Pumps for Process Industries

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This presentation will give a broad idea about selecting pumps in process industies. Design parameters are also discussed.

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Pumps for Process Industries

  1. 1. PUMPS for Process Industries Ranjeet Kumar M.Tech - Chemical
  2. 2. Equation of Energy <ul><li>A pump converts Electrical energy to Pressure Energy via Kinetic Energy. </li></ul><ul><li>Electric energy K.E. </li></ul><ul><li>K.E Pressure Energy </li></ul>Impeller Rotating Part Volute Static Part
  3. 3. Types of Pumps <ul><li>Centrifugal - Impeller & Volute </li></ul><ul><li>Reciprocating - Piston / Plunger </li></ul><ul><li>Rotary - Screw, Gear, Lobe, Progressive Cavity, Sliding Vane </li></ul><ul><li>Vertical - </li></ul><ul><li>Peristaltic - Series of rollers to push through tubing </li></ul>
  4. 4. Basis for selection of Pump <ul><li>Capacity – No. of pumps in parallel </li></ul><ul><li>Total Head – No. of stages </li></ul><ul><li>Physical, Chemical properties of Liquids </li></ul><ul><li>Viscosity @ Frictional Loss @ Power Required </li></ul><ul><li>Corrosive Fluid @ MOC </li></ul><ul><li>Site conditions </li></ul><ul><li>Source of Power </li></ul>>>>Capacity & Head required are most important selection criteria and define size of the pump.
  5. 5. Capacity <ul><li>Volume of liquid to be pumped in unit time </li></ul><ul><li>May vary as per Max, Min & Normal requirement </li></ul><ul><li>– design should be for Max capacity. </li></ul><ul><li>Its function of Impeller size and rotational speed for Centrifugal pump </li></ul><ul><li>Q = V * A : V = ω * r </li></ul>
  6. 6. Centrifugal Pump Design Problem <ul><li>Inability to deliver the desired flow & head </li></ul><ul><li>Seal problems (leakages, loss of flushing, cooling, quenching system, etc) </li></ul><ul><li>Pump & Motor bearings related problems (loss of lubrication, cooling, contamination of oil, abnormal noise, etc) </li></ul><ul><li>Leakages from pump casing, very high noise & vibration levels. </li></ul>Benefits of Centrifugal Pumps – low cost, easy maintenance, wide selection, & simple design.
  7. 7. Head of Pump <ul><li>Total Head = P discharge – P suction </li></ul><ul><li>Normal head test by vendor was done for water at 20°C. </li></ul><ul><li>Advantages of using Head-- </li></ul>
  8. 8. Physical Properties Consideration <ul><li>Specific Gravity  </li></ul><ul><li>1) Increases Power consumed directly. </li></ul><ul><li>2) Max suction lift inversely. </li></ul><ul><li>Viscosity  Pump efficiency decrease directly so Power required directly </li></ul><ul><li>Open or semi open impeller are better for highly viscose liquid. </li></ul><ul><li>Volatile liquid at boiling points require high NPSH. </li></ul><ul><li>Abrasive property of liquid or solid entrainment causes erosion and need specific MOC. </li></ul><ul><li>Corrosive liquid require specific MOC. </li></ul>
  9. 9. Solid content <ul><li>Centrifugal pump operation is most difficult when liquid handled contains solid particles. </li></ul><ul><li>Special attention required for selecting a centrifugal pump  </li></ul><ul><li>Open Impeller for solids > 2% </li></ul><ul><li>Large cross section in Impeller & Volute </li></ul><ul><li>Min No. of Vanes </li></ul><ul><li>Inspection holes in tha casing & suction passage </li></ul><ul><li>Abrasion resistant MOC </li></ul><ul><li>Smooth corners & edges in lines </li></ul><ul><li>Stuffing boxes sealed with clear fluid </li></ul>
  10. 10. Fig – Types of Impeller
  11. 11. <ul><li>Temperature of liquid  Direct Impact on physical properties of liquid & Vapor Pressure and MOC. </li></ul>
  12. 12. Site Conditions <ul><li>Altitude – P atm decreases with altitude & P atm has direct effect on NPSHa </li></ul><ul><li>Gas Dust Hazard – if the surrounding atmosphere is hazardous/inflammable  Flame proof & Dust proof MOC of Motor. </li></ul><ul><li>Stand by unit for vital application. </li></ul>
  13. 13. Selection of Pump – Capacity & Head < 200 cSt < 25 m Upto 1 m 3 /h Peristaltic > 2% < 25% < 600 cSt 10500 m < 300 m 3 /h Positive Displacement > 2% < 5% Max 1050 m < 350 m 3 /h Rotary < 2% Upto 20% < 200 cSt Upto 105 m Upto 7500 m 3 /h Centrifugal % Gas Solid Viscosity Head Capacity Type
  14. 14. Flow Rate Design <ul><li>Margins for rated/maximum capacity </li></ul>PFD indicates normal flow rate without any margin & the Maximum flow is Considered for sizing of the pump with margin 30% Waste Heat Boiler pump 25% Boiler Feed water pump 0% Recirculation pump 3-5% Large cooling water pump 0-5% Transfer pumps 0% Intermittent pumps 20-25% Reflux pumps 10% Continuous process pumps Margin Service
  15. 15. <ul><li>Minimum flow rate ???? </li></ul><ul><li>Under development…………. </li></ul>
  16. 16. Static Head <ul><li>Pump centre line as datum for Hydraulic calculation </li></ul><ul><li>Pump centre Line from ground (estimated) </li></ul><ul><li>Minimum level in Suction & Maximum level in Discharge tank. </li></ul>1.0 Above 200 0.9 100 – 200 0.7 0 – 100 Pump centre line above ground Flow Rate (m 3 /h)
  17. 17. Line Pressure Drop ? <ul><li>Under development </li></ul>
  18. 18. Pressure Drop for Control Valve <ul><li>The following criteria can be used for sizing the control valve </li></ul><ul><li>15~25% of the variable system drop is typically allowed. </li></ul><ul><li>On recycle and reflux pumps allow 1/3 of the variable system pressure with minimum of 0.7 bar. </li></ul><ul><li>For liquid system 0.7 bar </li></ul><ul><li>For system with large variable pressure drop ( >10 bar) ~15% of the variable pressure drop exclusive of control valve </li></ul>
  19. 19. Pressure Drop for Devices 0 Ultrasonic & electromagnetic Flow Meter 0.2 – 0.4 Corilolis Flow Meter 0.2 – 0.4 Vortex 0.02 – 0.05 Venturi Flow Meter 0.25 Orifice Flow meter 0.07 bar (continuous strainer) Y, T or Bucket type Strainer 1.0 bar Air cooler 0.35 – 0.5 bar per shell 0.7 bar per pass in tube side Shell & Tube type Heat Exchanger Press Drop (in bar) Devices in Flow Line
  20. 20. NPSH <ul><li>NPSHA = Suction Pressure – Vapor Pressure </li></ul><ul><li>NPSHA should be 2 – 3 ft more than NPSHR. </li></ul><ul><li>It is the pressure enough to prevent formation of vapor bubbles due to vaporization or release of dissolved gases in the Impeller. </li></ul><ul><li>Pressure increases along the impeller on collapse of vapors – Cavitation. </li></ul><ul><li>Cavitation – Noise, Vibration, Drop in performance curve, high wear & tear loss. </li></ul>
  21. 21. NPSHA optimization <ul><li>NPSHA can be increased by – </li></ul><ul><li>Raise the liquid level </li></ul><ul><li>Lower the pump </li></ul><ul><li>Reduce the friction losses in the suction line </li></ul><ul><li>Use a booster pump </li></ul><ul><li>Sub cool the liquid </li></ul><ul><li>NPSHR can be reduced by – </li></ul><ul><li>Slower speed </li></ul><ul><li>Double-suction impeller </li></ul><ul><li>Large impeller area </li></ul><ul><li>Oversize pump </li></ul><ul><li>Inducers ahead of conventional pump at suction side </li></ul><ul><li>Several smaller pumps </li></ul>NPSHR Rotary < NPSHR Centrifuge < NPSHR Reciprocating
  22. 22. Efficiency <ul><li>Efficiency = WHP/BHP </li></ul><ul><li>Overall efficiency reflects hydraulic, leakage & mechanical losses of pump. </li></ul><ul><li>η centrifugal < η reciprocating < η rotary </li></ul><ul><li>(50 – 80%) (50 – 90%) (70 – 90%) </li></ul>
  23. 23. Seals, pumps curves <ul><li>Under Development…….. </li></ul>

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