Discover how engineering excellence and heritage has driven Severn’s OCT TOV Butterfly Valve to deliver unmatched reliability in Seawater Application environments.
Severn’s research & development team has designed a Butterfly Valve Seawater Application that solves the problem of galvanic corrosion and meets strict fire test standards. Utilising the over 65 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, Severn’s 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 Severn’s Oblique Cone Technology (OCT) Seawater (SW) Triple Offset (TOV) Butterfly valve is a revolutionary type of valve designed primarily for use in sealine 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 65 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 Severn 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 Seawater Application 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 Severn’s OCT-SW Butterfly Valve Seawater Application 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.
Severn’s engineering heritage and technical expertise have led to the OCT TOV Butterfly Valve being future-proof for changes in the process conditions to provide increased versatility for the end user.
From the outset, Severn made flexibility a key driving force in the design of the Oblique Cone Technology (OCT) Triple Offset (TOV) Butterfly Valve. Due to Severns extensive diverse engineering heritage and excellence, our expert team of engineers understand that processes and application product demands change over time, whether it is the process conditions or the overall requirements of the valve for the end user. Due to this understanding, the Oblique Cone Technology Triple Offset Butterfly Valve has been designed to incorporate multiple seal options, all fully interchangeable with each other, providing maximum application diversity and usability to ensure safe operations and minimum downtime.
The Laminate seal is the “traditional” Triple Offset Valve seal and consists of multiple metal and graphite layers providing isolation sealing.
The OCT HS seal is a hybrid polymer metallic seal, this seal benefits from a primary metal seal and secondary polymer seal, this provides a reliable and repeatable bubble tight seal time after time. This can also be paired with PTFE packings when graphite being in contact with the line media is a concern. The polymer seal is fully compliant with EN ISO 80079-36 (ATEX).
The OCT SW Valve takes the hybrid sealing to the next level with its versatile high performance. Severn utilises the OCT-HS seal and has designed a valve that ensure there is no graphite in contact with the line media to remove the risk of costly galvanic effects such as internal corrosion leading to valve failure. Whilst doing so the OCT-SW also maintains firesafe certification.
Should the sealing requirement not become as critical, and process conditions become more arduous, the Laminate and Hybrid seals can be changed for the OCT-SS solid seal. As the name suggests it is a solid metallic seal, that can be made from hard-wearing alloys to add longevity to the sealing life of the valve in arduous conditions and can offer a control valve seat leakage.
Based on Severns comprehensive history of severe service control, our team of engineering experts work closely with operators and end uses to identify the correct seal and material selection to provide the maximum reliability and productivity further ensuring minimum downtime.
All the OCT seals are interchangeable and can be upgraded without the need for main valve components being replaced, further emphasising the OCT TOV Butterfly Valves versatility. The fully in field serviceable valve can be upgraded on-site without the need for specialist tools or knowledge, this further ensures that costly unplanned downtime and site waste is kept to a minimum, along with potential loss in production for the end user. All the seal options can be changed on site within a small space of time to ensure site maintenance costs are reduced by upgrading the existing valve rather than discarding and replacing with a commodity product each time.
Each OCT valve is specially designed to be versatile and ensure it has multiple purposes for multiple conditions whilst still delivering maximum performance. With the introduction of the interchangeable seal, these can be easily swapped out to match the end users’ requirements, should they change.
Plant support is booming for Severn.
The cautious global outlook that characterised the oil and gas industry for the past four years has driven a renaissance for established plant. Severn’s heritage in advanced engineering services for existing valve populations puts it at the forefront of growth in this arena. Since 2014, our established plant division Severn Unival has enjoyed exponential growth of 400%, putting its annual order book at £75m, emphasising that plant support is booming for Severn.
Divisional managing director Colin Findlay says leading operators are changing their approach to valve management. The depressed oil price drove a focus on operational efficiency, leading to a wave of new investment to improve the performance of existing assets. Recognising the level of dedicated engineering skill and expertise required to optimise control and choke valve performance, many operators have held competitive technical tenders to outsource this element of plant management efficiently. As the market picks up, this activity is accelerating with operators seeking to maximise performance and productivity.
“Technology is the core driver of efficient and reliable plant operations,” Colin explains. “Following the volatility of 2014 and the prolonged downturn experienced since, oil and gas operators have been keen to find stability and certainty. Investing in existing plant is the most prudent way to achieve this, and operators that continue with this approach alongside investment in new projects will have much surer foundations as the market begins to pick up again.”