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74 Cards in this Set
- Front
- Back
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Screw compressors are considered to be what kind of compressor? |
Rotary positive displacement compressor |
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Screw compressors are used to deliver what kind of pressure? |
Constant volume at Lower pressures |
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How can you increase the pressure of a Screw Compressor? |
Add multiple stages |
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What are two basic types of screw compressor? |
Single rotor and duel rotor |
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Which type is more Common? |
Dual rotor |
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Duel rotor screw compressors have two main categories which are? |
Wet and dry |
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In a wet screw conveyor which router is commonly driven? |
The male rotor (lobe) |
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What is the advantage of the dry screw compressor? |
Oil free air |
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How is the dry screw compressor normally cooled? |
Screws are sprayed with water |
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Which screw compressor require a timing gear |
dry dual rotor |
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Oil in a wet screw compressor is used to do what |
Lubricate, seal and cool the air end |
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What screw compressors are commonly called what? |
Air end compressors |
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What does the location of the discharge port determine? |
Pressure ratio of the compressor |
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What happens when the discharge port gets smaller? |
Pressure increases |
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What are the two lobe profiles of a screw compressor? |
Symmetrical and asymmetrical |
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Which lobe profile is most common today? |
The asymmetrical |
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What advantages does the asymmetrical lobe have? |
Asymmetrical lobes improve efficiency, increase volume and decrease leakage |
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Asymmetrical lobes have what type of clearance? |
Tighter clearance than symmetrical lobes |
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The male rotor has what type of profile? |
Helical lobe |
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The female rotor has what type of profile? |
Helical flute |
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4+6 asymmetric profile is used for what type of compressor? |
Oil injected |
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3+4 asymmetric profile is used for what? |
High volume flow low differential pressure applications |
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6+8 asymmetric profile is used for what |
High differential pressure and reduce volume flow |
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How is discharge pressure of a screw compressor determined? |
By the location of the inlet and discharge ports |
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Where is the rotor Support bearing located? |
Mounted to the end covers of the housing |
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Why is rotor end clearance on the discharge side important? |
It effects compressor efficiency |
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Rotor discharge end clearance is usually how much? |
.001 to .002 |
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Where must the fixed bearing be located? |
The discharge end |
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Thrust acts in which direction? |
opposite direction of airflow |
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The suction end of a screw Compressor has what type of bearings |
Floating |
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Wet screws do not require what? |
Timing gears |
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What purpose does the film of oil between the two rotors have? |
It allows the male rotor to directly drive the female rotor |
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Flooding the casing with oil eliminates the need for what? |
Seals between the compression chamber and the bearings |
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How much air can a single stage wet screw compressor compress? |
100 to 125 psi |
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Where does air enter the compressor? |
Through the inlet filter and inlet valve |
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What type of filter is generally used on an air compressor? |
Paper filter which traps particles down to 5 microns |
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What is the purpose of the air/oil separator? |
It separates oil from the air |
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What must the air passed through before it leaves the separator and goes into the system? |
The minimum pressure valve |
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What is the purpose of the minimum pressure valve? |
To build a minimum pressure inside the separator and Get oil flowing on start up |
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What is the first priority before sending air to the system? |
Getting the lubrication system working |
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What is the purpose of the minimum pressure valve on system shut down? |
To prevent discharge air from rushing back into the separator |
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Where would be a common location for a temperature probe? |
The compressor discharge |
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What does the temperature Gauge measure? |
Air temperature leaving the compressor |
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What should the average temperature of air leaving the compressor be? |
180-205 degrees Fahrenheit |
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Where does air go once it leaves the separator? |
The aftercooler to reduce moisture |
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What is the purpose of the blowdown valve? |
To vent pressure from the separator and prevent Oil from being pushed out the compressor filter |
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How is the blowdown valve usually Controlled? |
A solenoid |
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Oil free rotary screw compressor require _______ that wet compressors do not? |
Timing gears |
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The backlash of an oil free Rotary compressor should be more or less than its clearance between rotors? |
Les |
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Try screw comparison do not require what? |
Lubrication in the compression chamber |
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The main advantage of a dry screw compressor is what? |
Oil free air |
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What is another major requirement in a dry screw compressor? |
Shaft seal between the oil free compression chamber and Oil flooded area. |
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Dry screw compressors require what type of lubrication system? |
Separate lubrication system |
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Try screw air compressors use what type of cooling systems? |
Air cooled or water cooled |
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Where is the water and checked it on a dry screw compressor? |
Directly into the compression chamber |
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How does a moisture separator work? |
Spins air and throws out heavy drops of moisture |
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What happens to air as it’s cooled? |
It takes up less volume and requires less horsepower to compress it |
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What is the main difference between a dry screw in a wet screw compressor? |
Try screw compressors require a water separator |
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What screw compressors use what type of separator? |
Oil separator |
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Where is the minimum pressure valve located on a water injector dry screw compressor? |
top of the separator |
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What is the purpose of a minimum pressure valve on a wet injected dry screw compressor? |
Keeps the minimum pressure to inject the water |
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What is done with the cooling water in a water injector dry screw Compressor? |
It is recirculated and reused after being sent through the heat exchanger |
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Screw compressors are designed to run at what type of capacity? |
100% capacity at all time |
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What is suction throttling? |
Used to control the suction flow or discharge pressure in a compressor |
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What two modes does a compressor run in? |
Fully loaded or fully unloaded Open inlet valve or close inlet valve |
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How is displacement control achieved |
With turn valves, poppet valves and slide valves |
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What is the purpose of a mixing valve? |
Keeps oil at require temperature to prevent moisture |
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Moisture inside of the compressor causes what? |
Emulsification, rust and sludge buildup |
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What is the purpose of the oil pressure shut down switch pretty ******* clear? |
Shut unit down if pressure falls below preset limit |
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The oil cooler in an air compressor system is often combined with what? |
The after cooler |
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What is the purpose of the oil cooler? |
Remove heat from the oil before it goes back into the compressor |
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What are two types of oil cooler? |
Air to air or water cooled heat exchanger |
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What is the purpose of the oil stop valve? |
To stop the flow of oil as a compressor shuts down |
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How is the oil stop valve controlled? |
With the solenoid or air operated valve |
