Fuel storage tanks and dispensing systems are changing to accommodate new fuel products. The chemistry of fuel has changed, from the removal of lead and MTBE to additives such as ethanol. These changes were made mostly to comply with standards set by the EPA Fuels and Fuel Additive Regulations (40 CFR 79), which became effective in 1996. The new fuels are now more susceptible to moisture accumulation, separation, and potential bio-degradation accelerated by water. The lead was a natural poison to the microbes that grow in a moist environment, but now, with today’s lead-free fuels, microbial growth is occurring more readily. With alcohol-enhanced fuels, “phasing” can more easily occur, separating water, gasoline, and alcohol into three distinct layers. These conditions didn’t exist in the 1970s, 80s, or even most of the 90s. Furthermore, microbial activity is better understood today and was found to be much more common than previously realized. Above-ground storage tank owners and operators must be aware of such problems and immediately implement operations and maintenance procedures to help monitor and remove any contamination from their fuel storage tanks.
Fuels Are Changing
Overall, fuels have had to become cleaner to accommodate newer, cleaner-burning engines. While carburetors were common in the past, fuel injection systems are now used. A fuel injection system atomizes the fuel by forcibly pumping it through a small nozzle under high pressure. Fuel injection systems are more sensitive to contamination, thus requiring clean fuels. Operations and maintenance procedures for monitoring and removal of water have been a recommended practice for many years. Routine monitoring, inspection, and removal of sludge are needed to maintain your fuel quality in your above-ground fuel storage tank.
- Preparing For First Time Bio-fuels – Attention needs to be given to tanks prior to introducing bio-fuel products the first time. Ethanol and biodiesel blends act as cleaning agents and when introduced to your fuel storage tank it may loosen or dissolve contaminants from the tank wall. These contaminants typically collect at the bottom of your tank and can result in excessive clogging of your filter and even damage your engine if the contaminate reaches the fuel system.
- Switching between Gas and Diesel Fuels – If you are converting your fuel storage tank from storing one fuel to another, the tank and related dispensing equipment must be thoroughly cleaned, inspected, and verified to be compatible with the new fuel you wish to store. Extreme care needs to be taken to make sure gas does not commingle with any diesel product as well.
- Regulations – Contact your implementing agency for specific compatibility requirements. Many agencies may require owners who store bio-fuels to follow specific requirements, which could include submitting state-specific documentation.
You must notify your implementing agency at least 30 days before switching to any of the following products:
- Regulated substances containing greater than 10 percent ethanol
- Regulated substances containing greater than 20 percent biodiesel
- Any other regulated substance identified by your implementing agency
Fuel Contamination Types and Impact
- Water – High throughput in your fuel distribution/delivery structure allows less time for water to settle before it is delivered into your distribution system. Therefore, water may enter the storage system through the delivered product. Fuel is usually delivered warm, once it cools, water will naturally condense out and collect at the bottom of your fuel storage tank. Certain fuels are also more prone to attracting moisture. A fuel’s composition and temp affect the amount of water it can hold. The warmer the fuel, the more water it can hold in solution, when it is cooled, it will cause the water to be released and settle at the bottom of the storage tank. Open vents, low fill areas, and sloped tank installations also contribute to water accumulation. In addition, water can also enter damaged fill boxes, bad gaskets, loose fittings or plugs, spill buckets, and more.
- Sludge – Build-up results from the breakdown of the fuel itself. This naturally occurs over time and may include externally introduced contaminants that can enter the tank during construction, maintenance, or fuel delivery. Contaminants such as salts in the water can cause your fuel to degrade and may be detrimental to system components or cause fuel additives, necessary for maintaining the quality of fuel, to leave and enter the water. If you have reddish, scaly, gritty deposits, this may indicate corrosion or silt introduction into your fuel storage tank. Black or brown deposits can indicate water has degraded the fuel.
- Microbial Contamination – Damaging bacteria can grow with the presence of water in your tank, especially with newer fuels. Microorganisms thrive and grow to form a slime that breaks off and clogs small openings throughout your fuel storage system. This will be especially noticeable in filters, decreasing the life of your filters or even slow flow can be warning signals. This bacterial phenomenon is easily compared to mold. It begins to microscopically grow, unseen to the human eye but will eventually become visible. Some other indicators of contamination are plugged fuel lines, erratic tank gauge readings, frequent replacement of components such as valves, seals, and hoses. As the bacteria are digesting the fuel, it alters it to produce sludge and other materials that attack metal, rubber, and tank linings and coatings. If the byproduct reaches the engine fuel systems, it can plug fuel filters and cause build-up around injection nozzles. This results in inefficient combustion and unusual exhaust smoke.
Traditional methods of monitoring your fuel storage tank for water or contamination may not be adequate for modern fuels today. Usually, when water enters a tank, it settles to the bottom and is easy to identify through automatic tank gauge readings or dipping your tank with water finding paste. However, in fuels that contain an alcohol blend, and some biodiesel fuels, the water may combine with the fuel and make detection difficult. You need to check your fuel storage tank for water as frequently as possible, in fact, some may do this daily. You must remove all water found, check water bottoms for microbial contamination and treat with Biocide as needed.
- Automatic tank gauging – auto systems with water monitoring capability are another option. However, water sensors must be maintained to remain functional. Recommended maintenance and inspection schedules: Tanks using automatic tank gauging with water level sensors should be monitored daily. If a tank shows water one day and not the next, it may be an indication that water has been absorbed into an alcohol blend fuel or bio-diesel. If inconsistent water levels are observed by the automatic tank gauging records, additional water paste or bottom sample investigation should occur.
- Water Paste – Alcohol-compatible water paste on a gauge stick is a quick, easy, and inexpensive way to check for the presence of a water bottom in your storage tank. A variety of different water pastes have been developed to check for water in different fuels. Make sure that you are using the correct paste for the fuel. Special pastes to be used in ethanol fuels and biodiesel can be purchased from your fuel or fuel service provider. Read the directions provided with the paste to ensure that you are using the paste per manufacturer specifications. Not properly following the use instructions may lead to false or missed detection. If the paste indicates spotty or inconsistent water detection, this may be a sign of suspended water or accumulated sludge residing in the tank.
- Filters – Using a water sensitive filter, you can watch for reduced fueling speed. This is a sign of fuel contamination. Most manufacturers of dispenser filters offer a fuel filter that will contain water and most contaminates. Water absorbing filters catch water, causing the filter to expand and reduce fuel dispensing rates. If slow fuel flows are being encountered, an investigation for in- tank water or contaminates should occur.
- Periodic Sampling – You need to also pull periodic product samples from the inside of your tank bottom and inspect them. Check with your local petroleum equipment dealer or even your local fuel supplier for guidance on sampling devices & procedures.
Removing Water and Contaminants
When it is determined that water or contaminants are present in your above-ground fuel storage tank, action must be taken to remove them before the problem escalates. Uncontrolled water or contaminates will lead to phase separation, which results in losing the entire tank of fuel or dispensing fuel that causes damage to internal combustion engines.
- Fuel Filtration/Polishing – Fuel filtration and fuel polishing are methods that remove water and contaminants from the fuel without removing the fuel from the tank. There are many vendors that offer fuel filtration services. Fiber-optic technology or remote video cameras are two options to visually locate and observe the contaminate removal progress. Others use a variety of fuel circulation techniques to filter the water and contaminants out of the fuel.
- Tank Cleaning – There are two options to cleaning your tank, non-entry, which is cleaning without physical entry OR physical entry, which is a manned entry cleaning to scrub the contaminants from the tank wall.