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Absolute Pressure - The sum of
atmospheric and gauge pressure, its a pressure scale with zero point at
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
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
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
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
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
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
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
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
Non-return Valve - It's a valve that normally allows flow in one
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
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
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
Reciprocation - Its back-and-forth straight line motion or
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
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
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
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
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
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
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
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.
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