Microbial Influenced Corrosion

Microbes are living cells. There are two broad categories – aerobic and anaerobic. The majority of microbes affecting fuel are aerobic. That means they need oxygen to survive and multiply. Today’s highly oxygenated fuels supply the need. The process of removing sulfur actually adds oxygen to the fuel. Water contains oxygen, is necessary for microbial growth and is always present in fuel. It is virtually impossible to keep water out. As a result, microbial contamination is almost certain.

Microbes live off fuel. They are “hydrocarbon utilizing microbes – bugs” or humbugs as they are commonly known. They live in the suspended water, water vapor and water layers in the fuel. As they eat fuel, they produce acidic byproducts. Commonly found in fuel, acetic acid is a low-level acid that destroys metal in both the wet space of the tank and the dry space and vapor areas of the tank system. The result is corrosion. Other commonly found acids are formic acid, propionic acid and lactic acid. While there are others, these are the most prevalent.

All of the acids found in contaminated fuel cause corrosion, thus the term microbial influenced corrosion or MIC. All metal that is exposed both in the fuel and in the vapor space are susceptible to corrosion. MIC is a direct result of unmanaged fuel systems. Fuel cannot go unmanaged. Water levels must be continually monitored and immediately removed when found. Fuel sampling should be done on regular basis to identify the presence of water and other contamination. Fuel and tank cleaning are also a regular part of fuel management. Without a program in place, MIC will be a direct result.

What are the warning signs of MIC? For the fuel system owner, the signs are many. Below are some of the major warning signs:

  • Premature dispenser filter replacements
  • Corroded dispenser filters
  • Dispenser meter replacements due to corrosion
  • Corroded STP components
  • Frequent or repeated proportional valve replacement
  • Slow flow issues
  • Premature or repeated hanging hardware failures
  • Leak detector failures
  • Shear valve failure
  • Line and tank failure
  • Probe failure
  • What are the warning signs of MIC in engines and equipment?
  • Fuel injector failure
  • Faulty high pressure pump
  • Exhaust smoking heavily
  • Low compression
  • Engine runs rough at lower RPM
  • Engine does not start or is hard to start
  • Engine fails under load
  • Knocking or pinging issue
  • Fuel pump failure
  • Fuel filters clog prematurely or repeatedly
  • Fuel line failure

Whether a fuel system or an engine, the problem with MIC is serious and costly. Corrosion represents the single largest expense in the US economy, 6.2% GDP. For the fuel system owner, the liability of a potential fuel release is very real if fuel quality is not maintained. For the engine owner, failure is common. It has been noted that 90% of generators do not start or stop shortly after starting during an emergency. Over 75% of those engine failures are due to bad fuel.

Mobile Fuel Cleaning

There are numerous manufacturers and assemblers making fuel filtration equipment. What makes a filtration unit superior? Four criteria determine superiority.

It must be safe. Safety is first and foremost. Does it have a safety shut-off switch clearly marked and easily accessible?  Does it have both pressure and vacuum gauges that are in clear site while the system is in operation?  Are grounding reels and a grounding rod included? Are safety instructions understandable in the operations manual? Consider the kind of fuel you will be cleaning. Do you need explosion proof or intrinsically safe? Do you know the difference between the two? How important is it? Built-in safety components make some units better. Look for safety factors when researching which unit you will purchase.

Ease of use is essential. If a cleaning unit is too difficult to use in the field, then problems will arise. Are there too many controlling factors like valves and connections?  The simpler, the better. Manufacturing equipment that is easy to use does not happen accidentally. You want tanks and fuel clean, but you do not want it to require a rocket scientist to operate the equipment. Are the gauges, shut-off switch and valves easy to access, clearly labeled and within easy reach? Can one person safely and efficiently operate the unit fs2bwith minimal effort? Before buying a system, think about its operation in the field. Ask yourself, “Is it easy to use?”

How cost efficient is the equipment to operate? Does it require special filters or odd sized consumables? Does the pump and motor require a lot of maintenance? Is it built to last? Make sure you understand the cost of all consumables and be warry of any company that cannot clarify how much it costs to operate. Look for options like mesh filter housing inserts to use in place of bag filters.  Also, be aware of the high maintenance cost of pump types like air operated double-diaphragm pumps. Positive displacement pumps like the Dixon BladeMaster pump will cut maintenance and downtime costs considerably.

How flexible is your system? Can it only clean one type of product? Flex filtration is a significant advantage. Purchasing a cleaning unit that is capable of filtering all fuels makes sense. Make sure the unit will filter all of the products you need it to.  Also, ask yourself can it clean tanks and filter fuel if the need arises.  Most mobile units can do one or the other but not both.

Make a purchase that is safe, easy to use, cost efficient and flexible. Check out Dixon Pumps mobile cleaning and filtration line of products.



Tank Cleaning vs. Fuel Polishing


Tank cleaning and fuel polishing are two different processes. The question often asked, “Which one is better?” Are there any advantages to one over the other? Cost can be a determining factor as well as site downtime, if any. Tank cleaning is generally more expense. It usually requires fuel be removed and a chemical agent applied during cleaning. Once the tank cleaning process is completed, the old contaminated fuel is filtered back into the tank or new fuel is delivered. Either way the costs are higher than simply polishing fuel in place.

Opponents on either side of the cleaning and filtration industry will argue their points, but the solution is often determined by cost of service and downtime. Let’s be honest, for many tank owners cleaning versus polishing is a matter of economics. If the only economically feasible solution is to polish the fuel – then do it. It is better than leaving contaminated fuel in the tank. Ignoring the problem will only increase the cost of ownership.

However, there are times when a tank is so contaminated that it requires a tank cleaning with pressure and chemicals. Having been in the field cleaning tanks and filtering fuel for years, I have found around 20% of the tanks serviced needed tank cleaning in addition to fuel polishing.