Insulation Flashcards
What are the three main functions of insulation in industry?
- Help maintain temperature (increase efficiency)
- Sound reduction
- Preventing water condensation on cold surfaces
What are the three basic categories of insulation?
- Cryogenic
- Thermal
- Refractory
What type of insulation category would be used for temperatures below -101℃ (-150℉) to absolute zero?
Cryogenic insulation
What type of insulation category would be used for temperatures between -101℃ (-150℉) and +815℃ (+1500℉)?
Thermal insulation
What type of insulation category would be used for temperatures over +815℃ (+1500℉)?
Refractory insulation
How are cryogenic temperatures achieved (2 ways)?
- rapid evaporation of volatile liquids
- expansion of gases confined initially at pressures of 150 to 200 atm.
What is a Dewar flask?
A vessel that consists of two flasks, one inside the other separated by a vacuum.
Why is the inside of the outer flask and the outside of inner flask silvered in Dewar flasks?
To prevent radiant heat from passing across the vacuum
This type of insulation is common in cryogenic temperature ranges and is a lightweight, rigid material made up of completely sealed glass cells.
Cellular glass
What is the temperature range of cellular glass?
-273℃ to +482℃
This type of insulation can be identified by its dark colour and a rotten egg, sulphur smell when cut.
Cellular glass
What precautions need to be taken when handling cellular glass?
It is extremely abrasive
Wear gloves when handling it.
This type of insulation consists of approximately 50 to 100 layers per inch of aluminized mylar, and finds use as insulating blankets to shield people and equipment from radiation heat loss to space.
Super insulation
____ temperature thermal insulation applications include chilled water, direct refrigeration systems, and indirect refrigeration systems (brine).
Low
____ temperature thermal insulation applications include steam, hot fluids, and steam condensate.
Intermediate
____ temperature thermal insulation applications include turbine, chimneys, incinerators, and boilers.
High
While there is no perfect insulation, a thin layer of air resists the flow of heat about ____ times better than a good metallic conductor of the same thickness.
15,000
Why must the air pockets inside of insulation be small?
To prevent convection
If the air pockets are large, convection would take place, and transfer heat across the air gap.
What are the three categories of thermal insulation?
- fibrous
- cellular
- granular
These classifications are based off of how the insulation is made.
This type of thermal insulation is made from long, small diameter fibres that divide the air into tiny compartments, with the fibres being either perpendicular or parallel.
Fibrous thermal insulation
This type of thermal insulation uses the principle of dividing air pockets into tiny compartments, but does it with small individual cells separated from each other.
Cellular insulation
Foamed-in plastics such as polystyrene and polyurethane (Styrofoam) are examples of ____________ thermal insulation
cellular
This type of thermal insulation is made of small pieces of material with hollow spaces, but is not classified the same as cellular insulation since the gas is free to move between the individual spaces.
Granular insulation
Because the air is free to move, there is some heat loss through convection.
What type of insulation classification does vermiculite fall into?
Granular thermal insulation
This type of insulation often contains asbestos.
What are the four types of refractory insulation?
- castable refractories
- standard and specially shaped bricks
- gunnite mixes
- ramming mixes
This type of refractory insulation is made of materials that can withstand the high temperatures in furnances and kilns because of the weay the materials form a ceramic, glass, or crystalline bond when formed.
Castable refractories
These are dense, hard substances that can withstand teh abusive environments where they are used.
True or false: Castable refractories are often mixed with water and then poured or pumped into place.
True
This type of refractory insulation is mixed to specific consistency and then sprayed onto the surface requiring insulating.
Gunnite mixes
What holds gunnite refractory insulation onto the surface while is cures?
Special anchors
Gunnite is not sticky enough to bond to certain surfaces, along with different rates of expansion and contraction loosening the bond between the shell and refractory.
This type of refractory insulation comes pre-packaged and is hammered into place with a pneumatic air hammer.
Ramming mixes
What type of refractory insulation is used mainly for patching and filling in small areas?
Ramming mixes
This insulation property indicates the total rate of heat flow for the actual thickness of an insulating material.
Thermal conductance (C)
With insulation, the ____ (lower/higher) the C factor is, the better the insulation value is.
Lower
C = conductance
This insulation property is rated on a one-inch thck section of insulation.
Thermal conductivity (K)
With insulation, the ____ (lower/higher) the K factor is, the better the insulation value is.
Lower
K = conductivity
This insulation property refers to the resistance of heat from through a unit of area.
Thermal resistance (R)
This is a common rating for residential or building insualtion
With insulation, the ____ (lower/higher) the R factor is, the better the insulation value is.
Higher
R = resistance
True or false: Thermal resistance of insulation is based off of a one-inch thick section of material.
True
This is the same as thermal conductiviy, which is also rated on a one-inch thick section of insulation.
What effect does moisture have on insulation?
It reduces the insulation qualities
This is because water conducts heat.
What effect does vibration have on insulation?
It causes breakdown and dusting
What type of insulation is used with the coldes temperatures?
Cellular glass
What types of insulation can withstand the highest temperatures?
Ceramics
Decibel levels over ____dB and louder cause immediate auditory nerve destruction.
150
What is cladding or jacketing used for in regards to insulation?
To protect the insulation from moisture, chemical and mechanical damage.
According to Alberta OHS code, what is the decibel level where hearing protection is required?
85 dB in an 8 hour period
Where should vapour barrier be located in a structure or building?
In between the insulation and the warmer area
True or false: Bands and cladding must be made of different materials to prevent corrosion of the cladding or bands.
False
They must be made of the same materials to prevent corrosion.
Fibreglass and mineral wool are common examples of what type of insualtion?
Fibrous thermal insulation
Asbestos insulation is one of the most identifiable hazards in industry and was previously used for decades. What method is the most cost-effective means of dealing with it?
Encasement
This involves putting a protective coating over the asbestos to seal it.
Cryogenics applications in industry would be:
1) Large-scale production of oxygen and nitrogen
2) Direct refrigeration systems
3) Indirect refrigeration systems
4) Turbine chimneys, incinerators and boilers
1) Large-scale production of oxygen and nitrogen
When a fluid is heated, hotter and lighter fluids rise while colder, heavier fluids sink. This motion is called:
Natural convection
Forced convection is with some type of pump or blower.
Insulation is defined as any material that is:
1) a good conductor of heat or electricity.
2) a poor conductor of heat or electricity.
3) thermal.
4) refractory.
2) a poor conductor of heat or electricity.
Thermal properties of insulation are thermal conductance (C), thermal conductivity (K) and thermal resistances (R). Which of the following ratings would offer the best insulation?
Lower C and K factors and higher R value
Controlling noise level in the workplace is necessary because prolonged exposure to what decibel rating can permanently damage hearing?
70 decibels
What is the maximum surface temperature allowable for insulated equipment as stated in ASTM code 1055 to ensure personal protection from burns?
Below 58°C/136.4F°
Select the categories of insulation listed by temperature capability from coldest to hottest:
1) Refractory, thermal insulation, cryogenic
2) Cryogenic, refractory, thermal insulation
3) Thermal insulation, cryogenic, refractory
4) Cryogenic, thermal insulation, refractory
4) Cryogenic, thermal insulation, refractory
What is the main purpose of insulation?
To conserve energy
