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Glossary
| Absolute pressure: | One of two commonly used pressure measurements and is the sum of gauge pressure plus atmospheric pressure. | |
| Belt drive: | When the prime mover drives a pump through belts and pulleys. | |
| Cavitation: | Rapid formation and collapse of vapour bubbles in a moving fluid in regions of low pressure. | |
| Characteristic curve: | A graph showing the pump performance under varying conditions of flow, head, power, speed and efficiency. | |
| Direct coupling: | When a prime mover is directly connected in line with the driven unit by means of a coupling. | |
| Displacement: | The volume of liquid swept through or displaced by a piston or plunger in any single stroke. | |
| Driven unit: | A machine used for moving fluids, can take various forms using rotary or reciprocating motion. | |
| Driven unit: | Can take the form of an internal combustion engine, either diesel or petrol, or an electric motor requiring power, mainly A. C. Sometimes referred to as aprime mover. | |
| Efficiency (pump): | Ratio of the water horse power output to mechanical power input and expressed as a percentage. | |
| Entry head: | Head required to overcome the frictional resistance leading into a pipe entrance. | |
| Equivalent length: | A pressure loss through valves and fittings due to flow and is expressed interms of a straight pipe length of the same pipe diameter. | |
| Flooded suction: | An expression used in connection with pumps when the reservoir from which the liquid is drawn is above the centerline of the pump. Sometimes referred to as positive suction. | |
| Foot valve: | A non-return valve fitted at the bottom of a pump suction pipe in order to retain the water in the pipe. | |
| Forced circulation: | The imparting of flow motion by mechanical means (pump) to a fluid in any system circuit. | |
| Friction head: | Entrance and exit head losses due to velocity of flow in a pipe system and include pipe skin friction, as well as losses through valves and fittings. | |
| Gauge pressure: | One of two commonly used pressure measurements but refers to pressure above atmospheric. | |
| Head: | Is the vertical height measured from a datum point to the free surface of water in a system. | |
| Pressure gauge: | An instrument which is used for measuring fluid pressure, generally that above atmospheric. | |
| Priming: | The expulsion of air by completely filling the suction pipe and pump casing with liquid. | |
| Pump datum: | Term used in relation to the position of the pump suction and. discharge and normally taken as being the centreline of the pump shaft, i.e. the pump suctioneye. | |
| Pumo rating: | A sized pump selected on the basis of the required flow and total head. | |
| R.P.M. curve: | A curve on a graph which shows the speed of a prime mover which drives the pump. | |
| Rate of flow: | Sometimes referred to as capacity or quantity and is stated in units of volume per unit time. | |
| Shut off head: | Refers to a head condition at no flow. | |
| Split casing: | A term applied to a centrifugal pump indicating that the pump casing is composed of two sections which are normally bolted together. | |
| Static suction head: | The vertical distance between the centreline of a pump and the pumped liquid level. | |
| Suction lift: | An expression used in connection with pumps when the reservoir from which the liquid is drawn is below the centre line of the pump. | |
| Throttle: | When the flow of a liquid is reduced or controlled by means of a regulating device such as a globe valve. | |
| Total equivalent length: | The length of the longest circuit through which the liquid is pumped plus a length equivalent to the resistance offered by valves and fittings. | |
| Total delivery head: | The sum of static delivery head and friction head in the discharge pipe and fittings. | |
| Total suction lift: | The sum of static suction lift and friction head in the suction pipe and fittings. | |
| Total head: | The summation of both total suction lift and total delivery head in a pumping circuit. Commonly referred to as total dynamic head. | |
| Velocity head: | Kinetic energy due to directional travel equivalent to the height through which a body must fall in order to obtain a given velocity. | |
| Volute casing: | An impeller chamber which is constructed with a gradually enlarging passageway. | |
| Vortex: | A whirling fluid forming an area of low pressure or cavity at the centre ofa rapid circular path resembling a whirlpool. | |
| Water hammer: | Is a pressure that results from a sudden arresting of the velocity of flowof water in a closed circuit. |
