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.

Text of Pumps for Process Industries

  • PUMPS for Process Industries Ranjeet Kumar M.Tech - Chemical
  • Equation of Energy
    • A pump converts Electrical energy to Pressure Energy via Kinetic Energy.
    • Electric energy K.E.
    • K.E Pressure Energy
    Impeller Rotating Part Volute Static Part
  • Types of Pumps
    • Centrifugal - Impeller & Volute
    • Reciprocating - Piston / Plunger
    • Rotary - Screw, Gear, Lobe, Progressive Cavity, Sliding Vane
    • Vertical -
    • Peristaltic - Series of rollers to push through tubing
  • Basis for selection of Pump
    • Capacity No. of pumps in parallel
    • Total Head No. of stages
    • Physical, Chemical properties of Liquids
    • Viscosity @ Frictional Loss @ Power Required
    • Corrosive Fluid @ MOC
    • Site conditions
    • Source of Power
    >>>Capacity & Head required are most important selection criteria and define size of the pump.
  • Capacity
    • Volume of liquid to be pumped in unit time
    • May vary as per Max, Min & Normal requirement
    • design should be for Max capacity.
    • Its function of Impeller size and rotational speed for Centrifugal pump
    • Q = V * A : V = * r
  • Centrifugal Pump Design Problem
    • Inability to deliver the desired flow & head
    • Seal problems (leakages, loss of flushing, cooling, quenching system, etc)
    • Pump & Motor bearings related problems (loss of lubrication, cooling, contamination of oil, abnormal noise, etc)
    • Leakages from pump casing, very high noise & vibration levels.
    Benefits of Centrifugal Pumps low cost, easy maintenance, wide selection, & simple design.
  • Head of Pump
    • Total Head = P discharge P suction
    • Normal head test by vendor was done for water at 20C.
    • Advantages of using Head--
  • Physical Properties Consideration
    • Specific Gravity
    • 1) Increases Power consumed directly.
    • 2) Max suction lift inversely.
    • Viscosity Pump efficiency decrease directly so Power required directly
    • Open or semi open impeller are better for highly viscose liquid.
    • Volatile liquid at boiling points require high NPSH.
    • Abrasive property of liquid or solid entrainment causes erosion and need specific MOC.
    • Corrosive liquid require specific MOC.
  • Solid content
    • Centrifugal pump operation is most difficult when liquid handled contains solid particles.
    • Special attention required for selecting a centrifugal pump
    • Open Impeller for solids > 2%
    • Large cross section in Impeller & Volute
    • Min No. of Vanes
    • Inspection holes in tha casing & suction passage
    • Abrasion resistant MOC
    • Smooth corners & edges in lines
    • Stuffing boxes sealed with clear fluid
  • Fig Types of Impeller
    • Temperature of liquid Direct Impact on physical properties of liquid & Vapor Pressure and MOC.
  • Site Conditions
    • Altitude P atm decreases with altitude & P atm has direct effect on NPSHa
    • Gas Dust Hazard if the surrounding atmosphere is hazardous/inflammable Flame proof & Dust proof MOC of Motor.
    • Stand by unit for vital application.
  • 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
  • Flow Rate Design
    • Margins for rated/maximum capacity
    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
    • Minimum flow rate ????
    • Under development.
  • Static Head
    • Pump centre line as datum for Hydraulic calculation
    • Pump centre Line from ground (estimated)
    • Minimum level in Suction & Maximum level in Discharge tank.
    1.0 Above 200 0.9 100 200 0.7 0 100 Pump centre line above ground Flow Rate (m 3 /h)
  • Line Pressure Drop ?
    • Under development
  • Pressure Drop for Control Valve
    • The following criteria can be used for sizing the control valve
    • 15~25% of the variable system drop is typically allowed.
    • On recycle and reflux pumps allow 1/3 of the variable system pressure with minimum of 0.7 bar.
    • For liquid system 0.7 bar
    • For system with large variable pressure drop ( >10 bar) ~15% of the variable pressure drop exclusive of control valve
  • 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
  • NPSH
    • NPSHA = Suction Pressure Vapor Pressure
    • NPSHA should be 2 3 ft more than NPSHR.
    • It is the pressure enough to prevent formation of vapor bubbles due to vaporization or release of dissolved gases in the Impeller.
    • Pressure increases along the impeller on collapse of vapors Cavitation.
    • Cavitation Noise, Vibration, Drop in performance curve, high wear & tear loss.
  • NPSHA optimization
    • NPSHA can be increased by
    • Raise the liquid level
    • Lower the pump
    • Reduce the friction losses in the suction line
    • Use a booster pump
    • Sub cool the liquid
    • NPSHR can be reduced by
    • Slower speed
    • Double-suction impeller
    • Large impeller area
    • Oversize pump
    • Inducers ahead of conventional pump at suction side
    • Several smaller pumps
    NPSHR Rotary < NPSHR Centrifuge < NPSHR Reciprocating
  • Efficiency
    • Efficiency = WHP/BHP
    • Overall efficiency reflects hydraulic, leakage & mechanical losses of pump.
    • centrifugal < reciprocating < rotary
    • (50 80%) (50 90%) (70 90%)
  • Seals, pumps curves
    • Under Development..