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4th Year Refrig Sait 2020 > Industrial Refrigeration > Flashcards

Industrial Refrigeration Flashcards

1
Q

What are the 2 most common types of compressors used in industrial refrigeration (ILM)

A

semi-hermetic open drive Reciprocating and open drive Screw

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2
Q

Describe the operation of a high side float

A

as the refrigerant level rises in the condensor, the valve to the evaporator opens more to allow more refrigerant to flow.

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3
Q

Describe the operation of a low side float

A

as the refrigerant level rises in the evaporator, it closes the inlet more to maintain a constant level of refrigerant to feed to the low pressure reciever

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4
Q

What is the purpose of an Oil Pot

A

To recover oil that has been carried past the oil separator and logged in the system. Oil and Ammonia are not miscible so it does not get carried back to the compressor like typical refrigeration systems.

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5
Q

Describe how refrigerant flows in a Gravity flooded evaporator

A

evaporator is flooded and the natural convection and proper liquid pressure circulate the refrigerant

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6
Q

Describe how refrigerant flows in a Liquid Overfeed Evaporator

A

Refrigerant is pumped either by a mechanical pump or through the use of differential pressure

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7
Q

What is a critical factor in determining the capacity of an evaporative condenser used in industrial refrigeration

A

Wet Bulb Temperature (key word is evaporative meaning it relies on ambient conditions)

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8
Q

What is the advantage of a flooded evaporator

A

it provides a large area for heat transfer to come in contact with the saturated liquid

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9
Q

What is the purpose of the oil in a screw compressor

A

it cools, seals and provides rotor silencing

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10
Q

what type of oil separator is used with a screw compressor

A

coalescing separator

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11
Q

Why are solenoid valves seldomely used in industrial refrigeration

A

the valve is unable to generate enough force in the coil to open

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12
Q

what is anhydrous ammonia

A

ammonia that is relatively free of water and other impurities

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13
Q

why are ammonia TXV’s specially designed

A

to slow the rate of wire drawing

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14
Q

What are wet return lines

A

lines between the evaporator outlet and the low pressure reciever that carry saturated vapour and liquid

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15
Q

Class T machine rooms must provide fire resistive construction for ___ hour(s)

A

1 hour

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16
Q

Dead man valve is a _____ valve

A

spring closing

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17
Q

ammonia leaks can be detected by using___

A

Litmus paper (turns pink during presence)

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18
Q

Ammonia offers ___ btu/lb latent heat of evaporation

A

575 btu/lb

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19
Q

ammonia levels of ___ppm is permissable

A

25 ppm for an 8 hour work day and 40 hour work week

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20
Q

ammonia levels of ___ ppm must be limited to no more than 15 minutes

A

35 ppm

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21
Q

ammonia levels of ___ ppm are considered IDLH (immediately Dangerous to Life and Health)

A

300 PPM

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22
Q

ammonia exposure of ___ to ____ ppm is fatal in a few breaths

A

1700 - 2000 ppm

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23
Q

Ammonia is harmful to the Ozone (true/false)

A

false, zero global warming potential and no ozone depletion

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24
Q

Ammonia is classified as a __ refrigerant (A or B, 1-3)

A

B2 refrigerant

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25
Q

What type of ice is produced in industrial refrigeration

A

Flaked and blocked ice used for the fishery industry, but NOT BAGGED ICE

26
Q

What is the “return reverse” method used when piping lines on an ice rink

A

the concept that the first rung fed is the last to return refrigerant to promote even distribution

27
Q

how many alarm stages are required in a class T room and at what levels do they activate

A

3 stages, 25 ppm, 50 ppm and 200 ppm

monitoring company is notified at 2nd and 3rd stage

28
Q

a class T room exhaust fan and MUA will activate when ammonia levels reach ___ ppm or more

A

25 ppm

29
Q

Class t room doors must open ______

A

outwards

30
Q

Ammonia sensor in a Class T room must be located at ____ feet above finished floor

A

10 ft. must also be 10-30 cm from the cieling

31
Q

Where must the exhaust fan pull air from in a Class T room

A

Cieling, not the wall

32
Q

MUA supplies air to _____ part of a Class T room and is a(n) ____ fired MUA

A

supplies air at floor level and is indirect fired (but I wouldn’t nap in there

33
Q

Monitors for Class T rooms are located where?

A

outside the room, if it is inactive, treat room as hazardous location

34
Q

Eye wash stations for Class T rooms are typically located where

A

outside the room or in a flood room

35
Q

Plaquard for a Class T room will be located where and with what information listed on it

A

outside the room on the door, it will include the service company, type of refrigerant and charge, type of oil used including the ammount

36
Q

What switch is required outside the door of the Class T room and what does it control?

A

a switch to shut down all rotating equipment except MUA and EF. It must be

  • 7 feet above finished floor
  • in a red painted box with a breakable panel
  • include an emergency stop with blow off valve to release refrigerant to atmosphere
37
Q

What is the main purpose of a Class T room

A

to isolate the refrigerant charge from occupied areas

38
Q

To neutralize ammonia, ___ water for every ___ of ammonia is required

A

1 gal of water (8.33 lbs) for every 1 lb of ammonia

39
Q

refrigerant monitor must be tested every ____

A

every month

40
Q

what is the minimum ammount ventilation required in a Class T room

A

0.5 cfm per sq ft and 15 air changes per hour

41
Q

why do we not superheat Ammonia?

A

it gets too light and fluffy, lines of constant entropy go way out

42
Q

formula for overfeed rate

A

overfeed rate = Liquid Mass out / Vapour mass out
eg. 100 lbs supplied to the evap, 75 lbs return as liquid, 25 lbs return as vapour
OVERFEED RATE = 3:1

43
Q

formula for recirculation rate

A

recirculation rate = Liquid mass in/ vapour mass out
eg. 100 lbs supplied to the evap, 75 lbs return as liquid, 25 lbs return as vapour
CIRCULATION RATE = 4:1

44
Q

what is another name for the low stage compressor

A

Booster compressor

45
Q

Name 3 types of overfeed systems

A

Mechanical pump
Dump system
Double Pumper system

46
Q

compression ratio

A

Absolute discharge/absolute suction

47
Q

Interstage pressure formula

A

Sq root (absolute discharge x Absolute Suction)

48
Q

What is the common temperature for the brine used on ice rinks

A

10-12 F

49
Q

average approach on ice rink system

A

2 - 4 F degrees

50
Q

Ice rink temperature settings for pro/amateur/and figure skating

A

21/24/26 F

51
Q

how much slope is required on lines

A

.5” per 10 foot run

52
Q

hydrostatically trapped liquid ammonia will increase ____ psi for each Degree F increase in temperature

A

100 - 150 psi

53
Q 
when labeling ammonia lines, identify the colors
\_\_\_\_\_ liquid
\_\_\_\_\_ vapor
\_\_\_\_\_ low press (70 psi)
\_\_\_\_\_ high press(70.1 psi or higher)
A

orange - liquid
blue - vapor
green - low pressure
red - high pressure

54
Q

3 way valves fail to ____ path

A

90 degree bend route, not straight through

55
Q

Black iron pipe
1.5” and smaller is ____
2” - 6” is _____

A

1.5” is SCHED 80

2” - 6” is SCHED 40

56
Q

anything above 1.25” must be connected via____

A

Welding

57
Q

1.25” may be connected via threads however what consideration must be made

A

threaded connections have weakened wall at the joints

58
Q

supports must be attached to what and with what minimum size threaded rod

A

must be supported to building structure supports and with 3/8” rod minimum

59
Q

number of supports is determined with what 2 factors in mind

A

within 2 ft of the walls and every 10 ft

eg. for a 100 ft run there are 2 by the ends, and 96 ft = 9 supports. 11 supports total for 100 ft run, not 10

60
Q

how does one know when an oil pot should be drained?

A

when the oil pot is cold but not frosted

4th Year Refrig Sait 2020 (4 decks)

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