Pump Operating System
It is important to note that a pump station and pumping system have many important design
considerations withaviewto focuson aspectsthat directly contribute to its energy efficiency and life
cycle costing. While on this, station loss in a pump system is considered to be a very important key
factor in computing pump parameters for selecting suitable pump(s) for the system.
It is experienced that in many cases, Engineers as an act of conservativeness consider safety factors
while designing pumping Station resulting adverse impact to the operating system.
1. Safety Factor: Unnecessary safety factor drastically change the pattern of system curve affects
selectionof pumpswhich are tooperated awayfrom BEP resultinglossof energyinthe system.
Thisaspect triggersdispute amongstthe buyerandseller where buyer wrongly interpret pump
parameters to the seller and install over or undersized pumps in the system.
The Hazen-Williams equation is assumed to be relatively accurate for piping systems with
Reynolds Numbers above 105 (turbulent flow).
1 ft (foot) = 0.3048 m
1 in (inch) = 25.4 mm
1 gal (US)/min =6.30888x10-5 m3/s = 0.227 m3/h = 0.0631 dm3(liter)/s = 2.228x10-3 ft3/s =
0.1337 ft3/min = 0.8327 Imperial gal (UK)/min
2. SelectionofPump: It mustbe notedthat the patternof pumppowercurve has risingtrend with
the flow capacity in case of Radial Type Centrifugal pumps with low specific speed range.
Therefore,wrongselectionof oversized pumps will not only attract higher power but will limit
the range of operation that not fulfill the requirement of operation covering minimum and
maximumwaterlevel of the system where may reach the cut off point of operating condition
because of NPSH factor.
3. Site Condition: Site demography is of key importance to draw up actual piping layout for the
system where inmanycasesit has been noticed that there are significant difference between
the design layout and physical installation that adversely impact pumping system operating
condition. Let us realize that pump sizing and dimensions are the key factors in designing the
pump house layout while its of importance for Design Team consisting of Civil, Electro-
Mechanical Engineers to consult amongst themselves in arriving at the correct design
parameters for attaining desired plant efficiency.
4. Type of Pump Station: Pumping stations are designed according to the application and site
conditionsuchas pumpingwaterfroma WaterSource such as River, Canal, Lake, Reservoir etc.
Where Horizontal Centrifugal orVertical Turbine orMixedFlow Pumpstationsare designed with
Intake ForebayorChannel forwaterintake intothe pumpingstationtakinginto account various
design conditions such as intake water flow velocity, spacing of pumps inside or pump house
consideringmultiple pumps for parallel operation in order to maintain flexibility according to
the ongoing demand and provision for future demand as well.
Channel mountedInclined pumps are also installed at the river bed in some installation those
are generallydrivenbyDiesel orElectricdrive throughangulargeardrive andnecessarythrough
bearing keeping axial thrust component in mind.
Horizontal Centrifugal Pumps of Radial type of axially split types are also installed in the said
applicationwithsuctionpipesdrawingwaterfromthe watersource where NPSH condition is of
prime importance in order to ensure that pump does not suffer due to cavitation at the
minimum water level conditions. In some extreme cases Vacuum pump sets are put in the
system prior to starting of the main intake pumps certainly at an extra cost to the project
because of certain site constraints.
The river flow varies during the year but the hydro installation is designed to take a constant
flow.If the channel overflows there will be serious damage to the surroundings. Weir is put in
the system at the upstream of the forebay in order to ensure correct flow to the pumping
channel regardlessof river isinlow or in highflow.The intake structure isdesignedtoregulate
the flow to within reasonable limits when the river is in high flow. Further regulation of the
channel flow is provided by the spillways. A Sump Model Study at the design stage is of
significant importance prior to finalization of design in order to ensure efficient operating
De-silting is a regular process which at times are neglected affecting pumping system from
smooth pumping operation and damage to pumps due to unforeseen variation water flow to
the system with sand particle those are prone to cause abrasion damage to the pumps.
Accordingto the experience itisnoticedthatpumpsattainlongerlife withmaterial combination
such as 2 TO 2.5% Nickel Cast Iron Casing with SS to CA15 Impeller, SS410/416 Shaft with SS304
Sleeveswhere CA15Material hasan unique qualitytowithstandbothcorrosive andapplication.
5. Variable Frequency Drive: VFD has its significance in the pumping system in order to ensure
Head-Flow Characteristic through speed variation according to the demand of the system
without disturbing or wasting energy due to throttling method in varying the system head
6. Surge Analysis: Surges in pipelines carrying liquids are usually caused by opening, closing or
regulatingvalvesorpumpsstartingandstopping.These surges, also called hydraulic transients
may range inimportance from a slightpressure or velocity change to sufficiently high pressure
or vacuum to rupture the piping system, to damage pumping equipment and cause extensive
shutdowntime.Waterhammer,aresultof hydraulictransients,will occur when the total surge
pressure exceedsapproximately twice the value of the static pressure in the system when the
fluid is at rest. Surge protection analysis will be performed on critical sections of the piping
systemtoverifydesignandsurge control equipmentselection.If excess transient pressures are
predicted by the analysis, design and mechanical equipment application will be modified.
Hydraulicsurge control is a specialized field. If a detailed surge protection study is required, it
should be provided by engineers or consulting engineering firms specialized in this field.
Detailed pipeline surge analysis by an expert should be considered.
7. Starting Characteristics of Pumps:In normal casespumpsare recommended to start from crack
openconditionexpectforhighspecificspeedpumps where break away torque of drive motors
have 20% of FLT inorderfor smoothstartingof pumpswithoutstalling.Inthe event of extreme
conditions of discharge valve failure of pump in parallel operation with corresponding Non
Reverse Ratchet failure in case of Vertical Pumps, pump is required to start from reverse flow
condition where the drive motors are required to start from such extreme condition. In such
cases Double Cage Squirrel type or slip ring motors are recommended with higher starting
torque characteristics that can attain to the full load speed within the desired time without
stalling and overheating.
8. Pump Motor Control System: Whenit comesto buildanenergy efficient pumping system, the
choice of the appropriate motorcontrol systemandInstrumentation Panel is crucial in order to
measure and control Hydraulic, Thermal and Electrical Parameters for smooth and
uninterrupted operation of the system. However, it is also recommended according to
experience that control system is designed with a pragmatic view so that the system is not
prone to unnecessarytrippingdue insignificantconditionsthataffectsthe continued running of
the pumping system.
For detailed study, design and Turnkey solution in pumping system, all are welcome to
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