Download to read offline
Pumps.pptx
- 1. Pumps & PumpingSystems
- 2. CONTENT Introduction Type of pumps Assessmentof pumps Energy efficiency opportunities
- 3. INTRODUCTION What are PumpingSystems 20% of world’s electrical energy demand 25-50% of energy usage in some industries Used for Domestic, commercial, industrial and agricultural services Municipal water and wastewater services Objective of pumping system Transfer liquid from source to destination Circulate liquid around a system
- 4. INTRODUCTION Main pump components Pumps Primemovers: electric motors, diesel engines, air system Piping to carry fluid Valves to control flow in system Other fittings, control, instrumentation End-use equipment Heat exchangers, tanks, hydraulic machines
- 5. INTRODUCTION Pumping System Characteristics Head Resistanceof the system Two types: static and friction Static head Difference in height between source and destination Independent of flow Destinati on Source Stati c Hea d Stati c Hea d Flo w
- 6. INTRODUCTION Pumping System Characteristics Statichead consists of Static suction head (hs): lifting liquid relative to pump center line Static discharge head (hd) vertical distance between centerline and liquid surface in destination tank Static head at certain pressure Head (in feet) = Pressure (psi) x 2.31 / Specific Gravity
- 7. INTRODUCTION Pumping System Characteristics Friction head Resistance to flow in pipe and fittings Depends on size, pipes, pipe fittings, flow rate, nature of liquid Proportional to square of flow rate Closed loop system only has friction head (no static head) Friction head Flow
- 8. INTRODUCTION Pumping System Characteristics Inmost cases: Total head = Static head + friction head System Head Flow Static head Friction head System Curve System head Flow Static head Friction head System curve
- 9. INTRODUCTION Pumping System Characteristics Pump performancecurve Relationship between head and flow Flow increase System resistance increases Head increases Flow decreases to zero Zero flow rate: risk of pump burnout Head Flow
- 10. INTRODUCTION Pumping System Characteristics Pump operatingpoint Duty point: rate of flow at certain head Pump operating point: intersection of pump curve and system curve Flow Head Static Head Pump Performance Curve System Curve Pump Operating Point
- 11. INTRODUCTION Pumping System Characteristics Pumpsuction performance (NPSH) Cavitations or vaporization: bubbles inside pump If vapor bubbles collapse Erosion of vane surfaces Increased noise and vibration Choking of impeller passages Net Positive Suction Head NPSH Available: how much pump suction exceeds liquid vapor pressure NPSH Required: pump suction needed to avoid cavitation Industrial Energy Division
- 12. TYPE OF PUMPS PumpClassification Classified by operating principle PUMPS DYNAMIC CENTRIFUGAL SPECIAL EFFECT OTHERs (e.g. Impulse, Buoyancy) POSITIVE DISPLACEMENT ROTARY INTRERNAL GEAR EXTERNAL GEAR LOBE SLIDE VANE RECIPROCATING
- 13. TYPE OF PUMPS PositiveDisplacement Pumps For each pump revolution Fixed amount of liquid taken from one end Positively discharged at other end If pipe blocked Pressure rises Can damage pump Used for pumping fluids other than water
- 14. TYPE OF PUMPS PositiveDisplacement Pumps Reciprocating pump Displacement by reciprocation of piston plunger Used only for viscous fluids and oil wells Rotary pump Displacement by rotary action of gear, cam or vanes Several sub-types Used for special services in industry
- 15. TYPE OF PUMPS Dynamicpumps Mode of operation Rotating impeller converts kinetic energy into pressure or velocity to pump the fluid Two types Centrifugal pumps: pumping water in industry – 75% of pumps installed Special effect pumps: specialized conditions
- 16. TYPE OF PUMPS Centrifugal Pumps Howdo these work? Liquid forced into impeller Vanes pass kinetic energy to liquid: liquid rotates and leaves impeller Volute casing converts kinetic energy into pressure energy
- 17. TYPE OF PUMPS CentrifugalPumps Rotating and stationary components
- 18. TYPE OF PUMPS CentrifugalPumps Impeller Main rotating part that provides centrifugal acceleration to the fluid Number of impellers = number of pump stages Impeller classification: direction of flow, suction type and shape/mechanical construction Shaft Transfers torque from motor to impeller during pump start up and operation
- 19. TYPE OF PUMPS CentrifugalPumps Casings Functions Enclose impeller as “pressure vessel” Support and bearing for shaft and impeller Volute case Impellers inside casings Balances hydraulic pressure on pump shaft Circular casing Vanes surrounds impeller Used for multi-stage pumps
- 20. ASSESSMENT OF PUMPS Step1: Measure power consumed by the pump or power input Or, we can measure Voltage, Current and Power Factor and calculate power as follows: Power consumption (P) in kW = √3 × V × I ×Cos Φ Where, V = Voltage, I = Current and Cos Φ = Power Factor Step 2: Calculate the combined efficiency of pump and motor using following equation: Combined efficiency of pump and motor (%) = M × 9.81 × h × 100 %/ (P × 3600) Where, P = Power Input (kW), M = Fluid Flow (m3/Hour), h = Total differential head (mWC) Step 3: Use the following equation to determine pump efficiency: Pump Efficiency (%) = Combined Efficiency × 100%/ Motor Efficiency = M × 9.81 × h × 100%/ (Motor Efficiency × P × 3600) Step 4: We can also determine a KPI (Key Performance Indicator) for the pump system as: Specific power consumption = Power Consumption (kWh) /Fluid Flow (m3/Hour)
- 21. ASSESSMENT OF PUMPS Difficultiesin Pump Assessment Absence of pump specification data to assess pump performance Difficulties in flow measurement and flows are often estimated Improper calibration of pressure gauges & measuring instruments Calibration not always carried out Correction factors used
- 22.
- 23. ENERGY EFFICIENCY OPPORTUNITIES Selecting theright pump Controlling the flow rate by speed variation Pumps in parallel to meet varying demand Eliminating flow control valve Eliminating by-pass control Start/stop control of pump Impeller trimming
- 24. ENERGY EFFICIENCY OPPORTUNITIES 1. Selectingthe Right Pump Pump performance curve for centrifugal pump
- 25. ENERGY EFFICIENCY OPPORTUNITIES 1. Selectingthe Right Pump Oversized pump Requires flow control (throttle valve or by-pass line) Provides additional head System curve shifts to left Pump efficiency is reduced Solutions if pump already purchased VSDs or two-speed drives Lower RPM Smaller or trimmed impeller
- 26. ENERGY EFFICIENCY OPPORTUNITIES 2. ControllingFlow: Speed Variation Explaining the effect of speed Affinity laws: The affinity law describes the relations between power, head and flow with speed for centrifugal pumps. The laws are: Flow is directly proportional to Speed : Q N Head is directly proportional to square of Speed : H N2 Power is directly proportional to cube of speed : P N3 Where, Q = Flow Rate, H = Head, P = Power and N = Pump Speed Small speed reduction (e.g. ½) = large power reduction (e.g. 1/8)
- 27. ENERGY EFFICIENCY OPPORTUNITIES 2. ControllingFlow: Speed Variation Variable Speed Drives (VSD) Speed adjustment over continuous range Power consumption also reduced! Two types Mechanical: hydraulic clutches, fluid couplings, adjustable belts and pulleys Electrical: eddy current clutches, wound-rotor motor controllers, Variable Frequency Drives (VFDs)
- 28. ENERGY EFFICIENCY OPPORTUNITIES 2. ControllingFlow: Speed Variation Benefits of VSDs Energy savings (not just reduced flow!) Improved process control Improved system reliability Reduced capital and maintenance costs Soft starter capability Industrial Energy Division
- 29. ENERGY EFFICIENCY OPPORTUNITIES 3. ParallelPumps for Varying Demand Multiple pumps: some turned off during low demand Used when static head is >50% of total head System curve does not change Flow rate lower than sum of individual flow rates
- 30. ENERGY EFFICIENCY OPPORTUNITIES 4. EliminatingFlow Control Valve Closing/opening discharge valve (“throttling”) to reduce flow Head increases: does not reduce power use Vibration and corrosion: high maintenance costs and reduced pump lifetime
- 31. ENERGY EFFICIENCY OPPORTUNITIES 5. EliminatingBy-pass Control Pump discharge divided into two flows One pipeline delivers fluid to destination Second pipeline returns fluid to the source Energy wastage because part of fluid pumped around for no reason
- 32. ENERGY EFFICIENCY OPPORTUNITIES 6. Start/ Stop Control of Pump Stop the pump when not needed Example: Filling of storage tank Controllers in tank to start/stop Suitable if not done too frequently Method to lower the maximum demand (pumping at non-peak hours)
- 33. ENERGY EFFICIENCY OPPORTUNITIES 7. ImpellerTrimming Changing diameter: change in velocity Considerations Cannot be used with varying flows No trimming >25% of impeller size Impeller trimming same on all sides Changing impeller is better option but more expensive and not always possible
- 34. ENERGY EFFICIENCY OPPORTUNITIES 7. ImpellerTrimming Impeller trimming and centrifugal pump performance
- 35. ENERGY EFFICIENCY OPPORTUNITIES Comparing EnergyEfficiency Options Parameter Change Control Valve Trim Impeller VFD Impeller Diameter 430 mm 375 mm 430 mm Pump Head 71.7 m 42 m 34.5 m Pump Efficiency 75.1% 72.1% 77% Rate of Flow 80 m3/hr 80 m3/hr 80 m3/hr Power Consumed 23.1 kW 14 kW 11.6 kW
- 36.