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40 Cards in this Set
- Front
- Back
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what is air cooling? |
-the simplest means of cooling -the little fins in the cast provide a greater area for conduction and convection to dissipate the heat -drive pulley is usually geared like a fan to provide airflow -for bellow 88°C |
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what are the two types of liquid cooling? at what temperature are they used? |
-thermo-syphon cooling between 88°C to 121°C -circulated (pumped) cooling over 121°C |
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what is thermo-syphon cooling? |
-this system uses water or glycol for cooling and the cylinder must be cast with coolant passages. -as the water heats up in the cylinder water jackets, it travels by convection to a cooling tank. -the cooled water at the bottom of the tank then flows into the cylinder to cool it |
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what is circulated cooling? |
-the most common system used with industrial compressors -cold water is pumped into the cylinder near the discharge valves (where its hottest) and out near the suction valves in order to even out temperatures and reduce stresses caused by thermal expansion. |
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should cooling water enter from the top of the cylinder or the bottom? why? |
the bottom, to ensure there is no air trapped in the water jackets. |
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⭐️cooling water temperatures should be....⭐️ |
approximately 5-10 c above the inlet air temperature to avoid causing condensation in the cylinder. |
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what is the purpose of a bore liner? what are the two types? |
so when there is wear the liner can be removed and replaced rather than needing to replace to whole tube -dry liners -wet liners |
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what is a dry liner? |
it is a sleeve that fits inside the cylinder bore that does not come directly in contact with the coolant. -the walls are much thinner than in wetliners -good contact with the housing for efficient heat transfer -most common
picture page 6 |
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what is a wet liner? |
-wet liners come into contact with the coolant -they have a thicker wall to withstand compression pressures -flanged top and o-rings contain the coolant.
picture page 6 |
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how is a lubricated compressor lubricated? |
-they have a pressurized oil system that injects a number of drops of oil per minute. -the oil system must be at a slightly higher pressure than the cylinder -oil is normally carried out with the compressed gas to lubricate the discharge valves |
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what are clearance pockets and what are they used for? |
-some compressors have varied demand, it is necessary to provide some means of controlling compressor output. - it increases the size of the clearance volume -discharge pressure is not affected, only the output volume |
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if the clearance volume is increased does it increase or decrease compressor output? |
it decreases |
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when is a fixed volume clearance pocket used? |
when the compressor usually runs at full capacity or a specific reduced capacity on a regular basis |
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when is a variable volume clearance pocket used? |
when the output must be changed by varying amounts on a regular basis. its can be adjusted anywhere between fully open and fully closed |
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when can the VVCP be moved? how about the fixed volume pocket? |
-VVCP: only when the compressor is not operating -fixed volume: when the machine is either off or on |
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how are new cylinders tested? |
they are hydro tested to 1.5 times the maximum allowable working pressure of the cylinder |
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once the cylinder has been running for a few hours what needs to be done? |
the bolts need to be re torqued |
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what is preload? |
to ensure that the frame and distance piece is not supporting all the weight of the cylinder and piping, the cylinder support is preloaded to take some of the weight |
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how often should rod runout be checked regardless of maintenance? |
yearly, due to settled fondations |
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what is the primary reason rod runout is such a big deal? |
it is to keep the rod running straight through the piston rod packing |
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what are some factors that affect piston rod runout? |
-improperly shimmed crosshead -pipe strain -worn crosshead or wear bands -bent piston rod -twisted or settled main frame
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what are the five different types of packing? |
1)pressure breaker 2)radial cut 3)tangent cut 4)anti-extrusion or back up 5)wiper |
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when would a metalic packing ring be used? |
-when there is extremely high pressures -they need good lubrication and cannot be used where there is steam or other things that will thin out the lubricant |
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what is a the pressure breaker? (piston rod packing) |
- is is a single radial cut ring -it is found in the first cup -its purpose is to throttle the pressure allowed to enter the packing case. -allows a little bit of pressure through beacuse the other rings need to see a little so that they work. |
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which ring is the main sealing ring in a radial and tangent cut pair |
the tangent cut |
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are back up rings usually radial cut or tangent cut? |
radial cut |
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do the letters or markings on the packing seals face away from or towards the pressure? |
towards |
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a pair made of one radial cut ring and one tangent cut ring seals... |
in one direction only |
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two tangent cut rings together seals... |
in both directions |
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why are two tangent cut rings used closest to the distance piece? |
to prevent the escape of gas into the distance piece on compression and to prevent pulling gas in from the distance piece on the suction stroke |
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what is vented packing? |
-A vent is connected by internal passages to the area between the last two ring grooves and out to the vent connection on the flange -it's primary purpose is to act as a gravity drain for any oil or leaking gases so they can be vented to a safe discharge location |
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In lubricated packing what must be installed on the lubrication line |
A check valve, to prevent gas flowing back |
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How are non-lubricated packing cases cooled? |
O-rings seal off the coolant from entering the seals |
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Do the tension cut rings seal on the face of the next cup or on the machined recess inside of the cup? |
They seal on the flat face of the next cup |
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If a packing case has more than one lubrication line why do they need to be hooked up to separate pumps? |
To prevent oil from taking the path of least resistance, resulting in no oil being fed to the packing closest to the pressure |
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Which way do wipers face? |
The markings should be oriented to face the oil being removed |
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What type of cut do oil wipers have? |
They can be either radial or tangent cut |
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Decreasing suction pressure results in _______ compressor rod loading |
Increasing |
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A honed surface on the cylinder surface promotes what two things? |
1) cylinder and ring lubrication 2) ring sealing and break-in |
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Card # 40 |
Finished |
