Memoirs of a GDC intern

Next are the components on the rig floor starting with the noisiest part- the drawworks. It’s a JC-70D type and any one who did science in primary school would describe it as a large winch or drum with a large spool of drilling line wrapped around it. While standing close to it, you can easily understand how it works, driven by two massive DC motors each 800 kW via an air clutch and drive chain mechanism which you can hear whenever the driller activates control and releases the brake. 

Even more amazing is the automatic reeling and unreeling of drilling line as the travelling block is raised and lowered-of course I could understand how the leBus grooving system does all this for even multiple rolls of the drilling line and it would still arrange it so neatly on the drum. The function of the drawworks is to deliver the drill bit to and from its area of operation and to transmit the loads to the rig structure. To enable this, the drilling line is attached to an anchor on the drum on which the wire is spooled, and the wire is fed from a storage spool that I could see on the ground just behind the rig….of course the spool contains enough wire to last for long because I don’t remember there being a shortage of drilling wire that necessitated any pulling in of more wire from the spool. The wire from the spool is fed to the DLA-Dead Line anchor, then to the “fast line” of the crown block at the top of the derrick where it goes through a series of pulley sheaves and down through the travelling block sheaves before passing back to the crown again and onto the drawworks drum and once enough wire is spooled around the system, the rest is securely clamped to the DLA. The “fast line” is subjected to most wear and it’s the one I concentrated on most while lubricating. 

For its working, the drawworks has two DC motors fitted with toothed couplings connected to sprockets that use chains to drive even larger sprockets for more torque. The driven sprockets are bolted onto the drive shaft and do not rotate till the high or low gears are engaged when the driller selects the required clutch setting while raising the travelling block and drill string. Basically, normal operations involved engaging clutches and motors for any hoisting operation and disengaging to allow a free fall and braking to control gravity falling of loads. Of course I had learnt about the pneumatic clutches and this is the first place I saw it being applied…..ever heard of fawick pneumatic clutches…..same principle.