Pneumatic and hydraulic maintenance questions.
tzn789
APH-3-TMAv1.pdf
1. Using the nomogram and charts (FIGURES 1 and 2) on pages 4 and 5,
determine the diameter of a suitable air main for the distribution of
6 m3 min–1 FAD. System pressure is 6 bar, the length of the pipe run is
175 metres, and a maximum pressure drop of 0.3 bar is allowed.
The distribution main must also include the following :
• 4 bends (r = 2d)
• 2 elbow fittings
• 6 tee connectors
• 2 diaphragm valves.
2. Describe the relevant advantages and disadvantages of using steel, copper
or plastic pipe for a distribution main.
3. What problems may occur if a pipe is specified :
• larger
• smaller
than the optimum value?
4. A compressor delivers 300 � s–1 of free air into a pipe at a pressure of
6 bar gauge. Using the pressure drop formula:
calculate the minimum diameter of pipe if the pressure drop in a system is
to be limited to 0.3 bar when is delivered through a pipe of equivalent
length 160 m .
pressure drop = 800 2
5 31
lQ
Rd .
2
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5. Explain the difference in operation between a ‘macro’ and a ‘micro’ oil
mist lubricator. State where you would use a ‘micro’ in preference to a
‘macro’ lubricator.
6. List four possible causes of overheating on a multi-stage reciprocating
compressor.
7. Produce a system monitoring chart that could be used by a machine
operator to maintain a daily record of hydraulic system performance
details.
8. State the precautions to be taken when changing the fluid in a hydraulic
system from a mineral oil based hydraulic fluid to a fire resistant fluid.
3
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FIG. 1 Pipe sizing nomogram
100 100 90
70
60
50
40
35
30
25
20
15
80
5000
2000
1000
500
200
100
50
20
10
30
20
10
5.0
4.0
3.0
2.0
1.0
2
3
4
5
6
7 8 9
10
Reference line
Internal dia of pipe in mm
Flow of free air in dm3 s–1
Pressure drop through pipe in mbar m–1
Air pressure in bar
Medium weight steel pipe to BS 1387
80
65
50
40
32
25
20
15
4
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FIG. 2 Table of equivalent pipe lengths for valves and fittings as used on air
distribution systems
Equivalent pipe length in m.
Inner pipe diameter in mm. 25
3-6
1. 2
0. 3
1. 5
0. 3
0.15
2
0. 5
40
5-10
2.0
0.5
2.5
0.5
0.25
3
0.7
50
7-15
3.0
0.7
3.5
0.6
0.3
4
1.0
80
10-25
4. 5
1.0
5
1.0
0. 5
7
2.0
100
15-30
6
1. 5
7
1. 5
0.8
10
2.5
125
20-50
8
2.0
10
2.0
1.0
15
3. 5
150
25-60
10
2.5
15
2. 5
1. 5
20
4.0
Seat valve
Diaphragm valve
Gate valve
Elbow
Bend r=d
Bend r=2d
Hose conne- ction T-piece
Reducer d2d
d
r
d
r
Types of fitting
5
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