Glossary C

C frame adapter

  • Used to connect and align the pump to the motor with registered fits. (imperial dimensions. Called the D frame adapter in the metric system)


  • Center line average. A method of measuring surface finish in the metric system. Uses microns as a unit.

Canned pump

  • A non seal pump with the shaft, bearings and rotor contained in a can to prevent product leakage. Limited to pumping clean lubricating liquids.


  • Fluid flow measured in gpm, liters/min, M3/hr. etc.


  • The compound formed when carbon combines with an element. The carbides of metal are very hard and are often used as a mechanical seal face.

Carbon bushing

  • Used as a restrictive bushing in flushing applications, a thermal barrier in high temperature applications, a disaster bushing in an A.P.I. gland and to support a deflecting shaft in many mechanical seal applications.

Carbon/ graphite

  • A common mechanical seal face material chemically inert to most fluids with the exception of oxidizers, bleaches, halogens and a few other fluids.


  • A reduction of hydrocarbons resulting in the formation of carbonaceous residue that will interfere with the movement of a mechanical seal. Often called “coking”.


  • A cancer producing substance.

Cartridge seal

  • A self contained assembly containing the seal, gland, sleeve, and both stationary and rotating seal faces. Usually needs no installation measurement. Must be used if impeller adjustments are made. Cartridge seals are the standard for A.P.I. seal applications.


  • A chemical additive that decreases the time of a chemical reaction with out being affected by the reaction.


  • Cavities or bubbles form in the fluid low pressure area and collapse in a higher pressure area of the pump, causing noise, damage and a loss of capacity.

Center line design

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


  • The metric system unit of viscosity.


  • The kinematic unit of viscosity. Viscosity in centipoises divided by the liquid density at the same temperature, gives kinematic viscosity in centistokes.

Centrifugal pump

  • Moves liquid with centrifugal force. Available in circular and volute configurations.

Centrifugal separator

  • Sometimes called a cyclone separator. Uses centrifugal force to throw solids out of the fluid. Does not work very well in slurry seal applications.


  • A hard, chemically inert seal face material that includes products refereed to as silicone carbide.

Change of state

  • When a liquid flashes into a vapor, solidifies, crystallizes, cokes etc.


  • An “elastomer like” material manufactured by Green Tweed of England. Used to seal most solvents and other aggressive fluids.

Chloride stress corrosion

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

Chrome carbide

  • Forms when chrome forms with carbon in the heat affected zone during the welding of stainless steel. The use of low carbon stainless steel is recommended in these applications.

Chrome Oxide

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

Circular casing

  • Used with centrifugal pumps that circulate fluid rather than build head or pressure.

Clam Shell

  • Used to set the pitch (distance between convolutions) while heat treating a metal bellows core.

Close coupled

  • The pump impeller is mounted directly on the motor shaft. There is no separate bearing case.

Coated Face

  • A hard coating is plated or welded to a softer base material. Presents problems with different thermal expansion rates, the hard coating can “heat check” or crack. Not recommended as a seal face material.


  • A hard black substance that forms when petroleum products are over heated. It interferes with seal movement and will open the lapped faces.


  • When used in the content of mechanical seal faces, it refers to either a non metallic material or a combination of non metallic face inserted into a metal holder.

Compression set

  • The elastomer changes shape when it has been exposed to too much heat. Round O-rings come out square.

Concentric dual seal

  • One seal is located inside the other, with a common hard face shared by both of them. Because of its large radial space requirement the seal is usually limited to mixer type applications.


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


  • Condensed steam.


  • A natural circulation of fluid. The hot fluid (lighter) rises and the cool fluid (heavier) sinks.

Convection tank

  • Used to contain fluid between two mechanical seals. An enclosed heater or cooler can be used to control the barrier or buffer fluid temperature. Pressure or level gages can indicate which seal has failed.


  • Two metal bellows plates welded or formed together. To count the number of convolutions in a metal bellows you count the spaces between the bellows plates.

Cooling jacket

  • Surrounds the stuffing box of the pump to control the temperature of the fluid in the stuffing box. Usually molded into the back plate.

Corrosion resistant

  • Corrodes at a rate of less than 0.002 inches (0.05 mm) per year.


  • Used to connect the pump to the driver. It transmits torque and compensates for axial growth, but not for radial misalignment.

Critical speed

  • Any object made of an elastic material has a natural period of vibration. When a pump rotor or shaft rotates at any speed corresponding to its natural frequency, minor unbalances will be magnified. These speeds are called the critical speeds.


  • Very cold temperatures.


  • Directs the pumped liquid to the discharge piping.

Cyclone separator

  • A device used in some seal applications to separate solids from liquid by utilizing centrifugal force. Not very reliable.