For Distillate (Diesel) Fuels
Many distillate (diesel) fuel producers and fuel distributors have encouraged the fuel suppliers and fuel users to "get the water out" of their fuel delivery and storage systems before the on-set of cold weather.
All liquid water (moisture) in a diesel fuel or fuel oil will crystallize into a solid ice (freeze) at temperatures below 32 degrees F. These ice crystals will agglomerate together as the temperature drops lower and lower to form a blockage of the fuel delivery system (fuel line freeze-up). Accordingly, the fuel users have an added responsibility to (a) check the vehicle saddle tanks for water and (b) drain or pump out any visible water before the ambient air temperature drops below 32 degrees F.
Unfortunately, it is not possible to totally eliminate ALL of the moisture (water) present in a fuel delivery system. And, because water weighs 8.0 pounds per gallon and diesel fuel weighs less than 7.5 pounds per gallon, the water will separate from the diesel fuel and accumulate at the lowest points in the fuel delivery system (i.e. the bottom of the tank and fuel delivery lines).
All diesel fuel will contain a measureable amount of moisture ("dissolved" water in a diesel fuel will generally be 100ppm - parts per million or more). Over time, with increases and decreases in fuel temperature, this normal fuel moisture content will accumulate as "free water" and build up in the lowest parts of the fuel delivery system.
Free water in a diesel fuel system can be detected by the in-tank water monitoring equipment and it can also be detected by using waterfinder paste on the end of a tank measuring stick. Dissolved (inherent) water content is an integral part of the diesel fuel makeup and cannot be detected in the field. Dissolved water (moisture) must be determined in a laboratory by using a precision testing instrument such as a Karl Fisher Titration water detection or similar piece of laboratory test equipment.
Diesel fuel "De-Icers" additives (agents) have been used for many years to chemically lower the freeze point temperature of moisture present in distillate fuels. Such chemicals have a very low freeze point temperature and when bonded with the moisture molecules of moisture in a diesel fuel, these De-Icer additives will lower the freeze point of the resulting mixture.
But De-Icers (1) must be added in the appropriate volume for the amount of moisture present in the fuel system and (2) must physically bond with the moisture molecules in order to effectively lower the freeze point temperature of the water.
It is essential that any accumulation of free water in the storage container (storage tank or vehicle tank) be kept to a minimum. De-Icer agents have a strong affinity (driving force) for any water in the fuel delivery system. De-Icer additives will seek out the free water first and be drawn into the free water until the free water content is "fully saturated".
If a fuel storage tank has an inch or two of free water in the bottom, all of the De-Icer agent added to the diesel fuel will be drawn out of the diesel fuel and into the free water in the bottom of the tank. And, the diesel fuel itself will not be properly protected.
The same is true of a vehicle saddle (storage) tank. If the vehicle tank has one-fourth inch of water in the bottom, the dissolved moisture in the diesel fuel in the vehicle tank will not receive any measurable protection from freezing until the tank water bottoms are fully saturated.
It is also important to make certain the diesel fuel tanks do not have microbial activity in them. Microbiological activity (fungus & bacteria growth) generally requires water to propagate and they have the ability to encapsulate moisture content to further their growth process. Microbial growth will exacerbate wintertime fuel moisture problems by producing waste by-products and visible "slime" from their colony growth.
De-Icer agents are not biocides and, therefore, will not eradicate (kill) the microbial growth colonies in distillate fuels.
Types of De-Icer Agents
Isopropyl alcohol (IP): one of the first extensively used chemicals as a diesel fuel De-Icer that effectively resolved the fuel line freeze-up issues of the past. Unfortunately, IP is an extremely dry product and the major equipment manufacturers found that IP increased fuel system component wear and adversely affected the expected useful life of diesel powered equipment.
IP also is a very flammable product that decreases distillate fuel flash point temperatures resulting in increased handling problems and presenting increased safety hazards with the fuels.
Glycol Ethers (GCE): determined in the early 1980's to be the fuel De-Icers of choice and most fuel additive manufacturers today use one (or more) of the available GCE products. GCE additives are not nearly as dry as IP products and some GCE products can actually impart a small amount of lubrication to the fuel system.
Unlike IP many of the GCE additives do not have low flash point temperatures and thus do not negatively affect the diesel fuel flash point.
A diesel fuel additive manufacturer faces a multitude of issues when it comes to selecting a specific De-Icer agent for his formulated products. The most important of these issues is the overall compatibility of the De-Icer with the other chemical components to be blended in the finished diesel fuel additive.
The winter diesel fuel additive components (cetane improver, detergents, stabilizers, cold flow improver, lubricity agents and deposit modifiers) must be properly "balanced" with the De-Icer agents in order to effectively lower the operability temperature point of the finished diesel fuel. This balancing of chemical components will have a direct effect on the neat additive pour point and thus determine the handling and storage necessities of the additive.
De-Icer Treatment Amount
The amount of De-Icer formulated into a winter diesel fuel additive must be adequate to effectively de-ice a typical (normal) amount of dissolved moisture expected to be in the finished diesel fuel.
Generally a De-Icer treatment amount equal to 1 pint per each 100 gallons of diesel fuel will effectively lower the freeze point temperature of normal dissolved moisture content (100ppm or more) in a diesel fuel down to a fuel temperature of -40F or lower. This treatment volume represents the maximum dosage recommended by the equipment manufacturers to prevent any adverse effects on the fuel delivery system.
While incoming fuel deliveries into the fuel storage tanks should be treated on an on-going basis, it is recommended as a preventative maintenance program that vehicle tanks be individually treated twice during the winter season (a) once in the late fall / November and (b) again during the dead of winter - late January or early February.
Water is not a lubricant and, in fact, will decrease the lubrication value of the diesel fuel and any lubricity enhancer added to the diesel fuel. Water will rust and corrode the metal parts of a fuel delivery system and cause long-term deterioration of the fuel system.
Water harbors microbial growth and acts like a sponge to quickly absorb any dirt, debris and foreign materials found in the diesel fuel delivery system. Such contamination can increase wear and ultimately damage the fuel delivery system.
Water will also change to ice crystals (freeze) at temperatures of 32 degrees F or lower and act to plug fuel lines, filters and the fuel delivery system. Water in a fuel delivery system should be removed and any non-removable or dissolved moisture content should be properly treated with a De-Icer agent (additive) to lower the freeze point temperature. Such treatment should be undertaken before cold weather arrives.
©Copyright Amalgamated, Inc. 2009