Sulzer ABS PC 441 - Page 29

81307063I
EN
25
Logic used to calculate the pump capacity
First pump starting.
Whenthestartleveloftherstpumpisreached,thelastknown
lteredvalueoftheinowisstoredinthememory.
Afteranadjustabletime-delaytheactualpumpcapacitymeasured
bycalculatingthespeedofleveldecreasingtimesthestationpit.
Thetimedelayistheretoenablethepumpandsystemtoreachfull
capacitybeforeconductingthemeasurement.
Thepumpcapacitycalculationtimeisalsoavaluethatcanbeset/
adjusted.Thetimeneededtoachieveanaccuratevaluewilldepend
onparameterslikeforinstance:sizeofbasin,typeofpumpandthe
collectionnetworkdesigntomentionafew.
Logic used to calculate the outflow during a pump cycle
Theoutowcalculationisbasedonthecalculatedpumpcapacitytimestherunninghoursofthepump.To
enhancetheaccuracyevenfurtherthepumpcurveforeachpumpcanbeentered.Thecurveisthenusedto
adjustthecalculatedvaluetomatchtheactualhead.Whentheleveldropstheheadincreasesandmostlyalso
thepumpcapacity.Thiswillthenbeadjustedinaccordancetothepumpcurvedataentered.Ifconnectedtoa
VFD,therpmcanalsobeusedtocompensatetheoutowcalculation.
Logic used to re-calculate the inflow during a pump cycle
Asearliermentionedtheinowiscontinuouslycalculatedbasedonthelevelchangepertimeunitwhenno
pump is running.
Whenoneorseveralpumpsarerunningthecontrollerknowstheassumedoutowbasedonthecalculated
pumpcapacityandifenteredalsoadjustedtothepumpcurve,systemcurveandrpm.Thisnowmeansthat
thecontrollerknowswithwhatratethelevelshoulddecreasebasedonthepumpcapacityalreadycalculated.
Iftheleveldecreaseswithaslowerrateitisthenassumedthattheinowhasincreasedtobalancethecalcula-
tion.
Thecalculatedoutowisalsoafunctiononnumberofpumpsrunning.
Calculation scenarios when a new pump capacity value is NOT accepted
Basic calculation rules
1. The level must be between the high and low level set-points.
2. Thepumpcapacitycalculationsequencestartswhenthepump
start signal is given. The level value after a conducted measurement
must be below that point.
Basis for the calculation of indicated pump capacity
1. Fiverollingmeasurementsarecontinuouslyperformed,where
the two with highest deviation is deleted.
2. Basedonthreevaluesleftisanaveragecapacityvaluecalculated.
3. Shownarethefollowingcalculatedvalues:
• Nominalcapacity(averageofthe3outof5calculations).
The nominal value is used for the alarm handling.
• Lastpumpcapacity(lastperformedcalculation)
• Averagecapacitytodaytosevendaysago