T.D. Williamson (TDW) recently announced the successful development and field deployment of the Subsea 1200RC Tapping Machine, described by the company as its new compact remote-controlled subsea hot tapping machine. The system is said to be extremely lightweight, allowing hot tapping to be carried out from the safety of a Diving Support Vessel (DSV) or platform, resulting in significant safety benefits and improvement in operational control.
Subsea hot tapping of pipelines is performed for a variety of reasons, including tie-ins, pipeline repair, insertion of instrumentation, facilitating chemical injection or providing access for temporary isolation tools. The full process – which involves installing the hot tap assembly, performing the tap and recovering the hot tap machine – has invariably necessitated diver assistance.
This has meant that the potential for subsea hot tapping was inevitably shaped by human factors, namely the limits of where divers can operate. Diver operations are limited to those taking place in a maximum of 984 feet (300 m) of water depth, whereas a significant portion of existing subsea field infrastructure, as well as projected future developments, are in waters down to depths of 9,842 feet (3,000 m). Furthermore, the ability of divers to operate effectively in shallow water can be affected by environmental factors, such as in wave breaking zones.
The demands of deep water and the risks in shallow water have necessitated development of a completely diverless, remote-controlled system. Says Mike Benjamin, vice president, Offshore Pipeline Solutions for TDW, “The most critical part of the hot tapping process is the point at which the drill penetrates the pipe, which has now been rendered diverless by the Subsea 1200RC Tapping Machine. The direct control and visibility from a laptop will revolutionize hot tapping, giving way to a more efficient and safer process.”
While the installation of the hot tap assembly and subsequent removal of the machine will still require diver assistance when a pre-installed tee is not present, the performance of the tap itself is remotely-controlled by a TDW technician onboard the DSV or platform. The system is a topside-driven hot tap machine with “passive Remotely-Operated Vehicle (ROV) interface,” which means that it is a stationary ROV with its hydraulics and control system attached to the Subsea 1200RC Tapping Machine, and operated from an on-board laptop.
The new subsea system has demonstrated the feasibility of conducting the critical tapping operation entirely by remote control. But the system offers more than just reduction in diver activity, the safety benefits of which are obvious. The further benefits of the new technology are that it offers total control and visibility of the tapping operation where there was none before. Built-in sensors allow continuous recording of actual pressures, temperatures, rotation and movement of the pilot drill and cutter. They shed light on what is going on inside the enclosed space right at the heart of the cutting operation. The laptop-based program facilitates control remotely, rather than relying on the divers’ manual handling of the cutting process.
Benefits were demonstrated in the first field operation. The machine was tested and successfully deployed in 2011 on a tapping operation for a project in water depths of 298 feet (91 m). The tap size was 16-inches on an existing 28-inch gas pipeline. TDW performed the operation from a DSV. The cutting operation itself lasted approximately two hours. The entire operation was conducted safely, while flow through the gas pipeline continued uninterrupted.
George Lim, business development manager for TDW, said “We were thrilled with how well the Subsea 1200RC Tapping Machine performed. The safety benefits and operational control of the device resulted not only in a satisfied customer, but it highlighted the enormous potential of this new technology.”
The benefits of using the Subsea 1200RC Tapping Machine in offshore projects are expanding, says TDW. The experience gained with this remote-controlled tapping machine will inevitably enhance the development of completely diverless systems covering all activities involved in a hot tapping operation. Moreover, TDW says these benefits will easily be extended to onshore operations. A remotely-operated system automatically implies safe operations, for instance in emergency situations where pipeline intervention and repair takes place in dangerous environments following an incident. Web: www.tdwilliamson.com.