All-metal valves meet tighter LNG safety standards

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These are exciting times for the LNG industry with new technologies being  adopted for liquefaction and regasification, and as LNG is increasingly used in small-scale applications, particularly in transportation. However, there is evidence that some of the valves being used in LNG fuel systems do not meet tightening regulations that insist these critical components should be “fire-safe”.

By Duncan Gaskin*

Historically LNG has been shipped over long distances in large LNG carriers (LNGCs), with capacities of up to 260,000 cubic metres. The rules and regulations surrounding ships built for this purpose are well established and are known as the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code).

First adopted in 1983, the code provides an international standard for the safe carriage by sea of liquefied gases, among other substances, in bulk by prescribing the design and construction standards of ships carrying these cargoes and the equipment they are entitled to carry.

The code is currently being revised following a comprehensive five-year review that has taken into account latest advances in technology and to reflect new applications for LNG within the marine sector. The revised version is expected to be adopted by the International Maritime Organisation (IMO) in 2014.

“Fire-safe” cryogenic valves: One of the most important requirements of the IGC code is that LNG cryogenic valves are “fire-safe”. The IGC code explicitly states that “material having a melting point below 925°C should not be used for piping outside the gas tanks”.  Piping also includes the valves.

To meet this requirement and enhance safety of valves when used in marine applications, our engineers have designed an all-metal valve.  This means that if any valve is exposed to a fire on board a ship, the valve integrity is maintained and there is no leakage of gas through the seat of the valve that could cause a fire to escalate.

LNG as fuel: One of the most exciting developments currently taking place in marine transport is the increasing use of LNG as a marine fuel. LNG offers significant cost savings over existing marine fuels and significant reductions in pollutants that will allow ships to comply with ever-tighter environmental laws.

There are around 50 vessels currently sailing that run on LNG exclusively or as a dual-fuel. This is set to increase as ship-owners build new vessels or convert existing vessels to use LNG as a fuel.

In response to the increase in the use of LNG and other new fuels, the IMO is drafting the International Code of Safety for Ships Using Gases or Other Low-Flash Point Fuels (IGF Code) to create a set of standards similar to the IGC Code, but for fuel systems.

Currently there are interim guidelines that essentially follow the requirements of the IGC code, but the lack of definite rules and inexperience of LNG fuel applications has seen the adoption of sub-standard cryogenic valves for fuel systems. The full IGF code is likely to be approved at the IMO in 2015.

The IGC code explicitly requires components of valves to be able to withstand a temperature of 925°C. This has been adopted in the interim IGF guidelines. However, there is already evidence that cryogenic valves using PTFE or PCTFE seals, with a melting point below 400°C are being used in LNG fuel systems.  This is worrying from a safety point of view, as the valves installed in a fuel system need to keep their integrity at all costs or the engine could lose its fuel source. If that were to happen a ship could be left drifting at sea, potentially endangering crew and cargo.

LNG bunkering: A more recent development has been the publication of the OGP Draft 118683 guidelines for bunkering of LNG to ships. The guidelines were drafted by the International Association of Oil and Gas Producers (OGP) and International Organization for Standardization (ISO), and aim to give ship operators and LNG bunker providers safety guidelines on the bunkering of LNG. They are not formal IMO regulations at this stage, but may well form the basis of more legally binding regulations in the future.

More than ever the marine industry needs strong regulation to ensure the near impeccable safety record of transporting and using LNG for transport at sea is maintained as LNG is used in new applications.

(The photo above, courtesy of Viking Line, is of the company’s new ship, M/S Viking Grace, the world’s first passenger cruise vessel to be fuelled by LNG – making it the world's most environmentally friendly vessel of its kind. She entered service at the start of this year.)

* Duncan Gaskin is Sales Director of Bestobell’s Marine Valves Business Division.  UK-based Bestobell LNG has an extensive track record of supplying valves for the cargo-handling systems on LNGCs and FSRUs. Its valves meet the requirements of the IGC code and are approved by Class Societies that implement the IGC code standards. For more information visit www.bestobellvalves.com 

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