Pumps and Pumping Stations

BS Environmental and Sanitary Engineering

Pumps and Pumping Stations; Pumps – are devices used in transferring water or other liquids from one place to another through pipes. General Classification of Pumps: Positive Displacement Pumps: 1. Reciprocating Pump – A pump which operates with to-and-fro motion. A pump in which a piston or plunger alternately draws water into a cylinder on the intake stroke and then forces it out on the discharge stroke. They are high in first cost, require more room and need more skilled operation and maintenance. a. Lift Pump – the simplest of the reciprocating pumps and consists of a piston moving up and down in a cylinder or barrel. A lift pump cannot be raised water above 7.50 to 8.50 meter at a normal atmospheric pressure (101 KPa) due to: Loss of efficiency in the pump Friction in the intake place Impossible to obtain a perfect vacuum. b. Piston Pump or Plunger Pump – is a positive displacement reciprocating pump, in which a plunger is driven backwards and forwards, or up and down by a mechanical working head. It is also used to pump sewage sludge. c. Deep-well Piston Pump – When water is more than 7.5m below the ground, it is visually necessary to place the pump in or near the water in the well and pump from there. Water is forced up the drop pipe and out the delivery pipe. Single-acting Pumps – discharge water only on the “forward” stroke of the piston or plunger and draw it into the cylinder on the “back” stroke. Double- acting Pumps – discharge on both the forward and back strokes. a. Rotary type Pump – in which two rotating pistons or gears interlock and draw water into the chamber and force it practically continuously into the discharge pipe. There are two cams or gears which mesh together and rotate in opposite direction. Employed an impeller which has as number of spiral vanes. 2. Centrifugal or screw type – has an impeller with radial vanes rotating swiftly to draw water into the center and discharge it by centrifugal force. May have a single suction inlet, where water is admitted on one side of the impeller or a double suction inlet if water is admitted on both ends of the impeller. A centrifugal pump cannot operate unless the pump coding is full of water fuel water depth is 6m or less, use centrifugal pump. Submersible Pump – is basically a centrifugal pump complete with electric motors which are positioned under water in a suitable bored hole that delivers the water to the surface. Submersible Pump – is most widely used in deep wells, often in small installations, but of late more often in larger wells. It is a centrifugal pumps with the motor in the well, just below the impellers, the electric current being conducted down by a water- proof cable. They are used in river intakes and used for booster service in the distribution system. - Are suitable for deep wells where the required discharge exceeds the capability of jet pumps. These pumps are usually powered by an electric motor installed below the water level, directly

Pumps and Pump Installation

Prepared by: Engr. Ruel Galutan


coupled to the pump. Well water depth of greater than 20m, use submersible pumps or vertical line shall turbine pumps. Volute-type centrifugal pump – has spiral chamber which takes the water from the impeller and conveys it to the discharge pipe. Turbine Type – has a fixed diffusion ring between the impeller and the casing, the ring having passages to conduct the water to the casing and transform velocity head to pressure head in the process. 3. Deep-well Jet Pumps – A pump consisting of a revolving impeller in the pump housing which forced water down a pressure line to an ejector assembly below the water level. 4. Hydraulic Ram or Ramp Pump – A pump in which the power generated from flowing in an enclosed pipe is used to raise part of the water to a height above that from which the flow began. Hydraulic Ram – it is an impulse pump, the power being obtained by the impulse or ram generated when a moving mass of water is suddenly stopped. Use the energy of falling water to raise a smaller quantity of water to greater heights. This pump operates by taking advantage of the same forces that create water hammering in a system. Because of this, the hydraulic ram is often called an Impulse Pump. 5. Hydropneumatic Pressure System – A pumping system that provide water within pre-set flow and pressure ratings, automatically on demand. Three Basic Elements of the pressure System: 1. A pump (of any type or manufacturer) 2. A pressure sensing electric switch –opens and closes the electrical contacts causing the pump to stop and start. 3. Pressure vessel which contains an elastic medium, usually air. Foot valve – which is a check valve placed on the end of the suction pipe, may be used to keep water in the pump at all times. Axial Flow pumps – also known as propeller pumps, the rotation of the impeller or propeller is similar to that of the propeller of a boat, and the motion of the water is parallel to the axis of the shaft. Mixed flow Pumps or angular flow pumps – have an impeller with the vanes arranged spirally on a cone-shaped center. Steam turbine – consists of a steam jet striking vanes upon a wheel which is caused to rotate rapidly. Impulse Turbine – are operated by the velocity of the moving jet of steam Reaction turbines – employ both the velocity and the expansive force of the steam. Diesel engine – is an internal-combustion engine which burns low-grade fuel oil. They are specially adapted to plants of moderate size or where charges for electric current are high. Gasoline Engine – are so high in operating cost that continuous operation is uneconomical.

Valves and Piping details: 1. The foot valve on the suction line will hold priming the water in the pump. 2. Check valve is placed in the pipe on the discharge side to prevent backward surges of pressure which might injure the pump. It Will prevent backward flow of the water 3. On the outlet side of the check valve, a gate valve is usually placed to permit repairs to the check and to allow throttling if the pump is centrifugal type. 4. A gate valve is also necessary on the suction side of the pump if there is a positive suction head, so that repairs can be made. Pumps and Pump Installation



5. A pressure relief valve is sometimes placed on the discharge side of a reciprocating pump so that a stoppage or accidental closing of a valve in the discharge pipe will not cause harmful pressure to build up. 6. Pressure gage should be installed so that the operator may be informed at all times of the pressure maintained. Well Pumps 1. Hand Pumps – are used to raise water from shallow wells or cisterns. They are the most suitable to install for isolated small population and/or where there is an absence of electric power. They are normally installed over dug wells or tube wells. a. Pitcher Pump – it will raise the water to the ground surface with a lift limited to about 20 feet. b. Simple Force Pump –can operate with a suction lift of 20 ft and will also force water up through a pipe oh the discharge side. c. Deep-well Lift Pumps d. Deep-well force Pump

Miscellaneous Pumps: Jet pump – sometimes known as an ejector, the suction pipe leads to a throat a t which point a nozzle discharges steam, compressed air or water at high velocity. It is sometimes used by contractors to dewater excavations, including trenches for water pipes and sewers. - Consists of a nozzle which discharges the water into constricted throat muck like a venture. Jet pumps are usually selected when the suction lift required is greater than that of centrifugal pumps and the volume of water needed is relatively small. Well water depth is 20 m, use jet pumps. Diaphragm Pump – has a circular rubber diaphragm which is bolted to the pump cylinder on the edges and attached to a shaft at the center. Steam Vacuum Pumps – is used to dewater excavations and is therefore employed in the construction of water and sewer systems (i.e. Pulsometer Pump, Emerson and Nye).

Pump Application: 1. Low lift Service Pumps – are normally used in pumping raw untreated water from the source of supply to the treatment plant. 2. High Lift Service Pumps – are used in pumping water into the distribution system. 3. Well Service Pumps – are used in pumping water from a well. 4. Booster Pump – are used for increasing the pressure in the distribution system and to lift water to the storage tank. Booster Pumps are commonly used in outlying areas of the distribution system to avoid having low pressure areas or to serve higher elevations. 5. Standby Pumps – are pumps that are made available during period of high water demand or emergencies.




Pump Installation: 1. Pumps Connected in Series – When one pump is connected behind the other. Series connection will yield discharge equivalent to one pump and the head is approximately equal to the sum of the individual heads of the pumps is the system. 2. Pumps Connected in Parallel – If we place pumps in parallel, that is, one pump beside the other, they will both be working against the same external head, and will yield identical manometric heads. The capacity of two pumps working in parallel is found by adding their separate discharges together. Pump Selection: a. In the absence of electric power and in cases of isolated small population, hand pumps are recommended because of higher capital, maintenance and operating costs of diesel or gasoline engine driven pumps. b. If the well water depth is 6 meters or less, use centrifugal pump (maximum suction lift is 6m) c. If the well water depth is 6to 20 meters, use Jet Pumps d. If the well water depth is more than 20m, use submersible pumps or vertical line shaft turbine pumps



Pumps and Pumping Stations

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