Industrial Refrigeration

Question 1

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

Answer 1

semi-hermetic open drive Reciprocating and open drive Screw

Question 2

Describe the operation of a high side float

Answer 2

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

Question 3

Describe the operation of a low side float

Answer 3

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

Question 4

What is the purpose of an Oil Pot

Answer 4

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.

Question 5

Describe how refrigerant flows in a Gravity flooded evaporator

Answer 5

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

Question 6

Describe how refrigerant flows in a Liquid Overfeed Evaporator

Answer 6

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

Question 7

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

Answer 7

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

Question 8

What is the advantage of a flooded evaporator

Answer 8

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

Question 9

What is the purpose of the oil in a screw compressor

Answer 9

it cools, seals and provides rotor silencing

Question 10

what type of oil separator is used with a screw compressor

Answer 10

coalescing separator

Question 11

Why are solenoid valves seldomely used in industrial refrigeration

Answer 11

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

Question 12

what is anhydrous ammonia

Answer 12

ammonia that is relatively free of water and other impurities

Question 13

why are ammonia TXV’s specially designed

Answer 13

to slow the rate of wire drawing

Question 14

What are wet return lines

Answer 14

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

Question 15

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

Answer 15

1 hour

Question 16

Dead man valve is a _____ valve

Answer 16

spring closing

Question 17

ammonia leaks can be detected by using___

Answer 17

Litmus paper (turns pink during presence)

Question 18

Ammonia offers ___ btu/lb latent heat of evaporation

Answer 18

575 btu/lb

Question 19

ammonia levels of ___ppm is permissable

Answer 19

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

Question 20

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

Answer 20

35 ppm

Question 21

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

Answer 21

300 PPM

Question 22

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

Answer 22

1700 - 2000 ppm

Question 23

Ammonia is harmful to the Ozone (true/false)

Answer 23

false, zero global warming potential and no ozone depletion

Question 24

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

Answer 24

B2 refrigerant

Question 25

What type of ice is produced in industrial refrigeration

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

3 stages, 25 ppm, 50 ppm and 200 ppm | monitoring company is notified at 2nd and 3rd stage

Question 28

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

Answer 28

25 ppm

Question 29

Class t room doors must open ______

Answer 29

outwards

Question 30

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

Answer 30

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

Question 31

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

Answer 31

Cieling, not the wall

Question 32

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

Answer 32

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

Question 33

Monitors for Class T rooms are located where?

Answer 33

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

Question 34

Eye wash stations for Class T rooms are typically located where

Answer 34

outside the room or in a flood room

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

What is the main purpose of a Class T room

Answer 37

to isolate the refrigerant charge from occupied areas

Question 38

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

Answer 38

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

Question 39

refrigerant monitor must be tested every ____

Answer 39

every month

Question 40

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

Answer 40

0.5 cfm per sq ft and 15 air changes per hour

Question 41

why do we not superheat Ammonia?

Answer 41

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

Question 42

formula for overfeed rate

Answer 42

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

Question 43

formula for recirculation rate

Answer 43

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

Question 44

what is another name for the low stage compressor

Answer 44

Booster compressor

Question 45

Name 3 types of overfeed systems

Answer 45

Mechanical pump Dump system Double Pumper system

Question 46

compression ratio

Answer 46

Absolute discharge/absolute suction

Question 47

Interstage pressure formula

Answer 47

Sq root (absolute discharge x Absolute Suction)

Question 48

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

Answer 48

10-12 F

Question 49

average approach on ice rink system

Answer 49

2 - 4 F degrees

Question 50

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

Answer 50

21/24/26 F

Question 51

how much slope is required on lines

Answer 51

.5" per 10 foot run

Question 52

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

Answer 52

100 - 150 psi

Question 53

``` when labeling ammonia lines, identify the colors _____ liquid _____ vapor _____ low press (70 psi) _____ high press(70.1 psi or higher) ```

Answer 53

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

Question 54

3 way valves fail to ____ path

Answer 54

90 degree bend route, not straight through

Question 55

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

Answer 55

1.5" is SCHED 80 | 2" - 6" is SCHED 40

Question 56

anything above 1.25" must be connected via____

Answer 56

Welding

Question 57

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

Answer 57

threaded connections have weakened wall at the joints

Question 58

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

Answer 58

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

Question 59

number of supports is determined with what 2 factors in mind

Answer 59

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

Question 60

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

Answer 60

when the oil pot is cold but not frosted