Introduction
Testing of cooling water is one of the significant routine activities that are carried out on ships. This includes checking the condition of the main engine, auxiliary engines, boilers and other machinery’s cooling systems. Such control allows engineers to ensure the quality of the water and prevent its negative impact on the engine, for example, corrosion, scaling and overheating. In addition, monitoring also helps to maintain the engine’s efficiency during the voyage.
Cooling water testing is the process of checking the chemical and physical condition of water circulating through a ship’s cooling system. The test determines whether important parameters such as pH, chloride level, hardness, nitrite concentration and inhibitor concentration are within the recommended limits.
Depending on the type of cooling water treatment used on board, the testing procedure and acceptable values may differ. Therefore, the manufacturer’s instructions and the vessel’s water treatment program should always be followed.
The cooling water comes into contact with various metallic components such as cylinder liners, cooling jackets, pipes, heat exchangers and pumps. Poor quality water can gradually damage these components.
Regular testing helps to:
pH indicates whether the cooling water is acidic, neutral or alkaline. Maintaining the correct pH is important because highly acidic or excessively alkaline water can promote corrosion or damage system components.
The acceptable pH range depends on the engine manufacturer and treatment chemicals being used. The result should therefore be compared with the recommended onboard treatment limits.
Chloride testing is carried out to identify possible contamination, particularly from seawater. An increase in chloride concentration may indicate leakage through a cooler or heat exchanger.
A high chloride level should not be ignored because seawater contamination can accelerate corrosion in the cooling water system.
Hardness is mainly associated with calcium and magnesium salts present in the water. Excessive hardness can cause scale formation on heat transfer surfaces.
Scale acts as an insulating layer, reducing heat transfer and potentially causing higher operating temperatures. The hardness level should be maintained according to the water treatment manufacturer’s recommendations.
In systems using nitrite based corrosion inhibitors, the nitrite concentration is checked regularly. Nitrite helps protect ferrous metal surfaces from corrosion.
If the concentration becomes too low, corrosion protection may be inadequate. On the other hand, chemical treatment should not be increased blindly; the treatment manufacturer’s recommended range must be followed.
Some ships use different corrosion inhibitor formulations rather than nitrite based treatment. The specific active chemical recommended by the treatment supplier may therefore need to be tested.
The purpose is to confirm that sufficient chemical protection is available throughout the cooling system.
Poor cooling water condition can affect both the efficiency and reliability of shipboard machinery. If the water is not properly treated or monitored, it may lead to several operational problems.
The exact procedure depends on the test kit and chemical treatment system used on the vessel. A general procedure is as follows:
Cooling water testing represents a critical aspect of shipboard machinery maintenance which is relatively easy to perform yet very important. Periodic testing and inspection of such indicators as pH, chloride, hardness, inhibitor concentration and others contribute to the prevention of engine and other equipment degradation through corrosion, scale and other issues.
Appropriate measurements, accurate logging and timely treatment of the affected areas can eliminate many of the possible problems and ensure the continuous and reliable performance of the machinery.
The frequency depends on the engine maker, water treatment supplier, and the vessel’s maintenance procedure. Routine testing is normally required.
It helps detect possible seawater contamination in the cooling water system.
Correct pH helps maintain corrosion protection and prevents adverse effects on system components.
High levels of hardness-producing minerals can contribute to scale formation and reduce heat transfer efficiency.
Not automatically. The cause should be checked and chemical dosing should follow the approved treatment procedure and manufacturer’s recommendations.
Freshwater or treated demineralized water is commonly used in closed cooling systems, along with the appropriate corrosion inhibitor treatment.
A designated sampling point provides a representative sample of the circulating cooling water, helping ensure that the test results accurately reflect the system condition.
The abnormal result should be reported to the responsible engineer, the possible cause should be investigated and corrective action should be taken according to the manufacturer’s instructions and vessel’s water treatment procedure.
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