Environmental Controls

Question 1

What is the definition of dehumidification?

Answer 1

Defined as the removal of moisture vapor from the air to lower its dew point.

Question 2

What are the minimum requirements for a proper enclosure?

Answer 2

• Large enough to contain work area
• Not larger than capabilities of the dehumidification equipment
• Sturdy enough for intended work activities, potential loads, possible inclement weather
• Minimal leakage to maintain proper environmental conditions and to comply with regulations
• DH system designer will aid in selection of system

Question 3

What are air turns (air changes)?

Answer 3

The ratio of the volume of air flowing through a space in a certain period of time (air flow rate) to the volume of air flowing of that space

Question 4

How can high humidity and high levels of atmospheric pollution affect the corrosion rate?

Answer 4

High humidity and high levels of atmospheric pollution will corrode steel 15 to 20 times faster than steel exposed in a rural area of high moisture and low pollution

Question 5

What is relative humidity (RH)?

Answer 5

amount of water vapor in a given volume of air x 100%
_________________________________________________________
maximum amount of water vapor (if air is saturated) at
the same temperature

Warm air can contain or “hold” more moisture than cold air

Question 6

RH =

Answer 6

the ratio of the amount of water in the air at a given temperature to the maximum amount it could hold at the temperature, expressed as a %

Question 7

What are the two ways to reduce the relative humidity of that boundary layer

Answer 7

• Increase the surface temperature
• Reduce the moisture content by dehumidification

Question 8

What are the dehumidification types?

Answer 8

• Refrigeration
• Desiccants

Question 9

What is the boundary layer?

Answer 9

The layer of air immediately adjacent to the steel surface

Question 10

What is refrigeration?

Answer 10

• Ambient air is circulated over a system of refrigeration coils
• The condensation is collected and pumped out of the system

Question 11

What are desiccants?

Answer 11

Substances that naturally have a high affinity for water and can draw moisture directly from the surrounding environment

Question 12

What are the two types of desiccants?

Answer 12

• Absorbent = liquid materials
• Adsorbent = solid materials

Question 13

What is the consequence of interruption during dehumidification?

Answer 13

Could ultimately cost the project a significant amount of money due to downtime and potential work
- maintaining prepared surface
- coatings curing process

Question 14

When should dehumidification equipment be used?

Answer 14

Should be used whenever possible through the curing period to ensure a complete solvent release from applied coating

Question 15

You are the coating inspector on a project with dehumidification provided by a rotating bed type dehumidifier. The silica gel has become contaminated. What do you expect to happen with the silica gel?
A. It will continue working after heat regeneration
B. It will continue working after washing
C. It must be cleaned with a detergent
D. It can no longer adsorb moisture

Answer 15

D. It can no longer adsorb moisture

Question 16

What effect does the rotating bed dehumidifier have on the treated ambient air?
A. It is cooled and humidity is decreased
B. It is heated and the humidity increases
C. It is heated and the humidity decreased
D. It is cooled and the humidity increases

Answer 16

C. It is heated and the humidity decreases