Air Filter

Air filter  –
an insert piece mounted on an engine’s
intake system that contains a fabric, paper, or other
type of mesh assembly that traps dust and dirt while
allowing air to flow into the engine freely.

Air Filter Housing

Air filter housing  –
also described as an “air box”, this
plastic assembly houses and protects the air filter
from contamination by outside elements. On one
side of the housing is an inlet for fresh air to enter,
and on the other side is an outlet for filtered air to
exit and travel into the engine’s throttle body assembly .

Alternator
Alternator  –
the part of a vehicle’s electrical system that
converts mechanical energy from a drive belt and
pulley wheel into electrical energy to operate the
ignition system, electrical accessories, and charge
the battery. An alternator generates alternating
current (AC) and then transforms it into the direct
current (DC) used by automotive electrical systems.

Auxiliary Drive Belt

Auxiliary drive belt  –
a flexible rubber belt used to transmit
power from a crankshaft-driven pulley to another
pulley which supplies rotational power to an
accessory on the engine such as an alternator,
pump, cooling fan, or other.

Because drive belts are subject to constant rotation,

load, and heat, they are constructed in a similar
fashion as tires. An outer layer of rubber surrounds
internal steel and cord reinforcements to minimize
stretching and maximize strength when grip is
needed under load. A setup where one single drive
belt powers a number of devices is known as
a serpentine belt.

Camshaft Synchronizer
Camshaft synchronizer  –
Found on older engines originally
designed to use conventional distributors, camshaft
synchronizers replaced them - mounting in the exact
same locations. They’re driven off the camshafts,
and contain sensors that track the position of the
camshaft so the vehicle’s engine computer can
properly time ignition spark.

Carburetor
Carburetor  –
An assembly sitting on top of the
engine intake manifold  that combines vaporized fuel and
air to form a combustible mixture that can be burned
in an engine’s cylinders. The carburetor changes the
quantity of fuel and air in response to varying
conditions such as starting, idling, cruising, and full
power.

A “downdraft carburetor” is one in which air flows

downward through it and into the intake manifold. In
a “sidedraft carburetor”, the air inlets bring in air
horizontally. And an “updraft carburetor” features a
design where the air-fuel mixture flows upward to the
intake manifold.

Compressor
Compressor  –
Part of the air conditioning system, a
component driven by a pulley and belt running off the
crankshaft which serves to pump vaporized A/C
refrigerant out of the vehicle’s evaporator, pressurize
it, then deliver it to the A/C condenser. Compressors
are typically bolted onto the engine block directly, or
by way of a bracket piece.

Direct Fuel Injection

Direct Fuel Injection – A setup where fuel injectors
are mounted in the cylinder head instead of the
intake manifold assembly (see port fuel injection ).
Injectors spray fuel directly into the engine cylinder
where it then mixes with air delivered from the intake
manifold assembly. Most modern vehicles feature
direct fuel injection because it produces gains in
horsepower and economy.

Distributor
Distributor  –
An assembly with a rotating shaft that
delivers an electrical spark to each of the cylinders in
a gasoline engine. Typically mounted on the side of
the engine block, the distributor’s shaft is driven by a
gear on the crankshaft or camshaft. This shaft sits
inside the center of the distributor, with a rotor piece
at its top that spins under a distributor cap . The
distributor is timed to deliver spark to each cylinder
exactly when it’s needed to create combustion. For
more info on how distributors work, see our related
article .

Distributor Cap
Distributor Cap  –
the replaceable top-most section of
the distributor  assembly. The cap has a number of
terminals around its circumference, equal to the
engine’s cylinder count. As an attached rotor passes
under each terminal, electricity travels through the
cap and out into individual spark plug wires which
lead to the spark plugs.
Exhaust Manifold
Exhaust manifold  –
the first section of the exhaust system
which bolts directly over exhaust ports on the side of
the cylinder head(s). As exhaust exits the engine, it
passes into individual tubes on the manifold for each
cylinder. These tubes combine into a single pipe.
Inline engines feature only one exhaust manifold,
while V-engines have two, one on each side of the
engine.

Flex Plate
Flex Plate  –
Serving the same general function as
a flywheel, a flex plate is a metal disc mounted outside
the rear of the engine on the crankshaft where it
exits the engine block. Created for automatic
transmissions, flex plates are typically lighter and
thinner than flywheels because they’re designed to
flex as rpms increase to provide better mating with
the curved surface of a torque converter. Teeth
along the perimeter of the flex plate engage an
electric starter motor to crank the engine until it
begins firing on its own.

Flywheel
Flywheel  -
a large, heavy metal disc mounted outside
the rear of the engine on the crankshaft where it
exits the engine block. Its purpose is to smooth
engine vibrations and serve as a mating piece for a
manual transmission clutch disc. Teeth along the
perimeter of the flywheel also engage a small electric
starter motor to crank the engine until it begins firing
on its own. See also flex plate for automatic
transmissions.

Fuel Injectors
Fuel injectors  –
mounted on the cylinder head(s), these
are mechanical or electro-mechanical devices that
spray fuel in metered amounts into the intake
manifold or cylinders of a fuel-injected engine.

Fuel Injection Pump

Fuel injection pump  –
typically found on diesel engines, but
also used on older mechanical gas engine fuel
injection systems, these are driven off a gear from
the engine. After drawing fuel out of a line leading
from the fuel tank, the pump serves to further
pressurize fuel as needed before delivering it to the
injectors.
Fuel Rail
Fuel rail  –
a section of fuel line that feeds fuel to the
fuel injectors located at individual cylinders.

Glow Plug
Glow plug  –
an electrical plug, similar to a spark plug,
that preheats the combustion chamber of a diesel
engine to assist in cold starting, after which the plug
shuts off and stays off.

Harmonic Balancer
Harmonic balancer  –
a pulley which bolts to the front of the
crankshaft. As it rotates with the crankshaft, its mass
helps dampen crankshaft vibrations (also known as a
vibration damper).

Ignition Coil
Ignition coil  –
a pulse transformer designed to boost the
12 volt “primary” voltage received from the battery or
alternator to 20,000-30,000 volts upon the opening
and closing of the contact points.

It contains a primary winding of heavy wire that’s

wound in a circular configuration about 200 times. A
secondary winding made of much finer wire may
contain up to 22,000 turns. The current through the
primary winding produces a magnetic field in the coil,
which produces a much larger current in the
secondary winding.

Older vehicles are equipped with a single ignition coil

that sends the high voltage to the distributor to be
disbursed to each spark plug. Newer vehicles
without a distributor will feature one ignition coil per
cylinder – these slot in place on top of each spark
plug.

Intake Manifold
Intake manifold  -
an integrated assembly that sits atop the
engine, consisting of a series of tubes which
distribute the fuel/air mixture to each and every
cylinder. On V-shaped engine blocks, an intake
manifold typically sits between the two cylinder
banks while inline engines may mount the manifold
on the side of the cylinder head.

Intercooler
Intercooler – A small heat exchanger (similar to a
radiator) used on turbocharged or supercharged
cars. It reduces the temperature of the intake air
delivered through the turbocharger or supercharger
to the engine.

Motor Mount
Motor mount  –
rubber and steel supports bolt the engine
(and transmission) to the vehicle frame or unibody.
These supports absorb the twisting movements of
the powertrain caused by engine torque and abrupt
transmission shifts. Additionally, they isolate the
passenger compartment from vibration and noise.
Some motor mounts even feature cavities filled with
hydraulic fluid to enhance smoothness.

Oil Cooler
Oil cooler  –
a small heat exchanger used to lower the
temperature of engine oil or transmission fluid.
Racecars use variations of oil coolers for manual
gearbox and differential lubricants as well.

Oil Dipstick
Oil dipstick  –a long, thin metal rod used to measure the
level of oil in an engine oil pan. This rod sits within
a dipstick tube  assembly that runs all the way down to
the pan.
Oil Filter
Oil filter  –
a component designed to remove impurities
or particles of foreign matter from the engine oil. As
the oil leaves the oil pan to begin circulating through
the engine block, it first passes through the oil filter
where webbed channels catch and hold unwanted
debris until the filter is changed during routine
maintenance. Oil filters are either the fully-enclosed
disposable screw-on type, or the cartridge type
which sit inside an enclosed canister.

Oil Pan
Oil pan  –
a removable part of an engine mounted to the
bottom of the cylinder block that serves as the
engine's oil reservoir (also known as a sump). At the
bottom of the pan is a drain plug which allows oil to be
removed during routine maintenance.

Port Fuel Injection (PFI)

Port fuel injection (PFI) – A fuel injection setup
where fuel is sprayed into the intake ports to mix with
the incoming air inside the intake manifold runners.
The air/fuel mixture stays in the runners until an
intake valve opens and pulls it into the engine
cylinder. Fuel injectors are typically mounted in the
intake manifold runners as well.

Positive Crankcase Ventilation (PCV) Valve

Positive crankcase ventilation (PCV) valve  –
an emissions control
check valve in which unburned fuel vapors in the
crankcase are discharged back into the engine
intake system (usually via the intake manifold) and
pass through the cylinders instead of being
discharged into the atmosphere. PCV valves are
normally replaced as part of periodic maintenance.

Power Steering Pump

Power steering pump  –
a belt-driven pump driven off the
crankshaft pulley which pressurizes steering fluid in
order to reduce the amount of effort involved with
turning the steering wheel. These pumps are
typically bolted to the engine block directly, or by
way of a bracket. Some modern vehicles have
switched to all-electric power steering pumps.

Secondary Air Injection Pump

Secondary air injection pump  –
an air pump specifically
designed to inject fresh air into the exhaust ports (or
a thermal reactor) to achieve more complete
combustion of unburned fuel in the exhaust.
Normally, the pump will run for approximately one
minute after a cold start when the engine isn’t yet hot
enough to burn fuel efficiently.

Spark Plug
Spark plug  –
an electrical conductor inserted into the
combustion chamber of an internal combustion
engine to ignite the air-fuel mixture. High-tension
voltage jumps across a gap formed by two
electrodes to create a spark.

Starter
Starter  –
an electric motor that engages teeth on the
engine flywheel (or flex plate) and forces the engine
to rotate until it begins to run under its own power.

Sump
Sump – see oil pan

Supercharger
Supercharger  –
a pump that compresses air into a denser
charge before it reaches the cylinders. This denser
air can be combined with extra fuel to produce a
more forceful explosion in the cylinder and boost
engine output. Typically, a supercharger is driven
mechanically by the engine via a pulley off the
camshaft. As such, it is always “on”.

Thermostat
Thermostat  –
A heat-controlled valve used in an engine’s
cooling system to regulate the flow of coolant
between the engine and the radiator. Because
engines perform more efficiently within a narrow
temperature range, the thermostat closes off the
coolant flow to the radiator until the engine has
reached a pre-determined operating temperature.
Smaller thermostats are also used to regulate
coolant flowing into the heater core that creates
warmth in the cabin, and on automatic choke setups
found on older vehicles.

Throttle Body
Throttle body  –
the section of an engine’s intake system
in which the throttle valve (butterfly) is located.
Throttle bodies can be controlled by a manual
linkage hooked up to the accelerator pedal, or by a
computer-controlled servo motor.
Throttle Body Fuel Injection (TBI)
Throttle body fuel injection (TBI) – a type of fuel
injection system that injects fuel at the throttle body
via one or two injectors.

Timing Cover
Timing cover  –a specially shaped piece (usually made of
metal) that covers and seals timing gears and a timing
belt/chain  located at the front of the engine.

Trap Oxidizer
Trap oxidizer – found on some diesel engines, this
serves a similar role to the gasoline engine catalytic
converter. The trap oxidizer features a honeycomb
mesh that captures particulates emitted in a diesel’s
exhaust, holding them in place until they heat up
enough to a burn away completely. Typically, these
are mounted right outside the engine.

Turbocharger
Turbocharger  –
a turbine driven by exhaust gases leaving
the engine. As the gases are blasted into the
turbocharger housing, the outer turbine spins an
inner one that serves to compress different, fresh air
that’s on its way into the engine. This denser air can
be combined with extra fuel to produce a more
forceful explosion in the cylinder and boost engine
output. A control system (wastegate bypass valve ) limits
boost pressure to avoid damage.

Unlike a supercharger, a turbo does not consume

engine power. Instead, it makes use of otherwise
wasted energy in the exhaust stream to increase an
engine’s power. Producing almost no extra power at
idle, it will ramp up as engine rpms increase.

Vacuum Assist
Vacuum assist – when engine vacuum is used to
reduce the driver’s effort in performing functions
such as braking via a brake booster. Many engines
use vacuum pumps to create or heighten this pressure.

Valley Pan
Valley pan – some V-shaped engines use the space
underneath the intake manifold for a coolant
passage that runs through the base of the valley
between cylinder banks. The valley pan is essentially
a manifold piece that covers coolant pipes running
through it. A valley pan gasket is used to seal the
pan and prevent leaks. Depending on vehicle
application, a valley pan cover  may be utilized as well.

Water Pump
Water Pump  –
mounted on the front of the engine and
driven by gears or belt, a water pump pressurizes
coolant to keep it flowing through the engine block
and back to the radiator where it disperses heat.
NPSH – Nett positive suction head – total head at pump suction branch over and above the
vapour pressure of the liquid being pumped.

NPSHr – NPSH required – is a function of the pump design and is the lowest value of NPSH at
which the pump can be guaranteed to operate without significant cavitation. There is no absolute
criterion for determining what this minimum allowable NPSH should be, but pump
manufacturers normally select an arbitrary drop in total dynamic head (differential head) of 3%
as the normal value for determining NPSHr.

NPSHa — NPSH available – is a function of the system in which the pump operates and is equal
to the absolute pressure head on the liquid surface plus the static liquid level above the pump
centreline (negative for a suction lift) minus the absolute liquid vapour pressure head at pumping
temperature minus the suction friction head losses.

Cavitation – Process in which small bubbles are formed and implode violently; occurs when
NPSHa < NPSHr.

Density (specific weight of a fluid) – Weight per unit volume, often expressed as pounds per
cubic foot or grams per cubic centimeter.

Flooded Suction – Liquid flows to pump inlet from an elevated source by means of gravity.

Flow – A measure of the liquid volume capacity of a pump. Given in gallons per minute (GPM),
litres per second and cubic metres per hour.

Head – A measure of pressure, expressed in metres for centrifugal pumps. Indicates the height of
a column of water being moved by the pump (without friction losses).

Pressure – The force exerted on the walls of a tank, pipe, etc. by a liquid. Normally measured in
pounds per square inch (psi) or kilopascals (kpa).

Prime – Charge of liquid required to begin pumping action when liquid source is lower than
pump. Held in pump by a foot valve on the intake line or by a valve or chamber within the pump.

Self/Dry Priming – Pumps that draw liquid up from below pump inlet (suction lift), as opposed
to pumps requiring flooded suction.

Specific Gravity – The ratio of the weight of a given volume of liquid to pure water. Pumping
heavy liquids (specific gravity greater than 1.0) will
require more drive kilowatts.

Static Discharge Head – Maximum vertical distance (in metres) from pump to point of
discharge with no flow.

Strainer – A device installed in the inlet of a pump to prevent foreign particles from damaging
the internal parts.
Sump – A well or pit in which liquids collect below floor level; sometimes refers to an oil or
water reservoir.

Total Head – Sum of discharge head, suction lift, and friction loss.

Viscosity – The “thickness” of a liquid or its ability to flow. Most liquids decrease in viscosity
and flow more easily as they get warmer.

Valves

Bypass Valve – Internal to many pump heads that allow fluid to be r ecirculated if a given
pressure limit is exceeded.

Check Valve – Allows liquid to flow in one direction only. Generally used in discharge line to
prevent reverse flow.

Foot Valve – A type of check valve with a built-in strainer. Used at point of liquid intake to
retain liquid in system, preventing loss of prime when liquid source is lower than pump.

Relief Valve – Used at the discharge of a positive displacement pump. An adjustable, spring
loaded valve opens when a preset pressure is reached. Used to prevent excessive pressure
buildup that could damage the pump or motor.

Pump Installation Information

Static Head – The hydraulic

pressure at a point in a fluid when the liquid is at rest.

Friction Head – The loss in pressure or energy due to frictional losses in flow.

Discharge Head – The outlet pressure of a pump in operation.

Total Head – The total pressure difference between the inlet and outlet of a pump in operation.
Suction Head – The inlet pressure of a pump when above atmospheric pressure.

Suction Lift – The inlet pressure of a pump when below atmospheric pressure.

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professionals in pumping and power generation in Australia.

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The NPE branch network is strategically positioned to service all parts of Australia. These hire
branches are supported by a team of NPE representatives and field service crews.
Radial flow – Pumps of this type with single inlet impellers usually have a specific speed below
approximately 90 (4500) and, with double suction impellers, a specific speed below
approximately 135 (7000). This type is commonly referred to as a centrifugal pump.  In In
centrifugal pumps the liquid enters the impeller at the hub and flows radially to the periphery,
exiting perpendicular to the rotating shaft. - Figure 1.1.4.2
Mixed flow - This type of pump has a single inlet impeller where the flow enters axially and
discharges in a mixed axial and radial direction. Pumps of this type usually have a specific speed
from approximately 90 (4500) to 200 (10,000). - Figure 1.1.4.3
Axial flow - A pump of this type, sometimes called a propeller pump, has a single inlet impeller
with the flow entering axially and discharging nearly axially. Pumps of this type usually have a
specific speed above approximately 200 (10,000). - Figure 1.1.4.4

 Head (h) [H]– Head is the expression of the energy content of a liquid in reference to an arbitrary datum.  It
is expressed in units of energy per unit weight of liquid.  The measuring unit for head is meters (feet) of liquid. 
  
 Total head (H) [Htx]– This is the measure of energy increase, per unit weight of liquid, imparted to the liquid
by the pump, and is the difference between total discharge head and total suction head.  This is the head
normally specified for pumping applications because the complete characteristics of a system determine the total
head required.

 Rate of flow [Q]– The rate of flow of a pump is the total volume throughput per unit of time at suction
conditions.  The term capacity is also used. 
 
 Best Efficiency Point (BEP)– The rate of flow and total head at which the pump efficiency is maximum at a
given speed and impeller diameter. 

 Displacement (D)– For a positive displacement pump it is the theoretical volume per revolution of the pump
shaft.  Calculation methods and terminology may differ between different types of positive displacement pumps. 
  
 Net Positive Suction Head Available (NPSHA)– NPSHA is determined by the conditions of the installation
and is the total suction head of liquid absolute, determined at the first-stage impeller datum minus the absolute
vapor pressure in meters (feet) of the liquid at a specific rate of flow expressed in meters (feet) of liquid.  Note
that for positive displacement pumps the term Net Positive Inlet Pressure Available (NPIPA) is used and is
expressed in pressure absolute kPa (psi). 
  Net Positive Suction Head Required (NPSHR)– NPSHR is the minimum NPSH given by the
manufacturer/supplier for a pump achieving a specified performance at the specified capacity, speed, and
pumped liquid.  Note that occurrence of visible cavitation, increase of noise and vibration due to cavitation,
beginning of head or efficiency drop, and cavitation erosion can occur when margin above NPSHr is present. 
Note that for positive displacement pumps the term Net Positive Inlet Pressure Required (NPIPR) is expressed
in pressure absolute kPa (psi).   

o Net Positive Suction Head 3% (NPSH3)– For rotodynamic pumps NPSH3 is defined as the value
of NPSHR at which the first-stage total head drops by 3% due to cavitation.  This is determined by
the vendor by testing with water as outlined in. ANSI/HI 14.6 Rotodynamic Pumps for Hydraulic
Performance Acceptance Tests 

o Suction specific speed (S)– Suction specific speed is an index of pump suction operating
characteristics. It is determined at the BEP rate of flow with the maximum diameter impeller.
Suction specific speed is an indicator of the net positive suction head required [NPSH3] for given
values of capacity and also provides an assessment of a pump's susceptibility to internal
recirculation. Suction specific speed is expressed by the following equation: Suction Specific Speed

o Impeller - The bladed member of a rotating assembly of the pump which imparts the prinicpal force
to the liquid pumped.



o Casing - The portion of the pump that includes the impeller chamber and volute diffuser.  

o Volute - The pump casing for a centrifugal type of pump, typically spiral or circular in shape.



o Diffuser - A piece, adjacent to the impeller exit, which has multiple passages of increasing area for
converting velocity to pressure.

 
o Inducer - A single-stage axial flow helix installed in the suction eye of an impeller to lower the
NPSHR.


Absolute pressure: The absolute pressure is the sum of the gauge or dial

pressure and the atmospheric pressure (14.7psi). If your pump gauge reads
150 psi, then the absolute pressure will be 164.7 psi.

Absorbed Power: This is the sum of the hydraulic power (work done by

achieving the flowrate and head) and the frictional losses.

Acceleration: The rate of change of velocity. As velocity is measured in

distance per unit time (e.g. m/s), acceleration is measured in change in
velocity per unit of time (e.g. m/s2).

Accelerometer: A device that measures proper acceleration. Not necessarily

the rate of change of velocity, but the weight experienced by a mass at rest in
the frame of reference of the device. An accelerometer at rest on the surface
of the earth would measure an acceleration of 9.8 m/s2 normal to the surface
due to gravity.

Accumulator: A device used to prevent the pump cycling on and off each
time a tap is opened in a system. It acts to stabilize the pressure by providing
excess water storage in conjunction with a flexible bladder that is air
pressurized. As water flows out of the system, it is first pulled from the
accumulator tank, and as this tank empties, the pressurized bladder expands
to prevent the entire system from a pressure drop. Once the tank is empty, the
pressure of the system drops, the pump switches on and refills the tank.

Acoustic: Anything pertaining to sound or to waves generated by sound.

Acoustic resonance: Can occur in any closed or open pipe system due to

pump excitation pulsation frequency. This happens when the return of the
reflected pressure wave coincides with the generation of the next pulse of
pressure. In this case a standing wave is formed inside the fluid filled
chamber. This can cause catastrophic failure of systems.

Active metal: Prior to passivation, the formation of a thin oxide on the surface

of metals to protect them from corrosion, the metal is known as “active”.

Adapter: A coupling that connects the pump to the rest of the system. Allows
the pump to integrate with the downstream parts of the system.

Affinity laws: They are a set of laws that relate the variables of performance,
(impeller shaft speed, head, flow rate) to power. They are useful to compare
the performance of different pumps.

A-gap: The gap between the tips of the blades on an impeller and the inner
diameter of the case bore. If the A-gap is too small, this can be a factor in high
pump vibration whereas, if the A-gap is too large, recirculation may occur,
leading to pump inefficiency.

Air ingestion: Air leaks into the pump, causing cavitation and pump
performance degradation. Air ingestion can be due to leaking flanges, valves
located above the fluid line, porous intake lines, faulty shaft seals among
others.

Alignment: In the pump world, alignment refers to the alignment of the

centerline of the pump shaft with the centerline of the driver shaft. This is
critical, because a small amount of misalignment on the power end, results in
a large amount at the wet end, where the seals are usually located.

Allowable Pipe Stress: This is a measure of the allowable stresses in pipe

walls according to ASTM specification A-53, and A-106 among others. The
allowable pipe stress is given by the code for a given pipe construction
material, and temperature. From these factors, one can calculate the
allowable pressure permitted by code.

Alpha sintered: One form of Silicon Carbide. To bond SiC powder into

ceramics, the powder is sintered. At temperatures above 1700°C, the alpha
form of SiC is formed.

Ambient heat/pressure: The environmental conditions found where the

equipment is operating. In this case either the temperature (ambient heat) or
pressure (ambient pressure).

Angular contact ball bearing: These ball bearings have races that are
displaced with respect to each other along the bearing axis. This allows the
bearing to accommodate both radial and axial loads.

Annealing: To make metal stronger through a heating process. The metal is

heated to somewhat below its melting temperature.

Anodize: A treatment used in particular on aluminum. The treatment adds a

heavy layer of protective oxide coating.

A.N.S.I. Standard: Founded in 1918, the American National Standards

Institute is a non-profit organization that oversees the application of voluntary
standards for products. These standards apply to pumps manufactured in the
United States.

Anti-friction bearing: A ball or roller bearing that reduces friction. Major

consideration during maintenance.

Anti-rotation device:A device that prevents one rotating piece from rotating
with respect to a second adjacent part. Usually designed as a pin or key.

Anti Vortex Plate: An anti vortex plate does just what it says. It prevents the
formation of a vortex at intake suction points by increasing the path length.
Vortexes can cause disturbances at vertical intakes by allowing air to enter
the system along with the fluid being pumped.
A.P.I. gland: A seal gland that incorporates important safety features as
specified by the American Petroleum institute. The main component is a
Disaster bushing that prevents sparking of metal components in the event of a
bearing failure. Other components include a drain and vent connection and a
flushing connection.

API Plan 11: A specification from the American Petroleum Institute used in
single seal or in the primary seal of unpressurized dual seals. The purpose of
a mechanical seal flushing is to lubricate and cool a pump’s mechanical seal.
Plan 11 refers to the specifications to be used in a pump whose impeller has
back wear rings.

API Plan 13: A specification from the American Petroleum Institute used in
single seal or in the primary seal of unpressurized dual seals. The purpose of
a mechanical seal flushing is to lubricate and cool a pump’s mechanical seal.
Plan 13 refers to the specifications to be used in a pump whose impeller has
NO back wear rings.

API pump: The American Petroleum Institute has published a set of

standards (see API 610 to ensure pumps meet minimum safety, reliability and
maintainability standards. A pump that conforms to these standards is said to
be an “API pump”.

A.P.I. Specifications: Specifications recommended by the American

Petroleum Institute. These specify many safety features of pumps and piping
involved in pumping flammable or dangerous substances.

API 610: A standard for pumps used in the petrochemical industry published
by the American Petroleum Institutute. API 610 ensures that safe, reliable
pumps are used in a dangerous industry.

Application: The set of conditions that describe the pumping operation. The

description of the process of the particular pumping function. Includes the fluid
and the operating conditions.
ASME: American Society of Mechanical Engineers. Society that promotes the
“art, science and practice of multidisciplinary engineering and allied sciences
around the globe”.

Atmospheric pressure: The pressure that the atmosphere exerts. Measured

as the weight of a column of air of a certain cross section. At sea level, the
recognized value is 14.7 pounds per square inch (1.03 Kg per square cm).

AVS Standard: An old, obsolete standard that has been replaced by the
A.N.S.I.standard. The American Voluntary Standard (AVS), was first proposed
in the 1950s.

Axial flow pump: A common pump type that is essentially an impeller in a

pipe. The impeller is driven by an electric motor or petrol/diesel engine. The
propeller’s rotation causes the fluid to be pumped axially along the pipe.The
main advantage of this type of pump is that it has a comparatively high
discharge at a low head.

Axial split casing: A casing for a pump that is manufactured in two halves
and joined. The join runs along the axis of the pump.

Axial split pump: A pump (usually horizontal) containing an axially split

casing.

Axial Thrust: The forces acting along the axis, usually generated by the
pump impeller.

Axial Thrust Balancing: The principles of axial thrust are easy to

understand, an impeller wants to move in an axial direction with a lot of force.
As it cannot, the fluid moves instead. To help balance this thrust, a method
(balancing drum or balancing disk or both) is employed.

Absolute pressure: The absolute pressure is the sum of the gauge or dial

pressure and the atmospheric pressure (14.7psi). If your pump gauge reads
150 psi, then the absolute pressure will be 164.7 psi.

Absorbed Power: This is the sum of the hydraulic power (work done by

achieving the flowrate and head) and the frictional losses.
Acceleration: The rate of change of velocity. As velocity is measured in
distance per unit time (e.g. m/s), acceleration is measured in change in
velocity per unit of time (e.g. m/s2).

Accelerometer: A device that measures proper acceleration. Not necessarily

the rate of change of velocity, but the weight experienced by a mass at rest in
the frame of reference of the device. An accelerometer at rest on the surface
of the earth would measure an acceleration of 9.8 m/s2 normal to the surface
due to gravity.

Accumulator: A device used to prevent the pump cycling on and off each
time a tap is opened in a system. It acts to stabilize the pressure by providing
excess water storage in conjunction with a flexible bladder that is air
pressurized. As water flows out of the system, it is first pulled from the
accumulator tank, and as this tank empties, the pressurized bladder expands
to prevent the entire system from a pressure drop. Once the tank is empty, the
pressure of the system drops, the pump switches on and refills the tank.

Acoustic: Anything pertaining to sound or to waves generated by sound.

Acoustic resonance: Can occur in any closed or open pipe system due to

pump excitation pulsation frequency. This happens when the return of the
reflected pressure wave coincides with the generation of the next pulse of
pressure. In this case a standing wave is formed inside the fluid filled
chamber. This can cause catastrophic failure of systems.

Active metal: Prior to passivation, the formation of a thin oxide on the surface

of metals to protect them from corrosion, the metal is known as “active”.

Adapter: A coupling that connects the pump to the rest of the system. Allows
the pump to integrate with the downstream parts of the system.

Affinity laws: They are a set of laws that relate the variables of performance,
(impeller shaft speed, head, flow rate) to power. They are useful to compare
the performance of different pumps.
A-gap: The gap between the tips of the blades on an impeller and the inner
diameter of the case bore. If the A-gap is too small, this can be a factor in high
pump vibration whereas, if the A-gap is too large, recirculation may occur,
leading to pump inefficiency.

Air ingestion: Air leaks into the pump, causing cavitation and pump
performance degradation. Air ingestion can be due to leaking flanges, valves
located above the fluid line, porous intake lines, faulty shaft seals among
others.

Alignment: In the pump world, alignment refers to the alignment of the

centerline of the pump shaft with the centerline of the driver shaft. This is
critical, because a small amount of misalignment on the power end, results in
a large amount at the wet end, where the seals are usually located.

Allowable Pipe Stress: This is a measure of the allowable stresses in pipe

walls according to ASTM specification A-53, and A-106 among others. The
allowable pipe stress is given by the code for a given pipe construction
material, and temperature. From these factors, one can calculate the
allowable pressure permitted by code.

Alpha sintered: One form of Silicon Carbide. To bond SiC powder into

ceramics, the powder is sintered. At temperatures above 1700°C, the alpha
form of SiC is formed.

Ambient heat/pressure: The environmental conditions found where the

equipment is operating. In this case either the temperature (ambient heat) or
pressure (ambient pressure).

Angular contact ball bearing: These ball bearings have races that are
displaced with respect to each other along the bearing axis. This allows the
bearing to accommodate both radial and axial loads.

Annealing: To make metal stronger through a heating process. The metal is

heated to somewhat below its melting temperature.
Anodize: A treatment used in particular on aluminum. The treatment adds a
heavy layer of protective oxide coating.

A.N.S.I. Standard: Founded in 1918, the American National Standards

Institute is a non-profit organization that oversees the application of voluntary
standards for products. These standards apply to pumps manufactured in the
United States.

Anti-friction bearing: A ball or roller bearing that reduces friction. Major

consideration during maintenance.

Anti-rotation device:A device that prevents one rotating piece from rotating
with respect to a second adjacent part. Usually designed as a pin or key.

Anti Vortex Plate: An anti vortex plate does just what it says. It prevents the
formation of a vortex at intake suction points by increasing the path length.
Vortexes can cause disturbances at vertical intakes by allowing air to enter
the system along with the fluid being pumped.

A.P.I. gland: A seal gland that incorporates important safety features as

specified by the American Petroleum institute. The main component is a
Disaster bushing that prevents sparking of metal components in the event of a
bearing failure. Other components include a drain and vent connection and a
flushing connection.

API Plan 11: A specification from the American Petroleum Institute used in
single seal or in the primary seal of unpressurized dual seals. The purpose of
a mechanical seal flushing is to lubricate and cool a pump’s mechanical seal.
Plan 11 refers to the specifications to be used in a pump whose impeller has
back wear rings.

API Plan 13: A specification from the American Petroleum Institute used in
single seal or in the primary seal of unpressurized dual seals. The purpose of
a mechanical seal flushing is to lubricate and cool a pump’s mechanical seal.
Plan 13 refers to the specifications to be used in a pump whose impeller has
NO back wear rings.
API pump: The American Petroleum Institute has published a set of
standards (see API 610 to ensure pumps meet minimum safety, reliability and
maintainability standards. A pump that conforms to these standards is said to
be an “API pump”.

A.P.I. Specifications: Specifications recommended by the American

Petroleum Institute. These specify many safety features of pumps and piping
involved in pumping flammable or dangerous substances.

API 610: A standard for pumps used in the petrochemical industry published
by the American Petroleum Institutute. API 610 ensures that safe, reliable
pumps are used in a dangerous industry.

Application: The set of conditions that describe the pumping operation. The

description of the process of the particular pumping function. Includes the fluid
and the operating conditions.

ASME: American Society of Mechanical Engineers. Society that promotes the

“art, science and practice of multidisciplinary engineering and allied sciences
around the globe”.

Atmospheric pressure: The pressure that the atmosphere exerts. Measured

as the weight of a column of air of a certain cross section. At sea level, the
recognized value is 14.7 pounds per square inch (1.03 Kg per square cm).

AVS Standard: An old, obsolete standard that has been replaced by the
A.N.S.I. standard. The American Voluntary Standard (AVS), was first
proposed in the 1950s.

Axial flow pump: A common pump type that is essentially an impeller in a

pipe. The impeller is driven by an electric motor or petrol/diesel engine. The
propeller’s rotation causes the fluid to be pumped axially along the pipe.The
main advantage of this type of pump is that it has a comparatively high
discharge at a low head.

Axial split casing: A casing for a pump that is manufactured in two halves
and joined. The join runs along the axis of the pump.
 Axial split pump: A pump (usually horizontal) containing an axially split
casing.

Axial Thrust: The forces acting along the axis, usually generated by the
pump impeller.

Axial Thrust Balancing: The principles of axial thrust are easy to

understand, an impeller wants to move in an axial direction with a lot of force.
As it cannot, the fluid moves instead. To help balance this thrust, a method
(balancing drum or balancing disk or both) is employed.

 Head: A term in fluid mechanics to represent the energy stored in a fluid

due to the pressure exerted on its container. Measured as a length of fluid
where a standard of 10m is equal to one atmosphere, or 14.7 psi.
 Flow: The measurement of the liquid volume capacity of a pump. Often
given in litres per minute (L/min), litres per second (L/sec) and metres3 an
hour (m3/hr).
 Performance curve: A graph depicting the plot of total head vs flow
rate for a specific pump, with a specific impeller and set of characterisitics.
 Pipe friction loss: The loss in head due to the friction between the
process fluid and the walls of the pipes and joints.
 Friction Head: The force (pressure) required to overcome the friction
that is solely due to the inside of the pipes/fittings/pumps in a system.
 Total head: The sum of the head produced by the pump. It can be
calculated by subtracting the suction head from the discharge head. Also
referred to as Total Dynamic Head.
 Pressure: Is the ratio of a force over an area over which the force is
applied. Often measured in psi or kpa.
 Pressure drop: The difference in pressure between two areas of a
pump, or between the inside and outside of a container.
 Efficiency: The measured power out of a piece of equipment divided by
the power produced by the piece of equipment. Shown as a percentage.
 B.E.P.: Best Efficiency Point. The kinetic energy that a pump produces
is never converted with 100% efficiency to pressure energy. There are
always losses due to friction in the seals/bearings, friction of the pumped
fluid over the impeller, etc. The BEP is thevolumetric flow rate of the pump
for which the pump was designed to convert the most kinetic energy into
pressure energy.
 N.P.S.H.A: The net positive suction head available that can be used to
prevent cavitation within the pump. It is defined as static head plus surface
 pressure head minus the vapour pressure of the process fluid minus the
friction loss due to the piping, valves and fittings.
 N.P.S.H.R.: Net positive suction head required to keep a pump from
cavitating. A characteristic of the pump. Calculated by the manufacturer with
cold water.
 Cavitate: Formation of cavities (bubbles) in fluid flow applications in
areas of low pressure, causing a collapse in the high pressure area of the
pump and loss of capacity, excessive noiseand possibly damage.
 Specific Gravity (SG): The ratio of the density of a substance
compared to the density of a reference (usually water at 4°C).
 Viscosity: Resistance to gradual deformation of a fluid by shear or
tensile stress.
 B.H.P.: Brake horsepower. The measure of an engine’s horsepower
before the loss in power caused by any load (gearbox, etc.). Measured by
attaching a “De Prony brake” to the engine’s shaft.
 Flooded suction: If the pump is below the liquid source, and the
suction is fed bygravity. This is a preferred method for centrifugal pumps.
 Suction Static Head: The height difference between the surface of the
inlet reservoir and the centerline of the pump. If the tank is pressurized, this
pressure is also included.
 Suction Static Lift: A.K.A. suctions static head. Only occurs when the
pump is above the inlet reservoir.
 Specific speed: A dimensionless number used to characterize
turbomachinery. Normalises impellers to a speed in revolutions per minute
to that of a geometrically similar impeller if it were to deliver 1 gallon per
minute against 1 foot of hydraulic head.
 Impeller: A device that attaches to a rotating shaft and converts the
energy of motion, into the fluid being pumped.

BA: The width of the impeller in a pump. Commonly measured from the OD of

the impeller excluding the width of the impeller walls. This measure is
proportional to pump capacity.
Back plate: Used in some centrifugal pumps. The back plate consists of a
gland ring facing the bearing side where the mechanical seal or gland
packings are arranged in such a way that the pumped fluid cannot leak. The
other side of the back plate is situated towards the impeller and becomes one
of the wall between the suction casing.
Back pull out pump: A pump design that allows the entire power end of the
pump to be removed for maintenance/replacement while the wetend of the
pump remains in place.
Back-to-back: In the case of impellers, an arrangement where two impellers
are placed back to back on a single shaft sharing the same backplate. This
arrangement provides almost double the flow of a single impeller design.
Back to back double seal: A mechanical seal configuration typically used
when the process fluid is toxic, flammable, or hazardous. This seal is used to
prevent the process fluid or its vapour from leaking into the environment.
Back Vane: Part of the design scheme in impellers used to balance axial
thrust on an impeller.
"Bad actor" pump: A pump that fails more frequently than it should based on
its MTBF (Mean Time Between Failure).This pump is the type of pump that is
ripe for replacement or overhaul.
Balance Holes: Another impeller feature that helps to balance axial thrust.
Balance Ratio: The standard balance ratio is 70-30 used by most mechanical
seal companies. This means that 70% of the seal face area is exposed to the
hydraulic closing force, while 30% is not.
Balanced seal: The most effective tool to counter heat generation in the
stuffing box. The area of the seal face is reduced (i.e. balanced) to reduce the
heat generation between the two faces of the seal.
Ball bearing: A bearing that uses balls to maintain the separation between
the bearing faces.
Ball shuttling: A situation where the balls in a ball bearing rotate
perpendicular to their rolling axis. This can result in premature failure of the
bearing by accelerating the microscopic wear. This can be seen as an
appearance of a polished raceway.
Bar: Non-SI unit of pressure. Exactly equal to 100,000 Pa. About equal to the
atmospheric pressure at sea level.
Barometric pressure: Another term for atmospheric pressure. Often used in
weather reports.
Barrel pump: A pump used to transfer fluid from a barrel.
Barrier fluid/liquid: The fluid used between the two mechanical seals of a
double seal. Used to isolate the process fluid from the atmosphere. Also
known as buffer fluid.
Base circle: A reference circle in a volute design that is used as a basis
calculating the cutwater diameter. In most cases, the base circle diameter
corresponds to the maximum impeller diameter.
Base plate: The plate on which the pump and motor are mounted.
Bayonet: The mechanical seal drive lugs wear into the drive slots and prevent
the seal faces from moving forward to compensate for wear.
Bearing: A machine element that one part to support (i.e. bear) another. They
constrain relative motion between moving parts to only the desired motion
(e.g. rotation around an axis).
Bellows: Part of the design in a mechanical seal that prevents the build up of
deposits on dynamic gaskets.
Bellows plate: Metal bellows in mechanical seals contain thin stamped plates
welded together to form a convolution. Each of these plates is known as a
bellows plate.
Belt Drive: A series of belts and pulleys that transfer the torque from a drive
shaft to the required shaft at the correct speed.
B.E.P.: Best Efficiency Point. The kinetic energy that a pump produces is
never converted with 100% efficiency to pressure energy. There are always
losses due to friction in the seals/bearings, friction of the pumped fluid over
the impeller, etc. The BEP is thevolumetric flow rate of the pump for which the
pump was designed to convert the most kinetic energy into pressure energy.
Bernoulli's Law: Describes the behavior of fluid under varying conditions of
flow and height. Formulated by Daniel Bernoulli in 1738.
B-gap: The radial gap between the impeller vanes and the volute tongue or
diffuser vanes. Careful attention to this gap can keep vibrations down.
B.H.P.: Brake horsepower. The measure of an engine’s horsepower before
the loss in power caused by any load (gearbox, etc.). Measured by attaching a
“De Prony brake” to the engine’s shaft.
Bingham plastic: A material that behaves as a rigid body at low stress, but
flows as a viscous fluid at high stress.Mayonnaise and toothpaste are
common examples of this type of material.
Body bound bolts: A bolt/bolt hole configuration where there is an
interference between the bolt and its mating hole.
Bourdon pressure gauge: The Bourdon tube is a sealed tube that changes
shape in response to applied pressure, causing an attached indicator to reflect
a pressure change. This is the most common pressure sensing gauge in use.
Bowl (vertical turbine pump): In multi-stage vertical turbine pumps, the bowl
is the casing of one of the stages.
Brinnell hardness: A scale for measuring hardness of materials. It uses an
indenter to penetrate the material using a certain force, and characterizes the
indentation made.
Buffer fluid: The fluid used between the two mechanical seals of a double
seal (see barrier fluid).
Buna N: Commonly known as Nitrile rubber. It is a synthetic rubber that is a
copolymer between acrylonitrile and butadiene.
Bushing: An independent plain bearing that is inserted into a housing to
provide a bearing surface. For use in rotary applications.
Bypass line: A design that bypasses a portion of the pump system. This can
be from the discharge to the stuffing box, the stuffing box to the pump suction
or the pump discharge to any lower pressure point in the system.