Shah Deniz in the Azeri sector of the Caspian is close to producing first gas. The field’s TPG500 production jackup, the first of its kind outside the North Sea, includes a 200-ft high derrick, supplied by National Oilwell.
For transportation of personnel within the derrick, operator BP specified an explosion-proof elevator with a high carrying (450 kg) capacity, but also occupying the smallest possible footprint. The solution was provided by Alimak, which had worked with derrick suppliers on previous BP-led projects.
Following joint project planning with National Oilwell, most of the equipment was sent to Norway for pre-fitting to the partially assembled derrick. After subsequent transportation to Baku via ships and barges, the complete derrick was erected on the TPG500. An Alimak supervisor participated in final installation works, including connections to the elevator, which then underwent a comprehensive test before commissioning.
The end-result is an Ex-rated elevator with a carrying capacity of 500 kg, suitable for Zone 1, IIB and T3 environments. The elevator has a transit speed of 0.5 m/s, with four stopping levels, and is capable of travelling more than 150-ft to the top of the derrick.
Maximized floor area
To avoid unacceptable deflection, fixings have been inserted to secure the elevator’s guide rails at key structural points. This procedure necessitated stacking of the drive units and explosion protection electrical panel cabinets, while still retaining sufficient space for essential maintenance access.
Dual Ex drive motors, Ex brakes and the rotary drive system’s permanent mesh all ensure the elevator is locked firmly in place at all times. The over-speed governor and safety-stopping device is also permanently in mesh with the rack, preventing the elevator from falling, according to the spokesman.
The dual mechanical drive pinions and Ex-rated motors via reduction gears are engaged permanently in the vertical machined steel rack, guaranteeing positive control throughout. The elevator is therefore ‘driven’ in both the up and down direction.
Stopping and holding is controlled by the Ex-protected, electro-mechanical brakes, which were pre-tested by Alimak in Sweden under maximum load and speed. Another safety feature is a steel heat shield, which provides extra protection in the event of a blowout on the drillfloor. Alimak’s ‘wrap-round’ door solved the problem of how to minimize usable floor area.
“Unlike an internal elevator,” the spokesman explains, “a derrick elevator is at the mercy of both anticipated and unpredictable storm force winds.” To counter these forces, steel guide rollers have been fitted which are designed to retain the elevator cabin on its tubular steel support mast. Alimak’s design equations also took into account the platform’s pitch, roll and yaw.•
For more information, contact Anders Nilsson, Alimak. Tel +46 910 87000, fax +46 910 56690, [email protected], www.alimakhek.com
