be located remotely from press itself. Other applications may preclude power system from being able to be installed at top around crown structure of press. In these cases, power system and even controls may be designed into separate unit that is capable of being placed adjacent to press or away from press. S Stroke Control - The Ram travel of press may be controlled in variety of ways where most hydraulic presses are standard with Adjustable Retract Limit Switches so as to limit retract distance of Ram (also known as Up Limit Position). This can shorten cycle times by only utilizing required stroke for part loading and unloading. Other adjustable limits may include Slow Down Limit for deceleration from Fast Speed to Slow Speed; Bottom Stop Position and/or Bottom Stop Pressure etc. .

Shut Height - Its distance between bed bolster and raw bolster when raw is fully extended and is also known as closed Height. .

Stroke - It's the amount of possible Ram travel. Stroke is total distance that Ram can travel, from full extension to full retraction. .

Shut Height - It's the distance between bed bolster and ram bolster when ram is fully extended. Commonly known as Closed Height, as a standard, this dimension is usually within "0.25" due to assembly processes. Further, for precision shut height requirements, consult the factory. .

Scuffing - It's a wear mechanism that involves micro welding of asperities on contacting surfaces under conditions of high loading as well as high relative velocities. The micro welding is normally followed by roughening and increasing friction and rupture of welds. Slab Side Hydraulic Press or Straight Side Hydraulic Press - This style of hydraulic press makes use of solid side construction for guiding press and platen operation in larger applications. It also keeps press components properly aligned, within specified tolerances, and with minimized deflection. T Throat Clearance - Its distance from vertical centerline of Ram to frame member behind bed. This distance determines largest diameter piece which can be positioned with part centerline under center of Ram. .

Thermal Stability - It's a measure of chemical stability of fluid that is subjected to high temperatures and includes resistance to molecular scission or cracking. For hydraulic fluids, the said property is principally criterion for arriving at stability of additives. .

Thin-film Lubrication - Its a condition where film thickness of lubricant is such that friction between surfaces is determined by properties of surfaces and the viscosity of lubricants. .

Tribology - It's the science and technology of friction, lubrication and wear. Known as study of interacting surfaces in relative motion and all related engineering issues including subjects and practices of friction, lubrication, and wear. .

Trunnion - Its pair of short journals supported in bearings that are projected coaxially from opposite sides of component required to pivot about their axis. U Ullage - It's the volume of fluid that a vessel lacks from being full. .

Ultrasonic - It's a vibration with frequency higher than that normally audible to human ear. .

Unloading Valve - It's a Valve that by-passes flow to reservoir when set pressure is maintained on pilot port. .

Unload - Its releasing flow to reservoir. V Vacuum Press - It's a hydraulic press that features vacuum enclosed platen working areas for removing air, gas vapors and fumes during forming process. This vacuum style hydraulic press ensures consistent material flows and precise control over temperature and pressure. .

Vacuum Pressure - Its deficiency of fluid/flow resulting from too low temperatures, too high suction velocity or incorrect fluid viscosity. It leads to suction difficulties as well as pump damages. .

Valve, Proportioning - This valve is fixed differential pressure reducing valve having fixed spring and fixed differential area. Its used in braking systems for limiting magnitude of pressure to rear brakes. .

Vena Contracta - Its region of smallest cross section in fluid stream where fluid emerges from an orifice, it tends to contract in cross section reaching minimum and then expanding back to fill conduit. .

Viscosity Index - It's a measure of viscosity-temperature characteristics of fluid compared to two arbitrary reference fluids. .

Window Frame Hydraulic Press - It's a hydraulic press that has large open feed area/window that is especially designed for larger dies or where access to work area is important. These window style hydraulic presses offer minimal deflection as well as optimal cross head parallelism. .

Work Height - Its the distance from floor to top of bolster. .

Water Hammer - It's a process where there is vibration of conduit in fluid system because of rapid changes in liquid velocity due to valve closure. .

Wear Ring - Its an element that is used for preventing cylinder seals from being crushed and metal-to-metal contact from occurring through maintaining seal concentricity when side loads exist. .

Wobble Plate - It's a rotating canted plate in axial type piston pump that pushes pistons into their bores as it "wobbles." X X, Port - It refers to pilot signal port. X-ray Emission, Proton Induced PIXE - Its an X-ray emission spectrometer which is based on physics. It separates electrons from hydrogen atom and then accelerator drives protons at high speed for colliding with target/specimen. The spectrometer is capable of evaluating 72 elements simultaneously in one sample. Y Y, Port - It refers to pilot signal port. .

Yield Strength - Its stress at which material exhibits specified deviation from proportionality of stress and strain. .

Young's Modulus - It's the ratio of simple tension stress that is applied to material to resulting strain parallel to tension. Z Factor - here factor is defined by relation Z = PV/NRT and is based on assumption that at same reduced pressure and temperature all gases have same compressibility factor. .

Zero-lapped - It's a critical-center condition where spool land width is identical to port width. .

ZETA Rating - It's a contaminant abrasion rating system which allows Omega Life of component to be transformed to Zeta Life to reflect abrasive severity of the environmental contaminant. .

Z-Transform - It converts difference equations into algebra form and is normally used for handling discrete/digital samples.