Industrial Flashcards
What is a level control switch?
Magnetically actuated for close control of liquid level and maintains close control of liquid level. It is a metering device and can be used as a high side float.
What 2 types of compressors are used in industrial refrigeration?
screw and semi-hermitic
What is the benefit of screw compressors?
Require less maintenance and are efficient
What is the primary side of the ice rink?
The side that has the evaporative condenser and compressor which has the refrigerant in it.
What is the secondary side of the ice rink?
The ice sheet and evaporator which has the brine in it.
What are the 2 types of flooded evaporators used?
shell and tube and plate exchanger
In the flooded evaporator where is the primary (R-717) and secondary refrigerant (brine)?
In the shell and the brine is in the tubes
What does a surge drum do?
Prevents liquid from getting back to the compressor and is located on top of the flooded evaporator
What is the advantage of the plate heat exchanger?
It is smaller and less maintenance
Where is the high side float located and what does it do?
It is located between the condenser and evaporator. It responds to the load on the condenser. As the load increases it allows more liquid through the float valve into the condenser.
Where is the low side float located and how does it operate?
In the chiller or next to the chiller in a column of liquid. When liquid refrigerant level is low the valve allows liquid in to increase flow.
What is a high side float pilot operated valve?
Follows the rise and fall of the liquid column.
How does the evaporative condenser pump get its start?
Signal is received from discharge pressure control
Does oil cooling take priority over everything else? T or F
True
What is double indirect system?
Primary loop with two secondary loops
What is a reverse return system?
Keeps every pass across the rink the same distance to keep the pressure drop approximately the same.
25 ppm TLV/TWA
Exposure to 25 ppm for an 8 hour work day and a 40 hour work
week is permissible
35 ppm ST/STEL
Exposure to 35 ppm must be limited to no more than 15 minutes
300 ppm IDLH
Exposure to 300 ppm is Immediately Dangerous to Life and Health
For R-717 how many BTU’S for latent heat of evaporation?
575 btu/lbs
Why is R717 such a good refrigerant?
Because of its
ability to absorb heat while passing through an
evaporator of a refrigeration system. Has no Global Warming Potential or Ozone
Depletion Potential.
What level of toxicity and flammability is R717?
B2, it is toxic and has some flame propagation
Would you need a bigger compressor for R717 in comparison to R404a?
Yes, the specific volume is much larger than R404a
What happens in low alarm. (25ppm, lower than 35ppm)?
- Initiates MUA and Exhaust Fan.
• Will create a local alarm strobe/siren
• Will not dial out to monitoring or emergency services to allow minor problems to be repaired
What happens mid level (50ppm)?
- MUA/Exhaust continue to operate
- Local alarm strobe/siren continue to operate
- Monitoring company notified
What happens at high level alarm (200ppm)?
- MUA/Exhaust continue to operate
- Local alarm strobe/siren continue to operate
- Monitoring company notified
- Emergency Services notified
Where is the alarm sensor located?
Sensor location 10 ft above finished floor or 10-30 cm from ceiling
How many air changes need to happen in the mechanical room?
15 air changes per hour
How many pounds of water to one pound of ammonia in a deluge tank?
8lbs of water to 1lb of ammonia
What is different about the TX valve in DX ammonia system?
Has a 2 stage pressure drop to reduce wear from flashing
Why does the DX coil have to be large in ammonia?
To be able to superheat the refrigerant leaving the evaporator
How far does the relief pipe need to be pipe according to B52?
15ft above the roof or 25ft away from the building or windows
How high does the emergency valve/fire box need to be installed B52?
No less than 7ft
What’s the most popular method of freezing?
Air blast freezing
How is most industrial compressors, evaporators, and condensers piped?
In parallel
What is a multi stage or compound system?
Refrigerant flows in series through 2 or more compressors. Suction of the high side is discharge of low stage.
What temp do you use a compound system?
-10C 15F
How is de-superheating accomplished?
Using an inter cooler between compressors
What are the 2 types for feeding the evaporator?
Gravity flooded and liquid over feed
How is liquid feed different from gravity flooded?
You need a pump and a low pressure receiver
