Content
# Well #21 & Reservoir 2
140610
Adding Well #21 to SCADA
Control Narative
Control well based on tank level, rate of tank level drop
Objective is to only run the well when water is leaving the tank.
Using Rate of Change calculation from an ALMA block in the PLC.
- Start well 21 if ROC is not positive for 10 min and Res 2 level is between the Well 21 on and off setpoints.- Stop well 21 if ROC is positive for 10 min or Res 2 level reaches the Well 21 off setpoint.
Chloramination control- Start hypo and ammonia pumps when well starts.
Monitor-
Well flow rate (well running when flow > sp)
Tank 2 level
Hypo pump pulse
Ammonia pump pulse
Existing wiring from the well to Block Wall
Flow signal
120 V Start signal
I/O Needed-
| Type | Tag | Terminal(s) | PLC Point | SCADA Tag |
| --- | --- | --- | --- | --- |
| DI | HYPO_PLS | | | |
| DI | AMNA_PLS | | | |
| DO | WELL_CALL | | | |
| DO | CHEM_CALL | | | |
| AI | WELL_FLOW | | | |
PLC IP
192.168.100.130
Radio IP
192.168.100.230
Comms
W4 PLC handles communication and control.
Reads N17:0 to N17:9
Stores in R2_Read
Writes R2_Write 0-9
Stores in N16:0
Flow rate calculation
Flow meter range 0-1000 gpm
AI range 6250 - 20000 (13750)
Rate Of Change control
Using a ALMA alarm block in RSLogix to calculate the ROC of Res 2 in inches per second.Instruction Help:Calculated rate-of-change of the In value. This value is updated when the instruction is scanned following each elapsedROCPeriod. The ROC value is used to evaluate the ROCPosInAlarm and ROCNegInAlarm conditions.ROC = (current sample of In – previous sample of In) / ROCPeriod.
HMI Notes
Add indicators for W21.Chemical_Pump_Failure and General Alarm W21_Gen_ALM
Setpoint for W21.Delay_Timer[0].pre
Indicator for W21.Delay_Timer[0].acc
Indicator for R2_Write[0].4 (Well start d.o.)
Indicator for R2_Write[0].5 (Chem start d.o.)
Indicator for local hoa
Alarms
Well Fail W21_Failure_Alarm.InAlarm
Ammonia Pump Fail W21_Ammonia_Failure.InAlarm
Chlorine Pump Fail W21_Chlorine_Pump_Failure.InAlarm