Timer-controlled dosing

Timer-controlled systems are simple, low-cost systems which involve timing of flow through an orifice. Most include a sight glass or other means of checking the amount batched. A number of variables, such as changes in power supply, constriction of the measuring orifice and increased viscosity of the admixture can introduce considerable error. Timer-controlled units must be recalibrated frequently, and the plant operator must be alert to verify the proper admixture dose by observation of the calibration tube. They have been successfully used with... 

In reality, often the only practical benefit of using timer-controlled biocide dosing equipment is the increased assurance it provides, in that the biocide(s) will actually be dosed to the cooling system at the planned time and for the planned duration. If this is of vital concern to the operator or mandated by regulations, then so be it. 

The use of a chemical agent as an anti-foam is affected by an on-off algorithm with variable dosing time and time delay. If the presence of foam is detected, then the controller first activates a delay timer. This type of foam controller works with some delay and variable dosing time. If at the end of the delay period the foam is still present, then the dosing pump is activated and chemical agent is added to the bioreactor. If the foam is still detected at the end of this period, the combined system of delay and dosing is reactivated. With this method of controller, addition of any unnecessary anti-foam is prevented. 

To measure the rate of burning, fine wires of some low-melting metal (fuze wire) were threaded thru holes drilled diametrically thru the strand at accurately measured intervals (eg, 1r ). Two or more wires were used. Each wire was attached in series with an electric timer. The strand was mounted in a holder and placed vertically inside a dosed chamber. A given initial pressure was established in the chamber by using high, pressure N2. The initial temp was controlled by means of a constant-temp bath, and ignition of the strand was accomplished by means of a hot wire wrapped around it at one end... 

Feed is by electrically driven pump which is controlled by a timer. Dose control is not positive and frequent calibration is necessary to overcome effects of slight blockages by sedimentation, variations in viscosity and variations in power supply. The cheapest automatic system. 

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