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Grounding and Bonding Requirements for Dangerous Goods Facilities

Prevention of Electric Sparks at Flammable Liquid and Gas Transfer Facilities Guide

General

This practice covers procedures for the prevention of electric sparks that may cause fire during the transfer of a dangerous good having a primary or subsidiary classification of 2.1, 3, 4, or 5 to or from rail equipment and stationary bulk storage facilities.

Static electricity is generated when liquids move and come in contact with other materials. If the accumulation of static is sufficient, a spark may occur in the presence of a flammable vapor-air mixture, an ignition may result. Where a static spark and flammable mixture may occur simultaneously, suitable preventative measures are required to avoid ignition.

The accumulation of static charges may be prevented by bonding and grounding.

"Bonding" is the process of connecting two or more conductive objects together by means of a conductor.

"Grounding" is the process of connecting one or more conductive objects to earth, and is a specific form of bonding.

Bonding is done to minimize potential differences between metallic objects. Likewise, grounding is done to minimize potential differences between objects and the ground.

Application

These practices are intended to apply to all stationary bulk storage facilities on railway property or other property adjacent to private railway track serviced by the railway where dangerous goods, having a primary or subsidiary classification of 2.1, 3, 4, or 5, are loaded or unloaded.

In this practice:

"Flammable Gas" means any product, material or mixture that has a critical temperature less than 50o C, or an absolute vapor pressure greater than 295 kPa at 50o C or exert an absolute pressure in a vessel greater than 275 kPa at 21.1o C or 716 kPa at 54.4o C, and are ignitable at normal atmospheric pressure when in a mixture of 13 per cent or less by volume with air, or have a flammability range of at least 12.

Note: Typical compressed flammable gases include liquefied petroleum gases (propane, butane and methyl chloride).

"Flammable Liquid" means any liquid that gives off flammable vapors at or below a temperature of 61o C in a closed cup test.

Note: Typical liquids include: Naphtha, gasoline, petroleum solvents, certain paints, diesel and common alcohols.

Bonding and grounding, shall be provided where flammable liquids and compressed flammable gases are transferred to or from rail equipment. This practice applies to all new installations and for replacement on existing installations where general renewal or replacement is to be made.

This practice is intended to be complementary to Transport Canada's Transportation Act entitled Railway Prevention of Electrical Sparks Regulations SOR/82-1015. Should there be any conflict between this practice and SOR/82-1015, Transport Canada regulations shall govern.

Permanent Bonding and Grounding Connections

This section is intended to cover the permanent bonding and grounding connections required for the prevention of electric sparks at transfer facilities. Portable or temporary connections, which may be required, such as between the piping system and railway rolling stock, are not covered as this protection is not installed, operated or maintained by railway forces.

Bonding and grounding shall be completed as per the following requirements. Each section of track on which any part of rail equipment stands while flammable liquid or compressed flammable gas is being loaded or unloaded shall be protected in accordance with the following requirements:.

  • the sections of track shall be bonded at each rail joint
  • two rail bond cross-connections shall be installed between the two rails of each bonded track section, one near each end of the section
  • two No 6 A.W.G. stranded copper conductors shall be installed between the bonded track sections and the piping system that is to be used for the transfer. Conductors to be continuous from rail connection to the piping system
  • the bonded track sections shall be grounded with two ground rods. Each 10 feet (3 metres) long and at least 5/8 of an inch (15.875 mm) in diameter. Ground rods shall be separated at least 10 feet (3 metres) from each other and from any ground rod used for other purposes
  • ground rods shall be driven to a dept of at least 10 feet (3 metres). Where rock bottom is encountered at a dept of less than 10 feet (1.2 metres) they shall be buried in a horizontal trench
  • insulated rail joints shall be installed to electrically separate each bonded track section from all other track rails
  • insulated rail joints shall be installed to electrically separate each bonded track section from all other track rails
  • insulated rail joints must be located so as not to be bridged by rail equipment or by other means during the transfer operations
  • bonding and grounding conductors to be installed so as not to be subject to mechanical damage
  • other precautions shall be taken by the operator of the transfer facilities to provide additional protection as may be required under specific local conditions, such as insulated joints in the permanent piping system, additional grounding, temporary bonds between the piping system and rail equipment tank and other special measures
  • Rolling stock and highway cargo tanks must be grounded with temporary bonds connected between the piping system with a pull off connector attached so as to be in electrical contact with the rolling stock or a highway cargo tank, and before the dome or bottom loading valves are opened and must remain in place until the transfer is completed and all valves and dome covers have been closed and secured

Typical bonding and grounding connections for single transfer track- Diagram 1 (pdf 201 kb)

Typical bonding and grounding connections for multiple transfer track - Diagram 2 (pdf 290 kb)

Inspection and Maintenance

Permanent bonding and grounding shall be installed and inspected in accordance with (AREMA) American Railway Engineering and Maintenance of Way Association, Communication & Signals Manual of Recommended Practice.

A low resistance earth ground is essential for personnel protection. A periodic inspection program is recommended as per NFPA (29.4 Grounding System Inspection, Testing and Monitoring).