Emergency Braking of Fast Running Coal Handling Gantry Hoists
Worldwide bulk handling processes are realized by massive logistic chains. In ports ship unloaders are part of these logistic chains. Often they are realized as gantry cranes with cable grabs, equipped with increasing speeds for trolley drive and hoist dr
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Closure Drive
Hoist Drive Sea Side
Land Side
Grab Trolley
Auxiliary Trolley
Grab
Figure 1: Drive structure for ship unloader with auxiliary trolley
Ó Springer International Publishing Switzerland 2016 V. Litvinenko (ed.), XVIII International Coal Preparation Congress, DOI 10.1007/978-3-319-40943-6_20
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136
S. Vöth
2. Hoist structure Generally hoists consist of a drive train, to the ends of which loads are applied: At one end the motor and the brake are located, at the other end the load is attached. Relative transparent relations concerning the dynamic behavior of the hoist in different service conditions result out of this. At safety oriented hoists as partly in ship unloaders this looks a little bit different. To cover a rupture of the drive train an additional safety brake is located on the board disc of the rope drum. Thus a load can be applied in the middle of the drive train. In comparison to the general hoist structure a modified dynamic behavior of the hoist in general and the elastic drive train especially is the consequence. Especially for the case of emergency-off of safety oriented hoists with a safety brake on the rope drum disc high dynamic internal forces occur in the drivetrain. Thus exists the risk of component failure, which can be observed for crane equipment in practical applications (Schmeink, 2014). The failure of a component, especially the hoist gearing, results in consequences relating safety and availability. The actions of motor and brakes during a braking procedure are not permanent. In fact a sequence of omitting and adding loads on the drive train occurs. Especially the case of emergency-off is considered here with following chronological scenario: After activation of emergency-off and a dead time 'tM the motor torque is dropped out. Parallel the brakes get into action. Takes the brake application more time than the drop out of the motor torque, exist the dead times for the service brake 'tBB and the safety brake 'tSB. 3. Reference system For a closer look on the behavior a loss-free, partly redundant hoist with safety brakes is considered (Vöth, 2015). For the hoist represented as a rigid body model the behavior of load speed over time can be calculated. As a result for example the speed over time for different mechanical braking scenario out of hoisting/lowering the dead load respectively the full load are gained (figure 2). This assumes no variation of frictional behavior, practically given (Römer, 2012).
50
50
40 30 20
Heben
40 7,0s; 2633mm
Hoisting
Hoisting, Dead load
30
'tBB
20
1,2
'tSB
-20 -30
0,2
-10
0,4
0,6
1,0
1,2
Zeit t in s 1,4
1,6
'tSB
-20 -30 -40
-50
-50
-60
-60
-70
-70
Lowering, Full load
Figure 2: Speed characteristics for braking the dead load out of hoisting/lowering
1,8
1148mm
449mm
316mm
439mm
0,8
Lowering, Dead load
Senken
Lowering
-40
0
211mm
Time t in s
830mm
1,0
10
207mm
466mm
0,8
Hoisting speed vH in m/min
0,6
566mm
-10
0,4
359mm
0,2
296mm
0
267mm
'tBB
302mm
Hoisting speed vH in m/min
H
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