38 Questions
What is the fundamental difference between a hot oil system and a hot water heating system?
The fluid chosen has a higher boiling point in a hot oil system.
Why are heat transfer fluids, like hot oils, preferred in high temperature process applications?
They exhibit thermally stable properties at high temperatures.
What was a common issue with the original oils used in heat transfer systems?
They were unstable at temperatures above the rated stable temperature.
How do heat exchangers contribute to a hot oil system's operation?
By transferring the oil's heat to other fluids.
Why are heat transfer fluids, especially hot oils, used in metal working applications?
To ensure high-energy efficiency and heat transfer rates.
In jurisdictional regulations, why might systems employing heat transfer fluids be registered at a lower level?
Because they exhibit much lower vapor pressure than steam systems.
Why should the pump be located below the expansion tank?
To avoid cavitation in the pump suction
Why are centrifugal pumps preferred over gear pumps in liquid thermal systems?
They offer higher flow rates
Why are circulating pumps in thermal fluid systems often water-cooled?
To dissipate heat from the high-temperature fluid
What is a common auxiliary equipment found in liquid thermal systems?
Valves
Which major equipment is central to the return system in liquid thermal systems?
Pump
What hazard is posed by exposed piping systems in heat transfer fluid systems?
Risk of burn injury
Which pump type is preferred for liquid thermal systems in terms of enhancing heat transfer?
Centrifugal pump
What is the efficiency range of radiant heaters used in heat transfer fluid (HTF) systems?
40-50%
What is the primary function of the expansion tank in liquid thermal systems?
Allowing for oil expansion and contraction
What is the main advantage of using a combination radiant and convection heater in heat transfer fluid systems?
Higher efficiency
What is the purpose of lining the inner walls and floor of a fired heater with refractory brick and insulating material?
To contain heat inside the furnace
Why are leaks from heat transfer fluid systems considered hazardous?
They may form a flammable mist
What is the main advantage of using current HTFs over steam in heat transfer systems?
Simpler circuit design
In a vapour-based heat transfer system, what is the role of the saturated gas?
It works as the heat transfer medium
Why are liquid thermal systems preferred over vapour systems in some cases?
They are less expensive and less complex
What is the purpose of the expansion tank in a heat transfer system?
To allow the HTF to expand when heated
In liquid thermal systems, why are centrifugal pumps preferred over gear pumps?
Centrifugal pumps provide higher flow rates
What is the main drawback of using vapour-based heat transfer systems?
Higher complexity compared to liquid systems
What happens if the expansion tank level drops in a heat transfer system?
"A leak may have developed"
How can contaminants typically impact heat transfer in a system?
"Contaminants deposit and spoil heating surfaces"
"What can happen if cleaning fluids are left in a heat transfer system at startup?"
"Corrosion problems may occur within the system"
"Why is it important to monitor the level of the expansion tank daily?"
"To ensure no leaks have developed"
What is the main purpose of an expansion (or surge) tank in a hot oil system?
To allow thermal fluid to expand when heated or contract when cooled
Why is a low hot oil flow indicating device installed in the outlet line from the heater?
To indicate severe overheating and probable tube failure
What is the purpose of a high stack temperature indicator in a hot oil system?
To detect high furnace temperatures
What does the emergency shutdown device/switch in a hot oil system allow operators to do?
Manually shut down the plant if needed
Why is it recommended to leave the standby pump's suction valve open all the time in a hot oil system?
To maintain the pump at operating temperature
What purpose does a pressure/safety relief valve serve in a hot oil system?
To release excess pressure downstream of the heater
Why are two pumps usually installed in a hot oil system?
To provide a redundant pump for backup
What is the purpose of a high or low fuel level/pressure shutdown device in a hot oil system?
To prevent unstable burner operation due to high or low fuel conditions
What is meant by having an expansion tank 'feed' the system in case of a leak?
It replaces lost fluid due to leaks
Why should the temperature in the expansion tank be less than 60°C?
To prevent fluid oxidation inside the tank
Learn about the importance of cleaning the system and removing old fluid before replacing with fresh heat transfer fluid to prevent premature degradation. Understand the narrow operating range for efficient operation and avoiding tube wall degradation.
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