www.cos-mag.com
Mar 18, 2014

Little spark, big flame

By Amanda Silliker
Static electricity can pose many issues for the oil and gas industry

A
t 3:50 a.m. on Aug. 10, 2008, a massive fireball lit up the sky in northern Toronto caused by a series of explosions at a Sunrise Propane facility. Huge pieces of metal from exploding propane tanks flew through the air, shutting down major highways and evacuating 12,500 residents from their homes. About 200 firefighters were called to extinguish two rail tanks each containing up to 220,000 litres of propane that burned for more than five hours. The explosions killed a 24-year-old employee and a firefighter died of a heart attack. 

A fire marshal’s report, finalized 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 difficult 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 fire and you can say, ‘There’s the flashpoint’ 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 identified as the cause of many explosions and fires that destroyed or damaged facilities worldwide, including an airplane hangar, a gas station, a petroleum products company and an oilfield 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 contact, the surface electrical charges of the objects try to balance each other through the free flow 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 ignitable vapour or dust mixture, the result could be a fire or explosion. 

“A fire or explosion is always a possibility in the oil and gas industry because two of the three things needed to make it happen are virtually always there — hydrocarbons as a fuel and oxygen in the air,” according to a report by Scorpion 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, filtered, agitated, stirred or flow through pipes — which is of particular concern to oil and gas workers.

“There are more workers, newer workers, new activities, more fluids handled and in larger quantities… 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 fire and explosion caused by static electric discharge within the oil and gas industry:

Fuel and storage tanks: Those made of steel or fibreglass can develop a static charge between the liquid surface and the tank shell or metallic fitting in a non-metallic tank during filling.

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 dissimilar molecules such as water, oil and sediment in the flowback fluid collide and form positive and negative charges.

Fuelling operations: The flowing movement of flammable liquids like gasoline inside a pipe can build up static electricity. Liquids such as paraffin, gasoline, toluene, xylene, diesel, kerosene and light crude oils exhibit significant ability for charge accumulation and charge retention during high velocity flow.

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 fire or explosion caused by static electricity.

Reducing the flow rate of liquid is one technique because static electricity increases as the flow of flammables increase. An effective way to do this is by slowing processes down, says Astl.

“Reduce the amount of speed that’s happening when you’re filling, when transferring flammables. 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 flammable 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 flammable and more electrons are able to transfer,” says Astl. 

Bottom filling 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 reducing the generation of static electricity. A relative humidity of about 50 per cent is sufficient to avoid difficulties 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 conductive objects with a conductor that equalizes the potential charge between them. 

For example, metal dispensing and receiving containers should be bonded together with a special 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 different potential than the two things you’ve bonded together, so there could be a spark between that third thing.”

Grounding 

Grounding is connecting one or more conductive objects directly to the earth using ground rods, cold water copper pipes or building steel. Unlike bonding, grounding drains the static charges away.  

There are three types of grounding:

Permanent: This type of grounding would be used for objects that never move, such as a jet fuel tank at an airport. It would have a dedicated grounding field that would have a permanent, welded connection to the tanks.

Semi-permanent: This type of grounding is for items that are not moved on a regular basis but do need to move at some point, such as a large drum of material that sits in one spot for weeks or months but needs to be taken away to be refilled. For this, C-clamps that are connected to the ground source are used which screw in and form a really tight attachment and a very strong bond, says Astl.

Portable: Portable grounding is a temporary connection used for items that need to be moved all the time, such as at fill stations where flammable liquids are being poured into smaller drums. This is done by using hand-held clamps that are connected to the ground source. Clamps that have sharp points that cut through paint, dirt and rust are important because a bare-metal to bare-metal connection is necessary for proper grounding. 

Maintenance 

Oil and gas companies need to ensure their bonding and grounding systems are functioning properly, and that requires some diligence and maintenance, says MacGillivray. 

“You have to understand how the whole system works and that everything is operating as it should, parts are connected and grounded to a common ground, for example,” he says. “We really emphasize looking at the entire system and entire environment that you’re working in.”

A best practice is to have someone walk around the work sites to ensure the grounding and bonding equipment is in good working order on a regular basis, such as every other month.

“Often it’s unclear who does that work. Sometimes it falls on the plant electrician because it’s static electricity, sometimes it falls on an operations person, sometimes it’s the safety person; it falls between the gaps and companies need to stand up and say who is in charge of this and let’s get a proper system in place,” says Astl. 

It’s also important to monitor the level of resistance present in the metal circuits to make sure static electricity can dissipate through the wires and the bonding and grounding equipment. The industry standard for resistance is 10 ohms or less. Anything above that and the grounding circuit may be compromised. The resistance can be measured by using an ohmmeter along the whole assembly, or by using a fixed or portable static ground monitoring system. 

Worker considerations

The bodies of workers can accumulate static charges in excess of 10,000 volts in periods of low humidity, says Hastie. Cotton and cotton blends tend to generate less static electricity than clothing made of wool, silk, synthetic and polyester materials. 

Cenovus requires its workers to wear natural fibre clothing under their fire resistant clothing. And if workers get flammable material on them, they are trained to douse themselves immediately in water before removing clothing to avoid ignition by static electricity, says Hastie. 

Cenovus employees receive online training on bonding and grounding. They are responsible for grounding themselves in a safe location by touching the building or any grounding device at the work site after leaving their vehicle; before commencing work; frequently when working in a hazardous area; and prior to entry of compressor buildings or dehydrators.

Workers need to be trained on the right equipment and proper processes for bonding and grounding as well as using spark-resistant hand tools in potentially explosive environments.

Enform offers training courses around static electricity awareness, such as detection and control of flammable substances and fire prevention.

“We walk them through the basic concepts, how to identify an issue, how to detect an issue, and how to prevent an event,” says MacGillivray. 

At Cenovus, a pre-job hazard assessment is always required and the supervisor is responsible for identifying the potential static electricity sources and the necessary bonding and grounding requirements. 

Training for supervisor competency is a big focus for Enform right now, according to MacGillivray.

“We’re trying to make sure safety is part of the work, how you do the work, so not just pointing at a safety officer but having a supervisor who is competent to monitor that work in fact is taking place the way it should be.” 

While the predominant attitude across the industry toward static electricity is: “I have been doing my job for 10 years and have never had a problem,” it only takes one incident for everything to change, says Astl. More education and awareness around the hazards associated with static electricity is needed.

“You get just the right amount of humidity, just the right amount of splashing and it only needs to happen once and that facility is gone, that person is gone and it’s just not worth taking that risk,” says Astl. “Static electricity is something you can’t smell, you can’t sense, can’t notice until it’s too late.”

SIDEBAR

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 specific 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).

Bonding/grounding checklist

• Identify potential static buildup sources
• Consider ambient conditions
• Consider any liquid that has been agitated will produce static charges
• Ensure tankage and filling spouts are bonded together or in metallic contact
• Check that any ground cable is securely attached from containers to ground rod
• Ensure ground rod is in good condition
• Inspect bonding line
• Ensure grounding systems are in place for portable equipment
• Check that grounding systems are well maintained
• Check current continuity