40.Main engine cooling water test

Nitrite - Recommended Limits can be in the range of 700-2400 ppm as NO2. Please refer to the inhibitor Product Data Sheet for product specific control limits. The nitrite concentration should be maintained within the above recommended limits to effectively inhibit any corrosive or scaling action within a closed cooling system. Too high a concentration should be avoided to minimize the cost to maintain the system. Insufficient dosage can set up a condition where accelerated corrosion can occur in areas which become unprotected.

pH - Recommended Limits 8.3-10. The effectiveness of a corrosion inhibitor is restricted to within a certain pH range. Treatment ensures that this pH range is observed when the nitrite level is sufficiently maintained to prevent corrosion.

Chlorides - Recommended limit max. 50 ppm. The chloride value of the cooling water should be kept as low as possible, any increase in value whether sudden or gradual, will be an indication of sea water contamination. Check with engine manufacturer for other specified limits. If the chloride level exceeds 50 ppm, the possibility of corrosion in the system increases because chlorides have a negative effect on the passivation film created by nitrites. Therefore, until corrective action has succeeded in bringing the chloride level back down below 50 ppm, the nitrite level should be kept close to the upper limit (2400 ppm).