Gas and Air Dryers

Question 1

what is the “dew point”?

Answer 1

temperature where any further cooling would result in the condensation of water vapour

Question 2

what is the relative humidity of air that contains 14 grains of water but could hold 36 grains at that temperature?

Answer 2

14/36 - 38.88 - 40%

Question 3

how many grains of water are contained in one pound of water?

Answer 3

7000

Question 4

when gas is warmed its ability to hold moisture is ____________

Answer 4

increased

Question 5

an absorbent dryer uses ________________ material.

Answer 5

deliquescent

(salt based, absorb moisture + melt away)

Question 6

what are three types desiccants used in adsorbent dryers?

Answer 6

silica gel
activated alumina
molecular sieves

Question 7

what is the disadvantage of deliquescent materials used for drying?

Answer 7

salt can cause corrosion, the lower dew point is only about 10 degrees lower than incoming air

Question 8

what are two common types of plant air systems in use?

Answer 8

utility
instrument air

Question 9

what are the safety precautions to take when working on a compressed air system?

Answer 9

depressurize and de-energize

Question 10

why is an after cooler so important and what is “approach” temperature with respect to after coolers?

Answer 10

removes 60% of moisture from the air

temperature difference between cooling medium leaving the after-cooler and the temperature of the gas leaving the after-cooler

Question 11

in a deliquescent dryer, is the flow normally upward or downward through the bed?

Answer 11

upward

Question 12

what is relative humidity?

Answer 12

comparison between the amount of water a sample of air holds to the maximum amount it can hold if saturated.

Question 13

what is dew point

Answer 13

the temperature to which air must be lowered to in order for condensation of water vapour to begin

Question 14

True or False:

regenerative dryers often use a portion of the dried air for refrigeration of the saturated desiccant bed?

Answer 14

true

Question 15

True or False:

desiccants are most often a salt of some kind

Answer 15

false

Question 16

True or False:

there are forms of energy other than electricity that can be very harmful and equipment must be locked out to prevent injury?

Answer 16

true

Question 17

True or False:

as a sample of air that is partially saturated cools, relative humidity increases?

Answer 17

true

Question 18

True or False:

it takes more heat energy to change the phase of a change the volume of a liquid to a vapour without any change in temperature than it does to increase its temperature 1 degree without any phase change?

Answer 18

true

Question 19

what are the four types of air dryers?

Answer 19

adsorption
absorption
refrigeration
mechanical

Question 20

when working on a dryer, you must ____________ and ___________ the complete system, as well as lockout the compressor whenever possible

Answer 20

depressurize
isolate