The manufacturer of the main propulsion diesel engines on your harbor tug specifies the requirements for fresh water makeup for the closed, re-circulating fresh water cooling system as shown in the illustration. Which of the following examples of fresh water test results would be considered acceptable by the manufacturer for coolant makeup or initial filling? Illustration MP-WC- 05
• Compare each water property in the choices to the maximum limits listed in the CAT Minimum Acceptable Water Requirements table (chloride, sulfate, total solids). • Pay special attention to the units (all choices are in grains/US gal; the table shows both mg/L and grains/US gal). • Check that the pH value for each choice falls within the acceptable acidity range shown in the table.
• For each choice, is any value over the maximum grains/US gal allowed for chloride, sulfate, or total solids? Eliminate those first. • Which options have a pH that is outside the acceptable range, even if all the grains/gal numbers look good? • After you remove all options that fail any one requirement, what is the one option (if any) that still meets every single limit shown in the illustration?
• Verify the chloride value in grains/gal is ≤ the listed maximum (2.4 grains/US gal). • Verify the sulfate value in grains/gal is ≤ the listed maximum (5.9 grains/US gal). • Verify the total solids are ≤ 20 grains/US gal and the pH is between 5.5 and 9.0.
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