A clean cut

Cutting and sealing has been combined into a neat package in Interventek’s Revolution valve design. Elaine Maslin reports.

An in riser valve assembly, above, and landing string system, right. Images from Interventek.

A common plea in today’s cash-strapped, low investment environment is for technologies that can help make the industry more efficient – or even do more – at a lower cost.

Small technology firms, often set up by ex-operator or ex-major service firm staff who’ve seen and grabbed the opportunity to do things differently, are not short of offerings.

Interventek Subsea Engineering has developed an intervention system valve – the Revolution Valve – to address the short-comings seen in current systems.

Formed in 2014, the firm’s senior staff have spent time at Expro, FMC Technologies, BP, and Weatherford, among others.

The Revolution Valve, which won the Emerging Technology Award in last year’s Offshore Achievement Awards, is designed to cut slickline, braided cable and coiled tubing during intervention operations, should the need arise, and then, contain well pressure. It can cut intervention media up to and including 2in outer diameter, 0.203in wall thickness, 147 KSI tensile strength coiled tubing. A slim design, through use of a rotary actuator, means it can be used in in-riser and slim-line open water interventions.

Ball valves are predominantly used for this and are often used in series to compensate for their shortcomings, says Gavin Cowie, Interventek’s managing director.

Furthermore, moves towards larger bores and higher-pressure environments, and new requirements in API 17G, particularly around fatigue capacity, will only add to those pressures, he says. Interventek has designed a more compact valve that can cut and seal in one movement, while having separate cutting and sealing components to avoid damage to either.

The firm has a license agreement with Hunting, which has already been successfully using the valve in the field. The firm has also made a deal to supply 6.375in 15,000psi in-riser Revolution Valves to Louisiana-based Professional Rental Tools (PRT) to service the Gulf of Mexico.

Left: open valve. Right: closed valve.

“The starting point was a recognition that valves in the market place were not suitable,” Cowie says. “There were shortcomings with existing technology and these were becoming more apparent as industry increased requirements for larger bores and higher pressure applications.” In some cases, this had led to systems being built entirely from expensive exotic alloys, because of the larger bore size, but the same outer restriction, resulting in little wall section to play with.

The existing arrangement has been around a long time, he says. Ball valves, which rotate to create an open bore, or close it off, were used, with the edge of the bore used to cut then contain as it closed, using O-ring type seals.

“Historically ball valves were used, but they are built as containment devices. The process of cutting an intervention medium would damage the seal surface,” Cowie says. These valves were OK for 3in, 5000psi bores, but have become challenged with larger bore sizes and higher pressures, as well as issues created by higher temperatures and material degradation.

Interventek’s valve doesn’t contain elastomer seals and uses elements of ball valves and flapper valves in combination, to meet both cutting and containment requirements. It is a ball valve in that it rotates, but the corrosion resistant sealing surfaces are kept clear of the cutting edges until they are safely able to form a seal.

Hydraulic pressure is used to move the valve using a compact fractional turn rotary actuator, shaped to fit within the outer geometry of the tool, but not protrude, so it can be positioned inside a BOP, and allow intervention equipment to run through, but kept away from well fluids and sand, etc. Cowie says that axially-operated actuators are mechanically poorer and less efficient and take up more space. Because Interventek’s actuators are on the outside of the valve, they can also be serviced faster and more easily, Cowie says. “You can take it apart with simple hand tools and replace the actuator seals in five minutes,” he adds.

Interventek has used SolidWorks for 3D modeling, which enables you to create models which can reflect anything you can imagine, Cowie says, something which would have been more difficult in 2D programs. While 3D modeling isn’t new, wholescale adoption of a system like SolidWorks is, Cowie says. “That, coupled with an analysis capability, i.e. Ansys, lets you do extensive analysis of stress conditions and load regimes to optimize before manufacturing.”

Having manufacturers able to make the components also helps. Elements like the cam grooves, along which the sealing flapper moves on the inner surface of the valve, can be created using spark erosion. This uses a CNC machine to create a carbon electrode negative die, which has a current put through it to burn into the metal. Again, while this technique isn’t new, the speed at which it can been done – from 3D modeling to manufacturing – is. Instead of taking 6-12 months to create a ball valve, it is possible to manufacture a Revolution Valve in around 12 weeks.

The firm has its eyes on a couple of markets. The first is in-riser well completion and intervention landing string valves, using a 6 3/8in, 15,000psi version, which can be tailored to suit, for new subsea well developments and heavy intervention from mobile offshore drilling units using a drilling riser or BOP stack. The other is open-water light weight intervention systems, as either an open-water well control valve with compact versions of the valve, or as part of a subsea abandonment tree (a compact lightweight tree-on-tree system for use during well abandonments to allow well access without overstressing the Xmas tree).