Cooling system protection

After inspection and completion of required service, determine capacity of the cooling system from a cooling system protection chart or car owner s manual. A 50% concentration (—34°F [—37°C] freezing protection) is generally recommended. 

Motor with secondary cooling system protection against most solid material and splashing water... 

Safety. A large inventory of radioactive fission products is present in any reactor fuel where the reactor has been operated for times on the order of months. In steady state, radioactive decay heat amounts to about 5% of fission heat, and continues after a reactor is shut down. If cooling is not provided, decay heat can melt fuel rods, causing release of the contents. Protection against a loss-of-coolant accident (LOCA), eg, a primary coolant pipe break, is required. Power reactors have an emergency core cooling system (ECCS) that comes into play upon initiation of a LOCA. 

Filtration and water-knockout systems are used to clean up the gas before it enters a compressor. Cooling systems are sometimes required to maintain compressor discharge temperatures below 54°C to avoid damage to the pipeline s protective coatings. Automated compressor stations are typically staffed by maintenance and repair personnel eight hours per day, five days per week. Other stations are staffed on a 24-hour basis because personnel must start, stop, and regulate compressors in response to orders from the dispatch office. 

Theoretically, controUed deposition of calcium carbonate scale can provide a film thick enough to protect, yet thin enough to allow adequate heat transfer. However, low temperature areas do not permit the development of sufficient scale for corrosion protection, and excessive scale forms in high temperature areas and interferes with heat transfer. Therefore, this approach is not used for industrial cooling systems. ControUed calcium carbonate deposition has been used successhiUy in some waterworks distribution systems where substantial temperature increases are not encountered. 

Silicates. For many years, siUcates have been used to inhibit aqueous corrosion, particularly in potable water systems. Probably due to the complexity of siUcate chemistry, their mechanism of inhibition has not yet been firmly estabUshed. They are nonoxidizing and require oxygen to inhibit corrosion, so they are not passivators in the classical sense. Yet they do not form visible precipitates on the metal surface. They appear to inhibit by an adsorption mechanism. It is thought that siUca and iron corrosion products interact. However, recent work indicates that this interaction may not be necessary. SiUcates are slow-acting inhibitors in some cases, 2 or 3 weeks may be required to estabUsh protection fully. It is beheved that the polysiUcate ions or coUoidal siUca are the active species and these are formed slowly from monosilicic acid, which is the predorninant species in water at the pH levels maintained in cooling systems. 

Corrosion Inhibition. Another important property of antifreeze solutions is the corrosion protection they provide. Most cooling systems contain varied materials of constmction including multiple metals, elastomeric materials, and rigid polymeric materials. The antifreeze chosen must contain corrosion inhibitors that are compatible with all the materials in a system. Additionally, the fluid and its corrosion inhibitor package must be suitable for the operating temperatures and conditions of the system. 

Sodium benzoate is also finding increasing appHcation as a corrosion inhibitor. It is incorporated into paper wrapping materials for the prevention of mst or corrosion in the production of such diverse items as razor blades, engine parts, bearings, etc. It is also used in the automotive industry as a corrosion inhibitor in engine cooling systems (at 1.5%), mainly in Europe and Japan. Unlike in its appHcation as a preservative where free benzoic acid is required to provide antimicrobial action, it appears to be the benzoate ion that provides the corrosion protection. 

Figure 1.18(a) Screen protected drip proof (SPDP) squirrel cage motor (Cooling system ICOA1)... 

Figure 1.18(d) Cross-sectional view of a large screen protected motor showing the cooling circuit (Cooling system ICOA1) (Courtesy NGEF Ltd)... 

Provision of efficient drift eliminators of water cooling towers consideration of replacement by air cooling systems. Thermal insulation to protect personnel from contact with hot or cold surfaces prevention of water supply disruption by freezing. 

External events are accident initiators that do not fit well into the central PSA structure used for "internal events." Some "external events" such as fire due to ignition of electrical wires, or flood from a ruptured service water pipe occur inside the plant. Others, such as earthquakes and tornados, occur outside of the plant. Either may cause failures in a plant like internal events. External initiators may cause multiple failures of independent equipment thereby preventing action of presumably redundant protection systems. For example, severe offsite flooding may fli 1 the pump room and disable cooling systems. An earthquake may impede evacuation of the nearby populace. These multiple effects must be considered in the analysis of the effects of external events. 

Solar radiation may fall on outside walls or roofs, raising the skin temperature, and this must he taken into account. Most cold stores are huilt within an outer envelope which protects them from the elements and from direct sunshine. In cases where the insulation itself is subject to solar radiation, an allowance of 5 K higher outside temperature should he taken. Heat load must he estimated through all surfaces including piping, ducts, fan casings, tank walls, etc., where heat flows inwards towards the cooled system. 

Because of their surfactant and filming properties fatty amines such as coco-alkylamine acetate (and more especially diamines, such as tallow propylenediamine) are also occasionally employed in other types of water treatment programs. For example, they may be used as corrosion inhibitors for steel cooling systems, especially those smaller units where minimal operational control is provided. The amines must be continuously dosed to ensure good film formation (and thus corrosion protection), typically at 5 to 10 ppm active amine. They also tend to have good biostatic control properties, which provide a benefit of algal and bacterial control at no extra cost. 

C12-0085. What molality of ethylene glycol is required to protect the water in an automobile cooling system from freezing at - 20 ° C ... 

Lower chemical reactivity with non-target molecules is useful for another performance-related reason. Microorganisms prefer the protection and luxuriant environment in biofilms (the adherent microbial communities that cause detrimental surface-fouling effects in water cooling systems). Most (>99%) of the viable microorganisms in industrial systems are found in biofilms, not floating around freely in the bulk recirculating water. Compared to unstabilized chlorine or bromine, STABREX more effectively removes and disinfects biofilms as shown in Table 6. 

A measure is preventive if it prevents the occurrence of a runaway, a decomposition, or a hazardous secondary reaction. The system conditions remain close to operating conditions. Excessive increases in temperatures and/or pressures are avoided. Preventive measures include feed rate control systems, interlocks to prevent the reaction from starting unless sufficient diluent is present or the cooling system is working, and tests for the presence of catalysts or unwanted impurities. Preventive measures are always to be preferred over protective or mitigating (defensive) measures. 

Antifreeze. Any compound or mixture that lowers the freeing point of water can be referred to as antifreeze. The preponderant, commercial antifreeze is ethylene glycol diluted with water. Other organic compounds used occasionally are methanol, ethanol, and propylene glycol. The primary application is to protect automotive cooling systems from freezing. 

To increase equipment reliability and plant efficiency, corrosion inhibitors are used in boiler and cooling water programs to control fouling and deposition on critical heat-transfer surfaces. In cooling systems, corrosion inhibition is commonly achieved through the use of passivators, which encourage the formation of a protective metal oxide film on the metal surface ( 1). ... 

This ASTM manual has been developed by Committee D-15 on Engine Coolants and is a revision to ASTM Special Technical Publication (STP) 120B. This publication provides consumers with practical information and advice on engine coolants as well as cooling system chemicals, such as cleaning compounds and practices, antirusts, and stop-leaks. This fourth edition presents new information on coolants containing silicates for the protection of aluminum components in today s engines. 

Laws have been enacted in many states in an attempt to prevent the sale and distribution of deleterious antifreeze products, such as salt solutions or petroleum coolants. Even ethylene glycol engine coolants must be evaluated by testing and comparison of test results with specifications for engine coolant concentrate, such as ASTM D 3306. These tests ensure desired levels of antifreeze coolant concentrate and inhibitor are available to adequately protect cooling systems against freezing, boilover and corrosion (Fig. 2). 

Recent surveys have shown that over-concentration and under-concentration are common sources of cooling system problems. A minimum concentration of 33 1/3% is required to provide minimal corrosion protection. Maximum freeze protection is obtained at 68% by volume. Concentrations over 68% will adversely affect heat transfer, raise freezing point, and may cause inhibitors to precipitate from the coolant when the engine is operating. 

Automobile engine coolant systems properly protected by engine coolant meeting specification ASTM D 3306 do not require use of supplemental additives. Major coolant manufacturers discourage use of these supplements with their coolant in automobile cooling systems. 

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