25 May 2005
Water-Cooled Diesel Engine Cooling Systems. Water-cooled diesel
engine cooling systems are used mainly on large engines. The jacket cooling water
passes through a heat exchanger, rather than a radiator, where a separate cooling
water loop removes the heat from the jacket cooling water. These systems commonly
Vapor-Phase Diesel Engine Cooling Systems. Vapor-phase diesel
engine cooling systems, also called ebullient systems, use water that is heated to a
temperature at the boiling point or above the boiling point for pressurized systems.
Steam is formed from the cooling water as it removes heat from the system. The steam
produced in this way can be recovered and used for space heating. This type of system
requires significant amounts of makeup water and chemical treatment.
WATER TREATMENT FOR CLOSED SYSTEMS. Water treatment
programs for both closed hot water and closed chilled water systems are developed
primarily to control corrosion, although the programs may also control deposition and
microbiological organisms. If needed, scale deposition can be prevented by external
treatment (i.e., ion exchange softening) or can be controlled with inhibitors as described
in Chapter 4. Corrosion must be completely controlled by water treatment programs. If
corrosion occurs, corrosion products will eventually plug the system, resulting in
decreased operational efficiency and the need for cleaning. Microbiological growth is not
a concern in hot water systems, but can occur in chilled water systems and should be
controlled (see paragraph 5-2.3).
Makeup Water Requirements. Makeup water requirements for closed
systems are very small unless there are leaks in the system (see paragraph 5-2.4).
Closed systems should not be drained or purged unless there is evidence that indicates
the need to remove dirty water or sludge. For proper operation, makeup water in high-
temperature and medium-temperature water systems is deaerated (de-oxygenated)
using both mechanical and chemical methods and is also softened. Oxygen can be
removed from low-temperature water systems either chemically or mechanically to
prevent oxygen-induced corrosion. Chilled water systems can require partial softening if
the makeup water exceeds 250 ppm total hardness (as CaCO3). The makeup water
requirements are monitored carefully in systems of all types (see Table 5-1). If there is
an increase in the quantity of makeup water required, the leak should be found and
repaired quickly. After the repair, water treatment chemicals should be replenished