Elmac Technologies highlights ISO concerns over propagation of flames through tank PV valves

1st August 2008

With the recently introduced ISO/FDIS 28300:2008 (E) standard challenging the conventional wisdom that there is no need to fit a flame arrester to a storage tank, provided that a PV valve is installed, Elmac Technologies recommends that the gas storage industry heeds this latest piece of safety advice.

"Under the new ISO standard,” comments Elmac Technologies’ Managing Director, Dr. Martyn Cooling, “it is clearly stated that testing has demonstrated that a flame can propagate through a PV valve and into the vapour space of a tank.

"The standard also states,” he continues, “that tests have shown that ignition of a PV valve’s relief stream can result in a flashback to the pressure valve with sufficient overpressure to lift the pallet and allow the flame to enter the vapour space of the tank."

In line with API 2000 from the American National Standards Institute, the current edition of the Health & Safety Executive's HSG 176 document recommends that 'A flame arrester is not generally considered for use in conjunction with a pressure valve, because, even at low settings, the gas efflux velocity exceeds the flame speeds of most hydrocarbon gases'.

In light of the considerations outlined in ISO/FDIS 28300:2008 (E) for tanks with potentially flammable atmospheres, however, flame and explosion protection specialists, Elmac Technologies, firmly believe that tank users should err on the side of caution.

"We are in little doubt that the publication of ISO/FDIS 28300:2008 (E) will cause the API and the Health & Safety Executive to review their current recommendations," adds Dr. Cooling.

"Whilst industry has a reasonable safety record for tanks fitted with PV valves, the ISO reported test results clearly raise a question over current thinking. It, therefore, only seems appropriate to highlight this difference of opinion between the ISO, and both the API and HSG guidance. In our opinion, the most cautious approach is to follow the latest advice."

A note about ISO/FDIS 28300:2008 (E)

ISO/FDIS 28300:2008 (E) is intended for tanks containing petroleum/petroleum products, yet can also be applied to tanks containing other liquids. In such instances it is necessary to call on sound engineering practice and design.

The standard considers the causes of overpressure and vacuum; venting requirements; methods of venting, selection and installation of venting devices as well as the testing/marking of relief devices.

The standard covers the normal and emergency vapour venting requirements for above ground liquid petroleum/petroleum products storage tanks as well as above ground and under ground refrigerated storage tanks designed as atmospheric storage tanks/low pressure tanks.

About Elmac Technologies

In 2008, Elmac Technologies celebrates sixty years of expertise in the design and development of flame arresters for use in the worldwide gas processing and distribution industry, and can proudly claim to be the technical leader in flame and explosion safety systems.

Originally known as Elmac Engineering, the company developed its first flame arrester in 1948, for use with town gas, and rapidly established a global reputation for the design, manufacture and supply of products to enhance process safety in a broad range of industrial sectors. These sectors include the global oil, gas and petrochemical industries; bio-fuels, mining, pharmaceuticals and power generation; agro-chemicals and fertilisers; distillers, food, flavours and fragrance companies; waste treatment organisations and special equipment manufacturers (OEMs).

Acquired by KnitMesh in 2001, and re-branded ‘Elmac Technologies’ in 2007 to reflect better the high levels of innovation and enhanced protection offered by its products, Elmac Technologies has grown to become one of the premier brands in the global market for flame arresters.

Elmac can assist clients by specifying appropriate products for proposed new installations and plant retrofits. In addition, Elmac are able to provide advice on the positioning of these products in an installation and to evaluate the suitability of flame arresters already fitted. To support clients in meeting the 2006 EU ATEX Directive for flame arrester compliance, the company is also willing to undertake site visits to discuss existing installations and to provide technical presentations to enhance awareness amongst the engineering community.

With state-of-the-art commercial, manufacturing and test facilities in the UK and additional manufacturing centres in South Africa and the People’s Republic of China, Elmac Technologies is rapidly developing a comprehensive range of enhanced in-line and end-of-line deflagration arresters and in-line unstable detonation arresters. These devices are suitable for use in gas groups IIA, IIB3 and IIC having been rigorously tested in accordance with BS EN 12874:2001. The high-tech testing facilities can also be used to conduct experiments to demonstrate that proposed technical solutions meet client-specific requirements.

Elmac is also able to draw on the benefits of Computational Fluid Dynamics (CFD) to model the behaviour of a system in order to investigate the flow behaviour, including the study of flow patterns and the prediction of pressure drop. This information can be used to optimise designs for particular applications whilst avoiding the need for costly plant trials.

As part of an international group that also includes global knitted mesh specialists, KnitMesh Technologies, Elmac enjoys the financial stability necessary to continually innovate, research and develop the flame arrester solutions that will help bring greater safety to industry worldwide.

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About Elmac Technologies

For more information regarding Elmac Technologies and what we do, please go to the About Us page.