Artymiuk Jan: A new concept drilling hoisting systems rigs

and a valve with a varying pressure setting. The charge pump supplies the pumps with oil when extending
the cylinder. The pressure control valve controls the pressure at the B-side and returns the excess oil
to the tank when retracting the cylinder. The excess oil is conditioned in a cooler and a filter arrangement
prior to reaching the tank. This solution is implemented for the 14x450 kW pumps, handled by a distribution
manifold containing 112 cartridge valves switching 14 pumps individually between 4 closed loop systems.
Each main pump in the HPU is controlled by a closed loop regulator controlling the flow and the pressure
from each pump, [9]. The set point for the closed loop control of each pump is given from by the RamRig
control system.

Fig. 2. RamRig

new rig offshore concept.

Fig. 1. The main elements of the RamRig

hoist assembly,

showing the yoke (A), dolly (B), top drive (C), equalizer
assembly (D), lifting wires (E) and the ramcylinders (F)

Operation

Hoisting. Hoisting of loads is done by allocating the desired number of pumps for hoisting via the

operator stick giving the setpoint for the pump controller. Hence, the pumps will give an output flow
proportional to the stick input. The flow from the pumps is directly proportional to the speed of the cylinder
and the speed of the dolly. The load to be lifted determines the pressure. All loads are lifted with the same
speed and accuracy within the pressure limitations of the pumps. The valve blocks in the near vincity of the
cylinder serve two functions; securing the load when in the parked position and shifting the cylinder to act in
the regeneration mode. The regeneration mode shifts the cylinder to act as a plunger cylinder. With the
geometry of the cylinder, this indicates a half of the load and a double of the speed with the same power
available.

Regeneration of energy. The regeneration of energy is a storage of the power available when lowering

the cylinders. This is done by pressurizing the B- side of the pumps by shifting the variable pressure setting
valve in the distribution block. The B line is connected to the accumulator via a check valve. Independent of
the precharge pressure in the accumulator and the pressure created by the load, the accumulator is filled via