Closed loop system dosing

Nevertheless, there are still some cooling systems (especially closed-loop systems) that do not receive any form of chemical inhibitor dosing or other treatment. This situation typically persists because the operator either remains uneducated or skeptical concerning the benefits and cost-effectiveness of water treatment or relies on low-cost labor to provide regular manual cleaning. 

Many closed-loop hot/cold/chilled water systems are not treated, perhaps due to the mistaken notion that treatment is not required. Only when severe corrosion and fouling/blockages problems occur is something done, by which time it is normally too late to fully recover the situation. Closed-loop systems should always be cleaned, passivated, and treated. Treatment is most usually applied by means of a dosing pot (bypass feeder) installed on a bypass line. Some operators also install sidestream filters to remove suspended iron oxide. This is most probably not necessary if the... 

Isothiazoline is a widely used biocide, but it is not effective against anaerobic bacteria. It is deactivated by hydrogen sulfide leaks. Also, do not dose to closed systems (because of the presence of 0.2% copper and 2 to 3% magnesium salts, which are used as product stabilizers and can increase the risk of galvanic corrosion). Additionally, the high pH of closed-loop systems will hydrolyze isothiazoline. Automated feed systems may be useful for dosing isothiazolines due to the severe skin irritant nature of this material. 

Bohm, S., Timmer, B., Olthuis, W., Bergveld, P., A closed-loop controlled elec-trochemically actuated micro-dosing system. J. Micromech. Microeng. 2000, 10, 498-504. 

Absorption rate coefficients and permeability values obtained through different systems, i.e. in vitro or in situ, finally are determined with the objective in mind of predicting the fraction of a dose that will be absorbed through the intestine when the drug is orally administered. In order to use the data obtained in those systems it is essential to validate them properly. The present section reviews the capability of the parameters representatives of the absorption determining with different techniques to predict in vivo drug absorption in absence of any limited step (as dissolution or solubility) by means of the previously described model and Eq. (16). In particular, the absorption rate constant obtained with an in situ close loop assay, permeability through Caco-2 cell lines, and PAM PA models have been examined. 

Bohm S, Timmer B, Olthuis W, Bergveld P (2000) A closed-loop controlled electrochemically actuated micro-dosing system. J Micrmnechan Microeng 10 498-504... 

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