Acromet WG-602 Manual
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Contents
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406.1.3 Setting Proportional FactorProportional control of chemical dosing requires configuration according to various factors. The primaryfactors are the ratio between the system size and the rate the chemical dosing systems can feedchemicals, and the delay time between when the chemical level changes and when it is sensed by thecontroller.In large systems, changes in chemical levels occur slowly. The dosing systems must feed large amountsof chemicals for a long period of time in order for a change to be noticed. The chemicals also disperseslowly in larger systems. Smaller systems, on the other hand, react much more quickly.The length of time between the change and when the controller identifies the change also affectsproportional control. The controller can only identify water chemical levels after they have been distributedthroughout the system and have returned to the analyzer. This may be a long time after the chemicalswere released into the water. The controller, therefore, recognizes the chemical levels from dosingsettings in the past. The dosing systems continue feeding chemicals during this delay, causing chemicallevels to pass the set point, resulting in fluctuations.To prevent these fluctuations, the controller must reduce chemical dosing rates as it senses that chemicallevels are approaching the set point, taking the delay into account. The controller should also notovercompensate for the delay, which would cause chemical levels.In short, the larger the water system, the higher the p-factor.6.1.4 Setting Pump PeriodPump period is a single cycle during which the dosing pump operates and then rests. Proportional controldivides the pump period into two distinct phases: active and at rest.In general it is recommended to operate in a short cycle, i.e., 00:30 Sec. For large systems, or if youactivate solenoid valves, you may consider longer pump periods.6.1.5 Step By Step Proportional Settings1) Finish the installation of all controllers (electrical, water, feeding systems, and electrodes).2) Calibrate the controller to the water chemical values at the sample point.3) Set the proportional factor and the pump period of the chlorine and the pH at an initial setting.4) Let the controller operate the chlorinator and the pH correction devices and make sure that chemicalsare injected into the water.5) Watch the chlorine and pH as they change. We recommend that you record the values frequently sothat the process is closely monitored.a) If the values greatly exceed the set point, you need to decrease the proportional factor.b) If it takes too long to get to the set point, you need to increase the proportional factor.Note: In large systems the delay time between injection of the chemicals and receiving the change inthe controller can be very long (30 minutes or more). |
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