Severn’s Valve Innovation Cuts
Corrosion Risk for Offshore
Operators
Triple offset butterfly valves from Severn Glocon Group now benefit from a technical solution which
eliminates galvanic corrosion without compromising firesafe capability.
The OCT®SW innovation was driven by market feedback from offshore oil and gas operators in relation to
seawater service valves used for fire safety. It ensures graphite parts – which can increase the susceptibility
of neighboring metals to corrosion when exposed to seawater – do not contact line media.
S
eawater service valves play an integral role
feeding water in the event of fire on an
offshore platform or vessel. Their ability to
either supply or isolate sections of the water line
is a critical safety feature. Eliminating galvanic
corrosion while maintaining firesafe credentials
has been an enduring challenge for the industry.
Severn’s valve design overcomes this limiting
factor and has passed fire testing in accordance
with the latest editions of API 6FA, API 607 and
ISO 10497.
Mark Breese, Group Product Development
Manager, Butterfly Valves, says his team focused
on fully isolating graphite parts from line media,
or removing them from the valve entirely.
“Triple offset valves are generally constructed
with graphite packings, gaskets and laminated
metal/graphite seals,” Breese explains. “In
normal operation this noble material provides
good service, but increased risk of galvanic
corrosion in seawater applications has been an
ongoing concern for offshore operators. Our
team overcame significant technical challenges
to develop a sustainable solution that removes or
replaces graphite components from the valves.”
Granted a patent by the UK Intellectual
Property Office in 2018, Severn’s oblique cone
technology (OCT®) is central to this new
solution. For instance, the ‘infinite circle’
geometry of the design enabled the R&D
team to develop a hybrid seal technology that
eradicates the need for graphite.
To validate integrity, OCT®SW valves are
exposed to a stringent fire testing procedure,
involving a 30-minute burn where they are
bathed in flames. Valves are monitored for
leakage throughout the process. After a forced
cooldown period, they undergo further seat
and external leakage testing, and operational
capability is also verified.
“This is a landmark development which will
benefits many firesafe applications, not just
seawater service,” Breese continues. “The team
took steps to ensure the solution is compatible
with additional control valve features such as
anti-cavitation or low-noise trims, extending
its potential use beyond isolation service. It
can also be retrofitted into valves already in
operation.”
One early adopter of the new technology is
an offshore gas compression platform located
off Trinidad and Tobago. Severn has supplied
17 bi-directional OCT®SW valves to control
seawater in its fire safety system. They had to
achieve repeatable zero leakage and meet fire
safety testing standards as well as avoiding
wetted graphite inside the valves.
The double-flanged valve bodies were
manufactured in aluminium bronze for general
seawater resistance, and they also incorporate
internal and external anti-blowout protection.
This advanced safety feature ensures the shaft
cannot blow out, even if all external bolting is
accidentally removed.
As Breese explains: “Standard valve products
couldn’t satisfy this specification, but as we
specialise in arduous valve applications, we
were well-equipped to handle it. In fact, we
shipped to the end user one month ahead of
schedule.” •
More information about Severn is available at
www.severnglocon.com.