Standard Controlling and Dosing Systems
An essential task of water treatment is to condition industrial water, also known as internal treatment or correcting treatment. During operation the quality of the water changes. This could be caused by for instance the introduction of dirt and loading of corrosion products, thickening, emerging of gases, chemical reactions, contamination by contact with products or the increase of micro-organisms. The internal water treatment is aimed at maintaining an economic, ecological and disturbance-free operation by taking internal measures. Hereby, the most important tasks are:
- to avoid mineral sediments
- to minimize the corrosion of materials
- to control the biological growth
The internal treatment consists basically of measurement, control and dosing technologies. The most important controlling value is the electrolytic conductivity, a measure for the concentration of dissolved salts. Further controlling values could be the pH value and the redox potential. For specific problems process titrators or process photometers are used. Dosage can be done proportionally to quantities, time-controlled of dependent on quality.
For frequently ocurring problems standard systems are applied, as described in this product information. WAT systems are designed in modules so that they can easily adapted to specific problems of the plants. They consist of a high-quality dosing technology, well-proved control devices having manyfold functions (see also product information WAT Pilot 3) and having a high safety standard. The measuring and controlling technologies take all legally fixed prevailing conditions into consideration and meets the state-of-the-art standard of technology. The most important tasks for conditioning with standard controlling and dosing systems are:
Areas of Application
Open cooling-down plants
It is our task to lastingly make a disturbance-free, economic and ecological operation possible, i. e. free from mineral and microbiological sediments, sparing all materials existing in the cooling system and saving water by using environmentally compatible working materials. The technological standard to avoid mineral sediments is the so-called threshold stabilization. Thereby, active agents in small concentrations are added to the feed water proportionally to the amount, so that they prevent the cristallization of slightly soluble contents even at a high degree of supersaturation and, moreover, they protect metallic materials from corrosion. But the permissible salt content is limited so that a calculated maximum thickening factor must not be exceeded.
By a permanent monitoring of the electrolytic conductivity salt is added dependent on the quality and feed water having a dosage of hardening stabilizers and corrosion inhibitors that depends on the amounts of water is added to the circulating water. For a bacteriological control bactericides are added to the circulating water in intervals that are controlled by a timing programme. In order to avoid the loss of agents and the pollution of sewage there is a preliminary salting followed by salt blocking (WHG § 7a, appendix 31).
Air cleaner, air moistening
The conditioning of circulating water in air cleaners for air conditioning is basically done in a similar way. But there are higher requirements as to the quality of the circulating water. The protection from corrosion is mostly of minor significance, on the other hand there are hygienic requirements, toxicological security and the avoidance of salty aerosols coming into the fore (VDI 6022). Replacing or in addition of the bactericide dosing usually a bacteriological control is performed by ultraviolet degermation.
Feed water for steam generators
The most essential tasks during the boiler operation for generating steam are the stabilization of the residual hardness, the correction of the pH value, the dispersion of iron compounds and the chemical binding of residual oxygen . It might be also necessary or advisable to protect the steam and condensate systems from corrosion. The conditioning of the feed water is usually performed by a dosage proportional to the amount of water.
Feed water for closed circles
The protection from corrosion is the most important task in closed cold water circulations and in warm water heating plants. (For avoiding the emergence of stones see VDI 2035). The dosage is done proportionally to the amount of the additional water feeded in, the dosing pump is externally controlled by impulses given by the water meter.
Conditioning of drinking water
Drinking water having a higher content of alkaline-earth ions tends to produce scales in warm water generators and sanitary facilities, whereas soft water tends to an increased corrosion of materials. The drinking water systems could be protected by a dosage of suitable and for the application with drinking water admissible agents in proportional amounts. (So-called physical water treatment devices produce pulp matters and should be not used if drinking water is to be used as feed water for industrial water systems.)
