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Glossary of Pump Terms: T


  • Tandem seals: Two mechanical seals facing the same direction with low pressure barrier fluid in between them.
  • T.D.H.: Total Discharge Head. The sum of the static (differential) head and friction loss.
  • Tensile strength: The tensile strength is the force required to break something as it is being pulled apart axially.
  • Test baseplate: A specially designed support used during performance testing of a pump in a test well.
  • Test curve: A graph depicting the results of a performance test.
  • Thermal conductivity: A property of a material that designates how well the material can conduct heat.
  • Thermal imaging: Using an infrared (heat) sensitive camera to image machinery to find where the hotspots are.
  • Thermoplastic: A plastic material that can be melted over and over again without changing its properties. Used in injection molded plastics.
  • Thermosetting: Unlike a thermoplastic, this material can only be melted once. After it has cooled and set, it cannot be re-melted without losing its properties.
  • Thixotrophic fluid: A fluid whose viscosity decreases with agitation. E.g non-drip paint.
  • Thrust: Refers to the axial movement of the rotor. At start up the thrust can be axially in either direction depending on the balance of the rotor/impeller assembly.
  • Thrust bearing: A bearing that takes an axial load and locates the rotor axially.
  • T.I.R.: Total Indicator Runout (see below).
  • Torque: The tendency of a force to rotate an object around an axis.
  • Torr: A traditional unit of pressure. Historically equivalent to one “millimeter of mercury” in a barometer.
  • Torsional critical speed: The resonant frequency associated with the torsional deflection of a rotor. Different than later critical speed.
  • Total Dynamic Head: This term has been replaced by and is equivalent to “Total Head”.
  • Total head: The sum of the head produced by the pump. It can be calculated by subtracting the suction head from the discharge head.
  • Total Indicator Runout (T.I.R.): The runout (a non-true shaft is said to have “runout”) measured manually on a dial indicator.
  • Total Static Head: The discharge pressure minus the suction static head – including the difference between the surface pressures of the two (discharge & suction) tanks, if they are pressurized.
  • Transducer: A device that turns a mechanical (e.g. vibration) movement into an electrical signal that can be read or saved.
  • TransferringTo move a substance, usually a liquid, from one place to another.
  • Trip speed: A speed that “trips” an automatic shutdown of a pump to prevent damage by being overloaded.
  • Tungsten carbide: An inorganic compound made of equal parts tungsten and carbon. Roughly three times harder than steel. Used as a common hard face seal material due to it’s durability.
  • Turbulence: In fluid dynamics, this is non-laminar flow.
  • Turbulent: In fluid dynamics, this is a characteristic of fluid particles that are not undergoing laminar flow, but are generally flowing in one direction, but may go in any direction.
  • Two plane balancing: Removing residual unbalance in a rotor/impeller system by balancing in two planes rather than one.
  • Two-stage pump:A pump design containing two impellers operating in series. The discharge of the first stage is the input of the second stage
  • Two way balance: A method for balancing seals in two directions.