EDITOR’S NOTE: This article was submitted by Conidia (www.conidia.com), a marketer of fuel testing kits.
The microbes that can infect fuel sources are a naturally occurring phenomenon. The change in diesel fuel specifications with the addition of fatty acid methyl esters (FAME) and the reduction of sulfur make diesel more susceptible to attack by microorganisms. In addition, FAME holds more water in the fuel, making it difficult to successfully drain tanks and remove the water that is so essential for microbial growth.
The susceptibility to attack by microbes will vary with geographic location, climate and the amount of biofuel content, but without good fuel husbandry the risk of infection and associated negative impact on operational issues are high.
Microbial infection can affect any type of fuel storage tank, posing a significant risk to fuel storage operations. Prolonged periods of contamination will lead to the formation of a layer of biomass in the tank which creates organic acids that can start to corrode the inside of the tank. Wherever the biomass layers form, pitting corrosion will eat into the steel or aluminum of the tank and result in the need for remedial engineering work or even complete replacement of the tank.
If a layer of biomass becomes disturbed, the contaminants can become suspended within the fuel, creating “black fuel,” which can block outlet filters. Some companies choose to employ periodic cleaning of tanks as a risk management strategy to protect against contamination damage, but if the tank is not infected, this could be a waste of money and resources.
Manage Tank Risks
Conducting unplanned or unnecessary pre-planned maintenance adds a fixed, ongoing cost to an operation. A preventative risk management approach based on testing will result in a lower expenditure compared with the cyclical cleaning of tanks or conducting unplanned maintenance when an infection occurs.
Selecting the best testing solution for a particular application comes down to evaluating which option minimizes impact on operations in terms of time and cost while offering accuracy, reliability and, ultimately, the best return on investment within the context of a risk managed maintenance strategy.
To effectively manage risk, the operator must establish the potential impact and assess the likelihood of a contamination issue occurring. With an understanding of the differences in value between proactive and reactive maintenance, operators can formulate a strategy to optimize operating profits. Fundamentally, the operator needs to ask “How big of a problem is this to me?” and “What procedures offer best value to the business?” When it comes to fuel tank management, the market perception of the risk differs across the globe.
Husbandry, Not Management
The best practice is good fuel husbandry, not fuel management. To clarify: fuel husbandry manages the environment in which the fuel is stored and transported, whereas fuel management manages the fuel transfer processes.
Fuel husbandry is supported by a range of testing technologies. Growth testing methods such as the IP385 test count the number of colonies in a water and/or fuel sample. Result values vary between test methods. There is no mathematic correlation between different values from different tests; they are simply method-dependent, but some results may be easier to interpret than others.
Alert levels remain constant but are expressed in different units. Some are more easily interpreted than others, such as volumetric expression grams per liter (g/l) used in Conidia’s FUELSTAT® kits. Available methods of testing offer operators varying accuracies and take differing lengths of time. Some tests are suitable for on-site use and can give instant results. Other off-site testing options can take a considerable amount of time before test results are known and can be subject to cross-contamination.
FUELSTAT is an Immunoassay test kit. Immunoassays have long been used in the medical industry to provide quick and accurate testing to detect specific microorganisms or molecules. They use antibodies that bind to a specific antigen to detect its presence and produce a measureable signal in response to this binding that can be used to assess fuel contamination levels.
Microbial contamination correlates to the activity of microbial growth in the sample. The amount of antigen produced when microorganisms grow in the fuel is measured for a known sample size. This gives the amount of active microorganisms in the fuel—and an accurate indication of contamination levels.
Immunoassay test kits offer a high level of on-site control; are easy to use; give accurate levels of contamination of all major aerobic contaminants such as Hormoconis resinae, Yarrowia lipolytica and Pseudomonas aeruginata; and require very low investment. The speed and ease of use reduce the overhead required for good fuel husbandry and mean the mitigation of contamination risk can be easily managed in day-to-day operations. These tests also have no special disposal requirements apart from the usual procedures for the disposal of fuel. Immunoassay test kits offer users a quick return on investment and work in all middle distillate fuels.