Discover how engineering excellence and heritage has driven Severn’s OCT TOV Butterfly Valve to deliver unmatched reliability in Seawater environments.

Severn’s research & development team has designed a Butterfly Valve that solves the problem of galvanic corrosion and meets strict fire test standards. Utilising the over 60 years of engineering excellence, the team of technical experts achieved this by using Severn’s patented Oblique Cone Technology (OCT). The OCT-SW takes this patented technology to the next level by eliminating the need for graphite in the seal and maintaining firesafe capability.

What is galvanic corrosion and its costly effects?

The impact of galvanic corrosion on critical assets due to seawater process conditions is an enduring problem for offshore oilfields. At best, it increases the workload and repairs associated with planned shutdowns. At worst it can result in rapid or unexpected damage, leading to unplanned or emergency shutdowns. Either way, it is a costly problem which harms efficiency, putting additional pressure on plant operating costs. However, Severn have utilised their engineering heritage, research and development & repair intelligence knowledge to develop a valve that deals with the issue of galvanic corrosion head on.

Why does galvanic corrosion occur? The cause of galvanic corrosion (also referred to as ‘dissimilar metal’ or ‘bimetallic’ corrosion) is an electrochemical reaction between two different conductive materials in close proximity. It results in one – the least noble of the two – being preferentially corroded. To combat this risk, the general rule is ‘do not mix metals’. However, when it comes to the design and development of assets for harsh offshore environments, things are rarely that straightforward.

Modern critical safety systems used on offshore sites are often highly sophisticated

to cope with the extreme natural conditions and industrial challenges with which they must contend. They come with extreme technical demands but must manage physical ones too; systems that need to feed water to combat fires must be durable enough to cope with the corrosive effects of the sea. Seawater service valves play an integral role in the process and their ability to either supply or isolate sections of the water line is a vital safety feature. Therefore, eliminating galvanic corrosion while maintaining firesafe credentials has been an enduring challenge for the industry.

In recent years, the use of graphite sealing technology has surged. Graphite’s extreme range of properties and characteristics makes it an ideal material in many ways. It is soft, flexible, and easy to cut, but it has high heat resistance and is almost inert. However, it is also the only non-metal that can conduct electricity. Furthermore, its nobility exceeds that of noble metals including stainless steel, bronze, and titanium. Yet it is often paired with these materials in valve manufacture, in the form of seals, packings and gaskets. From a galvanic corrosion perspective, graphite has become not only the solution to problems but can often be the cause.

Traditionally, Triple Offset Butterfly Valves have used graphite materials in their construction, which can cause galvanic corrosion in seawater applications. This is a problem because it can significantly reduce the effectiveness of the valve’s sealing components, compromising safety and leading to potential costly unplanned downtime.

By working closely with end users and operators, Severn has recognized this issue, and with its significant engineering heritage and technical expertise, has designed a long-term solution. The Severn team of engineering experts designed a valve that either replaces the graphite components completely or stops them from contacting the line media. This significantly reduces the risk of galvanic corrosion in day-to-day operations and ensures the highest level of safety. Ensuring you achieve safe operations and minimal downtime.

The Oblique Cone Technology (OCT) Seawater (SW) Triple Offset (TOV) Butterfly valve is a revolutionary type of valve designed primarily for use in saline applications, such as offshore oil and gas operations. These valves play a pivotal part in safety systems, as they play a crucial role in firewater systems. Due to Severn’s engineering heritage and technical expertise in the oil and gas operations sector, this valve has been designed with over 60 years of engineering excellence ensuring it helps the end user achieve their core remit of safe operations and minimum downtime.

Severn has developed a hybrid polymer metallic seal that moves away from the use of graphite laminates. By utilising a primary metallic seal with a secondary polymer seal, not only have Seven removed the graphite from the seal but have additionally increased the valves isolation sealing capabilities and maintained the firesafe performance crucial for such critical applications. This coupled with isolating any graphite gaskets and packings from encountering the line media means that at no point during the normal operation of the valve do the graphite and seawater mix, eliminating the risk of galvanic corrosion and the costly effects it can have on production.

In addition to addressing the corrosion problem, Severn’s Butterfly Valves also meet important fire test standards such as API 6FA, API 607, and ISO 10497 accreditations. As such the OCT Valve is certified fire-safe and can be relied upon in critical emergencies for the end user and operators, ensuring safe operations and minimal downtime.

The team also took steps to ensure the valve design could not generate a spark and risk starting a fire itself. They followed the ISO/IEC 80079-36:2018 ATEX standard and ensured that no static charge could build within the valve. This additional element of care renders the new OCT-SW valve design suitable for a wide range of applications, beyond seawater service further emphasising the versatility of the valve design.

The OCT-SW can be manufactured from corrosion-resistant materials such as Aluminium Bronze, Super Duplex, and Titanium, with the added knowledge that anti-blowout protection comes as standard. Available in standard and non-standard face to face dimensions and various body styles such as lugged and double flanged, the valve can be easily retrofitted into existing pipeline spaces and is an ideal upgrade when operators are experiencing issues with galvanic corrosion.