Modular MDDM top drive designed to cut time for change outs, slash failures

Posted on 30 October 2009

In 2005, Transocean went in search of a “next-generation top drive” that could significantly improve operational performance to meet customer demands.

Specifications required for this new-generation design were tough, including a 99.9% uptime on an annual basis. Out of several ideas proposed by different equipment manufacturers, Aker Solutions’ MDDM (modular direct drilling machine) was selected. According to Aker, the MDDM’s increased performance would enable Transocean to drill wells up to 50,000 ft, with an overall design philosophy of reducing the total cost of ownership of a derrick drilling machine.

A contract was signed by October 2005, initiating a development phase with the two companies collaborating on the design and field-testing of the new top drive.

Transocean provided background data based on analysis of the downtime history of 72 top drives from various vendors over a five-year period. Design and the prototype were completed in 2007 and implemented on the Transocean Enterprise-class newbuilds.

MDDM design

Perhaps the most notable feature of the MDDM is its modular design. When an important component of the top drive breaks down, only that part is changed out, thus reducing the time required for change-out and repair and therefore overall downtime.

“We put a lot of effort into making the MDDM easy to take apart and put together again,” said Bjørn Rudshaug, vice president R&D for Aker Solutions. A lot of time was spent on clearly defining the different functions and splitting them up into different modules, then achieving optimal interaction at the interface between the modules, according to the company.

So what kind of time reduction can the user expect to see? According to results of a workshop test simulating the drilling rig environment, it takes less than 70 minutes to change out an AC motor. Some top drive designs require more than five hours for a motor change, he said. The time required to change out the main shaft on the MDDM is around eight hours, compared with approximately 72 hours with other top drives, he added.

The MDDM design also tackles downtime from the other end – the root cause of failure. A analysis of the bearing and main shaft was completed during the design phase, with Transocean creating a load chart for deepwater vessels based on actual measurements on their high-end deepwater rigs, according to Aker. This data set formed the basis for calculation of the main bearing in the MDDM, significantly reducing the risk for failure in this key component.

The analysis also showed that the lubrication and cooling system for the bearings were just as critical as the bearings – if the lubrication system fails without proper monitoring, a subsequent bearing failure was likely. This resulted in a redundant lubrication system, with two systems working independent of each other with full lubrication flow and pressure monitoring.

An identical analysis for motors also was done, finding that the motor cooling system was one of the main root causes for failure. A failure of the motor cooling system has the same effect of a failure of the motor itself. Once again, a redundant system was implemented, with a water-cooled AC motor that has a redundant cooling system.

Aker believes that redundant systems are key to planning out-of-service time. The company said that if the motor fails on the MDDM, it can still deliver 80% of full drilling performance with one motor. “It’s really designed to minimize downtime in every possible sense of the word,” Mr Rudshaug emphasized.

The top drive system also features a 1,200-ton or 1,250-ton lifting capacity, making it a powerful machine suitable for the deep and ultra-deep wells that

Transocean and other drilling contractors are drilling offshore. It also incorporates dual motors delivering 2,400 hp and more than 100,000 ft-lb of continuous drilling torque, another significant advance, the company says.

Safety also will be increased with the MDDM, with a remote-controlled multifunctional pipe handler that enables 360° continuous rotation capability. Additionally, the need for stabbing hands when handling casing has been removed, eliminating manual intervention.

Manriding operations also are eliminated by providing maintenance personnel a stable work platform to gain access to the top drive system.

Other features of the MDDM include:

• Continuous main shaft from power swivel through gearbox and pipe handler.
• Remote-controlled multifunctional pipe handler, enabling 360° continuous rotation capability.
• Auto-positioning to ensure safe, easy and accurate orientation.

The MDDM has already been installed in the derrick of Transocean’s sixth-generation ultra-deepwater drillship Discoverer Clear Leader. All Enterprise-class newbuilds are also equipped with the MDDM, Aker said.

Mr Rudshaug added that Aker is discussing the MDDM with other clients as well, though he said it was too early to provide details.

“All components are made from the highest quality, which means it’s not the cheapest top drive. But it is, from our opinion, the best,” he said. “It is the Lexus among top drives.”

Aker also has created the MDDM 1000, which uses the same modular design philosophy and many of the same key components, but adjusted for lower loads and smaller physical dimensions. The prototype of this machine is scheduled to be completed in Q3 2008, with delivery beginning in Q1 2009.

Drilling simulator

Through its recent acquisition of First Interactive, Aker has launched a new-generation drilling simulator that will enable realistic 3D visualization and real-time scenario-building. While the simulator will be primarily used for training of rig operators, it also holds great opportunities for the upgrade market, Mr Rudshaug said. First, a 3D model of an existing installation is made, then verified with offshore laser scanning. Then a control system is added to the rig so the simulator is fully integrated and reflects the rig. When changes are made – only on the simulator – the upgrade can be verified on the rig without costing the operator dayrate.

The upgrade can even be verified before it’s actually built, he said.

“This gives great opportunity for optimizing and reflecting the fact that the most expensive part of a drilling rig upgrade is the lost income of time spent on installation and commissioning. This time will be significantly reduced by this method.”

Mr Rudshaug explained that drawings on paper can be hard to imagine. But when it’s run like a video game as you’re sitting in a simulator chair, a much more direct picture can be formed of how the upgrade might work.

“It’s also good for optimizing procedures and movements and how things have done on the drill floor. We have great expectations,” he said. The simulator is based on the advanced drilling simulators that Aker has already sold in conjunction with drilling packages.

TorqueMaster

One of the newest rig innovations coming into the drilling industry to improve safety and efficiency is the high-efficiency jackup from Maersk Contractors, two recently delivered from Keppel FELS in Singapore and two still under construction. The four units will be identical, all featuring drilling packages from Aker.

Included in the drilling package is Aker’s TorqueMaster, which can make up and break out pipe, collars and casing from 2 3/8 in. to 20 in. It is based on two tongs that can be separated, with the main tong a gateless one that can rotate 360° continuously with a torque capacity of 150,000 ft-lbs. The machine also offers a makeup and breakout capacity of 50,000 ft-lbs between the main tong and drill floor and between the top drive and the backup tong.

To continue the trend especially seen in the North Sea of using remote operations facilities onshore to manage offshore work, a computer monitoring and executing system in the TorqueMaster allows for off-site monitoring. It also stores makeup and breakout information on the machine.

The Maersk Resilient, the first of the four high-efficiency jackups, went into operation in March 2008 and has been “a milestone for us because it was the first TorqueMaster that commenced operation,” Mr Rudshaug said.

As Aker and Maersk gained operational experience, he said, there have been some “teething problems” – with the HMI (human-machine interface) and with some extremely small-diameter production tubing. The fixes have been quick, however, he pointed out.

A TorqueMaster also is already working on StatoilHydro’s Heidrun platform with good results, he said. A total of 20 TorqueMasters have been sold to date.

Future, challenges

Aside from the industrywide challenge of finding qualified personnel, Aker is facing a unique challenge on the supply side coming from – of all places – the wind mill industry.

“The slew ring bearing we use in a lot of our equipment is the same type that many of the wind mills use, and the wind mill industry is draining the market of slew ring bearing,” he said. “We quote for 30 and the wind mill producers quote for 3,000. Who will get attention? It’s a big problem for us.”

On the technology side, Aker is looking towards integrated operations as the way forward. “We are striving to align the whole Aker Solutions into integrated operations thinking. How can we get the operation itself, not only the drilling operation but others too, to be more integrated?” Tools such as the drilling simulator is such an integration tool, but “there are more aspects to come. That’s a challenge we’re facing right now.”

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