SELF PRIMING CENTRIFUGAL PUMP

                                           SELF PRIMING CENTRIFUGAL PUMP

               PUMP CASING IS DIVIDED TO TWO CHAMBERS.  THE SUCTION CONNECTION IS PROVIDED AT THE TOP MOST OF THE FIRST CHAMBER SPACE. THE PUMP IMPELLER ROTATES INSIDE THE SECOND CHAMBER .THE SECOND CHAMBER CARRIES A DELIVERY  CONNECTION AT ITS TOP SIDE AND SHAFT BEARING AND GLAND AT ONE SIDE. A ROUND PASSAGE IS PROVIDED ON THE CHAMBER PORTION,FIRST IN FRONT OF THE IMPELLER A SMALL NOZZLE IS PROVIDED AT THE CENTER OF THE ROUND PASSAGE IS CONNECTED TO THE IMPELLER CHAMBER AND PRIMARY CHAMBER, A FLAP VALVE  WHICH IS EMPLOYED ON THE SUCTION LINE CONNECTION IS USED TO MAINTAIN THE VACCUM PRESSURE AT THE SUCTION LINE
    SUFFICIENT AMOUNT OF WATER IS ALWAYS MAINTAINED INSIDE THE CASING WHEN IMPELLER ROTATES IT SUCKS THE WATER AS WELL AS THE AIR-FROM THE SUCTION LINE THROUGH THE ROUND PASSAGE AND THROWS OUT TOWARDS THE DISCHARGE LINE AS THE DENSITY OF AIR IS LESS THE AIR ESCAPES OUT THROUGH THE DISCHARGE LINE AT THE SAME TIME SOME AMOUNT OF DISCHARGE WATER AGAIN COMES IN TO ROUND PASSAGE THROUGH THE SMALL NOZZLE.DUE TO CONTINUOUS OPERATION. THE AIR IN THE SUCTION LINE SLOWLY  PRIMED UP THROUGH THE DISCHARGE LINE.AS THE AIR IS COMPLETELY SENT OUT IN TURN VACCUM IS CREATED AT THE SUCTION LINE WHICH PASSES THE WAY FOR WATER TO ENTER THE PUMP

SELF PRIMING CENTRIFUGAL PUMP

HYDRAULICS VANE PUMP

VANE PUMP

                A rotor is mounted in a elliptical casing between closely fitted end plates. The slots, which are made radially in the rotor carries the vanes in it. The rotor shaft is located in escentrically in relation to the housing when rotor rotates the vane proceed from the point of shortest distance between rotor and housing increased space will be created between rotor and housing. This space fills with oil supplied through a peripheral value slot from the suction port. After  the maximum distance between rotor and housing has been passed. The space between rotor and housing decreases and oil is discharged through the opposite value port. The vanes are sliding out up to the outer track by means of centrifugal force. As the centrifugal force is insufficient to hold the vane against the track during high pressure, the pressure of oil is applied to the bottom of vanes through drilled holes and semi-circular groove made on the end plates. In this design the rotor is subjected to a heavy, unbalanced load the hydraulic pressure in the discharge area acts against the rotor resulting in heavy loading of the rotor bearings. This difficulty has been avoided by providing two intake and two discharge .diametrically opposite each other and thus the hydraulic loads on the rotor balance each other.in this design the vane track is made elliptoid instead of circular, having two minimum and two maximum centre distance

                Vane pumps are being made in both constant and variable discharge design the volumetric efficiency of vane pump is 90% and over. The direction of flow can be reversed by reversing the rotation of the pump

                vane pump requires great accuracy and close tolerance .commercial vane pumps are provided separate valve plates (port slot plate).the space in between suction and discharge ports called lap space is equal to the pitch distance of the vanes .in addition to the single pump a great number of combination of pumps are available these combination consists of two or more pumping units mounted in one casting

CONSTRUCTION MATERIALS

Externals (head, casing) - Cast iron, ductile iron, steel, and stainless steel.

Vane, - Carbon graphite,

End Plates - Carbon graphite

ADVANTAGES OF VANE PUMP

 Vane pumps are robust, self-priming.

 Vane pump provides uniform discharge with negligible pulsations.

 Vane pump vanes are self-compensating for wear.

 The vanes can be easily replaced.

 These pumps don't require check valves.

 They have relatively high efficiency.

DISADVANTAGES OF VANE PUMP

 Vane pumps cannot handle abrasive liquids.

Complex housing and many parts  

 Not suitable for high viscosity

Not suitable for high pressures , the pressure within the pump chamber increases, the vanes begin to lose the ability to maintain contact with the walls of the pump chamber.

TYPES OF VANE PUMP
There are two important types of vane pumps that are used in day today life:
1. Unbalanced vane pumps
a) Fixed displacement unbalanced pump
b) Variable displacement unbalanced pump
2. Balanced vane pump

1.UNBALANCED VANE PUMP

In the unbalanced vane pump, the rotor is mounted elliptical casing as off center. The rectangular vanes fitted radially on rotor slots regular intervals, these rectangular vanes are free to move in the radial slot. The vanes are thrown outwards due to the centrifugal force to form a seal against the fixed casing as the rotor starts to rotate. The eccentricity of the revolving rotor produces a partial vaccum at the suction side of the pump which causes the inflow of the liquid. This is carried to other side of the pump in the space between the rotor and the fixed casing. the pumping action occurs in the chambers on one side of the rotor and shaft. This design imposes a side load on the rotor and drive shaft. The pumping rates of these rotary pumps are varied by changing the speed of the rotor. But in unbalanced vane pump, the pumping rate can also be varied by varying the degree of eccentricity of the rotor, since this determines the amount of liquid carried through per cycle.

(a) Fixed displacement unbalanced vane pumps
In the fixed displacement unbalanced vane pump, a constant volume of fluid is discharged during each revolution of the rotor that is provided. This achieved by keeping the rotor housing eccentricity as constant and therefore the displacement volume is fixed.

 

(b)Variable displacement unbalanced vane pump
In the variable displacement unbalanced vane pump the housing can be moved with respect to the rotor. This movement changes the eccentricity and the displacement can also be varied. A hand wheel or pressure compensator can be used to move the can ring and thus to change the eccentricity.

2.BALANCED VANE PUMP
In the balanced vane pump, it consists of two intake ports and two outlet ports and they are diametrically opposite to each other. And also in the balanced vane pump an elliptical housing is used in balanced vane pump rather than cam ring that is used in unbalanced vane pump. This configuration creates two diametrically opposed volumes. The two high pressure zones balance the forces on the rotor shaft and hence complete hydraulic balance is achieved. These descriptions are the only difference from unbalanced vane pump other than this construction and working principle is as same as the unbalanced vane pump.

GEAR PUMP HYDRAULICS

GEAR PUMP

GEAR PUMP CONSISTS OF TWO SPUR GEARS CLOSELY FITTED IN HOUSING. ONE GEAR WHEEL IS CALLED DRIVE GEAR GETS THE POWER FROM AN ELECTRIC MOTOR OR DIESEL ENGINE AND DRIVES THE OTHER GEAR WHEEL. END PLATES ARE PROVIDED TO COVER THE SIDE OF THE HOUSING AND TO ACCOMMODATE THE GEAR WHEEL SHAFT BEARINGS. IN THE HIGH PRESSURE GEAR PUMP WEAR PLATES ARE USED IN BETWEEN THE END PLATE AND GEAR WHEELS. BEARING ARE USED TO SUPPORT THE GEAR WHEEL SHAFT.THE CLEARANCE BETWEEN THE MOVING PARTS AND STATIONARY PLATE IS VARY FROM 0.002” TO 0.005”. WHEN THE GEAR WHEEL ROTATES, THE OIL IS CARRIED AROUND THE PERIPHERY OF THE REVOLVING GEARS FROM THE SUCTION SIDE TO DISCHARGE SIDE.THE TEETHS ARE MESHING BETWEEN THE TWO GEAR AND THUS PREVENT RETURN OF OIL FROM THE DELIVERY TO SUCTION

GEAR PUMPS ARE BASICALLY HYDRAULICALLY UNBALANCED. THE PRESSURE THAT DEVELOPED AT THE DISCHARGE PORT HAS A TENDENCY TO CROWED THE GEAR WHEELS OVER AGAINST THE INTAKE SIDE OF THE HOUSING

            A SUCCESSFUL ATTEMPT HAS BEEN MADE TO BALANCE THE GEARS HYDRAULICALLY BALANCED PRESSURE IS CONDUCTED BY PASSAGES FROM THE PRESSURE PORT SUITABLE POCKETS DIAMETRICALLY OPPOSITE.

            GEAR PUMP DOES NOT EMPLOY GASKET,BUT BODY JOINTS ARE GROUND TO AN OIL TIGHT FIT AND ASSEMBLED WITH ‘O’ RING PACKING SERVICE HAVE BEEN BUILT IN CAPACITIES RANGING ACTION FROM A FRACTION OF A LITER TO 300 LITER AND ABOVE THE SPEED OF THE PUMP VARIES FROM 900 TO 3500 RPM AND IT CAN DEVOLOP200.KG/CM².PRESSURE.THE VOLUMETRIC EFFICIENCY OF A GEAR PUMP VARIES FROM 85% TO 90%. THE VOLUMETRIC LOSSES IN THE PUMP ARE CAUSED BY INTERNAL LEAK THROUGH THE MATTING SURFACE,LOSSES DUE TO THE JET ACTION AT THE LINE OF CONTACT OF THE TEETH AND LOSSES IN INLET PRESSURE DUE TO CENTRIFUGAL ACTION OF FLUID.

MATERIALS

• EXTERNALS (HEAD, CASING, BRACKET) - IRON, DUCTILE IRON, STEEL, STAINLESS STEEL, HIGH ALLOYS, CAST STEEL
• INTERNALS (SHAFTS) - STEEL, STAINLESS STEEL, HIGH ALLOYS,
• INTERNALS (GEARS) - STEEL, STAINLESS STEEL,HEAT TREATED OR NITRIDED
• BUSHING - CARBON, BRONZE, SILICON CARBIDE, NEEDLE BEARINGS
• SHAFT SEAL - PACKING, LIP SEAL, COMPONENT MECHANICAL SEAL,

 ADVANTAGES

1.ABILITY TO HANDLE A WIDE RANGE OF VISCOSITIES OF FLUID

2.LESS SENSITIVITY TO CAVITATION (THAN CENTRIFUGAL STYLE PUMPS)

3.RELATIVELY SIMPLE TO MAINTAIN AND REBUILD.

4.AS THE PUMPING ACTION IS QUITE FINITE, THE OUTPUT IS VERY CONTROLLABLE. DOUBLING THE SIZE OR SPEED, IN THEORY SIMPLY DOUBLES THE OUTPUT

 DISADVANTAGES

1.THE FLUID MUST BE FREE OF ABRASIVES.

2.THE DISCHARGE OF GEAR PUMPS MUST BE CONTROLLED VIA THE MOTOR SPEED. THROTTLING 3.THE DISCHARGE IS NOT AN ACCEPTABLE MEANS OF CONTROL.

4.GEAR PUMPS RELY ON PRECISION CLEARANCES AND HAVE SEVERAL ROTATING ELEMENTS. THIS 5.MAKES THEM MORE EXPENSIVE THAN A CENTRIFUGAL PUMP

6. GEAR PUMPS ARE LIMITED BY SIZE. WHEN LARGE BULK FLOW RATES ARE REQUIRED THEY     BECOME PHYSICALLY UNSUITABLE COMPARE TO OTHER PUMP TECHNOLOGY

TYPES OF GEAR PUMPS

 1. EXTERNAL GEAR PUMP

EXTERNAL GEAR PUMP

2. INTERNAL GEAR PUMP

INTERNAL GEAR PUMP

3. GEROTOR PUMP

GEROTOR PUMP

 

4. LOBE PUMP

LOBE PUMP

HYDRAULICS PUMPS

PUMPS

Pump is a device to induce fluid flow from one place to another place under pressure, hydraulics systems pumps are used to develop very high pressure to transfer energy from one place to another place.

Pumps are classified in many ways however they are classified as its way of mechanical working arrangement, fluid working principle and by its delivery

BY MECHANICAL OPERATION 

1. ROTARY PUMPS

2. SEMI ROTARY PUMPS

3. RECIPROCATING PUMPS

BY WORKING PRINCIPLE

1. DYNAMIC PRESSURE PUMP

2. POSITIVE   DISPLACEMENT  PUMP

BY DISCHARGE

1. CONSTANT DISCHARGE PUMP

2. VARIABLE DISCHARGE PUMP

3. VARIABLE AND REVERSIBLE DISCHARGE PUMP

ROTARY PUMPS

                A rotor or an impeller rotates inside housing and induces the fluid flow and pressure centrifugal pump, gear pump, vane pump, screw pump, axial and radial piston pump are rotary pumps suction and discharge valves are not employed in rotary pumps

SEMI ROTARY PUMP

                The rotor or its kind arrangement inside a housing moves only a less than half a circle in both the direction it is a hand operating pump. The flap valve arranged on the rotor is used for suction and delivery.

RECIPROCATING PUMP

                Piston pump and plunger pump are reciprocating pumps either it can be operated by hand or any other power this pumps are provided with suction and discharge valves. The suction valves are opened by suction pressure and the delivery valves are opened by fluid pressure. Small hand operated   reciprocating plunger pumps are used in hydraulic system for hydraulic jack, puller and pressure testing etc.

DYNAMIC PRESSURE PUMP

                In dynamic pressure pump a tangential acceleration is imported to the fluid and due to the movement of the fluid from centre to outer track, vacuum is created at the centre this vacuum is continuously filled with the fluid from the suction side because of atmospheric pressure or any other pressure. The tangential acceleration is imported to the liquid by centrifugal force. Centrifugal pump is a dynamic pressure pump. Mostly this type of pumps are used to transfer the fluid from  one place to another

POSITIVE DISPLACEMENT PUMP

                In positive displacement pump one or more chambers are filled while crossing suction port and the fluid is carried over and discharged at the discharge port by the chambers. This type of pump can develop high pressure. Vane   pump, gear pump, screw pump, axial and radial piston pump are positive displacement pumps

CONSTANT DISCHARGE PUMP

                All the positive displacement pumps are made as constant discharge pump. In this type of pump discharge fluid is always constant at particular rpm. The revolution is increased the discharge of fluid also increased and vice versa. gear pump, vane pump, axial piston pump, radial piston pump, screw  pump etc.

VARIABLE DISCHARGE PUMP

                In variable discharge pump the fluid discharge can be varied at given speed. Radial and axial piston pump vane pump are variable displacement pumps, a hand wheel or lever provided in this pump to alter the stroke length of the piston the quantity of discharge can be reduced or increased at a given speed by moving the lever or hand wheel 

VARIABLE AND REVERSIBLE DISCHARGE PUMP

                The quantity of discharge and direction of flow can be changed .in this type pump without altering the speed and direction of pump. The axial and radial piston pumps are examples the lever provided the pump control the stroke of the piston when the lever is neutral or center there would be no suction and discharge, when the lever is moved to right off center the pump begins to deliver the fluid through the one port and takes suction from other port, the lever is moved to opposite side off center the pump changes or reverse the direction of fluid