Brakes ( drilling rig ) – Readyzone


The draw works main brakes are used to stop the movement of the drill string prior to the arresting of the drill string in the rotary table by means of slips and for allowing drilling line to unreel while drilling ahead to maintain weight on bit. Most draw works use friction-type mechanical brakes, which provide a braking effect by means of physical contact between the rims of the hoisting drum flanges and a brake band. All hoisting drums are provided with two brake flanges, one on each side of the hoisting drum.

Each brake band consists of a flexible steel band with a number of friction-material brake blocks bolted to it. The brake bands are wrapped around the brake rims of the hoisting drum. One end is anchored to each end of an equaliser beam, which pivots at its centre and connects both bands to ensure that braking is shared equally by each band. The other end of each band is movable and is connected through a magnification linkage to the driller’s brake lever( see Figure 2 ).

Braking is achieved by lowering the brake lever, which, in turn, pushes the brake blocks against the rims of the rotating drum. As the brake blocks drag along the rim, the applied tension is magnified towards the fixed end. Hence, the fixed end of the brake band has more tension than the movable end. A driller of average build can apply a large braking force by merely putting pressure on the brake lever, owing to the magnification effect in the brake linkage mechanism.

Draw - Works

Fig. 2 – Schematic of the brake system.

Related Links:-

*  Derrick             *  Drill collar            *  Kelly Drive

*  Drill pipe          *  Rotary table         *  Swivel

*  Tool joint          *  Draw works         *  Drum shaft group

*  Cat shaft and coring reel group    *  Hoisting drum

*  Auxiliary brake    * brakes                                 

Reference : H. Rabia, Oil Well Drilling engineering-Principles and Practice

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