» Articles » Hobbs Valve provides solution to Galvanic Corrosion in duplex Butterfly Valves in offshore platforms.

Hobbs Valve provides solution to Galvanic Corrosion in duplex Butterfly Valves in offshore platforms.

Hobbs Valve can provide a solution to a common problem found in valves on offshore oil rigs; Galvanic Corrosion. Their solution is to remove all Graphite from their valve internals, so they can offer a fire-safe certified, duplex valve, which is non-graphite.

What is Galvanic Corrosion?

Galvanic Corrosion occurs when there is a difference in oxidation potentials of metallic ions between two or more metals. The greater the difference in oxidation potential, the greater the risk of Galvanic Corrosion. The less noble metal will corrode and the more noble metal will not corrode. Galvanic Corrosion occurs at or near the contact points of 2 metals or alloys with different electrode potentials.

Galvanic corrosion 2 Galvanic corrosion

Galvanic Corrosion is a huge problem in the offshore oil world, where dissimilar metals in valves react when in contact with seawater and subsequently leak and fail due to Galvanic Corrosion. These valves leakages and failures come at a significant costs, with an inability to pump oil resulting in lost revenue up to £2,000,000 per day and costs of minor valve repairs reaching £30,000 a time.

Valve leakages and valve failures due to Galvanic Corrosion

A major Oil & Gas Company were experiencing this exact problem in the triple offset butterfly valves in Super Duplex installed at one of their offshore oil platforms. The following internals of the valves contained graphite and so a typical galvanic corrosion process occurred, whereby the more noble metal (graphite) caused corrosion of the less noble metal (Super Duplex). This resulted in the valves seals leaking, which of course led to significant repair costs.

•Gland Packing - This consists of three rings of braided graphite with a ring of die formed graphite above and below to form a seal around the stem.

•End Plate and Body Seal Gaskets -These are made from nickel reinforced graphite sheet.

•Body Seal - This is made from a laminate of graphite sheets and Super Duplex Stainless Steel.

Hobbs Triple Offset Butterfly Valves constructed from specialist materials

Hobbs Valve are the only company who can offer a solution to overcome the problem of galvanic corrosion in valves installed in offshore oil rigs, at the same time as retaining Fire-safe Certified status.

Hobbs Valve removed all Graphite from their valve internals and replaced them with HNBR (Hydrogenated nitrile butadiene). HNBR is a rubber fibre and is not subject to Galvanic Corrosion. HNBR will not react with Super Duplex or any other metal, thus providing a cost-effective solution to galvanic corrosion.

Hobbs Valve cut out butterfly valve

Therefore, Hobbs Valve can offer a fire-safe certified, duplex valve, which is non-graphite. This really is a unique proposition and can save significant repair and replacement costs as well as avoiding hugely undesirable occurrences of downtime.

In July 2012, Hobbs Valve supplied 4 18” PN10 SuperDuplex HNBR triple offset butterfly valves to the offshore platform, with hopefully many more orders to come.

Will this innovation reduce the huge maintenance costs associated with the running of offshore oil rigs? Will this innovation have a significant impact on the occurrences of downtime?

Company Profile

Hobbs Valve Limited

Hobbs Valve are UK based and are at the forefront of innovation, designing and manufacturing high performance Triple Offset Butterfly Valves for the global Industries of Oil and Gas, Chemical, Petrochemical, Nuclear, Marine and Power.

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