Physical Properties of Engine Cooling Water

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Questions and Answers

What is the primary function of the plate type heat exchanger in the cooling system?

To generate distilled water

To increase the temperature of the water

To circulate seawater through the engine

To remove excess heat from the freshwater (correct)

Which circuit is used for low-temperature zone machinery?

High-temperature circuit

Low-temperature circuit (correct)

Seawater circuit

Distilled water circuit

How is the total quantity of low-temperature fresh water maintained in balance with high-temperature freshwater?

Through an expansion tank common to both systems (correct)

By adding chemicals periodically

Using the seawater central cooler

Via a backup cooling pump

What happens to heated water from the water jacket?

It is sent to the freshwater generator for efficiency Signup and view all the answers

What is the role of the electrical cooling water pumps in the high-temperature circuit?

To maintain a standby system when the primary is in service Signup and view all the answers

Why are chemicals added to the freshwater tank in the cooling system?

To ensure the water doesn't become corrosive Signup and view all the answers

Which system does the low-temperature circuit directly connect to?

The seawater central cooler Signup and view all the answers

What does the high-temperature circuit primarily consist of?

Jacket water system of the main engine Signup and view all the answers

What is the main purpose of using demineralized (distilled) water as cooling water?

To prevent corrosion of the cooling system. Signup and view all the answers

Why is untreated distilled water not recommended as cooling water?

It absorbs carbon dioxide from the air and becomes corrosive. Signup and view all the answers

What type of water is heavily discouraged for use in cooling systems due to its contamination levels?

Rainwater Signup and view all the answers

Which of the following is NOT a form of corrosion that can occur in cooling water systems?

Thermal corrosion Signup and view all the answers

What is scale in the context of cooling water systems?

Hard mineral coatings that impede water flow and heat transfer. Signup and view all the answers

Which of the following statements is true regarding the use of tap water as cooling water?

Softening may be necessary before use due to chalk deposits. Signup and view all the answers

What problem can arise from the product of corrosion in a cooling system?

Insulating scale that interferes with heat transfer. Signup and view all the answers

What should be added to distilled water to prevent it from becoming corrosive?

Corrosion inhibitor Signup and view all the answers

Which corrosion inhibitor is specifically used for protecting copper and copper alloys in diesel cooling water systems?

Benzoitriazole Signup and view all the answers

What is the recommended dosage range for Sodium silicate and Triethanol ammonium in diesel cooling water systems?

1000 to 2000 ppm Signup and view all the answers

Which inhibitor is suitable for treatment when aluminum alloys are present in diesel cooling water systems?

Sodium silicate Signup and view all the answers

What is the primary role of polyphosphate and polyelectrolytes in diesel cooling water systems?

Scale prevention Signup and view all the answers

What could be a consequence of poor cooling water treatment in an engine's cooling system?

Rapid corrosion processes Signup and view all the answers

What is the correct dosage for sodium mercaptobenzothiazole as a corrosion inhibitor?

300 to 500 ppm Signup and view all the answers

Why is it important to follow proper treatment procedures for cooling water?

To prevent corrosion and engine failures Signup and view all the answers

What is a potential operating issue that can arise from a bad cooling water quality?

Unexpected engine problems Signup and view all the answers

What should be done if abnormal deposits or rust are detected in the cooling water system?

Clean thoroughly and refill with newly treated water Signup and view all the answers

Which process is not part of the cleaning procedures for the cooling water system?

Refilling with saltwater Signup and view all the answers

Why is it recommended to hire a reliable specialist firm for cleaning the cooling water system?

They are familiar with hazardous cleaning chemicals Signup and view all the answers

What should be followed if cleaning the cooling water system is done without professional help?

Instructions from the supplier of cleaning chemicals Signup and view all the answers

What is the maximum allowable pH for cooling water before introducing a corrosion inhibitor?

9 Signup and view all the answers

Which of the following best describes the requirement for cleaning materials used in the cooling system?

Special chemicals that may be hazardous Signup and view all the answers

Which contaminant is monitored to ensure it does not exceed 50 ppm in cooling water?

Chloride Signup and view all the answers

What is the recommended frequency for checking the cooling water system during service?

Once a week Signup and view all the answers

What is the initial step before refilling the cooling water system?

Clean the system thoroughly Signup and view all the answers

What should operators be cautious about when using chemicals for cleaning?

The hazards associated with these chemicals Signup and view all the answers

What type of inhibitors are specifically recommended for use in cooling water systems?

Nitrite-borate based inhibitors Signup and view all the answers

What is the suggested procedure after cleaning the cooling water system?

Add newly treated water Signup and view all the answers

If the residue after evaporation exceeds 400 ppm, what action should be taken?

Replace with freshly treated water Signup and view all the answers

What potential issue might arise if the sulphate content in the cooling water increases?

Contamination from exhaust gas Signup and view all the answers

When testing the cooling water, how often should laboratory tests be conducted?

Every three months Signup and view all the answers

What should be checked if the chloride content in the cooling water is found to be increasing?

Seawater penetration into the cooling water Signup and view all the answers

Study Notes

Engine Cooling Water System Overview

Fresh water is stored in a tank, circulated to machinery, and cooled through a plate type heat exchanger with seawater to remove excess heat.
Heated water from the water jacket is utilized in a freshwater generator, enhancing fresh water production efficiency.

Cooling Water Circuits

Low-Temperature Circuit (L.T):
- Used for low-temperature machinery, connected directly to the main seawater cooler.
- Creates balance with the high-temperature (H.T.) freshwater system via a common expansion tank.
- Makeup water comes from the hydrophore system or distilled water tank using a feed water refilling pump.
High-Temperature Circuit (H.T):
- Comprises jacket water system of the main engine and operates at higher temperatures.
- Maintained by low-temperature fresh water; includes components like the FW generator and lube oil filter.
- Circulated by electrical cooling water pumps (one in service, one standby).

Chemical Properties and Treatment

Chemical additives are periodically introduced to maintain water quality and prevent corrosion.
Critical parameters for monitoring include pH, hardness, conductivity, turbidity, phosphates, sulfates, ammonium, chlorides, calcium, magnesium, aluminum, iron, zinc, silicate, nitrate, nitrite, chemical oxygen demand, and total organic carbon.

Quality Requirements for Cooling Water

Recommended to use only demineralized (distilled) water with corrosion inhibitors to prevent system corrosion.
Carbon dioxide from air exposure can make untreated distilled water corrosive.
Rainwater and tap water pose contamination risks; tap water may be used only after treatment if distilled is unavailable.
Sea water or saline-contaminated fresh water is strictly prohibited due to high corrosion risk.

Corrosion Issues

Corrosion is caused by chemical or electrochemical reactions, leading to the deterioration of metals into their ore forms.
Forms of corrosion affecting cooling systems include general wastage, pitting, crevice corrosion, galvanic corrosion, stress corrosion, and erosion corrosion.
Corroded materials can form insulating scales, impeding heat transfer and risking system failure.

Scale Formation

Scale comprises hard mineral coatings and corrosion deposits that accumulate in pipes and reservoirs.
Various corrosion inhibitors are used, such as:
- Disodium hydrogen phosphate, sodium silicate, triethanol ammonium, benzoitriazole, sodium mercaptobenzothiazole, and soluble oil for specific protective roles.

Monitoring and Treatment

Regular testing of cooling water quality is crucial; weekly checks are preferred, with laboratory analyses recommended every three months.
Any sudden changes in water parameters (e.g., chloride content) should prompt inspections for seawater ingress or contamination.
Cleaning of the cooling water system may be necessary if significant deposits or rust are found.

Cleaning and Maintenance Procedures

Cleaning involves degreasing and descaling, often requiring specialists for safe chemical handling.
Maintaining specific parameters, such as pH (7-9), total hardness (max. 75 ppm), and chloride levels (max. 50 ppm), is essential for effective corrosion control.
Mixing different types of inhibitors is discouraged to prevent adverse reactions.

Conclusion

Proper treatment and ongoing analysis of cooling water are essential for the reliable operation of engine cooling systems.
Inhibitors and cleaning protocols must align with manufacturer instructions to ensure system integrity and performance.

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Description

This quiz focuses on the physical properties of engine cooling water and its role in heat exchange processes. It explores how cooling systems use freshwater and seawater to efficiently manage excess heat in engines. Additionally, it covers the integration of heating elements for freshwater generation.