Adapter
- Connects and aligns the power end of an ANSI pump to the wet
end.
A.N.S.I.
Standard
- American National Standards Institute. A set of specifications
(envelope dimensions) for centrifugal pumps manufactured in the
United States
A.P.I. gland
- A seal gland that incorporates a non sparking disaster bushing
along with a vent and drain connection (quench), and a flushing
connection.
A.P.I. Specifications
- American Petroleum Institute Specifications. Usually adopted
by oil refineries for petroleum applications. Includes seal gland
and piping recommendations.
Absolute pressure
- Atmospheric pressure added to gauge pressure.
Active metal
- A corrosion resistant metal that has not been passivated. The
protective oxide layer has not formed.
Affinity laws
- They predict how capacity, head and horsepower are affected by
changes in the centrifugal pump impeller diameter or shaft
speed.
Air ingestion
- Air is coming into the stuffing box because of a negative
suction pressure.
Alignment
- The center line of the pump is perfectly aligned with the
centerline of the driver (usually an electric motor).
Alpha sintered
- A type of silicone carbide that does not contain silica.
Ambient heat/pressure
- The heat or pressure in the area where the equipment is
located.
Annealing
- To soften the metal by heating it to a predetermined
temperature somewhere below its melting point.
Anodize
- A treatment used on aluminum to put a heavy stable film of
oxide on the metal surface.
Anti-friction bearing
- Usually referring to a ball or roller bearing
Application
- A description of the fluid and operating conditions that we
are trying to pump or seal.
Atmospheric pressure
- At sea level, atmospheric pressure is 14.7 psi.
AVS Standard
- An old, obsolete standard that has been replaced by the
A.N.S.I. standard.
Back plate
- Used in some centrifugal pumps to position the stuffing box
and provide an impeller wear surface.
Back pull out pump
- A design that allows the wet end of the pump to be left on
the piping when the power end and adapter are removed. A.N.S.I.
pumps are designed this way.
Back to back double seal
- The rotating seal faces are facing in opposite directions.
The worst possible configuration. In the past this term was used
to describe a higher barrier fluid pressure between dual
mechanical seals.
Balanced seal
- A design in which the seal face closing area is reduced to
lower the closing force, and reduce the heat generation between
the faces.
Balance Ratio
- A 70/30 balance ratio means that 70% of the seal face
closing area is seeing the stuffing box pressure and 30% is not
seeing the pressure.
Ball bearing
- Consists of an inner race, an outer race, and a series of
balls between them. Often called a precision or anti friction
bearing.
Bar
- Metric term for one atmosphere of pressure.
Barrier fluid
- The high pressure fluid that is circulated between two
mechanical seals. The fluid should enter the bottom and leave the
top to prevent air pockets.
Base plate
- The pump and motor mount on this unit. The pump and motor
feet closest to the coupling should be doweled to the base
plate.
Bayonet
- The mechanical seal drive lugs wear into the drive slots
and prevent the seal faces from moving forward to compensate for
wear.
Bearing
- Supports the rotating shaft and allows it to turn with a
minimum amount of friction. Could be either sleeve or
anti-friction type
Bellows
- Can be manufactured from metal or non metallic materials to
eliminate flexing, rolling or sliding elastomers in mechanical
seal designs.
Bellows plate
- A thin, stamped disc. Two are welded together to form a
convolution.
Bernoulli's law
- A moving stream of liquid or gas exerts less sideways
pressure than if it were at rest. The result is that things seem
to be drawn into the stream, but they are really being pushed in
by the higher pressure from outside.
B.E.P.
- The best efficiency point. It is the point where the power
coming out of the pump (water horse power) is the closest to the
power coming into the pump (brake horse power) from the driver.
This is also the point where there is no radial deflection of the
shaft cause by unequal hydraulic forces acting on the
impeller.
B.H.P.
- Brake horse power. The actual amount of horsepower being
consumed by the pump as measured on a pony brake or
dynamometer.
Body bound bolts
- The bolt has an interference fit with the bolt
hole.
Brinnell hardness
- A method of measuring the hardness of metal parts and hard
seal faces. Above 350 the standard machining operations of
turning, boring, drilling, and tapping become
uneconomical.
Buffer fluid
- The low pressure fluid that is circulated between dual
mechanical seals.
Buna N
- Some times called Nitrile. A common elastomer used in the
sealing of oil or water. Sensitive to Ozone attack and therefore
has a short shelf life.
Bushing
- A close fitting support device used to restrict flow
between two liquids, thermally isolate a hot liquid, support the
rotating shaft, break down pressure etc. Commonly made of carbon
or Teflon.
Bypass line
- Used to either re-circulate fluid from the pump discharge
to the stuffing box, the stuffing box to the pump suction, or the
pump discharge to a lower pressure point in the system.
C frame adapter
- Used to connect and align the pump to
the motor with registered fits. (imperial dimensions. Called the D
frame adapter in the metric system)
C.L.A.
- Center line average. A method of measuring surface finish in
the metric system. Uses microns as a unit.
Canned pump
- A non seal pump with the shaft, bearings and rotor contained
in a can to prevent product leakage. Limited to pumping clean
lubricating liquids.
Capacity
- Fluid flow measured in gpm, liters/min, M3/hr.
etc.
Carbide
- The compound formed when carbon combines with an element. The
carbides of metal are very hard and are often used as a mechanical
seal face.
Carbon bushing
- Used as a restrictive bushing in flushing applications, a
thermal barrier in high temperature applications, a disaster
bushing in an A.P.I. gland and to support a deflecting shaft in
many mechanical seal applications.
Carbon/ graphite
- A common mechanical seal face material chemically inert to
most fluids with the exception of oxidizers, bleaches, halogens
and a few other fluids.
Carbonizing
- A reduction of hydrocarbons resulting in the formation of
carbonaceous residue that will interfere with the movement of a
mechanical seal. Often called "coking".
Carcinogen
- A cancer producing substance.
Cartridge seal
- A self contained assembly containing the seal, gland, sleeve,
and both stationary and rotating seal faces. Usually needs no
installation measurement. Must be used if impeller adjustments are
made. Cartridge seals are the standard for A.P.I. seal
applications.
Catalyst
- A chemical additive that decreases the time of a chemical
reaction with out being affected by the reaction.
Cavitate
- Cavities or bubbles form in the fluid low pressure area and
collapse in a higher pressure area of the pump, causing noise,
damage and a loss of capacity.
Center line design
- The pump is suspended on feet attached to the sides of the
volute instead of the bottom. Used in higher temperature (>
100°C) pumping applications.
Centipoise
- The metric system unit of viscosity.
Centistoke
- The kinematic unit of viscosity. Viscosity in centipoises
divided by the liquid density at the same temperature, gives
kinematic viscosity in centistokes.
Centrifugal pump
- Moves liquid with centrifugal force. Available in circular and
volute configurations.
Centrifugal separator
- Sometimes called a cyclone separator. Uses centrifugal force
to throw solids out of the fluid. Does not work very well in
slurry seal applications.
Ceramic
- A hard, chemically inert seal face material that includes
products refereed to as silicone carbide.
Change of state
- When a liquid flashes into a vapor, solidifies, crystallizes,
cokes etc.
Chemraz®
- An "elastomer like" material manufactured by Green Tweed of
England. Used to seal most solvents and other aggressive
fluids.
Chloride stress corrosion
- Occurs in the 300 series of stainless steel. Caused by a
combination of tensile stress, chlorides and heat. No one knows
the threshold values.
Chrome carbide
- Forms when chrome forms with carbon in the heat affected zone
during the welding of stainless steel. The use of low carbon
stainless steel is recommended in these applications.
Chrome Oxide
- The passivated layer that forms on the 300 series of stainless
steel.
Circular casing
- Used with centrifugal pumps that circulate fluid rather than
build head or pressure.
Clam Shell
- Used to set the pitch (distance between convolutions) while
heat treating a metal bellows core.
Close coupled
- The pump impeller is mounted directly on the motor shaft.
There is no separate bearing case.
Coated Face
- A hard coating is plated or welded to a softer base material.
Presents problems with different thermal expansion rates, the hard
coating can "heat check" or crack. Not recommended as a seal face
material.
Coke
- A hard black substance that forms when petroleum products are
over heated. It interferes with seal movement and will open the
lapped faces.
Composite
- When used in the content of mechanical seal faces, it refers
to either a non metallic material or a combination of non metallic
face inserted into a metal holder.
Compression set
- The elastomer changes shape when it has been exposed to too
much heat. Round O-rings come out square.
Concentric dual seal
- One seal is located inside the other, with a common hard face
shared by both of them. Because of its large radial space
requirement the seal is usually limited to mixer type
applications.
Concentricity
- When the parts share the same center line they are concentric
to each other.
Condensate
Convection
- A natural circulation of fluid. The hot fluid (lighter) rises
and the cool fluid (heavier) sinks.
Convection tank
- Used to contain fluid between two mechanical seals. An
enclosed heater or cooler can be used to control the barrier or
buffer fluid temperature. Pressure or level gages can indicate
which seal has failed.
Convolution
- Two metal bellows plates welded or formed together. To count
the number of convolutions in a metal bellows you count the spaces
between the bellows plates.
Cooling jacket
- Surrounds the stuffing box of the pump to control the
temperature of the fluid in the stuffing box. Usually molded into
the back plate.
Corrosion resistant
- Corrodes at a rate of less than 0.002 inches (0.05 mm) per
year.
Coupling
- Used to connect the pump to the driver. It transmits torque
and compensates for axial growth, but not for radial
misalignment.
Critical speed
- Any object made of an elastic material has a natural period of
vibration. When a pump rotor or shaft rotates at any speed
corresponding to its natural frequency, minor unbalances will be
magnified. These speeds are called the critical speeds.
Cryogenic
Cutwater
- Directs the pumped liquid to the discharge piping.
Cyclone separator
- A device used in some seal applications to separate solids
from liquid by utilizing centrifugal force. Not very
reliable.
D frame adapter
- Used to connect and align the pump and motor (manufactured in
metric dimensions). The Imperial version is called a "C" frame
adapter.
D-Gun process
- A metal spray process used to put a hard surface on a softer
metal. This is the normal method of applying nickel base tungsten
carbide. It is preferred over the popular Plasma Process if you
arre manufacturing a mechanical seal face.
D.I.N. standard
- The German standard for industrial products.
Damping
- The physical touching of a component to arrest vibration.
Dead ending
- Isolating the stuffing box. No recirculation or flushing lines
in or out.
Deflection
- Movement or displacement of the shaft in a radial
direction.
Density
- Measured in gm/cm2 or lb/in 2 A measure
of the weight of the fluid. A better term than specific
gravity.
Dial indicator
- A tool used to measure concentricity or displacement of a
shaft.
Dilatant
- A liquid that thickens (increases its viscosity) with
agitation.
Disaster bushing
- Used in A.P.I. glands to support the shaft in the event of a
bearing failure, or to prevent product from rushing to atmosphere
after a seal failure. The close clearance (0.025 inch or 0.5 mm.)
directs most of the leakage through a drain connection in the seal
gland to an appropriate container.
Discharge recirculation
- Connecting a line from the discharge side of the pump to the
stuffing box. Should be used with a close fitting bushing in the
end of the stuffing box to increase the stuffing box pressure. A
common application when pumping a fluid close to its vapor
point.
DN factor
- Do not use precision bearings if the bearing bore
(millimeters) x rpm. is 300,000 or greater
Double balanced seal
- Hydraulically balanced in both directions. A desirable
feature, but seldom provided by seal manufacturers.
Double seal
- An out dated term describing two seals in a pump. The latest
terminology is "dual seals". In the past the term was used to
describe a higher pressure barrier fluid between dual seals.
Double suction pump
- The rotor is suspended between two bearings with the fluid
entering on either side of the impeller. Used at higher
capacities.
Double volute
- A centrifugal pump design that incorporates two cut waters to
prevent shaft deflection when the pump is operating off of the
B.E.P. Lowers the efficiency of the pump and therefore seldom used
on smaller size impellers.
Drive lugs
- These lugs or pins transmit the torque from the set screws to
the seal face.
Dry running
- Running without fluid at the seal face.
Dual Seal
- Two seals running in various configurations: back to back,
tandem, face to face, or concentric.
Ductility
- The property of a metal that lets you give it a great deal of
mechanical deformation without cracking.
Dynamic elastomer
- The rubber part that has to move to move or flex to compensate
for seal face wear or shaft movement.
Dynamic head (system head)
- The pump head created by friction in the piping system.
Effective diameter
- In metal bellows terminology it is the calculated diameter
where the pressure penetrates between the metal plates. This
number is used to determine the hydraulic balance diameter of the
seal face.
Efficiency
- Power out of the equipment divided by power in.
Elastic range
- The stressed part retains its memory and returns to its
original shape.
Elastomer
- A rubber like material that, when compressed and then released
will return to 90% of its original shape in less than five
seconds.
Electrolysis
- A process involving chemical change caused by the passage of
an electric current through a liquid.
Endurance limit.
- Beyond this point the metal will fatigue without increasing
the stress.
E.P.A.
- Environmental protection agency. A government agency with a
mandate to protect the environment.
E.P.R.
- Ethylene propylene rubber. The most common elastomer used in
the sealing of water based and higher pH materials. Cannot be used
in petroleum products.
Extrusion
- Permanent displacement of a portion of the O-ring into a gap,
under the action of fluid pressure.
Eye of the impeller
- The center of the impeller, where the fluid enters.
Face combination
- The materials chosen for the lapped seal faces. Usually a
grade of carbon graphite running on a hard face material.
Face to face seals
- Two seals running against a common seal face. The barrier
fluid pressure is always lower than stuffing box pressure.
Face flatness
- Measured by an optical flat and a monochromatic light. The
measurement is read in helium light bands (.0000116 inches or 0,3
microns).
Face lubrication
- The fluid or vapor that sometimes exists between lapped
mechanical seal faces.
Face pressure
- The sum of all the loads on the seal face including the spring
load, hydraulic load and shaft axial thrust, divided by the area
of the seal face. This face load is reduced by friction between
the sliding elastomer and the shaft or sleeve.
Filled carbon
- Contains organic or inorganic materials that might be
sensitive to temperature, or be attacked by the fluid you are
sealing. Usually a low cost carbon.
Filter
- A devise used to remove solid particles from liquid. It
removes smaller paricles than a strainer.
Finite element analysis
- A computer generated method of predicting seal face
distortion.
Flashing
- A rapid change in liquid state from a liquid to a gas.
Flatness
- Measured by Helium light bands (0.0000116" or 0,3 microns) as
opposed to surface finish that is measured by R.M.S. or
C.L.A.
Flexibility factor
- Same as L3/D4 Used to predict shaft
bending problems.
Flexible member
- The portion of the seal containing the springs or
bellows.
Flexible shaft
- A shaft with an operating speed higher than its first critical
speed
Fluid
- The material assumes the shape of its container. It could be
either a liquid or a gas.
Flurocarbon
- Genetic term for the elastomer called Viton®. Viton is a
Dupont Dow elastomer product.
Flush
- Putting an outside liquid into the stuffing box of the pump at
a pressure higher than stuffing box pressure. All of this liquid
mixes with and dilutes the pumped fluid.
Foot
- Supports the wet and power end of the pump and attaches it to
the base plate.
Force
- Created whenever pressure works on an area. The units are
pounds. (F = P x A)
Formed metal bellows
- Manufactured by stretching and compressing the metal bellows
material. Not usually used in mechanical seals because of its high
spring rate.
F.P.M. (fpm.)
- Feet per minute. When used in the context of seals it is
measured at the center of the seal face.
Francis vane impeller
- The most popular impeller shape with a specific speed between
1500 and 4000.
Free length
- The uncompressed axial length of a seal.
Frett or fretting
- Damage or grooving caused by the removal of the protective
oxide that is formed on most corrosion resistant metals. It
happens when a softer material (rubber) rubs against a hard shaft
or sleeve. A common problem with low cost O.E.M. mechanical seals
and bearing grease or lip seals.
Fugitive emission
- The government has designated certain chemicals as hazardous
to the environment. If any of these chemicals is released to the
atmosphere they are called fugitive emissions.
Galvanic series
- A list of metals with those on the top of the list being
attacked by those lower down in the list. The father apart on the
list, the faster the attack.
Gasket
- Used between two static surfaces to provide a seal. Made from
a variety of deformable materials.
Gland
- The part that holds one half of the mechanical seal and
attaches to the stuffing box.
Grease seal
- A spring loaded elastomer seal commonly used to seal bearings.
Sometimes called a "lip seal". Not a good choice for sealing the
bearing casing of a pump. A labyrinth or face seal would be a
better choice.
Halogen
- Elements that attack carbon. Fluorine, bromine, chlorine,
astatine and iodine.
Hard face
- A seal face either rotating or stationary. The most common
materials are silicone carbide, ceramic, tungsten carbide,
Stellite, Ni-resist. The hard face must be the wider seal
face.
Harmonic vibration
- Vibtrating in harmony with something near by. This can be a
big problem for bearings in stationary or non running
equipment.
Hastelloy "C"
- A nickel rich, corrosion resistant metal used for mechanical
seal springs and metal bellows because it is not sensitive to
chloride stress corrosion.
Head
- The equivalent height of the liquid. 20° C. water is used
as the standard where 10 meters (33.9 ft.) of water equals one
atmosphere (14.7 psi. or 1 bar). The term head is used instead of
pressure in the centrifugal pump business.
Helium Light Band
- A method of measuring seal face flatness. One helium light
band equals 0.0000116 inches or 0.3 microns. Seal faces are
normally lapped to within three helium light bands of
flatness.
Horse power
- 33,000 foot pounds per minute. A common method of measuring
work.
Hydraulic balance
- A method of reducing mechanical seal face loading by reducing
the seal face closing area.
Hydraulic force
- Occurs any time pressure acts on a seal face area. Force times
distance divided by time is a measurement of work done.
Hydrocarbon
- A petroleum product consisting of hydrogen and carbon.
Hydrodynamic force
- Generated at the seal faces because, for all practical
purposes, liquid is not compressible.
Hydrodynamic seal
- Special geometric features on the seal face that provide lift
by taking advantage of the rotation of one seal face upon the
other.
Hydrogen embrittlement
- A premature fatigue of metal caused by the presence of free
hydrogen. This is a major cause of ceramic breakage in hot water
seal applications, and bearing fatigue if moisture penetrates into
the bearing case.
Hydronium ion
- An ion formed by the transfer of a proton from one molecule of
water to another. Used to determine the pH of a substance. Each
step increases by a factor of ten.
Hydrostatic seal
- Maintains a controlled gap between the seal faces by balancing
the open and closing forces. There is a small amount of leakage
across the faces when the shaft is rotating. Used in some
compressor applications, but not very practical for the chemicals
found in the process industry.
Hysteresis
- The delay or lag that causes seal faces to open.
I.D.
I.S.O.
- International standards organization. Sets pump and seal
standards for the metric community.
Impeller
- Attaches to the end of the shaft to impart energy to the fluid
being pumped. Available in open, semi- open and closed
designs.
Impeller eye
- The center of the impeller or the point where fluid enters the
impeller.
Impeller setting
- Open impellers require a clearance between the volute or the
pump back plate depending upon design. This clearance must be set
when the pump is at operating temperature and must be reset to
compensate for wear. (0.015" to 0.020" or 0,04 mm to 0,05 mm is
typical)
Impeller shroud
- the plates located on one or both sides of the impeller vanes.
Prevents solids from penetrating behind the vanes.
Impeller vane
- Located between the eye and the discharge side of the
impeller. Directs the flow of the liquid to the outside diameter
of the impeller.
Implode
- The opposite of explode. Bubbles implode in the higher
pressure areas of the pump making noise and causing damage to the
metal parts. This is normally called cavitation
Inclusion
- A non metallic slug of material which has become entangled in
the metal during its manufacture. A severe problem in thin cross
section metal bellows manufacture.
Inducer
- A small axial flow vane that attaches to the impeller of a
centrifugal pump to increase the N.P.S.H. available.
Induction motor
- The most common type used in industry. Has a slippage of 2 to
5 percent compared to synchronous motors.
Inline pump
- Mounted in the piping. No base plate or alignment
required.
Internal recirculation
- A loss of efficiency caused by liquid flowing through wear
rings or the impeller to volute clearances.
Intergranular corrosion
- A corrosion of the grain boundaries in the body of the
material.
Iteration
- A technique used in impeller design. You repeat the action
until you get to the final result. Very difficult to do until the
new computer programs became available.
Jacket
- Usually refers to the heating/ cooling jacket surrounding the
stuffing box on some pumps.
Joule
- A metric unit for the measurement of heat. Defined as the
energy required to move one Newton over one meter.
Kalrez®
- An "elastomer like" material manufactured by E.I. Dupont that
is used to seal most solvents and other aggressive fluids. It is
available in several different grades.
Kilowatt
- One thousand watts. The normal unit for work in the metric
system
kPa
- A metric unit for pressure. 100 kPa = one atmosphere.
L3 / D4
- A guide line for determining pump shaft stiffness where the
length of the shaft is compared to its diameter. This number
should be below 60 in imperial units and 2.0 in metric units.
Labyrinth seal
- A non contacting seal utilizing a tortured path for the escape
of the fluid. Utilizes a series of pressure drops to reduce the
leakage.
Lantern Ring
- A device used to supply lubricant to packing. Usually located
in the middle of the packing ring set.
Linear pressure drop
- A straight line pressure drop across the lapped seal faces.
Seldom happens.
Line bearings
- Position the rotor or shaft radially. Normally of the sleeve
type.
Line bored
- When the drilling or boring is done on a jig that insures
every component is in a straight line.
Lip Seal
Low flow
- A condition that can cause excessive heat inside the pump
volute. A temperature rise of 10°C (18°F) across the
operating pump is considered excessive. Usually caused by
throttling a pump discharge valve.
Lubricant
- Any fluid that will maintain a film thickness of one micron or
more at its operating temperature and load.
Mach number
- The relationship between a moving body and the speed of sound
in that locality which can vary with temperature, altitude and
there fore pressure.
Magnetic drive
- A type of seal less pump that is pretty much limited to
pumping clean lubricating liquids. Similar in concept to a canned
pump.
Magnetic seal
- Uses magnetic materials rather than springs to keep the lapped
seal faces together. Limited to non corrosive fluids because of
the magnets.
Magnetite
- Iron oxide ( Fe3O4). A protective
coating the forms on iron pipe to prevent further rapid corrosion.
Usually black or maroon in color. Can be very destructive to
mechanical seal components until the oxide stabalizes. We often
find these iron pipes in new hot water systems
Mating ring
- Another name for the hard face in a mechanical seal. It can be
either rotating or stationary.
Mean Diameter
- The middle diameter. Usually refers to the center of the seal
face. The term is commonly used with metal belows seals to
describe the middle diameter of the bellows plate.
Mechanical seal
- A positive sealing device used to seal all fluids (liquids and
gases). The primary seal is a set of lapped seal faces that are
installed perpendicular to the shaft.
Metal bellows
- Used in mechanical seal designs to eliminate the need for a
dynamic elastomer.
Metal fatigue
- A breakage of the metal caused by the bending and flexing of a
metal part beyond its endurance limit.
Micro Organisms
- Used in a variety of chemical processes. Can cause corrosion
of stainless steel if they penetrate the passivated layer and
attack the carbon content of the stainless steel.
Minimum flow
- A condition that can cause excessive heat inside the pump
volute. A temperature rise of 10°C (18°F) across the
operating pump is considered excessive. Normally caused by
throttling a pump discharge valve.
Miscible
- When one liquid mixes or blend with another liquid. Same as
soluble.
Modulus of elasticity
- Refers to the stiffness of the material. The higher the
modulus the stiffer the shaft. Most pump shafts have similar
modules numbers. Also called Young's modulus. The relationship of
stress to strain. If seal faces have a high modulus they are less
likely to distort under pressure.
Moment of inertia
- Referring to rotation about an axis. In the pump business it
refers to a formula that describes the shape of the shaft. A solid
shaft would have a different moment of inertia than a hollow
shaft.
Monochromatic light
- A single color light used with an optical flat to read seal
face flatness.
Negative pressure
- Less than atmospheric pressure.
N.P.S.H.A.
- The net positive suction head available to prevent cavitation
of the pump. It is defined as: Atmospheric pressure + gage
pressure + static pressure - vapor pressure - friction loss in the
suction piping.
N.P.S.H.R.
- Net positive suction head required to stop a pump from
cavitating. This number is given to you by the pump manufacturer.
Since the number was generated by testing with cold fresh water,
it can be lowered in some cases if you are pumping hot water or
some hydrocarbons.
Newton
- A metric unit of force. Kilogram x gravity.
Newtonian fluid
- A fluid that does not change viscosity as it is agitated.
Non lubricant
- The fluid that will not maintain a film thickness of at least
one micron at its operating temperature and load. A concern with
mechanical sealing.
O.D.
O.E.M.
- Original equipment manufacturer. The pump or seal company, not
the distributor of the products.
Oil analysis
- A sensible preventative maintenance technique to check the oil
for solids, water etc.
Oil life
- Lubricating oil has a useful life of about thirty years at
thirty degrees centigrade if it is not contaminated.
Oil mist
- A lubrication system where oil and air are mixed and sent into
the pump bearing case. Not friendly to the environment.
Operating length
- Measured after the seal has been compressed the proper amount.
The measurement is usually made from the face of the stuffing
box.
Optical flat
- A high quality glass lapped flat on one side and used with a
monochromatic light to read seal face flatness.
O-ring groove
- The space into which an O-ring is inserted. Dynamic O-ring
grooves use a different dimension than static O-ring grooves.
OSHA
- Occupational and Safety Health Act. Government regulations
that affec the sealing business. OSHA 1910 is one of the more
important that impacts the training of seal mechanics and
operators.
Over hung impeller
- Not supported with bearings on either side of the
impeller.
Oxidizer
- Combines with carbon to form carbon monoxide or carbon
dioxide. The oxidizers attack all forms of carbon including the
seal face and any black O-rings in the system.
Ozone
- Created by oxygen atoms combining with oxygen molecules in a
high energy atmosphere .Will prematurely age Buna rubber. Ozone
forms in the shop as a result of the sparking of electric motor
brushes.
P.D. Pump
- Positive displacement pump. It can pump a high pressure or
head, but at a low volume.
P.V. Factor
- An attempt to correlate the relationship between the pressure
and the velocity at the mechanical seal faces. Unfortunately
carbon graphite is sensitive to P, but not to V so the correlation
does not work too well.
Packing
- The soft rings that mechanical seal replace to stop leakage.
Packing must leak because it works on the theory of a series of
pressure drops to reduce the stuffing box pressure to the point
where the leakage is acceptable. A minimum of five rings of
packing is required to do this.
Parallel operation
- The pumps are discharging to a common header. It is important
that the impeller speed and outside diameters be the same or one
of the pumps will throttle the other.
Pascal
- A metric unit for pressure. 100 kPa = one atmosphere.
Passivated
- The protective oxide layer (ceramic) has formed on the metal
surface.
pH
- A measure of the acidity or the alkalinity of a fluid. The
scale ranges from 0 (acid) to 14 (alkali) with 7 considered
neutral.
Physicals
- Same as the specifications.
Pipe strain
- The strain on the pump volute caused by the piping. It will
cause excessive mechanical seal movement and can cause contact
between rotating and stationary pump and seal components.
Pitting
- Surface voids caused by corrosion, erosion or cavitation.
Plasma spray
- A method of putting a hard coating on a base material. Not
recommended for mechanical seal faces.
Plastic range
- If you stress metal enough, it stretches through the elastic
range, its yield point and ends up in the plastic range where it
loses its memory.
Positive displacement pump
- Called a PD pump. Gear, sliding vane, progressive cavity, lobe
etc. the capacity determined by the pump speed. The maximum head
is determined by the horsepower available and the casing
strength.
Power end
- The end of the pump that attaches to the power source and does
not get wet from the pumpage. The bearings are in this part.
Power factor
- A measure of how the voltage leads or lags the amperage.
Plastic range
- The metal has been stressed beyond its yield point and will
not return to its original shape.
Precision bearing
- Ball or roller bearing as opposed to a sleeve or babbitt
bearing.
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