• Cylinder Hoisting Rig (CHR)

    The cylinder hoisting rig is a field-proven main hoisting system with integrated heave compensation for offshore drilling and well intervention vessels. The system has competitive performance for tripping pipe and heave compensation. Parallel wire ropes routed over large sheaves provide mechanical redundancy and significantly increase safety as well as minimizing wire rope wear. This results in wire change-out intervals of 5-10 years, thus coinciding with special periodic surveys and effectively eliminating the need for cut and slip in operation.



    The second-generation cylinder hoisting rig is more compact and energy efficient with significantly lower and near-constant power consumption even in the heaviest and fastest trip-out lifts. This significantly decreases peak power loads on the generators, enabling smaller power plants to be installed on offshore vessels and operated at a higher efficiency. These combined benefits result in a longer lifetime. The compactness of the new CHR brings with it significant weight, footprint, and cost reductions by the removal of an external compensator. The patented transformer power unit powers the hoisting cylinders, quadruples the useable energy of an accumulator, and flattens the system’s power consumption.  

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    The transformer power unit enables active and passive heave compensation by transforming accumulator power to the required power at the cylinders. This is superior to solutions using external compensators or specialized active or integrated accumulators because it does not add extra fluid volume to the system, which would decrease the system stiffness. Therefore, the CHR maintains a high system natural frequency and enables higher system stability and control precision. The result is a highly responsive and accurate heave compensation system providing high position accuracy, low weight-on-bit, and tension variation while drilling, landing, and locked to bottom.

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    In a worst-case black-out with no power source, passive compensation can continue by opening a direct connection between cylinders and accumulator, turning the CHR into a conventional hydraulic-pneumatic compensator.


    Added value for drilling contractors include:

    • Initial and running costs of offshore vessels are decreased by the significantly lower and near-constant power demands, with up to 80% reduction compared to conventional solutions. This allows smaller electric generators to be installed on drilling vessels and operated at higher efficiency, reducing wear.
    • Energy consumption reduction ranges from 15% - 70% in tripping operations, giving significant fuel savings compared to a hoisting system with a conventional HPU.
    • The CHR with TPU has its own independent transformer accumulator energy storage system with unmatched combination of high cycle capacity, life-time, and useable energy density compared to alternative solutions. This provides full power smoothing capability for the CHR without the need to load a drilling vessel’s battery energy storage system. This extends the vessel’s battery life-time and lowers its capacity requirements, ultimately providing significant savings.
    • The CHR with TPU can be interfaced with a vessel’s batteries if desired. This would further reduce power consumption and allow the CHR to charge the vessel’s batteries.
    • Hoisting cylinders act as actuators and load bearing structure, allowing weight and cost of drilling tower or derrick to be significantly reduced. 
    • Weight, cost, and footprint reductions due to integrated heave compensation functionality.
    • Superior safety from high responsiveness in active heave compensation as well as continuous passive heave compensation in worst-case black ship scenarios.
    • Wire change-out intervals of 5-10 years, coinciding with special periodic surveys (SPS) and eliminating the need for cut and slip in operation.
    • Retractable main hoisting cylinders provide low center-of-gravity, resulting in larger setback capacity and operational window during transit.
    • Integrated active and passive heave compensation in the main hoisting cylinders of the CHR eliminates need for external compensator system, saving weight, cost, and footprint.  

    Key features:

    Superior safety 

    • Tried-and-true hydro-pneumatic passive compensation can last days up to weeks in complete blackout with no back-up power.
    • Hoisting and lift-off can be performed in complete black ship.
    • Triple hydraulic safety barrier for load control with load holding valves, gate valves, and pumps.
    • Parallel hoisting wire ropes and cylinders provide mechanical system redundancy 
    • No single point of failure, which can lead to overall system failure.
    • Anti-recoil function for protection against string-parting events during drilling.
    • Well intervention mode for anti-recoil protection also ensures no lock-up of heave compensation in locked-to-bottom operations.
    • Satisfies offshore standard DNV-OS-E101.

    Peak power shaving

    • Up to 85% decreased power consumption for the same hoisting performance compared to systems with traditional HPUs.
    • Unrivalled integrated power peak shaving capability, giving a near-constant power consumption throughout entire load and speed range. Innovative transformer power unit and smart active power control algorithms absorb the required amount of power in the transformer accumulator to smoothen out power consumption. 
    • Vessel power plant/generators will benefit greatly from low and constant power consumption because this enables smaller generators to be installed while also increasing life-time due to smaller power variations.
    • Higher energy efficiency as the hydraulic power (pressure and flow) transfer between the accumulator energy storage and cylinder actuators is transformed by the transformer power unit and no longer controlled through flow throttling like on conventional systems, thus eliminating considerable amounts of heat-dissipated energy loss.
    • The TPU enables quadrupled useable energy density in an accumulator compared to an accumulator in a conventional system. Traditional systems require a higher pressure in the accumulator for its stored energy to be utilized, which is not the case when using the TPU. When combined with the elimination of flow throttling, the useable energy is quadrupled in a same-size accumulator compared to conventional systems.
    • Energy recuperation is inherent in a hoisting system with an accumulator, but the amount of recuperation is far superior in the second generation CHR due to the increased energy density and higher energy efficiency of using the transformer power unit. Interface to offshore vessel battery is also available as an option for further power reduction and to enable the hoisting system to recharge vessel battery.
    • The cylinder hoisting rig has a fully sized and independent transformer energy storage system for enabling low and constant power consumption. This provides full power smoothing capability without requiring power from a vessel’s battery energy storage system, thus extending vessel battery life-time and lowering its capacity requirements.

    Maximum up-time

    • No down-time to cut and slip enabled by parallel wire ropes and excellent sheave-wire wear characteristics.
    • Change intervals on wire between 5-10 years depending on type of operation (well intervention vs drilling). 
    • Low sheave rotational speed and large diameter minimizes wear.
    • In-field changeable wire groove segments for easy maintenance and wire wear.
    • Mechanical and hydraulic redundancies with parallel wire ropes, sheaves, and cylinders allow continued operation even when two cylinders are removed. 
    • Modularized design of transformer power unit stacks means the hoisting system can be operated even with TPU stacks being offline or taken out.


    • Quick and practical performance upgrades enabled by modularized design (e.g 1250 to 1500 short ton capacity). 


    See Table 1 below for typical system specifications. The system parameters are very flexible in the design phase with many variations being attainable outside of the table values (including higher capacity).   

    Second Generation Cylinder Hoisting Rig (CHR) with Transformer Power Unit (TPU)
    Hoisting capacity at elevator (short tons) 750100012501500
    Hoisting height (m)38 or 5138 or 515151
    Hoisting speed max (m/s)2,52,52,52,5
    Passive and active heave compensation stroke (m)7,627,627,627,62
    Passive heave compensation peak load capacity at elevator (short tons)750100012501500
    Active heave compensation force (+/- short tons force)125165125150
    String-break protectionIncludedIncludedIncludedIncluded
    True passive compensation in complete blackoutIncludedIncludedIncludedIncluded
    Integrated power smoothing (no rig battery required)IncludedIncludedIncludedIncluded
    Auto drillerIncludedIncludedIncludedIncluded
    Well intervention mode (anti-recoil and lock-up protection)OptionOptionOptionOption
    Power regeneration to rig batteryOptionOptionOptionOption
    Transformer boost*OptionOptionOptionOption
    Condition Based MonitoringOptionOptionOptionOption
    Ready for Arctic operationsOptionOptionOptionOption

    *Transformer boost requires higher installed power, but provides even higher hoisting speeds.

    An optimized layout and lower hoisting speed can achieve the same (or better) tripping speeds at a lower cost than simply increasing hoisting speed. The most suitable solution depends on the layout requirements. 

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