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Second Year Millwright > Compressors > Flashcards

Compressors Flashcards

0
Q

What is atmospheric pressure at sea level?

A

1.01 bar, 14.7 psi, 101.4 3K PA

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1
Q

What is difference between PSIG and PSIA

A

PSIG-psi gauge
PSIA-psi absolute or PSI atmosphere

At zero PSIG there is 14.7 PSIA

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2
Q

When temperature is increased in an enclosed space, the temperature does what?

A

The temperature increases

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3
Q

If the flow rate is constant, and the velocity is decreased, there will be an increase or decrease in pressure?

A

Increase in pressure

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4
Q

Is a compressor more or less efficient at higher altitudes

A

Less efficient

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5
Q

What is the name of the compressor that has power pistons and compression pistons sharing the same crankshaft?

A

An integral compressor

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6
Q

What are three common devices for measuring pressure?

A

Barometer, manometer, bourdon tube

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7
Q

What is the purpose of the crosshead and guides?

A

To keep the piston rod centered through the packing to minimize leakage from the compression cylinder

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8
Q

How is the piston locked onto the rod?

A

It is locked on a shoulder and nut or on a taper with a locknut

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9
Q

In an integral compressor what is the name of the rod connecting from the crankshaft?

A

Master connecting rod

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10
Q

What is a distance piece?

A

It houses the crosshead and cross head guides and oil wipers

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11
Q

What are the two types of airflow?

A

Laminar and turbulent flow

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12
Q

What is the purpose of an intercooler?

A

It increases efficiency. A bonus is it also draws out some moisture

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13
Q

What is the purpose of an aftercooler?

A

To remove moisture

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14
Q

What are three things that all pressure vessels must have?

A

Gauge , drain, and safety relief valve

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15
Q

A safety valve should be set at what pressure in the system?

A

It should be set no higher than the lowest maximum pressure rating of any part in the system

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16
Q

What is the purpose of a multistage compressor?

A

To achieve higher pressures

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17
Q

What causes reciprocating compressor valves to open?

A

The pressure differential

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18
Q

Name two types of positive displacement compressors

A

Reciprocating and rotary compressors

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19
Q

How can you increase the pressure in a compressor arrangement

A

Increase the temperature, decreased container size, put more volume in it, Stage it,

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20
Q

What opens and closes the reciprocating compressor valves?

A

Air pressure differential

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21
Q

What is the difference between a single and double acting compressor?

A

A single acting compressor creates pressure on one side of the piston and the double-acting creates pressure on both sides

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22
Q

What is the function of the crosshead and guides?

A

To keep the piston rod centered through the packing to minimize leakage from the compression cylinder

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23
Q

What is the minimum number of cylinders to make it multistaged?

A

Two

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24
Q

Can you have multiple cylinders on a single stage compressor if so what is it for?

A

Yes you can have multiple Saunders all single stage it is used for larger volume of compressed air or gas

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25
Q

What is the main purpose of the intercooler?

A

To cool the air between stages of compression and increase efficiency

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26
Q

A double acting compressor will generate how many compressions strokes per revolution of the crankshaft?

A

Two

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27
Q

What are the effects of high altitude on a compressor?

A

The higher altitude has less atmospheric pressure so the compressor is less efficient.

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28
Q

What are the two main types of reciprocating compressor unloaders?

A

Inlet valve unloader, pressure switch unloader, bypass unloader

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29
Q

Cooler air makes the compressor?

A

Decreases the amount of power required to compress a gas so it is more efficient

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30
Q

After coolers are used for what?

A

To remove moisture after compression is complete

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31
Q

What are three things every air receiver must have?

A

Gauge, drain, safety relief valve

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32
Q

Any compressor system, the pressure relief valve can be set no higher than what?

A

It must be set no higher than the lowest maximum pressure rating of any part in the system

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33
Q

Define clearance volume?

A

Clearance volume is the space between the piston in the cylinder head when the piston is at top dead center

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34
Q

Define clearence pockets?

A

Clearance pockets increase the clearance volume to reduce compressor efficiency

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35
Q

Define Rod loading

A

Rod loading refers to the sum of the suction and discharge pressures acting on both sides of a double acting compressor piston

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36
Q

Why is Rod reversal necessary?

A

In order to allow oil to flood around around the crosshead pin and connecting rod pin bushings

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37
Q

Before starting work on a compressor what must you do?

A

It was purge the compressor that invented. it must run to purge it.

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38
Q

What are the two ways a piston is retained on the rod?

A

It is locked against the shoulder with a nut, or on a taper with a locknut.

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39
Q

What are the two types of air flow?

A

Laminar flow, turbulent flow

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40
Q

What is the purpose of the receiver?

A

It is used to store the compressed air and to take up fluctuations in demand and allow the system pressure to very within reasonable limits

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41
Q

What are the four components to be compressor valve?

A

Seat,sealing elements,guard, and assembly elements

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42
Q

Valve lift refers to what?

A

How far the lift is away from the ceiling element

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43
Q

Too much of valve lift causes what?

A

Valve flutter or multiple impacting

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44
Q

What are three advantages of synthetic ceiling elements?

A

Lighter weight, reduced noise level, limited damage to other compressor components in the event of failure.

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45
Q

What are the added advantages of v shaped sealing elements

A

Better airflow, reduced turbulence

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46
Q

Which valve has the least restriction of flow?

A

Concentric ring

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47
Q

Of the two valves intake and exhaust which one generally needs to be replaced more often?

A

Exhaust

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48
Q

What Applications are dampened disk valves suitable for?

A

High-speed applications

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49
Q

When are poppet valves a good choice?

A

They are well-suited to applications where there is condensate or other liquids in the gas stream

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50
Q

What is a good practice when one spring any set shows wear?

A

The entire set should be replaced

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51
Q

What are the three measurements on the channel valve?

A

Left check, side clearance, and end clearance

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52
Q

What is a common we in the field to check valve sealing?

A

A leak test fill the seat parts of the valve with the fluid and observe the leakage rate for a set period of time

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53
Q

Pertaining to valves, what is one cause excessive Rod load?

A

Installing a discharge valve backwards or mixing up the suction and discharge valves will cause excessive rod loading

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54
Q

What is atmospheric pressure at sea level?

A

14.7 PSIA

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55
Q

What is the definition of a vacuum?

A

Vacuum occurs when the pressure in a building or container is less than the pressure surrounding it which is normally atmospheric pressure

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56
Q

What are three common devices for measuring pressure?

A

Barometer, manometer, boardon tube

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57
Q

Define pascals law

A

It states that pressure applied to a confined or static fluid is transmitted equally in all directions while being transmitted at right angles to the surface

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58
Q

Define Bernoullis principal

A

It states that if the velocity of a fluid increases the pressure decreases the same happens in reverse

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59
Q

What is special about a labyrinth compressor

A

It has a special design that allows it to run without oil

60
Q

Name to compressor types that run without oil

A

Labyrinth compressor and diaphragm compressor

61
Q

What is an integral compressor?

A

It is an engine and compressor combined into one frame and one common crankshaft

62
Q

How frequently are compressor booster stations needed in kilometers?

A

Every 150-300 km along the pipeline

63
Q

When pressure is increased in an enclosed space, what happens to the temperature?

A

It increases

64
Q

What is the purpose of the crosshead and guides?

A

To keep the piston rod cantered through the packing to minimize leakage from the compression cylinder

65
Q

How is the piston connected to the rod?

A

It is locked against a shoulder, or on a taper with a locknut.

66
Q

What is the distance piece?

A

It fits between the cylinder and main frame to prevent contamination between the cylinder gasses and oil from the crankcase. It houses the crosshead, guides and oil wipers

67
Q

What are some examples of unloaders?

A

Start/stop, inlet valve unloaders, bypass, variable volume pocket

68
Q

What is the purpose of an intercooler?

A

It cools the gas, to increase efficiency. The bonus is that it draws out some moisture.

69
Q

What is the purpose of an aftercooler?

A

To remove moisture

70
Q

What are three types of air dryers?

A

Desiccant type, deliquescent dryer, and refrigeration type

71
Q

What must all pressure vessels have?

A

Gauge, drain, and safety relief valve

72
Q

What is the setting on a safety relief valve?

A

It must be set no higher than the lowest maximum pressure rating of any part of the system

73
Q

What must you do if a higher than 5:1 compression ratio is needed?

A

It must be staged

74
Q

Define swept volume

A

Refers to the volume of air that is swept or pushed out of the cylinder on the compression stroke

75
Q

Define clearance volume

A

The space between the piston and cylinder head when piston is at TDC

76
Q

Why is rod reversal necessary?

A

To allow oil to flood around the crosshead pin and connecting rod pin

77
Q

What are the four components of a valve?

A

Sealing element, valve seat, valve guard, assembly elements

78
Q

What is the best flowing valve?

A

Concentric ring valve

79
Q

Which valve is good for high speed applications?

A

Dampened disc

80
Q

Which valve is well suited for air streams with moisture in it?

A

Poppet valve

81
Q

Explain the leak test on valves

A

Fill the seat ports of the valve with a fluid and observe the leakage rate over a set period of time

82
Q

When one spring shows signs of wear, what should be done?

A

The whole set should be replaced.

83
Q

What would be a consequence of mixing up suction and discharge valves?

A

It would cause excessive Rod loading

84
Q

What is a common type of piston?

A

Trunk style (single acting only)

85
Q

Is the ring land diameter smaller or larger than the skirt?

A

Smaller

86
Q

What is a full floating piston pin?

A

They are free to move inside the con Rod bushing and piston bushing. They are held in with snap rings and are the most common.

87
Q

What is a semi floating pin?

A

It is locked into either the con Rod, or the piston and rotate on the other

88
Q

Define Rod runout

A

It means that the Rod is not running totally straight through the packing

89
Q

What are some causes of Rod runout

A

Worn piston rings, crosshead misaligned, crosshead guides worn, improper preload, setscrew on jamnut incorrect

90
Q

What are some common materials for piston rings.

A

Cast iron, lead bronze, tin bronze, and synthetics (Bakelite, or Teflon)

91
Q

Name three types of piston ring joints

A

Butt joint, angle joint, and step joint (for higher pressure applications)

92
Q

What is the purpose of a rider band?

A

To prevent the piston from touching the cylinder and to support the weight of the piston and half the piston Rod

93
Q

Which rider ring is used if it passes over a valve port?

A

The uncut rider ring

94
Q

What is the most common system of cooling in industrial compressors?

A

Circulated liquid cooling

95
Q

What must be the temperature of the cooling liquid at the cylinder be, and why?

A

It should be set approx 5.5 degrees warmer than the incoming gas, so it doesn’t cause condensation inside the cylinder

96
Q

Name the types of cylinders

A

Cast integral, wet liners, dry liners

97
Q

Give the procedure for checking for cylinder wear

A

Check it inline with crankshaft, and at 90 degrees in several locations

98
Q

What pressure are cylinders hydro tested to?

A

1.5 times their maximum allowable working pressure

99
Q

What should be done to a cylinder that has been honed or deglazed?

A

Should be washed with hot soapy water.

100
Q

Name the four types of packing rings

A

Pressure breaker, radial cut, tangent cut, backup ring

101
Q

Which ring does the most sealing

A

Tangent cut ring

102
Q

Which is the only ring used singly?

A

The pressure breaker ring

103
Q

What ring combination is used on a double acting cylinder

A

Two tangent cut rings dowels together

104
Q

In lubricated packing where is the oil distributed?

A

It enters through the flange at the top and is directed near the pressure side, but not all the way to pressure breaker

105
Q

Where is liquid cooled packing entering ?

A

It enters at the bottom so that no air can get trapped

106
Q

Where is the oil wiper packing found?

A

On the crank side of the distance piece

107
Q

What is proper ratio when setting clearance in piston and cylinder head?

A

2/3 head end, 1/3 crank end. This allows for expansion from heat.

108
Q

What is the purpose of the distance piece

A

It allows access to the oil wipers

109
Q

What is the purpose for multiple compartment distance pieces?

A

In applications where a complete sealing of an explosive gas from the compression chamber must exist

110
Q

What are some ways to balance an opposing throw compressor?

A

Use a balance nut, or different metals in the Pistons. A larger piston made of aluminum will weigh same as a smaller one of steel

111
Q

What are the two types of connecting rods?

A

Straight cut, and bias cut. Bias is less common and you use them when you must pull the connecting rod out through the cylinder bore

112
Q

What are the four main jobs of lubrication?

A

Lubricating, cooling, ceiling, prevent corrosion, reduces wear

113
Q

What type of lubrication system is commonly found on small compressors?

A

Splash lubrication system

114
Q

Name some causes of low oil pressure

A

Increased clearance in bearings, air enters the oil lines, plugged oil filter

115
Q

What are the two common systems for supplying metered amounts of oil?

A

Pumped a point system, and divider block or divider valves

116
Q

Which system allows for individual adjustment to each point?

A

Pump to point

117
Q

What is the operating pressure of the divider system above the last stage cylinder pressure?

A

10% higher

118
Q

What must be done after servicing the divider lubrication system?

A

You must bleed the air out of the lines after servicing

119
Q

Paper element filters down to what?

A

3-5 microns

120
Q

Before locking out a compressor what two things must be done?

A

It must be purged first with an inert gas and then vented

121
Q

After any kind of worker service on the compressor it’s always a must to do this before you start it again?

A

Bar the compressor over one complete revolution two is preferred

122
Q

Where would you find an articulating rod?

A

In an integral type compressor

123
Q

When torquing Bolts on rods what is the minimum number of steps used?

A

Must be done in a minimum of three stages

124
Q

What is a bump check used for?

A

A method to determine whether a bearing is worn enough to warrant further dismantling

125
Q

When sizing a compressor foundation what are the four things to take into consideration?

A

The size, weight, vibration characteristics, and the type of driver

126
Q

What is a wire alignment used for checking?

A

Bearing location measurements

127
Q

When referencing bouncing as a rule the greater number of compressing cylinders the?

A

Fewer the number of vibrational forces will occur

128
Q

When performing a crank deflection test in the dial has a reading of five mills what might be the cause?

A

Soft foot, bent crankshaft, improper installation of compressor

129
Q

Why do we need bearing spread?

A

We need it for location and to keep in place during installation

130
Q

Bearing crush is used to?

A

It is used for good seating and good heat transfer

131
Q

What are dowels and locking tabs used for?

A

Anti-rotation device

132
Q

Why do we have clearance pockets on the compressor and where are they located?

A

They are used to provide a means of controlling the output to meet the demand and are located at the head and

133
Q

What is the primary reason for keeping rod run out within limits?

A

To limit wear and increase sealing

134
Q

Which ring is used by itself and where is it located?

A

The pressure breaker ring. It is located closest to the cylinder or pressure end

135
Q

In a two ring set which ring faces the pressure?

A

Radial ring

136
Q

Dots or letters on the rings face towards or away from the pressure?

A

Towards the pressure

137
Q

What are liquid cooled packing case is normally used for?

A

Oil free applications

138
Q

What happens if the surface of the piston rod is scratched or damaged?

A

It will ruin the seal of the packing

139
Q

We inspect and measure cylinders to see if they are?

A

Straight, round, and within specified dimensions

140
Q

What is the purpose of the connecting rod?

A

To convert rotating motion to reciprocating motion

141
Q

Where are cracks likely to be located on the crank?

A

The corner of the fillets, and around oil holes

142
Q

How does a dynamic system make pressure?

A

It restricts flow to get pressure

143
Q

When does valve flutter or multiple impacting occur and what do you do to correct it?

A

It occurs at high speeds and is fixed by using a dampening desk

144
Q

What should be done to the valve chair bolt when removing the valve?

A

The valve chair boat should always be backed off before removing the valve cover

145
Q

Is compressor rotation the daily check?

A

No. It is only done on installation or when a major service is done

146
Q

What are some examples of daily checks?

A

Oil levels , fluid levels , water temperature

147
Q

What is the purpose of the preload?

A

It is used to compensate for thermal expansion so the rod runs true when at operating temperature

Second Year Millwright (8 decks)

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