In the drawworks for lowering and withdrawing a load, in particular a drilling or a drilling plugging device, in particular for use on floating drilling platforms, which drawworks has at least one brake arrangement for braking and holding the load, an emergency brake device is provided for producing an additional braking force.
1. A drawworks for lowering and withdrawing a load, having at least one brake arrangement for braking and holding the load, and an emergency brake arrangement provided for producing an additional braking force, wherein the emergency brake arrangement comprises an additional brake device which can be engaged alternatively to the brake arrangement, wherein a control device is provided which compares a respective braking-power setpoint with a parameter characteristic of a braking-power actual value achieved by the brake arrangement and, in the event of a differential value of braking setpoint braking actual value>0, activates the emergency brake device so that the differential value corresponds approximately to 0, the maximum total braking power preferably being ≦130% of the braking power setpoint.
2. The drawworks as claimed in claim 1 , wherein the brake arrangement has at least one brake shoe acting on a rotary part and a device for applying a braking force to the at least one brake shoe, the emergency brake arrangement being designed in such a way that an additional device for optionally exerting an additional braking force on the rotary part is provided.
3. The drawworks as claimed in claim 2 , wherein the device for applying a braking force to the at least one brake shoe comprises a spring arrangement applying the braking force to the at least one brake shoe.
4. The drawworks as claimed in claim 3 , wherein the device comprises an arrangement which acts in the opposite direction to the spring arrangement and is intended for controlling the braking force exerted on the brake shoe.
5. The drawworks as claimed in claim 4 , wherein the additional device comprises an arrangement for displacing a seat absorbing the reaction forces of the spring arrangement.
6. The drawworks as claimed in claim 5 , wherein the additional brake device is a hydraulically actuated device.
7. The drawworks as claimed in claim 1 , wherein the brake arrangement and emergency brake arrangement are designed in such a way that in each case at least one hundred percent of the maximum braking power required can be achieved.
8. The drawworks as claimed in claim 1 , wherein the construction of the emergency brake arrangement at least essentially the same as that of the brake arrangement.
9. The drawworks as claimed in claim 1 , having at least one gearbox coupled on the input side to a drive motor and interacting on the output side with a summation gear, wherein the emergency brake arrangement is arranged on at least one of an input side and an output side of at least one of the gearbox and the summation gear.
10. The drawworks as claimed in claim 1 , wherein the emergency braking arrangement is formed by a feeding device for the controlled or regulated lowering, holding or withdrawal of the load, this feeding device being suitably designed for braking and holding the maximum hoisting capacity of the drawworks.
11. The drawworks as claimed in claim 10 , wherein the feeding device comprises an electrically, hydraulically or pneumatically driven motor.
12. The drawworks as claimed in claim 11 , wherein the feeding device comprises a gearbox, to which the motor is coupled.
13. The drawworks as claimed in claim 12 , wherein the motor can be coupled to the gearbox via an additional gear shaft.
14. The drawworks as claimed in claim 12 , wherein the motor can be coupled to an input shaft of the gearbox for a main drive motor for the drawworks.