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Saturday, May 28, 2011

Engine calculations


Engine displacement
The volume swept by piston in IC engine in a single movement from TDC to BDC.
  
Displacement= (π/4) * stroke * bore * bore * number of cylinders

Stroke length 
In reciprocating engine the piston moves in one direction first and then exactly opposite direction(TDC to BDC and BDC to TDC).Each of the movement is called stroke or stroke length.

Stroke lenght= engine displacement /(0.7854 * bore *bore *number of cylinders)

Compression Ratio

In an internal combustion engine, the ratio of the volume between the piston and cylinder head before and after a compression stroke is called compression ratio.A compression ratio of six means that the action of the piston compresses the mixture to one-sixth its original volume.

Compression ratio = (swept volume + total chamber volume) / total chamber volume 

 

Cylinder bore diameter

Cylinder bore diameter = square root of [engine displacement/(stroke X 0.7854 X number of cylinders)] 

Swept volume
 
The volume of cylinder swept by the piston while move to TDC to BDC or BDC to TDC is called swept volume.

Swept volume (cc) = cylinder bore diameter (inches) X cylinder bore diameter (inches) X stroke (inches) X 12.8704 


Cylinder Lubrication System


Cylinder lubrication system provided smooth reciprocating motion of piston in cylinder liner
Function of cylinder lubrication system
  1. To protect piston rings from corrosion by providing  lowest friction and wear
  2. Provide a uniform thin layer which helps to prevent combustion gas leakage 
  3. Helps to reduce cylinder liner temperature
  4. Helps cylinder liner,piston and piston rings to withstand in high temperature and pressure
Different components of Cylinder lubricating system
A typical cylinder lubrication system(MAN B&W engine)
  1. Electric motor
  2. Worm gear set
  3. Ball type sight glass
  4. Handle for feed adjustment
  5. Pump casing
  6. Rocker shaft
  7. Rocker
  8. Electric heater
  9. Ball sight glass
  10. Valve ball
  11. Screw
  12. Camshaft with cam
  13. Oil drain line
  14. Oil inlet
  15. Pressure line

General description
The lubrication pump is driven by a electric motor via a worm gear set.The individual plunger operated by the camshaft via rockers.Each of the pistons sucks oil from the oil space and pressure it through ball valve system.The pressure line feed the oil to the lubricating point of the engine cylinder.Oil supply pump automatic collect the oil by the float valve.Oil temperature is maintained by the electric heater and keep it about 50 degree celsius and viscosity about 115-150 cst .

All the balls in the sight glass must be floating at same level.Rising height of the ball depends upon delivered quantities,temperature and oil viscosity.




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Thursday, May 26, 2011

LO auto backwash filter


Lube Oil auto backwash filter used to discharge sludge from filter automatically at a certain time interval.
Main Components 
  1. Filter Candle
  2. Candle housing
  3. Candle cover
  4. Pressure valve
  5. Servo motor
  6. Gear arrangement
  7. Cylinder barrel
  8. Solenoid valve
  9. Compressed air bottle
  10. Pressure gauge
    How it works?  
    Lube oil entered in the filter candle,the impurities are filtrate and settle down. After a certain time interval the solenoid valve open the port for compressed air enter to the cylinder chamber to force the barrel backward,so that all the sludge discharged.After the sludge discharged solenoid valve allow the other port for compressed air to enter in the cylinder to force the barrel forward so that discharge port get closed.Every time only one unit of filters sludge get discharged.Servo motor at the top of the filter allow to rotate the discharge port of every single unit through a gear arrangement.The air entered in the filter to force the sludge get stacked with filter outward and release toward the head of the candle set cover.There is a valve arrangement for air release.Filtrated lube oil flow through engine or duplex filter(in some cases) through outlet pipe.  
    Problems 
  1. Auto backwash filter get jammed
  2. Trouble in automatic sludge discharge
  3. Trouble in manual sludge discharge
  4. Gear teeth brake down 
 
          Possible Causes
  1. Low quality lube oil
  2. Lube oil contaminated with dust or carbon diposits
  3. 'O 'ring damage in cylinder barrel
  4. Faulty solenoid valve
  5. Corrosion in gear teeth 
          Solutions
  1. Clean all the filters with proper cleaning agent(generally diesel and compressed air)
  2. Check the 'O' rings and change if needed
  3. Check the solenoid valve and change if needed
  4. Check all the compressed air line
     


Tuesday, May 24, 2011

Crank shaft




The crankshaft is mainly of the semi built type, made from forged or cast steel throws. At the aft end, the crankshaft is provided with the collar for the thrust bearing, and the flange for the turning wheel and for the coupling bolts to an intermediate shaft.
At the front end, the crankshaft is fitted with the collar for the axial vibration damper and a flange for the fitting of a tuning wheel. The flange can also be used for a Power Take Off, if so desired. Coupling bolts and nuts for joining the crankshaft together with the intermediate shaft are not normally supplied.





Components of crank shaft
  1. Crank shaft bearing or main bearing
  2. Thrust bearing
  3. Counter weight
  4. Flywheel mounting flange
  5. Vibration damper
  6. LO holes
Types of crank shaft
  1. Semi Built-Constructed with parts by parts for one unit and then connected together
  2. Fully Built-Constructed by casting and totally make only one part
  3. Welded-Constructed part by part,then welded together 
Crank shaft inspection
  1. Check abnormal sound
  2. Check oil Spot
  3. Check cracks
  4. Check crankshaft bearing
  5. Check balance shaft bearing
  6. Check the Oil passages
  7. Check any loosen bolts
  8. Connecting rod journal surface
  9. Check alignment of the shaft
Read about how crankshaft alignment check
      Read Details


      Monday, May 23, 2011

      Turbocharger fault


      The most common turbocharger fault is due to incorrect operator actions (Not allowing the engine to idle when started and before stopping), poor maintenance and not using the correct type of oil. A turbocharger can rotate at up to 160,000 revolutions per minute under full power, therefore the rotor bearings require adequate lubrication. Worn bearings and seals will allow oil to pass into the engine! Another problem is if the air hoses to and from the turbocharger leak due to damaged or loose hose clips allowing air to escape.

      Low fuel pressure


      Low fuel pressure could be either poor fuel supply to the injectors or the injectors are worn and not holding the fuel pressure. The best way to diagnose this is to look at the fuel supply in 3 areas.

      1. A. Low pressure supply from the tank to the fuel injection pump. The supply from the tank to the injection pump via the lift pump should be about 2 to 5 bar (30 to 70 psi).
      2. B. Fuel is delivered from the injection pump to the injectors at approx. 175 atmos.
      3.  Once the fuel is delivered to the injectors at the relevant pressure it must lift the needle and spray finely atomised fuel into the cylinder.

      Engines trouble shooting by the color of smoke


      Generally a diagnosis as to what’s wrong with a diesel engine can be identified by the colour of smoke coming from the exhaust pipe. There are three basic colours - ‘Black’, ‘White’ and ‘Blue’.

      Black Smoke
      This is due to an air to fuel ratio imbalance, either the fuel system is delivering too much fuel or there’s not enough clean air (oxygen) for complete combustion, a few things to look for are:-
      A. Faulty injectors
      B. Faulty injector pump
      C. Dirty or blocked air cleaner
      D. Turbocharger faulty
      E. Problems within the cylinder head or inlet valves not seating due to a build up of carbon
      F. Over fuelling
      G. High altitude operation

      White Smoke
      This is normally caused by the fuel being injected and not burning correctly. The smoke will ‘Sting’
      your eyes. This problem can be caused by any of the following:-
      A. Injection pump timing incorrect
      B. Fuel starvation to the injection pump
      C. Low engine compression
      D. Water in the fuel
      E. Water entering the combustion chamber
      F. Faulty head gaskets and cracked cylinder liners & heads are a common cause of water entering the cylinder.

      Blue Smoke
      Blue smoke will be emitted when the engine is burning oil, this can sometimes be accompanied by oil coming out of the end of the exhaust pipe, common problems are:-
      A. Worn cylinder liners or piston rings
      B. Piston rings sticking
      C. Faulty valves stem seals
      D. Engine over full with engine oil
      E. Dilution of the engine oil with fuel
      F. Wrong ‘Grade’ of oil, I.E. Too thin
      G. Too good a quality of oil in an old ‘Classic’ engine, I.E. Using semi synthetic or fully synthetic oil.
      E. The engine not being ‘Worked’ hard enough, all diesel engines need hard work otherwise the cylinder bores can become ‘Glazed’.

      Sunday, May 22, 2011

      Exhaust valve damage


      General Damage
      1. Exhaust valves 'O' ring damage occur
      2. Roto cap stacked
      3. Tiny gap between valve and valve seat
      Possible Causes
      1. High exhaust gas temperature
      2. Failure of cooling system
      3. Valve get corrosion by friction
      Maintenance Work 
      1. Change the 'O' rings
      2. Use high temperature resistant grease around 'O' rings
      3. Do Lapping operation in valve and valve seat interface surface until they adjusted correctly

      4. Control the exhaust gas temperature
      Extreme Damage 
      1. Valve get bended 
      2. Valve get broken
      3.  Some parts of the valve melt down
      Possible Causes
      1. Engine runs long time with high exhaust gas temperature 
      2. Failure of cooling system
      3. Auto ignition take place in different times
      4. Valve bended
      5. The material of exhaust valve is not perfect(can't withstand long time in high temperature)
      Maintenance Work 
      1. Change the valve
      2. Control the exhaust gas temperature
      3. Use a valve constructed with proper composition of metals

      Wednesday, May 18, 2011

      LO duplex filter


      LO duplex filter
      LO duplex filter used to filtrate LO leaving from LO auto backwash filter and entering to the engine.Generally candle type filter used.In the center of the candle set a magnet candle used to keep the candle set compact.A flow direction changing valve attached between tho chambers.


      Tuesday, May 17, 2011

      Charge air filter


      Charge air filter

      Fuel Pump

      Fuel Pump

      Charge air inter cooler



       Inside this post
      • Intercooler Introduction
      • How it works
      • Heat transfer calculation
      • Problems
      •  Treatment precess


      Charge air inter cooler used to cool charging air coming from compressor unit of Turbo Charger.Charge air coolers are located between the turbo charger and the engine air inlet manifold. When the air is compressed by the turbocharger or supercharger, it is also heated, which causes its density to decrease.
      MAN B&W interclloer
      MAN B&W intercooler


      Cooling the combustion air by a charge air cooler prior to sending it into the engine, the density of the air increases which permits more air to enter the engine and increases the power and efficiency of the engine..For proper combustion of fuel,it is required to maintain charge air temperature to a certain limit.(For MAN B&W 9L 58/64 engine the range is 45-55 degree Celsius).

      How it works?

      Hot air coming from the turbocharger(compressor unit) flows through air passage inside the intercooler. The turbocharger air transfers heat to the tubes, warming the tubes and cooling the turbo air. Outside water passes over the tubes. Heat is transferred from the hot air to cool water occurs. This is how the turbocharger air is cooled down.

      The theoretical heat transfer occur

      The amount of heat transfer occur between two fluids(air and water) can be calculated from the following equation,
                            Q = m x Cp x dT

      Q =is the energy transferred.

      m= is the mass flowrate (lbs/minute) of fluid
      Cp =is the heat capacity of the air. It is about 0.25 for air and 1.0 for water.  .
      dT= is the difference in temperature between the inlet and outlet. 


      Intercooler Materials 
             
      Tube
      Tubes
      • Aluminium (Light Weight)
      • Aluminum-Brass alloy
      • Copper
      • Nikel 
      • Mild steel(cheap)
      • Stainless steel (heavy duty)
      • Aluminium tube with Zinc Sprayed(corrosion resistant)
      Fin
      Fins
      • Usually Aluminium(temperatures lower than 150°C)
      • Aluminium alloy
      • Copper( for over 150°C charge air temperature)
      • Tin Plated Copper( for over 150°C charge air temperature)
        Frame
        For applications, carbon steel and Rolled Naval Brass are widely used materials for side panels and middle mirrors respectively. Stainless steel can also be used for applications if desired. The construction must be well designed for the robustness and resistance to vibration of the unit.

        Intercooler Problems
        • Low heat transfer rate-Due to scale formation in tubes and fins external and internal surface
        • Leakage in tubes-Due to corrosion or life time get over 

        Corrosion in fins
        Fins get staked
        • Fins get staked together-Due to excess pressure
        • Corrosion in fins
        • Structural damage-Due to external pressure
        Treatment Precess 

        Treatment process consist of few steps.
        • Removing dust,Carbon deposits and other impurities with the help of compressed air
        • Submerging the cooler in Chemical mixed water
        "If the condition become very bad then pour degreaseer on the cooler and keep it in dry state 4 ti 5 hours" 
        • Attached heater and maintain the temperature about 45 degree celsius
        • Provide compressed air line under the cooler
        • Keep in this condition about 12 hours(sometime vary)
        • Draw it from water and spray normal water until all the impurities gone
        • Provide compressed air to remove water particle from the cooler
        "During compressed air and water spraying, always spray such a way that fins are not bended"


         

        Plate type heat exchanger


        Plate type heat exchanger used to transfer heat between two fluids.
        Plate type heat exchanger
        Construction
         Frame
        The heat exchanger consists of a frame plate (Head), a pressure plate (Follower), a carrying bar, a lower bar and a column. Tightening bolts are
        used to press the plates together. This is depending on the type of heat exchanger and can be different in some applications. 
        Plates
        The plate package consists of plates with a groove along the rim of the plate and around the ports. The number of plates is, as well as size and dimension, dependant on the thermal output required. Depending on the application stainless steel or titanium plates might be used.

        Gaskets
        The groove provided in the plates holds the special gasket. The purpose of this gasket is to prevent intermixing of the media and leakage to the outside. The gaskets are selected to suit the actual combination of temperature, chemical environment and possible other conditions to be considered. They can be supplied in Viton, Nitrile or EPDM.

        Plate and Pattern types
        Cooling plate can be classified in various sections, according to their pattern type,gasket use and place to use.

        Installing 
        Operation
        Maintenance
        Problems and Solving
        Different problems associated with heat exchanger  and their possible solutions are is listed below

        ProblemsCausesSolutions
        Water
        Test Test

        HFO auto backwash filter


        HFO auto backwash filter
        HFO auto backwash filter consist of circular disc attached together.There are many reasons customers are switching from standard filter housing to Automatic Backwash Systems.
        • Reduces process/system downtime
        • Reduces operator exposure
        • Reduces maintenance cost
        • Reduces labor costs
        • Reduces filter element disposal and
           Replacement cost
        • Increases productivity

        HFO manual backwash filter





        HFO manual backwash filter used when auto backwash filter get jammed.Manual backwash filter allow the conditioning HFO to pass toward the viscosity  controller by filtering dust and other impurities.

        HFO duplex filter


        HFO duplex filter
        HFO duplex filter used to finally filtrate fuel oil leaving from HFO purifier.After filtrate it stored in service tank.Usually candle type filter used.

        Oil Bath Chamber


        Oil Bath Chamber used to filtrate the charge before entering turbocharger.Air filters attached to a chain which is rotate with the help of a motor.Generally a  worm gear system used.Oil bath sump contains oil.When the filters are rotate it becomes wet with oil and the air passing the filter,if contains dust,dusts are attached with the oil and only dust free air is allow to pass through the filter.

        Oil bath air filter
        Oil bath air filter
        Gear assembly




        Filters attached to the chain grove bu cir-clip.When rotate at the top and bottom position it makes a 'U' turn.The oil attract the dust particle and due to inertia falls into the sump.

        Charge Air System


        Atmospheric air contain dust,impurities,moisture & different gasses. For the complete combustion of fuel properly treated air necessary.The temperature,humidity,purity and flow rate maintained by charge air system.Several steps and equipments are used in charge air system.
        General Description

        There are two major components of a charge air system, the turbocharger and the charge-air cooler (or inter cooler). These products work in conjunction with one another and most often than not when one is working irregularly the other is also.
        The air from the atmosphere first filtrate in primary air filter where dust(usually big size)separated from charge air.Then passed through oil bath chamber where rest of dusts are filtrated.Then passed through the turbocharger where charge air compressed,the temperature also increased,so used a cooling system named charge air cooling system.Compressed charge air passed through inter cooler where charge air cooling water used as a cooling fluid.Then through intake manifold and expansion piece charged into combustion chamber.


        Monday, May 16, 2011

        HFO Booster Module or HFO fuel conditioning module or viscosity booster


        Heavy fuel oil (HFO) have a viscosity  listed as 180cst at 50 deg.C.The diesel engines  requires HFO with viscosity of about 25cst at 95-100 deg.C.So HFO Booster Module or HFO fuel conditioning module or viscosity booster used to reduce the viscosity of HFO.

        Flow Diagram of HFO Booster Module Operation

        Main Components
        1. Change over valve
        2. Mixing tank
        3. Fuel heater
        4. Back wash filter
        5. Viscosity controller
        6. Control panel
        7. Booster pump

        General Description
        Change over valve used to regulate the flow of either Diesel or HFO.Then through some valve and flow meter enter in mixing chamber where HFO mixed with Diesel.Fuel booster pump used to transfer fuel to HFO to heating chamber and heated by either electrical heater of steam then enter into filter(auto and manual backwash filters).Viscosity controller used to keep the viscosity in required value.

        Sunday, May 15, 2011

        LO Separator


        LO Separator

        HFO Purifier


        HFO Purifier used to separate sludge and water content from HFO.Separation takes place in separator bowl,which is driven by an electric motor(A) via a worm gear(D) transmission.The separator bowl rotates at a very high speed generation a sub centrifugal force.Sludge and water particle then separated from HFO.


        Unseparated oil is feed to the bowl through the oil inlet and separated oil leaves the bowl through clean oil outlet.Separated sludge and water are collected inside the bowl periphery and are discharged at intervals through the sludge discharge port.


        Components

             1.    Oil inlet
             4.    Oil Outlet
             5.    Water outlet
             10.  Conditioning water inlet
             15.  Opening water inler
             16.  Closing and make-up water inlet
              a.   Upper paring chamber
             A.    Flow control disc
              aa.  Oil paring chamber
             B.    Small lock ring
             C.    Level ring
             D.    Distributor
             E.    Top disc
             F.     Bowl hood

             G.    Bowl disc stack
             H.    Large lock ring
             I.     Sludge space
             ii.     Sludge space
             J.     Bowl body
             K.    Sliding bowl bottom
             L.    Operating slide
             M1.  Nozzle
             M2.  Nozzle
             N.     Dosing ring
             O.     Spring
             T.      Upper paring disc
             U.     Oil paring disc
             V.      Inlet pipe
             VV.   Distributing cone
              W.    Bowl hood seal ring
              X.    Drain valve
             Y1.   Opening chamber
             Y2.   Closing chamber
              Z.    Control paring disc
             ZZ.   Spring support

        Mechanism

        The bowl body and bowl hood with seal ring are held together by the large lock ring. Housed in the bowl ate the distributor, the distributing cone and the disc stack into which the uncleaned oil flows from the inlet pipe,and where the separation takes place.Uppermost in the disc stack is the top disc.The top disc neck and the level ring form a paring chamber where the paring disc pumps the cleaned iol out of the bowl. The flow control disc is clamped to the bowl hood paring chamber. Separated water is drained off intermittently through the flow control disc and the upper paring disc.
        In the lower part of the bowl is the sludge discharge mechanism,comprising the sliding bowl bottom ,the operating slide the dosing ring,springs and spring support. The sludge discharge mechanism is operated by the opening and closing via the control paring disc.The operating water is confined to the opening and closing chambers by the nozzles and the drain valve.

        Sludge discharge function

        When charge discharge occurs only sludge and  water are discharged.It may however contain some emulsion oil.The sludge is discharged through a number of ports in the bowl wall.Between discharges these ports are covered by the sliding bowl bottom,which forms an internal bottom in the separation space of the bowl.The sliding bowl bottom is passed upwards against a seal ring by the hydraulic force of the operating water underneath.Discharge is effected by draining off those water .The sliding bowl bottom is then passed upwards by the lowers force above, thereby uncovering tor ports through which the sludge is discharged from the bowl.
        Operating water to the sliding bowl bottom is supplied through a paring disc device under the bowl.The operating water is fed through two different pipes for closing and opening functions.Closing water is supplied during he sludge discharge sequence and ,at intervals during the separation sequence ,by the solenoid valve, During the separation sequence the supply of closing water is the replce possible leakage and is termed make up water.Closing eater is supplied from and operatiion water tank posinned above he separator.Opening water is supplied from the hogh pressure system.

        Sludge discharge cycle

        Sludge discharge cycle can be divided into four different stages
        1. Before sludge discharge
        2. Initiation of sludge discharge 
        3. Sludge discharge
        4. After sludge discharge
        Before sludge discharge
        • Space under sliding bowl is filled
        • Sliding bowl bottom is pressed against seal ring as force f2 is greater than f1
        • Operating slide keeps drain valves closed by means of the force f produced by coil spring
        • Valve V% is closed
        • Separation continues and water and solids move towards the periphery of the bowl and sludge is collected in the sludge space.

        Initiation of sludge discharge
        • Applies for oil with high,medium or low free water content.i.e. no displacement water is added.
        • Solenoid valve MV16 continuous open
        • Solenoid valve MV15 opened for approximately 3 seconds
        • Opening chamber Y1 in dosing ring N is filled
        • Water force f3 increases and exceeds spring force f
        • Operating slide L moves downwards, thereby opening drain valve X
        • Space below sliding bowl bottom K is drained and force f2 decreases
        • Low flow-rate through nozzle M1
        • Overflow to closing chamber Y2 in dosing ring N begins
        Sludge discharge
        • Space below the sliding bowl bottom K is drained and force f2 becomes less than f1
        • Sliding bowl bottom K moves downwards and discharge of sludge and water takes place through port I in the bowl wall.Force f1 decreases rapidly.
        • The closing chamber Y2 in closing ring N has become filled and force f4 equals f3 .Spring force f pushes the operating slide L upwards and closes the drain valve X.
        • The chambers in closing ring N and continuously drained through nozzle M1 and M2
        • The s[ace below the sliding bowl bottom K is filled from the operating water tank via the open solenoid valve MV16.Force f2 increase
        • Force f2 now exceeds the decreased f1,thus forcing he sliding bowl bottom upwards into the closed position.
        After sludge discharge
        • Sliding bowl bottom K is forced into closed position
        • The space below the sliding bowl bottom is now filled and force f2 is restored completely
        • Solenoid valve MV16 closed
        • The chamber is closing ring N are drained through nozzles M1 and M2
        • The separating space above the sliding bowl bottom K is filled.Force f1 increases to normal valve
        • New reference valve is determined and stored
        • If conditioning water must be added this will be performed after the reference value has been stored
        • Solenoid valve MV16 closed after and addition of conditioning water The value resumes intermittent opening and closing.


              Pneumatic Pump or Diaphragm pump


              Pneumatic pump runs with the aid of compressed air.It also called diaphragm pump because diaphragms are used to compressed the fluid(for delivering) and creating vacuum(for fluid intake). 

              Components 

              pneumatic pump
              • Pumping Chamber
              • Ball valves
              • Diaphragm(air and fluid side)
              • Suction manifold
              • Delivery manifold
              • Pneumatic exchanger




              Working Principle

              The compressed air introduced by the pneumatic exchange chamber, pushes the piston forward, lifted  the ball from seat.Then air compressed one side of the diaphragm and force the liquid  through the delivery valves.Other side of the diaphragm  creates a vacuum and intakes the fluid(liquids are forced into the tank, which is filled with atmospheric air).Once the cycle is completed,pneumatic exchanger divert the air direction and this cycle is continuing.

              Reciprocating Pump


              Reciprocating pump runs by the principle of pushing the liquid by a plunger,piston or bucket that executes a reciprocating motion through a cylinder.


              Main Components

              Main component of a reciprocating pump are
              • Piston or Plunger or Bucket
              • Suction line
              • Delivery line
              • Suction valve
              • Delivery line
              • Crank and connecting rod
              • Liquid container or cylinder
              • Packing (used as liquid seal)
              • Casing of crankcase
              • Bearing for crankshaft and connection rod
              • Reduction gear

              Working Principle


              Through the suction line liquid is filled to the cylinder through suction check valve.Then the piston connected with crankshaft through connection rod push the liquid and the liquid is discharge through delivery line.Electric motor usually used power up the crankshaft.Rotary motion convert into reciprocating motion.When piston moves from bdc to tdc it creates a vacuum which helps to suck liquid to the cylinder.

              Discharge and Efficiency calculation


              Discharge of a reciprocating pump is calculated by the following equation

              Q=(ALN)/60

              Where,
              Q= Discharge in m3/s
              A= Cross section area of piston or cylinder in m2
              L= Stroke length in m
              N= Speed of the crankshaft in R.P.M

              The efficiency of reciprocating pump is calculated by the following equation

              Efficiency= P(out) / P(in)


              Advantages of using Reciprocating Pump


              Following are the advantages of using reciprocation pump
              • High efficiency
              • It can produce high pressure
              • Change in pressure does not affect the flow rate
              • Have a function of self priming

                Disadvantages

                • It provide a pulsating flow
                • For high viscous fluid suction stroke is difficult
                • Gives low volume rate of flow
                • Cost is high
                • Maintenance process is difficult due to close fitting moving parts

                Screw type pump



                The screw type pump can generate a multitude of frequency components in the vibration spectrum. Thread wear or damage will usually produce strong harmonics of the thread rate, which is the number of threads times the RPM.
                Screw pump
                screw type pump

                Theory


                Screw pumps are a unique type of rotary positive displacement pump in which the flow through the pumping elements is truly axial. The liquid is carried between the screw threads on one or more rotors. The liquid is then displaced axially as the screws rotate and mesh. In other types of rotary pumps, the liquid is forced to travel circumferentially, however the screw pump has an axial flow pattern and low internal velocities

                Capacity



                The delivered capacity of any screw pump is the theoretical capacity minus the internal leakage. In order to find the capacity of a screw pump the speed of the pump must be known. The delivered capacity of any rotary screw pump can be increased several different ways. The capacity can be increased by simply increasing the speed, increasing the viscosity, or decreasing the differential pressure. The capacity of the pump depends on several factors

                • Diameter of the screw
                • Speed of the screw
                • Number of flights mounted on the screw shaft
                  • Flights: Single, double, and triple flights are often used. Flights are also known as helixes. With each increase in flights, there is a 20% increase in capacity. Therefore, a single flight pump has a capacity that is 80% of a double flight pump, which in turn has a capacity that is 80% of a triple flight capacity. The three-flight pump can handle the most capacity in the least amount of space.
                • Angle of inclination of the screw
                  • The greater the angle of inclination, the lower the output. The output lowers approximately 3% for every degree increase over a 22 degree inclination.
                • Level of influent in the influent chamber
                • Ratio of the diameter of the screw shaft to the outside diameter of the screw flights
                • Clearance between screw flights and trough
                 Advantages


                • Wide range of flows and pressures
                • Wide range of liquids and viscosities
                • Built-in variable capacity
                • High speed capability allowing freedom of driver selection
                • Low internal velocities
                • Self-priming with good suction characteristics
                • High tolerance for entrained air and other gases
                • Minimum churning or foaming
                • Low mechanical vibration, pulsation-free flow, and quiet operation
                • Rugged, compact design -- easy to install and maintain
                • High tolerance to contamination in comparison with other rotary pumps

                Disadvantages



                • Relatively high cost because of close tolerances and running clearances
                • Performance characteristics sensitive to viscosity change
                • High pressure capability requires long pumping elements


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