the mc nally institute glossary

8/4/2019 The Mc Nally Institute Glossary

http://slidepdf.com/reader/full/the-mc-nally-institute-glossary 1/37

Adapter

y Connects and aligns the power end of an ANSI pump to the wet end.

A.N.S.I. Standard

y American National Standards Institute. A set of specif ications (envelo pe dimensions) for

centrif ugal pumps manuf actured in the United States

A.P.I. gland

y A seal gland that incorporates a non sparking disaster bushing along with a vent and drain connection (quench), and a f lushing connection.

A.P.I. Specif ications

y America

nPetr

oleum I

nstitute Speci

f icati

ons. Usually ad

o pted by

oil re

f ineries

for petr oleum applications. Includes seal gland and piping recommendations.

Absolute pressure

y Atmospheric pressure added to gauge pressure.

Active metal

y A corr osion resistant metal that has not been passivated. The pr otective oxide layer hasnot formed.

Aff inity laws

y They predict how capacity, head and horsepower are aff ected by changes in thecentrif ugal pump impeller diameter or shaf t speed.

Air ingestion

y Air is coming into the stuff ing box because of a negative suction pressure.

Alignment

y The center line of the pump is per f ectly aligned with the centerline of the driver (usuallyan electric motor).

Alpha sintered

y A type of silicone carbide that does not contain silica.



Ambient heat/pressure

y The heat or pressure in the area where the equipment is located.

Annealing

y To sof ten the metal by heating it to a predetermined temperature somewhere below its

melting point.

Anodize

y A treatment used on aluminum to put a heavy stable f ilm of oxide on the metal sur f ace.

Anti-f riction bearing

y Usually ref erring to a ball or r oller bearing

Application

y A description of the f luid and o perating conditions that we are trying to pump or seal.

Atmospheric pressure

y At sea level, atmospheric pressure is 14.7 psi.

AVS Standard

y An o

ld,o bs

olete sta

ndard that has bee

nreplaced by the A.N.S.I. sta

ndard.

Back plate

y Used in some centrifugal pumps to position the stuffing box and provide an impeller

wear surface.

Back pull out pump

y 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

y 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



y A design in which the seal face closing area is reduced to lower the closing f orce, and

reduce the heat generation between the faces.

Balance Ratio

y A70/30 balance rati

o m

eans

that 70%of the

seal face cl

osing area i

s seeing the

stuffing box pressure and 30% is not seeing the pressure.

Ball bearing

y Consists of an inner race, an outer race, and a series of balls between them. Often

called a precision or anti friction bearing.

Bar

y Metric term f or one atmosphere of pressure.

Barrier fluid

y 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

y 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

y The mechanical seal drive lugs wear into the drive slots and prevent the seal faces

from moving f orward to compensate f or wear.

Bearing

y Supports the rotating shaft and allows it to turn with a minimum amount of friction.

Could be either sleeve or anti-friction type

Bellows

y Can be manufactured from metal or non metallic materials to eliminate flexing,

rolling or sliding elastomers in mechanical seal designs.

Bellows plate

y A thin, stamped disc. Two are welded together to f orm a convolution.



Bernoulli's law

y 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.

y 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 f orces acting on the impeller.

B.H.P.

y Brake horse power. The actual amount of horsepower being consumed by the pump

as m

easured

on a p

ony brake

or dyna

mometer.

Body bound bolts

y The bolt has an interference fit with the bolt hole.

Brinnell hardness

y 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

y The low pressure fluid that is circulated between dual mechanical seals.

Buna N

y Some times called Nitrile. A common elastomer used in the sealing of oil or water.

Sensitive to Ozone attack and theref ore has a short shelf life.

Bushing

y 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



y 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 f rame adapter

y Used to connect and align the pump to the motor with registered f its. (imperialdimensions. Called the D f rame adapter in the metric system)

C.L.A.

y Center line average. A method of measuring sur f ace f inish in the metric system. Usesmicr ons as a unit.

Canned pump

y A

nonseal pump

with the sha

f t, beari

ngs a

nd r

oto

r con

tained i

na ca

nto

prevent pr

oductleakage. Limited to pumping clean lubricating liquids.

Capacity

y Fluid f low measured in gpm, liters/min, M3/hr. etc.

Carbide

y The compound formed when carbon combines with an element. The carbides of metal arevery hard and are of ten used as a mechanical seal f ace.

Carbon bushing

y Used as a restrictive bushing in f lushing applications, a thermal barrier in hightemperature applications, a disaster bushing in an A.P.I. gland and to support a def lecting

shaf t in many mechanical seal applications.

Carbon/ graphite

y A common mechanical seal f ace material chemically inert to most f luids with theexception of oxidizers, bleaches, halogens and a f ew other f luids.

Carbonizing

y A reduction of hydr ocarbons resulting in the formation of carbonaceous residue that willinter f ere with the movement of a mechanical seal. Of ten called "coking".

Carcinogen



y A cancer pr oducing substance.

Cartridge seal

y A self contained assembly containing the seal, gland, sleeve, and both stationary and

r o

tating seal

f aces. Usually

needs

noinstallati

onmeasureme

nt. Must be used i

f impeller adjustments are made. Cartridge seals are the standard for A.P.I. seal applications.

Catalyst

y A chemical additive that decreases the time of a chemical reaction with out being aff ected

by the reaction.

Cavitate

y Cavities or bubbles form in the f luid low pressure area and collapse in a higher pressure

areaof

the pump, causingno

ise, damage and a l

oss

of capacity.

Center line design

y The pump is suspended on f eet attached to the sides of the volute instead of the bottom.Used in higher temperature (> 100°C) pumping applications.

Centipoise

y The metric system unit of viscosity.

Centist

oke

y The kinematic unit of viscosity. Viscosity in centipoises divided by the liquid density at

the same temperature, gives kinematic viscosity in centistokes.

Centrif ugal pump

y Moves liquid with centrif ugal force. Available in circular and volute conf igurations.

Centrif ugal separator

y So

metimes called a cyclon

e separator. Uses ce

ntrif ugal

force t

othr

owso

lidso

utof

thef luid. Does not work very well in slurry seal applications.

Ceramic

y A hard, chemically inert seal f ace material that includes pr oducts ref ereed to as silicone

carbide.



Change of state

y When a liquid f lashes into a vapor, solidif ies, crystallizes, cokes etc.

Chemraz®

y An "elastomer like" material manuf actured by Green Tweed of England. Used to seal

most solvents and other aggressive f luids.

Chloride stress corr osion

y Occurs in the 300 series of stainless steel. Caused by a combination of tensile stress,chlorides and heat. No one k nows the threshold values.

Chr ome carbide

y Forms

when

chr o

mefo

rmsw

ith carbon

in

the heat aff

ected zon

e during the

weldi

ngof

stainless steel. The use of low carbon stainless steel is recommended in these

applications.

Chr ome Oxide

y The passivated layer that forms on the 300 series of stainless steel.

Circular casing

y Used with centrif ugal pumps that circulate f luid rather than build head or pressure.

Clam Shell

y Used to set the pitch (distance between convolutions) while heat treating a metal bellowscore.

Close coupled

y The pump impeller is mounted directly on the motor shaf t. There is no separate bearingcase.

Coated

Face

y A hard coating is plated or welded to a sof ter base material. Presents pr o blems with

diff erent thermal ex pansion rates, the hard coating can "heat check" or crack. Notrecommended as a seal f ace material.

Coke



y A hard black substance that forms when petr oleum pr oducts are over heated. It inter f ereswith seal movement and will o pen the lapped f aces.

Composite

y When

used in

the con

tentof

mechanical seal

f aces, it re

f ers t

oeither a

nonmetallicmaterial or a combination of non metallic f ace inserted into a metal holder.

Compression set

y The elastomer changes shape when it has been ex posed to too much heat. R ound O-rings

come out square.

Concentric dual seal

y One seal is located inside the other, with a common hard f ace shared by both of them.

Becauseof

its large radial space requirement the seal is usually limited t

omi

xer typeapplications.

Concentricity

y When the parts share the same center line they are concentric to each other.

Condensate

y Condensed steam.

Convecti

on

y A natural circulation of f luid. The hot f luid (lighter) rises and the cool f luid (heavier)

sinks.

Convection tank

y Used to contain f luid between two mechanical seals. An enclosed heater or cooler can beused to contr ol the barrier or buff er f luid temperature. Pressure or level gages can

indicate which seal has f ailed.

Convoluti

on

y 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



y Surr ounds the stuff ing box of the pump to contr ol the temperature of the f luid in thestuff ing box. Usually molded into the back plate.

Corr osion resistant

y Corr o

des at a rateof

less than

0.002 inches (0.05 mm) per year.

Coupling

y Used to connect the pump to the driver. It transmits torque and compensates for axialgr owth, but not for radial misalignment.

Critical speed

y Any o bject made of an elastic material has a natural period of vibration. When a pumpr otor or shaf t r otates at any speed corresponding to its natural f requency, minor

un bala

nces

will be mag

nif ied. These speeds are called the critical speeds.

Cryogenic

y Very cold temperatures.

Cutwater

y Directs the pumped liquid to the discharge piping.

Cyclone separator

y A device used in some seal applications to separate solids f r om liquid by utilizingcentrif ugal force. Not very reliable.

D f rame adapter

y Used to connect and align the pump and motor (manuf actured in metric dimensions). The

Imperial version is called a "C" f rame adapter.

D-Gun pr ocess

y A metal spray pr

ocess used t

oput a hard sur

f ace

ona s

of ter metal. This is the

normalmethod of applying nickel base tungsten carbide. It is pref erred over the po pular Plasma

Pr ocess if you arre manuf acturing a mechanical seal f ace.

D.I.N. standard

y The German standard for industrial pr oducts.



Damping

y The physical touching of a component to arrest vibration.

Dead ending

y Isolating the stuff ing box. No recirculation or f lushing lines in or out.

Def lection

y Movement or displacement of the shaf t in a radial direction.

Density

y Measured in gm/cm2or lb/in

2A measure of the weight of the f luid. A better term than

specif ic gravity.

Dial indicator

y A tool used to measure concentricity or displacement of a shaf t.

Dilatant

y A liquid that thickens (increases its viscosity) with agitation.

Disaster bushing

y Used i

nA.P.I. gla

nds t

osupp

ort the sha

f t in

the eventof

a bearingf ailure,

or to

prevent pr oduct f r om rushing to atmosphere af ter a seal f ailure. The close clearance (0.025 inch

or 0.5 mm.) directs most of the leakage thr ough a drain connection in the seal gland to an

appr o priate container.

Discharge recirculation

y Connecting a line f r om the discharge side of the pump to the stuff ing box. Should be used

with a close f itting bushing in the end of the stuff ing box to increase the stuff ing box pressure. A common application when pumping a f luid close to its vapor point.

DNf act

or

y Do not use precision bearings if the bearing bore (millimeters) x rpm. is 300,000 or

greater

Double balanced seal



y Hydraulically balanced in both directions. A desirable f eature, but seldom pr ovided byseal manuf acturers.

Double seal

y An o

ut dated term describin

g two

seals in

a pump. The latest termino

lo

gy is "dual seals".In the past the term was used to describe a higher pressure barrier f luid between dualseals.

Double suction pump

y The r otor is suspended between two bearings with the f luid entering on either side of theimpeller. Used at higher capacities.

Double volute

y A ce

ntrif ugal pump desig

nthat i

nco

rpo

rates two

cutw

aters to

prevent sha

f t de

f lecti

on

when the pump is o perating off of the B.E.P. Lowers the eff iciency of the pump and

therefore seldom used on smaller size impellers.

Drive lugs

y These lugs or pins transmit the torque f r om the set screws to the seal f ace.

Dry running

y Running without f luid at the seal f ace.

Dual Seal

y Two seals running in various conf igurations: back to back, tandem, f ace to f ace, or concentric.

Ductility

y The pr o perty of a metal that lets you give it a great deal of mechanical deformation

without cracking.

Dynamic elast

omer

y The rubber part that has to move to move or f lex to compensate for seal f ace wear or

shaf t movement.

Dynamic head (system head)

y The pump head created by f riction in the piping system.



Eff ective diameter

y 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 f ace.

Eff iciency

y Power out of the equipment divided by power in.

Elastic range

y The stressed part retains its memory and retur ns to its original shape.

Elastomer

y A rubber like material that,

when

co

mpressed and the

nreleased

will retur

nto

90%of

itsoriginal shape in less than f ive seconds.

Electr olysis

y A pr ocess involving chemical change caused by the passage of an electric current thr ougha liquid.

Endurance limit.

y Beyond this point the metal will f atigue without increasing the stress.

E.P.A.

y Envir onmental pr otection agency. A gover nment agency with a mandate to pr otect theenvir onment.

E.P.R.

y Ethylene pr o pylene rubber. The most common elastomer used in the sealing of water based and higher pH materials. Cannot be used in petr oleum pr oducts.

Extrusi

on

y Permanent displacement of a portion of the O-ring into a gap, under the action of f luid

pressure.

Eye of the impeller

y The center of the impeller, where the f luid enters.



Face combination

y The materials chosen for the lapped seal f aces. Usually a grade of carbon graphiterunning on a hard f ace material.

Face t

o f ace seals

y Two seals running against a common seal f ace. The barrier f luid pressure is always lower than stuff ing box pressure.

Face f latness

y Measured by an o ptical f lat and a monochr omatic light. The measurement is read in

helium light bands (.0000116 inches or 0,3 micr ons).

Face lubrication

y The f luid or vapor that sometimes exists between lapped mechanical seal f aces.

Face pressure

y The sum of all the loads on the seal f ace including the spring load, hydraulic load andshaf t axial thrust, divided by the area of the seal f ace. This f ace load is reduced by

f riction between the sliding elastomer and the shaf t or sleeve.

Filled carbon

y Contai

nso

rganico

r ino

rganic materials that might be se

nsiti

ve t

otemperature,

or beattacked by the f luid you are sealing. Usually a low cost carbon.

Filter

y A devise used to remove solid particles f r om liquid. It removes smaller paricles than astrainer.

Finite element analysis

y A computer generated method of predicting seal f ace distortion.

Flashing

y A rapid change in liquid state f r om a liquid to a gas.

Flatness



y Measured by Helium light bands (0.0000116" or 0,3 micr ons) as o pposed to sur f acef inish that is measured by R.M.S. or C.L.A.

Flexibility f actor

y Same as L

3

/D

4

Used to

predict shaf t be

ndin

g pr o blems.

Flexible member

y The portion of the seal containing the springs or bellows.

Flexible shaf t

y A shaf t with an o perating speed higher than its f irst critical speed

Fluid

y The material assumes the shape of its container. It could be either a liquid or a gas.

Flur ocarbon

y Genetic term for the elastomer called Viton®. Viton is a Dupont Dow elastomer pr oduct.

Flush

y Putting an outside liquid into the stuff ing box of the pump at a pressure higher than

stuff ing box pressure. All of this liquid mixes with and dilutes the pumped f luid.

Foot

y Supports the wet and power end of the pump and attaches it to the base plate.

Force

y Created whenever pressure works on an area. The units are pounds. (F = P x A)

Formed metal bellows

y Ma

nuf actured by stretchi

ng a

nd c

ompressi

ng the metal bell

ows material. N

ot usuallyused in mechanical seals because of its high spring rate.

F.P.M. (f pm.)

y Feet per minute. When used in the context of seals it is measured at the center of the seal

f ace.



Francis vane impeller

y The most po pular impeller shape with a specif ic speed between 1500 and 4000.

Free length

y The uncompressed axial length of a seal.

Frett or f retting

y Damage or gr ooving caused by the removal of the pr otective oxide that is formed on

most corr osion resistant metals. It happens when a sof ter material (rubber) rubs against ahard shaf t or sleeve. A common pr o blem with low cost O.E.M. mechanical seals and

bearing grease or lip seals.

Fugitive emission

y The gover nment has designated certain chemicals as hazardous to the envir onment. If any

of these chemicals is released to the atmosphere they are called f ugitive emissions.

Galvanic series

y A list of metals with those on the to p of the list being attacked by those lower down in the

list. The f ather apart on the list, the f aster the attack.

Gasket

y Used bet

ween

two

static sur f aces t

opr ov

ide a seal. Madef r o

m avariety

of defo

rmablematerials.

Gland

y The part that holds one half of the mechanical seal and attaches to the stuff ing box.

Grease seal

y 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 f ace sealwo

uld be a better cho

ice.

Halogen

y Elements that attack carbon. Fluorine, br omine, chlorine, astatine and iodine.

Hard f ace



y A seal f ace either r otating or stationary. The most common materials are silicone carbide,ceramic, tungsten carbide, Stellite, Ni-resist. The hard f ace must be the wider seal f ace.

Harmonic vibration

y Vibtrati

ng i

nharm

onyw

ith so

methingnear by. This ca

nbe a big pr

o blem

for beari

ngs i

n stationary or non running equipment.

Hastelloy "C"

y A nickel rich, corr osion resistant metal used for mechanical seal springs and metal

bellows because it is not sensitive to chloride stress corr osion.

Head

y The equivalent height of the liquid. 20° C. water is used as the standard where 10 meters

(33.9f t.)

of w

ater equalson

e atmo

sphere (14.7 psi.o

r 1 bar). The term head is usedinstead of pressure in the centrif ugal pump business.

Helium Light Band

y A method of measuring seal f ace f latness. One helium light band equals 0.0000116

inches or 0.3 micr ons. Seal f aces are normally lapped to within three helium light bandsof f latness.

Horse power

y 33,000

foot p

ounds per mi

nute. A c

omm

onmeth

odof

measuringwo

rk.

Hydraulic balance

y A method of reducing mechanical seal f ace loading by reducing the seal f ace closing

area.

Hydraulic force

y Occurs any time pressure acts on a seal f ace area. Force times distance divided by time isa measurement of work done.

Hydr ocarbon

y A petr oleum pr oduct consisting of hydr ogen and carbon.

Hydr odynamic force

y Generated at the seal f aces because, for all practical purposes, liquid is not compressible.



Hydr odynamic seal

y Special geometric f eatures on the seal f ace that pr ovide lif t by taking advantage of ther otation of one seal f ace upon the other.

Hydr

ogen

embrittlement

y A premature f atigue of metal caused by the presence of f ree hydr ogen. This is a major cause of ceramic breakage in hot water seal applications, and bearing f atigue if moisture

penetrates into the bearing case.

Hydr onium ion

y An ion formed by the transf er of a pr oton f r om one molecule of water to another. Used to determine the pH of a substance. Each step increases by a f actor of ten.

Hydr

ostatic seal

y Maintains a contr olled gap between the seal f aces by balancing the o pen and closingforces. There is a small amount of leakage acr oss the f aces when the shaf t is r otating.

Used in some compressor applications, but not very practical for the chemicals found in the pr ocess industry.

Hysteresis

y The delay or lag that causes seal f aces to o pen.

I.D.

y Inside diameter.

I.S.O.

y Inter national standards organization. Sets pump and seal standards for the metric

community.

Impeller

y Attaches t

othe e

ndof

the shaf t to

impart energy t

othe

f luid bei

ng pumped. A

vailable i

n

o pen, semi- o pen and closed designs.

Impeller eye

y The center of the impeller or the point where f luid enters the impeller.

Impeller setting



y Open impellers require a clearance between the volute or the pump back plate dependingupon design. This clearance must be set when the pump is at o perating temperature and

must be reset to compensate for wear. (0.015" to 0.020" or 0,04 mm to 0,05 mm istypical)

Impeller shr o

ud

y the plates located on one or both sides of the impeller vanes. Prevents solids f r om

penetrating behind the vanes.

Impeller vane

y Located between the eye and the discharge side of the impeller. Directs the f low of the

liquid to the outside diameter of the impeller.

Implode

y The o pposite of ex plode. 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

y A non metallic slug of material which has become entangled in the metal during itsmanuf acture. A severe pr o blem in thin cr oss section metal bellows manuf acture.

Inducer

y A small a

xial

f low

vane that attaches t

othe impeller

of a ce

ntrif ugal pump t

oincrease the N.P.S.H. available.

Induction motor

y The most common type used in industry. Has a slippage of 2 to 5 percent compared to synchr onous motors.

Inline pump

y Mounted in the piping. No base plate or alignment required.

Inter nal recirculation

y A loss of eff iciency caused by liquid f lowing thr ough wear rings or the impeller to voluteclearances.

Intergranular corr osion



y A corr osion of the grain boundaries in the body of the material.

Iteration

y A technique used in impeller design. You repeat the action until you get to the f inal

result. Very diff

icult to

do

until the

new

co

mputer pr o

grams became available.

Jacket

y Usually ref ers to the heating/ cooling jacket surr ounding the stuff ing box on some pumps.

Joule

y A metric unit for the measurement of heat. Def ined as the energy required to move one

Newton over one meter.

Kalrez®

y An "elastomer like" material manuf actured by E.I. Dupont that is used to seal mostsolvents and other aggressive f luids. It is available in several diff erent grades.

Kilowatt

y One thousand watts. The normal unit for work in the metric system

kPa

y A metric u

nitfo

r pressure. 100 kPa =on

e atmo

sphere.

L3/ D

4

y A guide line for determining pump shaf t stiffness where the length of the shaf t iscompared to its diameter. This number should be below 60 in imperial units and 2.0 in

metric units.

Labyrinth seal

y A non contacting seal utilizing a tortured path for the escape of the f luid. Utilizes a seriesof pressure dr o ps to reduce the leakage.

Lanter n Ring

y A device used to supply lubricant to packing. Usually located in the middle of the packing ring set.



Linear pressure dr o p

y A straight line pressure dr o p acr oss the lapped seal f aces. Seldom happens.

Line bearings

y Position the r otor or shaf t radially. Normally of the sleeve type.

Line bored

y When the drilling or boring is done on a jig that insures every component is in a straight

line.

Lip Seal

y See grease seal.

Low f low

y A condition that can cause excessive heat inside the pump volute. A temperature rise of 10°C (18°F) acr oss the o perating pump is considered excessive. Usually caused by

thr ottling a pump discharge valve.

Lubricant

y Any f luid that will maintain a f ilm thick ness of one micr on or more at its o peratingtemperature and load.

Mach number

y The relationship between a moving body and the speed of sound in that locality whichcan vary with temperature, altitude and there fore pressure.

Magnetic drive

y 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

y Uses magnetic materials rather than springs to keep the lapped seal f aces together.

Limited to non corr osive f luids because of the magnets.

Magnetite



y Ir on oxide ( Fe3O4). A pr otective coating the forms on ir on pipe to prevent f urther rapidcorr osion. Usually black or mar oon in color. Can be very destructive to mechanical seal

components until the oxide stabalizes. We of ten f ind these ir on pipes in new hot water systems

Mating ri

ng

y Another name for the hard f ace in a mechanical seal. It can be either r otating or

stationary.

Mean Diameter

y The middle diameter. Usually ref ers to the center of the seal f ace. The term is commonly

used with metal belows seals to describe the middle diameter of the bellows plate.

Mechanical seal

y A positive sealing device used to seal all f luids (liquids and gases). The primary seal is a

set of lapped seal f aces that are installed perpendicular to the shaf t.

Metal bellows

y Used in mechanical seal designs to eliminate the need for a dynamic elastomer.

Metal f atigue

y A breakage of the metal caused by the bending and f lexing of a metal part beyond its

endura

nce limit.

Micr o Organisms

y Used in a variety of chemical pr ocesses. Can cause corr osion of stainless steel if they

penetrate the passivated layer and attack the carbon content of the stainless steel.

Minimum f low

y A condition that can cause excessive heat inside the pump volute. A temperature rise of 10°C (18°F) acr oss the o perating pump is considered excessive. Normally caused by

thr o

ttling a pump discharge

valve.

Miscible

y When one liquid mixes or blend with another liquid. Same as soluble.

Modulus of elasticity



y Ref ers to the stiffness of the material. The higher the modulus the stiff er the shaf t. Most pump shaf ts have similar modules numbers. Also called Young's modulus. The

relationship of stress to strain. If seal f aces have a high modulus they are less likely to distort under pressure.

Mo

mentof

inertia

y Ref erring to r otation about an axis. In the pump business it ref ers to a formula that

describes the shape of the shaf t. A solid shaf t would have a diff erent moment of inertiathan a hollow shaf t.

Monochr omatic light

y A single color light used with an o ptical f lat to read seal f ace f latness.

Negative pressure

y Less than atmospheric pressure.

N.P.S.H.A.

y The net positive suction head available to prevent cavitation of the pump. It is def ined as:

Atmospheric pressure + gage pressure + static pressure - vapor pressure - f riction loss in the suction piping.

N.P.S.H.R.

y Net p

ositi

ve sucti

onhead required t

osto p a pump

f r o

m cavitati

ng. This

number is gi

ven to you by the pump manuf acturer. Since the number was generated by testing with cold

f resh water, it can be lowered in some cases if you are pumping hot water or somehydr ocarbons.

Newton

y A metric unit of force. Kilogram x gravity.

Newtonian f luid

y A

f luid that d

oes

not cha

nge

visc

osity as it is agitated.

Non lubricant

y The f luid that will not maintain a f ilm thick ness of at least one micr on at its o perating

temperature and load. A concer n with mechanical sealing.

O.D.



y Outside diameter.

O.E.M.

y Original equipment manuf acturer. The pump or seal company, not the distributor of the

pr o

ducts.

Oil analysis

y A sensible preventative maintenance technique to check the oil for solids, water etc.

Oil lif e

y Lubricating oil has a usef ul lif e of about thirty years at thirty degrees centigrade if it is

not contaminated.

Oil mist

y A lubrication system where oil and air are mixed and sent into the pump bearing case. Not f riendly to the envir onment.

Operating length

y Measured af ter the seal has been compressed the pr o per amount. The measurement isusually made f r om the f ace of the stuff ing box.

Optical f lat

y A high quality glass lapped f lat on one side and used with a monochr omatic light to readseal f ace f latness.

O-ring gr oove

y The space into which an O-ring is inserted. Dynamic O-ring gr ooves use a diff erent

dimension than static O-ring gr ooves.

OSHA

y Occupati

onal a

nd Sa

f etyH

ealth Act. Gov

er nme

nt regulati

ons that a

ff ec the seali

ng business. OSHA 1910 is one of the more important that impacts the training of seal

mechanics and o perators.

Over hung impeller

y Not supported with bearings on either side of the impeller.



Oxidizer

y Combines with carbon to form carbon monoxide or carbon dioxide. The oxidizers attack all forms of carbon including the seal f ace and any black O-rings in the system.

Ozon

e

y Created by oxygen atoms combining with oxygen molecules in a high energy atmosphere.Will prematurely age Buna rubber. Ozone forms in the sho p as a result of the sparking of

electric motor brushes.

P.D. Pump

y Positive displacement pump. It can pump a high pressure or head, but at a low volume.

P.V. Factor

y An attempt to correlate the relationship between the pressure and the velocity at the

mechanical seal f aces. Unfortunately carbon graphite is sensitive to P, but not to V so thecorrelation does not work too well.

Packing

y The sof t rings that mechanical seal replace to sto p leakage. Packing must leak because itworks on the theory of a series of pressure dr o ps to reduce the stuff ing box pressure to

the point where the leakage is acceptable. A minimum of f ive rings of packing is requiredto do this.

Parallel o peration

y 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 thr ottle the other.

Pascal

y A metric unit for pressure. 100 kPa = one atmosphere.

Passivated

y The pr otective oxide layer (ceramic) has formed on the metal sur f ace.

pH

y A measure of the acidity or the alkalinity of a f luid. The scale ranges f r om 0 (acid) to 14(alkali) with 7 considered neutral.



Physicals

y Same as the specif ications.

Pipe strain

y The strain on the pump volute caused by the piping. It will cause excessive mechanical

seal movement and can cause contact between r otating and stationary pump and sealcomponents.

Pitting

y Sur f ace voids caused by corr osion, er osion or cavitation.

Plasma spray

y A meth

odof

putting a hard c

oati

ngon

a base material. No

t reco

mmended

for mecha

nicalseal f aces.

Plastic range

y If you stress metal enough, it stretches thr ough the elastic range, its yield point and endsup in the plastic range where it loses its memory.

Positive displacement pump

y Called a PD pump. Gear, sliding vane, pr ogressive cavity, lo be etc. the capacity

determined by the pump speed. The ma

ximum head is determi

ned by the h

orsep

ower available and the casing strength.

Power end

y The end of the pump that attaches to the power source and does not get wet f r om the pumpage. The bearings are in this part.

Power f actor

y A measure of how the voltage leads or lags the amperage.

Plastic range

y The metal has been stressed beyond its yield point and will not retur n to its originalshape.

Precision bearing



y Ball or r oller bearing as o pposed to a sleeve or babbitt bearing.

Pressure dr o p

y Ref erring to the loss of pressure f r om the outside to the inside of the mechanical sealf aces

or acr

oss the i

ndiv

idual rings

of packi

ng.

Press f it

y The best way to insert a carbon/graphite f ace into a metal holder. The carbon will shear to conform to the holder's irregular shape. Usually done with an arbor press.

Pressure gradient

y The pressure dr o p between the seal f aces. Usually illustrated by a wedge.

Pressure head

y The pump head exerted by atmospheric pressure or any additional pressure that might bein the vessel.

Pump cur ve

y A diagram supplied by the pump manuf acture to describe the relationship between thehead and the capacity of a particular pump using various size impellers. The cur ve also

include information about eff iciency, horse power consumption, N.P.S.H. required, etc.

Pumpo

utvane

y Located behind the impeller shr oud in some impeller designs to lower stuff ing box

pressure. Should no be used in hot well condensate pumps or any pump running with anegative stuff ing box pressure.

Pumping ring

y Used with a convection system to get circulation between two mechanical seals.

Absolutely necessary if oil is used as a barrier f luid because of oil's poor specif ic heat..

Pusher seal

y A design that has a spring loaded dynamic elastomer or rubber like part. A very poor

design that should be avoided.

Quench



y The intr oduction of a f luid outside the seal to cool the pr oduct, or dilute any leakageacr oss the seal f aces.

Quill shaf t

y A h

ollow

shaf tw

ith ano

ther shaf t inside it.

Radial

y 90 degrees to the centerline of the shaf t.

Radial bearing

y In an end suction centrif ugal pump it is the bearing located closest to the stuff ing box.

This bearing handles most of the radial loads put on the impeller.

Reaction

bon

ded

y A method of manuf acturing silicone carbide mechanical seal f aces. These materials aresensitive to caustic and some other high pH liquids.

Renkin scale

y Used to measure low temperatures in the Fahrenheit scale. Similar to Kelvin which isused to measure low temperatures in the Centigrade system.

Repeller

y A second impeller used to lower the stuff ing box pressure.

Reverse balance

y A common type of hydraulic balance used on outside mounted mechanical seals.

Rigid shaf t

y A shaf t with a r otating speed lower than its f irst critical speed.

RMS

y R oot mean square. A measure of sur f ace f inish or smoothness. Metric uses C.L.A. or centerline average for the same purpose.

R ock well "C"

y The scale most of ten used to measure hardness of the hard seal f ace.



R otating seal

y When the spring loaded or moveable portion of the seal r otates with the shaf t.

Run out

y Twice the distance that the center of the shaf t is displaced f r om the axis of r otation.

Seal f aces

y The lapped f aces that that pr ovide the primary sealing in a mechanical seal.

Seal lif e

y Seals sh

ould ru

nleak

f ree u

ntil the sacri

f icial

f ace (usually carb

on/ graphite) is

wor n away. More than 85% of the mechanical seals in use today f ail prematurely.

Seal only pump

y The pump does not have a conventional stuff ing box so it could not be supplied with sof t packing.

Self align

y A method of keeping both mechanical seal f aces square to the r otating shaf t.

Self sintered silicone carbide

y Same as Alpha sintered. No f ree silica present. Can be used in caustic and higher pH liquids.

Series o peration

y The pumps are connected with the discharge of the f irst pump discharging to the suction of the other. The speed and impeller widths must be the same or the diff erence in

capacities could cause cavitation or over heating pr o blems.

Shaf t packing

y The sof t packing supplied by pump manuf acturers. Most of these leaking packings are

being replaced by mechanical seals.

Shelf lif e



y Usually ref ers to the seal elastomer. Buna "N" is the biggest pr o blem because of Ozoneattack.

Shore "A"

y A scale used t

omeasure elast

omer hard

ness.

Shut off head

y The maximum head that the pump can generate with a given impeller outside diameter and horsepower driver.

SiC

y Silicon carbide. A common mechanical seal f ace material. A type of ceramic.

Sintered material

y Formed f r om a powder as o pposed to being melted and poured into a mold.

Skidding

y A term used in describing how an impeller slides on the solids in the bottom of a mixer.

Sleeve bearing

y A non precision bearing. Usually manuf actured f r om carbon, Tef lon. brass etc., Allows

too

much axial a

nd radial m

oveme

ntfo

r mo

st mechanical seal applicati

ons.

Slender ness ratio

y Another name for L3/D

4

Slip stick

y An alter nating slipping and sticking of the seal f aces caused by a poor lubricant between the f aces. Will cause vibration pr o blems at the seal f ace unless the vibration is dampened.

Slurry

y Solids in liquid. It is impossible to def ine when the quantity and size of the particles becomes too much for the mechanical seal.

Sof t foot



y The tendency for one of the pumps f eet to rise when the hold down bolt is loosened. Very bad for alignment.

Soluble

y When on

e liquid disso

lv

eso

r mix

esw

ith ano

ther liquid.

Span

y The width of the metal bellows. The distance f r om the inside diameter to the outsidediameter.

Specif ic Gravity

y A measure of the weight of a liquid. Fresh water at 4°C (39°F) is given a value of one. If the liquid you are questioning will f loat on water the specif ic gravity is less than one. If it

sinks, it is higher tha

n on

e. Density is a better term.

Specif ic heat

y Ref ers to the amount of calories or BTUs required to raise a quantity of a liquid onedegree.

Specif ic speed

y A formula that describes the shape of a pump impeller. The higher the specif ic speed theless N.P.S.H. required.

Speed of sound

y In air it is 1090 f eet per second, in water it is 4800 f eet per second.

Spool piece

y Usually ref ers to a seal and bearing combination that is supplied for some mixer applications. It depends upon the application, but this is not a good idea if there are

already two anti-f riction bearings already installed on the shaf t

Springfo

rce

y The force on the seal f aces caused by the spring compression.

Stainless steel

y Alloy steels containing a high percentage of chr omium.



Static head

y The maximum height the liquid is being pumped as long as you take into consideration the siphon aff ect in some piping systems.

Station

ary seal

y The spring loaded or moveable portion of the seal does not r otate with the shaf t. Must beused when the seal sur f ace speed exceeds 5000 f pm. or 25 meters per second.

Stiffness ratio

y Another name for L3/D

4

Strain

y A measure

of the am

ountof

defo

rmation

pr o

duced in

a substance

when

it is stressed.

Stress

y A measure of the intensity of the load applied to a material. Stress is ex pressed as the

load divided by the cr oss-sectional area over which it is applied.

Stress relieve

y To take residual stress out of an o bject. This is very important with lapped seal f aces;especially those that have been inserted into a metal holder.

Stuff ing box

y That portion of the pump that held the packing and now holds the mechanical seal.

Stuff ing box pressure

y Between suction and discharge pressure but closer to suction pressure.

Suction head

y The head

onthe sucti

onside

of the pump. Y

ou subtract it

f r o

m the discharge head to

determine the head being pr oduced by the pump. It is a sum of the static, pressure andf riction heads.

Suction recirculation

y Piping f r om the bottom of the stuff ing box back to the suction side of the pump. Used to lower pressure and circulate liquid in the stuff ing box.



Suction specif ic speed

y A formula that will predict one of the types of cavitation. Pumps should be purchasedwith a number below 8500 (10,000 metric)

Sur f ace speed

y A measure of the f eet per minute the seal f ace or some other component is moving.

Synchr onous motor

y Runs with out slippage. Used in elevators and compressors f requently, but seldom used in pumping. Pumps mostly use induction or "squirrel cage" motors.

System cur ve

y A descripti

on of

w

hat the pump is required to

per fo

rm. The pumpw

ill pumpw

here thesystem cur ve intersects the pump cur ve.

System head

y The head caused by f riction in the piping. valves and f ittings.

Tandem seals

y The seals are f acing in the same direction with a low pressure barrier f luid circulating between them.

T.D.H.

y Total discharge head. A combination of the suction head and the head being pr oduced bythe pump.

10-2

inches

y A way to write 0.01 inches.

Tensile strength

y The strength measured when the part is being pulled axially.

Thermal conductivity

y A measure of the material's ability to conduct heat. This is a very important f actor in the

selection of mechanical seal f aces.



Thermal imaging

y A tr oubleshooting piece of equipment that will let you see hot spots in the equipment.

Thermo plastic

y A plastic material that can be sof tened or melted repeatedly without change of pr o perties.

In jection molded parts are manuf actured with Thermo-plastic materials.

Thermosetting

y A plastic material that can be sof tened and molded but cannot be re-used or reverted to itsoriginal state.

Thixotr o phic f luid

y The

visc

osity

of the

f luid decreases

with agitati

on. N

ondrip pai

nt is a

nexample

of such a

f luid.

Thrust bearing

y Locates the r otor or shaf t axially. Normally located clse to the coupling.

Torr

y One millimeter of mercury. Used in both the imperial and metric systems a a unit of measurement in vacuum ser vice.

Total head

y The amount of head pr oduced by the pump. Discharge head minus suction head. If suction head is a negative number it is added to the discharge head.

Thrust

y In a centrif ugal pump it ref ers to the axial movement of the shaf t. The thrust can betowards the wet or power end of the pump and at start up it thrusts in both directions.

Thrust bearing

y Designed to take the axial thrust in pump applications. It is usually located next to the

coupling and is of ten supplied in a "double r ow" conf iguration.

Transducer

y Attached to the pump and used to send a vibration signal to a meter where it can be read.



Tungsten carbide

y A common hard f ace seal material available in several grades depending upon hardnessand corr osion resistance. Co balt and nickel are the two most common types.

Turbulence

y Disturbed f luid. Can cause cavitation pr o blems in a centrif ugal pump. Of ten caused by an elbow located too close to the pump suction inlet.

Two way balance

y A method of balancing a mechanical seal in two directions. A very important

consideration in dual seal applications.

Un balanced seal

y Not hydraulically balanced to generate low heat at the seal f aces. Typical of original

equipment designs.

Unf illed carbon

y Containing carbon/ graphite and nothing else. Filled carbons contain inorganics that will

be sensitive to some chemicals and temperature extremes. Unf illed carbons are the pref ereed seal f aces.

U.S.C.S.

y United States Customary System. Al dimensions are in inch units.

Variable speed motor

y Used to contr ol f low in a system by varying the f requency of the motor. Recommendedfor circulating systems and any other system where the main head is f riction losses in the

piping system.

V.D.M.A.

y A Germa

nsta

ndard

for mecha

nical seals.

Vacuum

y Any pressure less than atmospheric. Can present a pr o blem for the elastomer in many

seal applications.

Vane passing syndr ome



y A type of cavitation caused by the impeller/ cutwater clearance being too small.

Vapor pressure

y Below this pressure, the liquid at this temperature will vaporize.

Vaporize

y The f luid passes f r om a liquid to a gaseous state. If this happens at the seal f aces the seal

f aces will be blown o pen.

Velocity

y A measurement of the speed of the liquid in the system. Measured in f eet or meters per

second. The pump is a constant velocity device.

Velo

city head

y Part of the total head calculation. Derived f r om the formula h = V2/2g

Vent

y To remove air or gas f r om the system. It is important to vent the stuff ing box in vertical

pumps to prevent the seal f aces f r om running dry.

Vibration Damping

y Imp

orta

nt in

metal bellow

s seal design

s. The elasto

mer acts as avibrati

ondamper i

nthe

other seals. The vibration can chip carbon f aces, destr oy anti-r otation drive lugs, ando pen the lapped seal f aces.

Viscosity

y Resistance to pouring. Higher viscosities can restrict seal movement. Centrif ugal pumps

can handle a maximum viscosity similar to 30 weight oil at r oom temperature. Above thisviscosity a positive displacement pump should be used.

Viton®

y An E.I. Dupont Dow manuf actured elastomer widely used in the sealing industry. Thegeneric name is f luor ocarbon. Many of these compounds are attacked by water and

steam.

Volute casing



y Derives is name f r om a spiral shaped casing surr ounding the pump impeller. It convertsvelocity energy to pressure energy.

Vortex Pump

y A type

of pump used

for e

xcessi

ve s

olids. The impeller is recessed i

nto

thevo

lute. Averylow eff iciency design, but practical in many applications.

Vortexing liquid

y Creating a "whirlpool aff ect" that can draw air into the suction of the pump.

Water Horse Power (W.H.P.)

y The calculated horse power coming out of the pump using the formula WHP = head x gpm/3960

Watt

y A measure of power. 746 watts equals one horsepower.

Wave spring

y A disc washer used when axial space is at a premium. Does not allow very much axialtravel of the seal.

Wear ring

y Used with closed impeller pumps to restrict leakage f r om the high pressure side of the pump to the low pressure side. Should be replaced when the recommended clearance is

doubled.

Welded metal bellows

y A seal design used to eliminate the use of elastomers. Excellent for cryogenic and hotapplications. Not as eff ective for hot petr oleum applications because of "coking"

pr o blems

Wet e

nd

y The part of the pump that gets wet f r om the pumping f luid. Includes the volute, stuff ing

box, impeller wear rings, and shaf t or sleeve

Yield point

y Where the metal passes f r om the elastic to the plastic range

the mc nally institute glossary

Documents