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The objective for all sizes of rigs today is overall drilling performance. It is generally accepted that the best performing rigs are those that have top drives and AC Drawworks with the control systems that make them work faster, smoother, safer and automatic. This application is cost efficient and effective for Doubles and Triples.  On Range III singles cost, weight and space are further major considerations.

The advantage of advanced range III singles over doubles and small triples is that they are light, move fast with much fewer loads, have no set back and very small drill floors. Many have been successful at removing hands from the drill floor for all conventional pipe handling. Because of their push toward more mechanization, tripping speeds are improving. The advantage is lost somewhat when they try to put an AC top drive and AC Drawworks in the smaller mast (smaller than 250T due to weight, cost and space). As a result, hydraulic top drives are applied to singles (and many doubles) up to 250T. On the hoisting side of drilling performance, AC Drawworks started off limited in speed because they are sized for torque. They hit corner HP once on their hoisting curve. Mechanical transmission Drawworks (5-speed) can hit corner hp 5 times within their hoisting curves. The question becomes how do we keep Range III systems smaller, lighter and more efficiently moved but increase the hoisting capacity and achieve the performance that comes with the AC Drawworks and control systems and do it all cost effectively?

The answer is hydraulic hoisting. The problem with hydraulic hoisting in the past has been that in cylinders a typical design applies 2 possible speeds (one full surface area 1:1 and one regenerating oil from  the rod end back to the blind end 2:1). This results in very slow tripping speeds when moving empty blocks or smaller string weights unless very large hydraulic flows are delivered. Maximum hoisting force is determined by what is needed for stuck casing but about 90% of the work is done lifting string weight that ranges from 60% down to 10% of maximum capacity. Therefore a hydraulic cylinder (or AC Motor) is sized for maximum capacity and only works at 50% of hook load capacity most of the time. This makes the required hydraulic flow requirements too high for practical application.

Enter the Automated Rig Technologies’ Multi Displacement Hoisting Cylinder System where we have surface area ratios of 1:1 up to 6:1 in a virtually conventional cylinder. This product now matches the speed and force control of an AC Drawworks, can trip at full speed like a mechanical transmission Drawworks and can come down as fast as a free fall brake controlled mechanical system.

The Multi Displacement Hoisting Cylinder System has been designed to optimize prime mover power requirements and rig load weights.  Additionally it provides auto-driller capabilities in two modes of operation: rate of penetration (ROP) and weight on bit (WOB).  This system offers the advantages of high power to weight ratio and speed adjustability of a hydraulic system as well as optimization of horsepower transmission at speeds characteristic of a conventional geared system with up to a 6:1 cylinder displacement ratio change. By selectively choosing the right combination of cylinder bore, main rod and pilot rod diameters, a customized five speed transmission can be applied. The three surface areas of the cap end of the cylinder are further augmented by using regeneration of oil from the rod end of the cylinder. The end result is five “transmission” ratios that range from 1:1 up to 6:1.  Conventional cylinder hoisting systems have two typical design ratios; 1:1 and up to 2:1 using standard regenerative circuits. The final product can trip empty, ¼ or ½ hoisting capacity loads at speeds equal to or exceeding the old mechanical Drawworks. Weight on bit and rate of penetration control rivals AC and in fact the programming is the same.

The major technical hydraulic advantage for the Multi Displacement Hoisting Cylinder System over existing hydraulic hoisting cylinder systems is that it requires up to three times LESS hydraulic pump flow and oil storage to move the hoisting system at the same speed as conventional standard regenerative designs. Since the combined surface area of the cylinder is the same as its conventional counterpart, maximum lifting force remains unchanged. This “Hydraulic Transmission” optimizes power from the engines and reduces waste of power using full hydraulic flow and pressure during most times of the tripping cycle. Further hydraulic efficiencies are applied by sharing available flows and horsepower for the top drive with the hoisting system.