48 Questions
EASY Why is propylene glycol used instead of ethylene glycol in certain situations?
Because it is less toxic
What is the primary reason for not mixing ethylene glycol and propylene glycol?
They can cause inhibitors to precipitate
What is the purpose of adding corrosion inhibitors to glycol heat transfer fluids?
To prevent corrosion caused by the reaction of glycol with oxygen
Why is automotive glycol not recommended for industrial closed loop systems?
Because it has a shorter life span
What is the typical pH range of a glycol system with adequate inhibitor?
Between 9 and 9.5
What happens to the pH of a glycol system if the inhibitor is consumed?
It decreases to below 8
Which glycol requires the most pumping power?
Propylene glycol
Which glycol has the lowest specific heat?
Propylene glycol
What is the advantage of using propylene glycol over ethylene glycol?
It is less toxic
What is the minimum glycol concentration recommended to avoid biological fouling?
20%
What is the advantage of using glycol systems in remote sites?
They require less monitoring
What happens to the heat transfer capacity of a system when converted from water to glycol?
It decreases by 50%
Why should automatic municipal water make-up not be used in glycol systems?
It dilutes the mixture and reduces its freeze point
What type of water should be mixed with glycol according to glycol manufacturers?
Demineralized, distilled, or deionized water
What is the maximum level of chlorides permitted in dilution water for glycol systems?
25 ppm
Why should glycol not be used directly in a boiler or heater system?
It breaks down when exposed to high heat transfer surface temperatures
MEDIUM What is the primary reason for the higher cost of glycol systems compared to water systems?
Higher cost of glycol compared to water
What is the minimum recommended glycol concentration to prevent biological fouling?
20%
Why are glycol systems a better option for remote sites?
They require less monitoring
What is the purpose of using a special tank and pump system for make-up in glycol systems?
To prevent dilution of the glycol mixture
What is the maximum level of sulfates permitted in dilution water for glycol systems?
25 ppm
Why is a heat exchanger necessary between the boiler and the closed loop system?
To prevent glycol breakdown
What is the effect of using automatic municipal water make-up in glycol systems?
It dilutes the glycol mixture and reduces its freeze point
What is the recommended range of glycol concentrations for temperatures between −15 to −20°C?
30-35%
What is the chemical formula of ethylene glycol?
(CH2OH)2
Why do glycol heat transfer fluids require corrosion inhibitors?
To prevent the formation of organic acids that increase corrosion
What happens when ethylene glycol and propylene glycol are mixed together?
Inhibitors precipitate and the mixture gels
What is the primary difference between propylene glycol and ethylene glycol in terms of freeze protection?
Propylene glycol requires a higher concentration to provide the same freeze protection
Why is it important to monitor the pH of a glycol system?
To determine if the inhibitor is being consumed
What is a common problem that can occur in glycol systems if the pH drops below 7?
The system requires a full internal cleaning and replacement of the glycol solution
What is the main reason why propylene glycol is more viscous than ethylene glycol?
It has a different chemical structure
What is a common service offered by glycol suppliers to help maintain the effectiveness of their products?
Free inhibitor analysis
HARD What is the primary reason why glycol systems require corrosion inhibitors?
To prevent corrosion from oxygen
What is the effect of mixing ethylene glycol and propylene glycol together?
Inhibitors precipitate out and the mixture gels
Why is it important to monitor the pH of a glycol system?
To check if the inhibitor is being consumed
What happens to the pH of a glycol system if the inhibitor is consumed?
The pH decreases
Why is propylene glycol more viscous than ethylene glycol?
Because of its chemical structure
What is a common problem that can occur in glycol systems if the pH drops below 7?
The system likely requires a full internal cleaning and replacement of the glycol solution
What is a service offered by some glycol suppliers?
Inhibitor analysis
What is the primary reason why glycol systems require less monitoring compared to water systems?
Because glycol systems are less prone to biological fouling
What happens to the heat transfer capacity of a system when converted from water to glycol?
It decreases by over 50%
Why is corrosion a concern in glycol systems?
Because glycol reacts with oxygen to form organic acids
What is the purpose of using a special tank and pump system for make-up in glycol systems?
To prevent dilution of the glycol mixture
What is the recommended minimum glycol concentration to prevent biological fouling?
20%
What is the maximum level of total hardness permitted in dilution water for glycol systems?
100 ppm
Why should glycol not be used directly in a boiler or heater system?
Because it breaks down when exposed to high heat transfer surface temperatures
What is the primary reason why propylene glycol is more expensive than ethylene glycol?
Because it is less toxic than ethylene glycol
What is the recommended concentration range of ethylene glycol for temperatures between −35 to −40°C?
45 – 55%
Study Notes
Glycol in Closed Systems
- Glycol is added to prevent freezing damage in closed system heating or cooling water.
- There are two main types of glycol: ethylene glycol [(CH2OH)2] and propylene glycol [C3H8O2].
- Ethylene glycol is toxic, while propylene glycol is not, making it suitable for use where food products are involved.
Characteristics of Glycols
- Glycols are more viscous than water, requiring more pumping power.
- Propylene glycol is the most viscous and requires a higher concentration to provide the same freeze protection as ethylene glycol.
- Both glycols have lower specific heats than water, with propylene having the lowest.
- Propylene glycol is more expensive than ethylene glycol.
Recommended Glycol Concentrations
- Table 3 shows the recommended glycol concentrations to achieve desired freeze protection:
- Temperature range −35 to −40 °C: 45-55% ethylene glycol, 50-54% propylene glycol
- Temperature range −15 to −20 °C: 30-35% ethylene glycol, 35-40% propylene glycol
- Glycol concentrations should never be less than 20% to prevent biological fouling.
Converting to Glycol Systems
- Glycol systems require less monitoring and are suitable for remote sites.
- Glycol solutions transfer less than half the heat of water, reducing heat transfer capacity by over 50%.
- Converting a water system to a glycol system increases costs and requires greater pumping power.
Maintenance and Inhibitors
- Glycol reacts with oxygen to form organic acids, increasing corrosion.
- Corrosion inhibitors are added to glycol heat transfer fluids.
- pH levels indicate the presence of adequate inhibitor, with a pH range of 9-9.5 being optimal.
- Test kits are available to check inhibitor levels.
Important Considerations
- Automotive glycol should not be used in industrial closed-loop systems.
- Ethylene glycol and propylene glycol should not be used together.
- Glycol should not be used directly in boiler or heater systems.
- A heat exchanger should be used between the boiler and the closed-loop system.
Glycol in Closed Systems
- Glycol is added to prevent freezing damage in closed system heating or cooling water.
- There are two main types of glycol: ethylene glycol [(CH2OH)2] and propylene glycol [C3H8O2].
- Ethylene glycol is toxic, while propylene glycol is not, making it suitable for use where food products are involved.
Characteristics of Glycols
- Glycols are more viscous than water, requiring more pumping power.
- Propylene glycol is the most viscous and requires a higher concentration to provide the same freeze protection as ethylene glycol.
- Both glycols have lower specific heats than water, with propylene having the lowest.
- Propylene glycol is more expensive than ethylene glycol.
Recommended Glycol Concentrations
- Table 3 shows the recommended glycol concentrations to achieve desired freeze protection:
- Temperature range −35 to −40 °C: 45-55% ethylene glycol, 50-54% propylene glycol
- Temperature range −15 to −20 °C: 30-35% ethylene glycol, 35-40% propylene glycol
- Glycol concentrations should never be less than 20% to prevent biological fouling.
Converting to Glycol Systems
- Glycol systems require less monitoring and are suitable for remote sites.
- Glycol solutions transfer less than half the heat of water, reducing heat transfer capacity by over 50%.
- Converting a water system to a glycol system increases costs and requires greater pumping power.
Maintenance and Inhibitors
- Glycol reacts with oxygen to form organic acids, increasing corrosion.
- Corrosion inhibitors are added to glycol heat transfer fluids.
- pH levels indicate the presence of adequate inhibitor, with a pH range of 9-9.5 being optimal.
- Test kits are available to check inhibitor levels.
Important Considerations
- Automotive glycol should not be used in industrial closed-loop systems.
- Ethylene glycol and propylene glycol should not be used together.
- Glycol should not be used directly in boiler or heater systems.
- A heat exchanger should be used between the boiler and the closed-loop system.
Glycol in Closed Systems
- Glycol is added to prevent freezing damage in closed system heating or cooling water.
- There are two main types of glycol: ethylene glycol [(CH2OH)2] and propylene glycol [C3H8O2].
- Ethylene glycol is toxic, while propylene glycol is not, making it suitable for use where food products are involved.
Characteristics of Glycols
- Glycols are more viscous than water, requiring more pumping power.
- Propylene glycol is the most viscous and requires a higher concentration to provide the same freeze protection as ethylene glycol.
- Both glycols have lower specific heats than water, with propylene having the lowest.
- Propylene glycol is more expensive than ethylene glycol.
Recommended Glycol Concentrations
- Table 3 shows the recommended glycol concentrations to achieve desired freeze protection:
- Temperature range −35 to −40 °C: 45-55% ethylene glycol, 50-54% propylene glycol
- Temperature range −15 to −20 °C: 30-35% ethylene glycol, 35-40% propylene glycol
- Glycol concentrations should never be less than 20% to prevent biological fouling.
Converting to Glycol Systems
- Glycol systems require less monitoring and are suitable for remote sites.
- Glycol solutions transfer less than half the heat of water, reducing heat transfer capacity by over 50%.
- Converting a water system to a glycol system increases costs and requires greater pumping power.
Maintenance and Inhibitors
- Glycol reacts with oxygen to form organic acids, increasing corrosion.
- Corrosion inhibitors are added to glycol heat transfer fluids.
- pH levels indicate the presence of adequate inhibitor, with a pH range of 9-9.5 being optimal.
- Test kits are available to check inhibitor levels.
Important Considerations
- Automotive glycol should not be used in industrial closed-loop systems.
- Ethylene glycol and propylene glycol should not be used together.
- Glycol should not be used directly in boiler or heater systems.
- A heat exchanger should be used between the boiler and the closed-loop system.
This quiz covers the use of glycol in industrial cooling systems, including the differences between ethylene glycol and propylene glycol, and the importance of using the non-toxic type in food-related applications. Learn about the properties and safety considerations of these substances.
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