Despite being a relatively routine activity in the oil and gas sector, subsea exploration is not cheap to perform, costing up to a million dollars a day for vessels, ROVs and personnel. To avoid unplanned downtime – and the associated additional expenditure – it is essential that mission critical equipment is readily available and does not suffer connectivity issues. Christian Taylor, Engineering Team Leader at Bulgin, discusses the challenges associated with developing new solutions for this market.
Remotely operated underwater vehicles (ROVs) are integral to the oil and gas industry’s subsea operations. In the region of 500 ROVs are in active field use at any one time – with a further 2,000 on standby globally – performing a range of exploratory and maintenance activities on the seabed at depths well beyond the capabilities of manned submersibles. As the name suggests, ROVs are not autonomous, but are linked to the host ship via a neutrally-buoyant tether to allow direct operator input at depths of up to 7,000 metres. Downtime to resolve communication issues is a major problem for the industry, with ROV hire alone costing up to $100,000 a day, plus the significantly higher costs of chartering and crewing the host vessel. Robust connectivity solutions that maintain an effective link between the operator and ROV are essential, ensuring unplanned and unnecessary downtime is avoided.
Subsea exploration – a connectivity challenge
ROVs are frequently required to operate in harsh conditions – rough seas, thick sediment and very deep water – and the design of connections between the ROV and its umbilical tether have traditionally depended on ‘heavy engineering’ solutions to ensure reliability. However, this approach has a significant drawback, as connectors designed to continuously withstand extreme pressures and corrosive environments for many years are often very difficult to access or terminate and de-terminate; termination of ROV tethers for deployment can routinely take up to 24 hours. The inefficiency of this process, coupled with its potential for costly delays, led the industry to investigate alternative connectivity strategies, turning to other automation markets for possible solutions to enable ROV tethers to be terminated and de-terminated in an hour or less.
Built to withstand extreme environments
The Bulgin name is synonymous with dust and waterproof connectivity solutions for a vast array of applications, and the company has extensive experience in developing innovative connectivity solutions for use across multiple engineering disciplines. However, even for a company with such wide-ranging expertise, the high value/low volume subsea applications market presents a truly unique set of challenges that require completely bespoke solutions, rather than off-the-shelf mass produced connectors.
Using its broad knowledge of environmental sealing and connector design, the Bulgin team has developed the ROV Tether Connector, a novel device that provides a quick yet secure mating solution. Its circular design, 316 stainless steel casing and threaded collar locking mechanism offer uninterrupted power, data and fibre optic connectivity. To enable operation at the high pressures associated with working at depths of 3,000 to 7,000 metres, the Tether Connector is a compensated unit, using free flow of dielectric oil from the ROV itself to provide dynamic pressure balancing.
‘Cross-talk’ between the high voltage power lines (up to 5 kV) and low voltage data lines is one of the biggest challenges to overcome with this type of multi-feed connector. Ideally, the screening path from the umbilical tether through the connector interface and into the ROV should be uninterrupted but, when the bulk of the individual connectors for each feed are taken into account, this is not practical. The problem is resolved by using a combination of carefully designed connector geometry and screening materials to isolate the various power, data and optical feeds. Anticipating that power and data demands are likely to vary with each generation of ROVs, the Bulgin team chose a modular internal construction, future proofing the Tether Connector and simplifying reconfiguration for new applications.
An exceptional solution for subsea applications
Bulgin’s combined connectivity expertise and bespoke engineering capabilities have enabled it to develop a truly unique solution for the subsea market; the ROV Tether Connector. This innovative solution provides complete environmental sealing and reliable operation to depths of 7,000 metres, and allows rapid and reliable tether coupling to be accomplished in as little as 30 minutes.
For more information about Bulgin products, please visit: www.bulgin.com