DETROIT DIESEL 53
Fuel, Oil and Coolant Specification
13.3
ENGINE COOLANT
Engine coolant is considered as any solution which is circulated through the engine to provide the means for heat transfer
from the various engine components. In general, water containing various materials in solution is used for this purpose.
The function of the coolant is basic in the design and the successful operation of the engine and must be carefully
selected and properly maintained.
COOLANT REQUIREMENTS
A suitable coolant solution must meet the following five basic requirements:
1. Provide for adequate heat transfer.
2. Provide a corrosion resistant environment within the cooling system.
3. Prevent formation of scale or sludge deposits in the cooling system.
4. Be compatible with the cooling system hose and seal materials.
5. Provide adequate freeze protection during cold weather operation.
Normally requirements I through 4 are satisfied by combining a suitable water with reliable inhibitors. When
operating conditions dictate the need for freeze protection, a solution of suitable water and an ethylene glycol
type antifreeze containing adequate inhibitors will provide a satisfactory coolant.
WATER
Any water, whether of drinking quality or not, will produce a corrosive environment in the cooling system. Also, scale
deposits may form on the internal surfaces of the cooling system due to the mineral content of the water. Therefore,
water selected as a coolant must be properly treated with inhibitors to control corrosion and scale deposition.
To determine if a particular water is suitable for use as a coolant when properly inhibited, the following characteristics
must be considered. The concentration of (1) chlorides, (2) sulfates, (3) total hardness and (4) dissolved solids. These
materials are objectionable for a number of reasons: chlorides and/or sulfates will accelerate corrosion, while hardness
(percentage of magnesium and calcium present) will cause deposits of scale. Total dissolved solids may cause scale
deposits, sludge deposits, corrosion or a combination of these. Chlorides, sulfates, magnesium and calcium are among
but not necessarily all the materials which make up dissolved solids. Water, within the limits specified in Tables 'I and'2,
Figure A, is satisfactory as an engine coolant when proper inhibitors are added.
CORROSION INHIBITORS
A corrosion inhibitor is a water soluble chemical compound which protects the metallic surfaces of the cooling system
against corrosive attack. Some of the more commonly used corrosion inhibitors are chromates, borates, nitrates, nitrites
and soluble oil. Depletion of all types of inhibitors occur through normal operation and therefore strength levels must be
maintained by the addition of inhibitors at prescribed intervals.
CHROMATES: Sodium chromate and potassium dichromate are two of the more commonly used water system corrosion
inhibitors. However, the restrictive use of these materials, due to ecology considerations, has de-emphasized their use in
favor of nonchromates. Care should be exercised in handling these materials due to their toxic nature.
Chromate inhibitors must not be used in ethylene glycol antifreeze solutions. Chromium hydroxide, commonly called
"green slime", can result from the use of chromate inhibitors with permanent type antifreeze. This material deposits on
the cooling system passages, reducing the heat transfer rate, and will result in engine overheating. Engines which have
operated with a chromate inhibited water must be chemically cleaned before the addition of ethylene glycol type
antifreeze. A commercial heavy duty descaler should be used in accordance with the manufacturer's recommendation for
this purpose.
SOLUBLE OIL: Soluble oil has been used as a corrosion inhibitor for many years. It has, however, required very close
attention relative to the concentration level due to adverse effects on heat transfer if the concentration exceeds 1% by
volume. For example: 1-1/4% of soluble oil in the cooling system increases fire deck temperatures 6% and a 2-1/2%
concentration raises fire deck temperature up to 15%. Soluble oil must not be used as a corrosion inhibitor.
NON-CHROMATES: Non-chromate inhibitors (borates, nitrates, nitrites, etc.)
provide corrosion
April, 1974
SEC. 13.3
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