Diesel Contamination

​Stopping Soft Sticky Stuff 

gel
Soft contaminants cause a wide a assortment of problems from premature filter clogging to engine deposits and tank corrosion. If you are experiencing rapid filter plugging or sudden equipment failure, soft sticky stuff is very likely the cause.There are several different sources of soft substances, some of which are easy to understand and others that are harder to predict. While filtration can help stop the problem from spreading onto your equipment, the best solution is to prevent these soft organics from ever forming. 

GELLING  
Gelled fuel is not really a contamination issue, but is often thought
of as such. In fact, gelling is a natural phenomena based on the cloud point of the fuel blend in use. If proper precautions are not taken, wax will precipitate out of diesel at low temperatures, rapidly disabling filters, slowing fuel flow, and subsequently stopping the engine if immediate steps are not undertaken. There are several different ways to address 
diesel gelling issues: 

Temperature: If you live in a warm or hot climate, you will likely never experience gelled fuel. But for the rest of the world, it can be a real problem. More and more fleets are parked inside over night to avoid problems starting them in the morning. Tank heaters are also used. For most, though, keeping fuel warm at all times is not a viable option for preventing gel formation. If you already have gelled fuel, you can either wait for the weather to change, or try moving the vehicle indoors to warm up. Sometimes just removing and warming the fuel filter can be enough. On occasion, waxy fuel caught in a filter or pump intake will not re-liquefy no matter how much it is warmed. In this case, an irreversible change in the fuel's chemistry has likely taken place rather than simple gelling. 

Fuel selection: It is very important to make the proper fuel selection. Ideally, everyone would run on pure #1 diesel in cold weather. This is very effective, but not always practical due to cost or lack of availability. If you are experiencing cold weather operability issues, adding #1 to your tank or increasing the percentage of #1 in your bulk fuel purchases should help. Adding a hydrocarbon with a lower freeze point can be a good way to lower the cloud point of your fuel. 

Cold flow improver: When gelling occurs, wax crystals precipitate out of the fuel and plug fuel filters, leading to engine failure. Cold flow improvers are designed to improve low temperature operability by modifying the size and shape of these wax crystals in order to enhance fuel flow and help prevent filter clogging issues. In the past, cold flow improvers worked very well, but in recent years their effectiveness has been reduced. ULSD is not as responsive to the beneficial effects of cold flow improvers as higher sulfur fuels were, and just as significantly, fuel filters have become much more efficient than required in the past. Today's filters catch and hold very small contaminants, including both hard and soft particulate. 

High efficiency filters are required to protect modern engines. Equipment manufacturers regularly specify filtration down to 2 microns. Even modified wax crystals will frequently be caught by medias capable of this level of filtration. Unfortunately, the cold climate user may need to do a balancing act between adequate engine protection and frequency of filter changes. The filter that catches everything yet lasts forever has not yet been invented.

BIODIESEL 
Biodiesel is notorious for problematic cold weather performance; the most usual cause of this is glycerin (glycerols) agglomerating together and falling out of solution when the fuel cools off. Biodiesel and biodiesel blends have higher cloud points, pour points and cold filter plugging points than petro diesel. Most equipment operators cannot directly control the amount of bio diesel in their fuel deliveries. In colder climates, refineries and distributors will typically reduce the percentage of biodiesel used in blended fuels during winter months. They do the best they can to predict weather patterns and prevent problems for their customers while complying with governmental requirements for total biodiesel use. If they blend in more during the summer, then they can reduce usage in the winter. In areas with extremely cold winters, such as Canada, the government may allow 0% biodiesel during winter months. Suppliers cannot, however, control the fuel that is already in your tank. Be sure that summer fuel is used up before the weather turns cold. 

Similarly, long haul truckers should avoid using fuel purchased in warm areas when they travel into the cold. Blending calculations are made based on local conditions and long term weather patterns. Problems are generally worse when using poorer quality biodiesel that has not been properly processed. In this case, solids can form in large quantities and at temperatures approaching 61°F/16°C. A good distributor who purchases their fuel from consistently high quality sources can be your best defense against poor quality biodiesel.

Once solid glycerin has formed, it most likely will not melt at normal ambient temperatures. It must be physically removed through tank cleaning and/or filtration. It can take as little as a few spoonful of glycerin to disable a filter, so if you do not thoroughly clean your tank, expect to use a large number of filters before it flushes itself out. To avoid clogging filters on your entire fleet, it is best to install bulk filtration at your tank. In the presence of glycerin, these filters will clog rapidly as well, but they isolate the problem at the tank so that your equipment keeps running. Bulk filters, especially heavy duty spin-ons, are much faster and easier to change than filters installed on equipment working out in the field. 

ADDITIVE DROP-OUT 
Additive that precipitates out of fuel behaves very similarly to glycerin. It will not re-liquefy, so once these soft solids have appeared, tank cleaning and/or filtration are the only real options. The diesel user can, however, take precautions to avoid these problems. 

Quality control: Only accept delivery of fuel from reputable sources, certified to meet all local standards. 

Remove contaminants before they enter your tank: Install a bulk filtration system at the inlet to your tank. This will ensure that you do not take possession of soft solids that have formed prior to delivery. It will not only protect your equipment, it also protects the diesel that is already in your tank and the tank itself. Limit your exposure to risk. Don't let a bad load contaminate the diesel you already own. 

Block free water: If you suspect that a large amount of free water is sometimes delivered along with your fuel, install water blocking filters at the inlet to your tank. These filters allow only dissolved water to pass. When confronted with free or emulsified water, they will absorb a modest amount, than act like a fuse to stop flow. This prevents free water from entering your tank and provides you with the means to have a serious conversation with your supplier. 

Rapid turnover: If possible, take delivery of warm, fresh diesel and use it before it cools off. This can be possible for large volume users located in close proximity to a refinery. Rapid fuel turnover can be helpful, as it limits the time available for soft contaminants to form in the tank. 

Proper additive usage: More is not better. Use only additives that are needed to bring your fuel up to performance specifications. Carefully follow the manufacturer's dosage and blending instructions. If possible, leave this up to professionals with advanced training and specialized equipment. 

Keep your tank dry: Water is a common contributor to fuel stability problems, including additive instability. Most additive precipitates can be avoided if diesel is kept dry (i.e. below the saturation point). Keep tank bottoms drained of free water and install appropriate breathers to keep ambient humidity out. A steady stream of dry air fed across the tank's headspace can be extremely helpful.​