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Putting Lpg Gas Pipe to the Test

By Malcolm Birchall, application engineer, Orange County Ltd

The main recommendation of the ICL Inquiry is that all underground metallic service lpg vapour pipework should be replaced with MDPE (plastic) pipework. However, the inquiry did not seem to consider some inherent deficiencies in MDPE pipework, only its corrosion resistance.

In May 2004, an explosion caused a catastrophic building collapse at ICL Plastics Ltd in Glasgow, resulting in nine deaths and 45 serious injuries to site personnel. There were many factors that contributed to the disaster, but the main cause identified was the failure of the steel lp gas pipe, caused by corrosion.

Clearly, the problem from the point of view of the lpg gas pipe owner is determining the actual condition of any underground pipe carrying hazardous products. Testing underground lpg pipes proves their integrity on the day, but pipes cannot be tested every day – or can they?

Brugg Pipesystems manufactures a number of high integrity pipe systems that can be continuously monitored by permanent leak detection. In the case of an lp gas leak, these systems will immediately give an audible and visual indication of the leak; in addition they can also be interfaced to pumps and valves to shut down the process.

Orange County has been distributing Brugg Flexwell pipework to the major lp gas suppliers and lpg autogas forecourt industries in the UK for more than 12 years. In that time, we have supplied over 150,000 metres of lpg gas liquid pipework on over 1,200 projects for the underground lpg transfer market.

Brugg Flexwell lp gas safety pipe is a flexible composite pipe consisting of a single or double walled, helically convoluted pipe made from corrosion resistant stainless steel 316 material encased in an extruded polyethylene outer jacket. The pipe has been specifically designed and developed for the reliable transfer of hazardous or flammable liquids, including lpg gas in its vapour or liquid phases, and it can be safely installed below or aboveground.

Brugg Flexwell lpg pipe is completely factory tested and is manufactured in standard lengths of 1,000 metres, but can also be produced to order in continuous length up to 2km, dependant on bore size. The pipe has a maximum working pressure of 25 bar and a minimum burst pressure of over 100 bar. Each batch produced is subjected to two burst tests to check the strength, consistency and quality and subjected to a helium leakage pressure test.

Brugg Flexwell pipe is designed with a minimum design life of 30 years, with many installations exceeding this milestone. It is long lasting, lightweight and strong, and the system is quick and easy to install by rolling or pulling into position.

Pipe is typically supplied as a site specified length in a coil or as a longer length on a wooden reel; handling of the lpg pipe is similar to a cable or heavyweight hose. Pipe end connections use a compression type graphite seal to produce a gas tight termination and are available in threaded or flanged configurations.

No hot work is required and most connectors are fitted onsite using only hand tools. All pipe assemblies are subjected to a leak pressure test when installed and terminated at site, before and after back filling.

Leak detection systems approved to EN13160 Class 1 are available to permanently monitor the completed lp gas pipe system for leaks, meaning that a pipe system does not have to be shut down to be tested.

Brugg Flexwell lpg pipe has a number of advantages over traditional steel or plastic pipes. Stainless steel 316 is highly corrosion resistant and is used extensively by the offshore industry to resist the severe corrosion that affects unprotected carbon steel caused by the atmospheric conditions.

Stainless steel is impervious to liquids and is not permeable to gases. Non-metallic pipework is permeable to a degree, and may need a permeation barrier to reduce permeation to an acceptable level. Permeation barriers are not usually continuous over electrofusion joints. All underground lpg gas pipework is vulnerable to damage where it comes out of the ground. Metallic pipework is tougher and more resistant to mechanical damage than non-metallic pipe.

In contrast to MDPE, Brugg Flexwell pipe is immune to ultraviolet and ozone degradation and is suitable for both underground and aboveground lpg installations. It can withstand much higher temperatures than MDPE and is therefore more resistant to fire. The typical melting point of MDPE is 120-1300C and the typical melting point of stainless steel is 1,5100C.

MDPE pipework can only be installed when surrounded by clean ground and cannot be installed unprotected above ground level. Brugg pipework can be run above and below ground and in both concrete trenches and ducts. Brugg Flexwell pipe cannot be damaged by rodents and is suitable for burial in contaminated ground.

Stainless steel is conductive and will dissipate static charge. Normal MDPE pipework can act as an insulator. Brugg pipework is therefore easier to ground where there is any danger of building up a static charge due to the velocity of the medium passing through the pipework.

Contact Orange County Ltd on 01388 813433 www.orangecounty.co.uk

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