ROTORCOMP NK 31 - Pressure Dew Point of Compressed Air; Cold Starts

8.2
[en] 02/2014
Installation and operating manual - NK 31ROTORCOMP VERDICHTER
8.1.5 Pressure dew point of compressed air
Example:
1*) Temperature of the intake air is 20°C/68°F,
humidity is 50 %, resulting in an absolute
humidity of approx. 8.6 g/m
3
in the intake air.
At a pressure of 10 bar, the pressure dew
point is approx. 51°C/124°F.
2*) Temperature of the intake air is 40°C/104°F,
humidity is 90 %, resulting in an absolute hu-
midity of approx. 45.6 g/m
3
in the intake air.
At a pressure of 10 bar, the pressure dew
point is approx. 92°C/198°F.
8.1.6 Temperatures
Note
The optimum operating temperatures for the
screw compressor system can only be achieved
if the oil circuit components (thermostat, cooler,
fan, etc.) have been properly designed and the
supply and exhaust air temperatures of the instal-
lation room and the compressor system make
this possible.
The entire thermal economy must be calculated.
8.1.7 Condensate damage
The relative humidity and the nal operating
pressures must always be taken into account
in accordance with the selection graph for the
working temperature of the thermostat element
and for the compressor operating temperature in
order to prevent condensate from forming in the
system.
8.1.8 Cold starts
During compressor cold starts, the viscosity
of the oil must enable the sufcient, immediate
supply of the compressor with lubricant following
starting while taking into account the higher pres-
sure losses in the oil circulation which is still cold.
The higher cold-starting power requirement must
not overload the compressor drive.
50
45
40
35
30
25
20
15
10
5
0
-5
-10
24,7
19,5
15,2
11,8
9,0
6,9
5,1
3,8
2,8
2,0
1,5
1,0
0,7
32,9
25,9
20,3
15,7
12,0
9,1
6,9
5,1
3,7
2,7
2,0
1,3
0,9
41,1
32,4
25,3
19,6
15,0
11,4
8,6
6,4
4,7
3,4
2,4
1,6
1,1
49,4
38,9
30,4
23,6
18,1
13,7
10,3
7,6
5,6
4,1
2,9
1,9
1,3
57,6
45,4
35,5
27,5
21,1
16,0
12,0
8,9
6,6
4,8
3,4
2,3
1,5
65,8
51,9
40,5
31,4
24,1
18,3
13,7
10,2
7,5
5,4
3,9
2,6
1,7
74,0
58,4
45,6
35,4
27,1
20,6
15,4
11,5
8,4
6,1
4,4
2,9
1,9
82,3
64,9
50,7
39,3
30,1
22,8
17,2
12,7
9,4
6,8
4,9
3,2
2,2
30% 40% 50% 60% 70% 80% 90% 100%
Determination of absolute humidity
in intake air [g/m
3
]
Relative humidity
Temperature of intake air [°C]
Absolute humidity
in intake air [g/m
3
]
6 bar
7 bar
8 bar
9 bar
10 bar
11 bar
12 bar
13 bar
14 bar
15 bar
Pressure dew point [°C]
0 -5 -10 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
1*) 2*)
2*)
1*)
45,6
8,6
51 °C 92 °C
Figure 8-1 Pressure dew point graph