Canadian Occupational Safety (COS) magazine is the premier workplace health and safety publication in Canada. We cover a wide range of topics ranging from office to heavy industry, and from general safety management to specific workplace hazards.
Issue link: https://digital.carswellmedia.com/i/351662
February/March 2014 15 BIG FLAME Static electricity can pose many issues for the oil and gas industry BIG BIG BIG BIG FLAME FLAME Static electricity can pose many issues for BIG BIG FLAME BIG BIG BIG A t 3:50 a.m. on Aug. 10, 2008, a mas- sive fi reball lit up the sky in northern Toronto caused by a series of explo- sions at a Sunrise Propane facility. Huge pieces of metal from exploding propane tanks fl ew through the air, shutting down major highways and evacuating 12,500 residents from their homes. About 200 fi refi ght- ers were called to extinguish two rail tanks each containing up to 220,000 litres of propane that burned for more than fi ve hours. The explosions killed a 24-year-old employee and a fi refi ghter died of a heart attack. A fi re marshal's report, fi nalized in July 2010, stated it was a propane leak that resulted from a hose failure during a "tank-to-tank" transfer from one cargo truck to another. When the propane escaped, it evaporated and came into contact with "a competent ignition source resulting in a vapour cloud explosion." While the incident made headlines again in 2013, as Sunrise was found guilty of nine offences under the Occupational Health and Safety Act, the ignition source still remains unknown. Over the years, the court heard arguments for a number of possible sources, including lightning, a cellphone and static electricity. Static electricity is a likely ignition source in cases like this, but it is diffi cult to prove, says Brian Astl, president of Lind Equipment in Markham, Ont. "It's not like someone pours gasoline in one area and lights it on fi re and you can say, 'There's the fl ashpoint' and it's obvious… it's hard to go back and say, 'I can see where that little spark happened,'" he says. "It's a tiny little thing, but a tiny little thing that can make a huge problem." In 2013 alone, uncontrolled static electricity was identifi ed as the cause of many explosions and fi res that destroyed or damaged facilities worldwide, including an airplane hangar, a gas station, a petroleum products company and an oilfi eld chemical plant. These incidents have contributed to a growing concern about static electricity within the oil and gas industry. Static electricity is the electric charge generated when there is friction between two things made of different materials or substances. When in con- tact, the surface electrical charges of the objects try to balance each other through the free fl ow of electrons. When separated, they are left with either an excess or shortage of electrons causing both objects to become electrically charged. If these charges don't have a path to the ground, they become "static" and if the static electricity is not eliminated, the charge will build up and jump as a spark to a grounded or less highly charged object. If this spark occurs in an ignit- able vapour or dust mixture, the result could be a fi re or explosion. "A fi re or explosion is always a possibility in the oil and gas industry because two of the three things needed to make it happen are virtu- ally always there — hydrocarbons as a fuel and oxygen in the air," according to a report by Scor- pion Protective Coatings in Cloverdale, Ind. "Add an ignition source and the right conditions, and everything needed for combustion is there." Static electricity can build up when liquids move in contact with other materials, such as when they are poured, pumped, fi ltered, agitated, stirred or fl ow through pipes — which is of par- ticular concern to oil and gas workers. "There are more workers, newer workers, new activities, more fl uids handled and in larger quan- tities… it makes the importance of being current in practices and diligent in practices much more relevant for today's workplace," says Cameron MacGillivray, president and CEO of Enform, the safety association for Canada's upstream oil and gas industry in Calgary. According to Scorpion's report, there are a variety of equipment and facilities at risk of fi re and explosion caused by static electric discharge within the oil and gas industry: • Fuel and storage tanks: Those made of steel or fi breglass can develop a static charge between the liquid surface and the tank shell or metal- lic fi tting in a non-metallic tank during fi lling. • Propane gas cylinder processing facilities: The propane present in the air can be ignited by static electricity. • Frack tanks: Static charges can build up and ignite residual oil and trapped gases in the tank. Static electricity can be generated when dissimi- lar molecules such as water, oil and sediment in the fl owback fl uid collide and form positive and negative charges. • Fuelling operations: The fl owing movement of fl ammable liquids like gasoline inside a pipe can build up static electricity. Liquids such as paraffi n, gasoline, toluene, xylene, diesel, ker- osene and light crude oils exhibit signifi cant ability for charge accumulation and charge retention during high velocity fl ow. • Natural gas pipelines: Friction caused by dust or constrictions in the pipe can cause static buildup on pipes used to transport natural gas. If there is a negative charge inside the pipe, it will attract an opposite equal charge through the soil and to the outside of the pipe. When the pipe is uncovered, the charge outside the pipe can arc. PREVENTION There are a number of process improvements that can be put in place to help prevent the likelihood of a fi re or explosion caused by static electricity. Reducing the fl ow rate of liquid is one tech- nique because static electricity increases as the fl ow of fl ammables increase. An effective way to do this is by slowing processes down, says Astl. "Reduce the amount of speed that's hap- pening when you're fi lling, when transferring fl ammables. Obviously there are operational and economic constraints — no one wants to dribble material from one thing to another — but people need to make that trade-off on their own," he says. Slowing processes down also reduces the amount of splashing of the fl ammable liquid. This is important because static electricity increases as the liquid's surface area of contact increases. "You can image water splashing in a container; it comes out as a stream and as it hits the bottom, it spreads out across all the surface area that's given at the bottom of that container, so now you have more surface area contact for the fl ammable and more electrons are able to transfer," says Astl. Bottom fi lling a container through a long dip pipe is a generally accepted practice for reducing the amount of splashing. Agitating the liquid less is another useful technique, says David Hastie, safety advisor at Cenovus Energy in Foster Creek, Alta. "You're going to eliminate some liquid so it won't be agitated as much or move it without agitating it as much and building up the static electricity," he says. Humidity control is another method for reduc- ing the generation of static electricity. A relative humidity of about 50 per cent is suffi cient to avoid diffi culties with static electricity, according to the National Fire Protection Association. "The less moisture there is in the air, the more static charge can build up because the charge cannot leak off with a lack of moisture, so atmospheric conditions do play a role," says MacGillivray. BONDING Bonding is a common control for static electricity. It is the process of connecting two or more con- ductive objects with a conductor that equalizes the potential charge between them. For example, metal dispensing and receiving containers should be bonded together with a spe- cial metal bonding strap or wire before pouring. But it is important to note that bonding does not eliminate the static charge. "It introduces danger when you add any sort of third party," says Astl. "It can be a person or another object, if you introduce that for whatever reason into the process, that item is at a differ- ent potential than the two things you've bonded together, so there could be a spark between that third thing." By Amanda Silliker RESOURCES There are several internationally recognized standards published by reputable organizations including the American Petroleum Institute (API), American Society for Testing and Materials (ASTM) and National Fire Protection Association (NFPA), which target specifi c problems related to static electricity. Four important and widely referenced examples include: • API RP 2003, Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents. • API RP 2219: Safe Operation of Vacuum Trucks in Petroleum Service (2005). • ASTM D 4865, Standard Guide for Generation and Dissipation of Static Electricity in Petroleum Fuel Systems. • NFPA 77: Recommended Practice on Static Electricity (2007).