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Technical Bulletin


Electric Continuity for Dissipation of Static Electricity

Hanging hardware (e.g. nozzles, hoses, swivels, breakaway couplings) must be conductive in order to dissipate any static charge that is generated while fuel is being dispensed. Conductivity of any product is obtained by either a metal-to-metal contact path from inlet to outlet or by the use of non-metallic electrically conductive materials (e.g. rubber formulated for use in fuel hoses). Since conductivity is important to public safety, these components are tested to a maximum resistance by certifying bodies such as Underwriters Laboratory (U.L.) and Underwriters Laboratory of Canada (U.L.C.) as recommended by the national fire codes. Both U.L.1,2,3 and U.L.C.4 require that the electrical resistance of individual nozzles, swivels, and breakaway couplings not exceed 500,000 ohms (0.5 meg ohm) and hoses should not exceed 70,000 ohms per foot.

To obtain accurate resistance measurements, it is recommended that a megohmmeter5 capable of a test voltage of 500 volts direct current (Vdc) be used. This test voltage is required by both the UL 3301 and CAN/ULC-S644:20164 standards.

A 500 volt test is an established industry standard. The condition of the metal-to-metal contact is of such a nature that a standard low voltage ohmmeter (3 to 9 volts) may or may not show continuity of the product that is continuous. For example, small gaps from pipe sealant, lubricants or the use of non-metallic electrically conductive materials, may lead to poor or intermittent readings on a low voltage ohmmeter (3 to 9 volts). Therefore, a low voltage ohmmeter may lead to faulty or inconsistent results, whereas a megohmmeter set at 500 Vdc will give more consistent results. It is recommended that a megohmmeter capable of 500 Vdc with a resistance range of 500,000 ohms be used. Use of the low voltage meter may result in the unnecessary replacement of products that will dissipate static charges.

REFERENCES

1UL 330, Hose and Hose Assemblies for Dispensing Flammable Liquids, Eighth Edition, June 30, 2017.

2UL 567, Emergency Breakaway Fittings, Swivel Connectors and Pipe-Connection Fittings for Petroleum Products and LP-Gas, Tenth Edition, May 7, 2014.

3UL 2586, Hose Nozzle Valves, First Edition, April 29, 2011.

4CAN/ULC-S644:2016, Standard for Emergency Breakaway Fittings for Flammable and Combustible Liquids, Third Edition, August 2016

5NFPA 77, Recommended Practice on Static Electricity, 2014 Edition, Section 3.3.30, Page 77-8.

Form No. STBCONDUCT (Rev. 2, 2/1/18)