Closed cooling systems

To maintain environmental impact at a minimum, cooling-tower systems must be designed to abate both thermal and chemical pollution in blowdown stream. The latter is accomplished by treating blowdown prior to discharge or reuse. Sedimentation and other methods prepare blowdown streams for discharge to the natural environment. Evaporation or reuse permits a closed cooling system. 

Its use in formulations rapidly increased in the 1970s and 1980s, as that of chromate began to decrease, and it is now widely used in both open and closed cooling systems. However, molybdenum is expensive, and some negative publicity concerning U.S. environmental acceptability in recent years (mostly ill-founded) has done little to improve its image or reduce its price. 

Sodium nitrite is incorporated into formulations for both open and closed cooling systems and acts as an anodic inhibitor. It is a good passivator but requires a relatively high dose rate to ensure that all anodic areas within a system are protected from the risk of pitting corrosion. The dose rate has to be increased when high chlorides or sulfates are present. 

Use Closed cooling systems particularly diesel engines, cooling tower systems. 

Most cooling towers are open-recirculating types in which heat rejection mainly is accomplished by evaporation of water. There also are closed cooling systems (of which an automobile radiator would be typical), from which heat is dissipated by the forced flow of air across radiation sections. In some combination systems, heat from closed cooling circuits is transferred through heat exchangers into circulating water which is cooled by evaporative systems. 

Concentration Cells. Locations encouraging such attack are common in closed cooling systems. Consider metals riveted together, as in Figure In the crevice. 

Some of the amine type emulsifiers and inhibitors are potentially destructive to copper alloys in the circulating system, also. One other type inhibitor that has been used effectively for many years in closed cooling systems is generically identified as "borate-nitrate." These combinations use sodium nitrite, buffered by alkaline borates, and silicates with supplemental inhibitors such as mercaptobenzothiazole, thiazole or benzo-... 

The corrosion testing techniques described can also be used in closed cooling systems, once-through cooling systems, boiler feed water systems, etc. 

Electrode holders with a closed cooling system have proven themselves very well in practice in a number of cooling designs. They work largely without any problems however it is imperative to pay extremely close attention to the cooling water quality. Water treatment and water recirculation systems are required to prevent build up in the internal cooling chamber of the electrode and reduce cooling costs. 

When microorganisms are involved in the corrosion of metals, the situation is more complicated than for an abiotic environment, because microorganisms not only modify the near-surface environmental chemistry via microbial metabolism but also may interfere with the electrochemical processes occurring at the metal-environment interface. Many industrial systems are likely to contain various structures where MIC and biofouling may cause serious problems open or closed cooling systems, water injection lines, storage tanks, residual water treatment systems, filtration systems, different types of pipes, reverse osmosis membranes, potable water distribution systems and most areas where water can stagnate. 

The exciter can be provided with either an open or a closed cooling system. 

With a closed cooling system, the filter housing is replaced with supply and exhaust air channels connected to the cooler housing of the generator. 

If the reactor has a closed cooling system, it is recommended to use a thermal conductance type level meter composed by an electric heater and a differential thermocouple, to measure the liquid level inside of the reactor vessel. This method does not have good accuracy to determine precisely the level position, however, it is the safest way to assure that the reactor core is covered by the cooling liquid. 

Since most of the research reactors are open type reactors, usually only two values of pressure are measured, the "underpressure" in the reactor room, and the pressure in the pneumatic system. When the reactor has a closed cooling system, the pressure in the cooling system is also measured. Pressure transmitters are divided into two parts, the sensor (called primary element), and the conditioning circuit. The primary element is an elastic mechanical component which is used to transform pressure (or differential pressure) into displacement (proportional to the pressure), and the conditioning circuit is used to transform displacement into an electronic signal. Usually the transmitter is... 

---