51
8.2
Intermittent duty
Operation must be interrupted whenever the highest permissible operating time is reached. The following breaks are
necessary depending on the duty rate c.d.f. of the electric chain hoist:
Duty rate c.d.f.
Break (min)
15 %
5 times running time
20 %
4 times running time
25 %
3 times running time
30 %
2.5 times running time
40 %
1.5 times running time
50 %
1 times running time
60 %
0.66 times running time
Table 15: Duty rate for intermittent duty
8.3
Example
The electric chain hoist SK 030/52 type 500/1-8 is to lift loads of 500 kg to a height of 3 m.
Performance data:
load capacity
500 kg
lifting speed
8 m/min
– high speed;
duty rate
40 %
– high speed;
At the beginning of the lifting operation the electric chain hoist has a temperature of approx. 20 °C.
c.d.f.
= 0.75 min
The hoist can be operated for approximately 30 min. without a break. This means
40 cycles x 500kg load = 20000 kg transported load.
After 30 minutes of operating time, 1.5 minutes break for each minute of operating time must be taken (i.e. 3 times
the operating time). This break is usually necessary for slinging and taking off loads.
Caution!
Cooling periods are imperative for extreme lifting heights (from 10 metres on).
Low lifting speed should only be used for precise lowering and lifting of loads. It is not
suitable when greater lifting heights shall be driven through.
Option
:
To protect the lifting motor a thermal overload device is offered as an option (24 Volts low
voltage control is required!).
9
Duty rate of the electric trolleys
If the hoist is equipped with an electric trolley the operators have to take care of the duty rating of the trolley as well.
This especially applies to very long track systems.
Electric trolley type
Duty rate
Running time (t
B
in min)
Trolleys with a
single
speed
40 %
30
Trolleys with a
double
speeds
40/20 %
30*
* The ratings are relevant for the fast travelling speed.
Table 16: Duty rate for electric trolleys
3 m (lifting) + 3 m (lowering)
8 m/min
Summary of Contents for STAGEKET
Page 55: ...55 13 Example of Declaration of Conformity...
Page 56: ...56 14 Example of Declaration of Incorporation...
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