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Ensuring the security of natural gas odorising process

01 November 2006

Stäubli HCB couplings provide the secure, reliable, quick release connections that are required by natural gas odorising systems, as they can be disconnected with the absolute minimum of spillage. Natural Gas does not have a characteristic smell; if the gas was used in this condition, leaks in the system could occur without detection, leading to catastrophic results. Robinson Brothers of West Bromwich have been involved in the Gas Odorant business for over 40 years, manufacturing the chemicals that will impart the recognisable ‘gas’ smell to alert all to the possible danger of a leak.

Over the years the chemicals used for gas odorising have changed from tetrahydrothiophene in the 1960’s to a combination of mercaptan and sulphide today. A property of this mixture is that, even when diluted to a few parts per million, it retains the smell associated with Town Gas. Consequently the handling of these chemicals needs to be strictly controlled to ensure no escape occurs that could result in a false gas leak alert. This is particularly important when the highly concentrated odour additive, which is injected into the local gas supply, is being transferred into storage tanks.

Robinson Brothers Ltd supplies gas odorant in the UK. RBL engineers recognised that it was necessary to have reliable leak and odour free connectors between their odorant transfer hoses and the gas distribution sites. They called in Stäubli to advise on the type of connectors they should use.

Tony Quinney, Site Engineering Manager at Robinson Brothers commented, “We had good experience of Stäubli’s quick release connectors on other high integrity applications so, when this requirement arose, they were the natural choice to advise on a dry break, reliable and robust coupling with next to no loss in containment.”

Stäubli recommended a connector that had only recently been introduced to their range, the HCB 28; designed specifically for applications where any leakage at all is absolutely unacceptable. HCB couplings are of a flush faced, non-spill design, preventing any air inclusion in the system when connecting as well as avoiding any spillage on disconnection. The initial HCB range introduced a few years ago included sizes up to DN25, in response to market demand for larger sizes, the range has been extended up to DN80 sizes. The new larger couplings are designed for use in bulk filling situations when any leakage at all must be avoided. These couplings were ideal for Robinson’s challenging gas odorisation application requirements.

All of the HCB connectors feature the Stäubli patented bayonet locking system which provides a safe, quick and reliable connection. The locking system provides a positive feedback response, ensuring a high integrity connection and eliminating any chance of mis-connection. On the new larger sizes, the coupling can be fitted with a hand operated wheel if required.

The changeover to the new connectors at Robinson’s started in April 2005 following extensive testing. Gradually each of the odorisation stations are being fitted with a specially developed version of the HCB 28 couplings as well as all the hoses and equipment on their fleet of delivery vehicles. A set of HCB 28 couplings have been on test at Robinson’s for over 2 years. No leaks have occurred in any of the couplings and they have simplified the refilling process significantly.

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