Budget Busters For Municipalities - Cold Flow Problems

Heading into the winter, we’ve been reminded of the problems that local and private groups (city and county governments, small to medium businesses) have with their budgets. The problem of predicting the future and weathering the unexpected equipment issues that arise every year.

One of the problems that our business and government friends up north see hit them pretty hard is the annual winter diesel fuel gelling problem. Now, Bell Performance has been located in Florida since the mid-1930s (thanks, Robert J. Bell!), so we don’t see fuel gelling during the winter time. Unless it’s some of the local fleets and bus groups that have to use biodiesel blends – those can gel when the temperature drops down to just 45 or 50 degrees F.

But if you’re responsible for maintaining buses or trucks or diesel equipment up north – New York, New Jersey, Chicago, Boston, Michigan – you can’t afford to ignore what the cold does to diesel fuel. And what it does to the equipment running on it.  Nothing will shut down a diesel engine faster than a fuel filter clogged with wax dropping out of gelled diesel fuel. Then there’s the expense of downtime, lost service, towing, service time, and work. Not to mention the headache of a sizeable unexpected cost that will sap the budget.

Knowing Your Fuel's Temperature

Professional fuel users have a good idea when they need to add a cold flow improver because they generally know the cloud point and plug point temperatures of their fuel. They keep track of outside temperatures so that they have an idea ahead of time when they need to break out the cold flow improver (since it needs to be in the fuel before the fuel gets too cold).

In general, satisfactory operation should be achieved in most cases if the blended fuel is 6 degrees C above the "10th percentile minimum ambient temperature" for the fuel's area. This term may not mean anything by itself, but it's supposed to be the temperature that isn't supposed to be below for more than 3 days out of a given 30-day period.  This is different for different areas and different times of year. For example, Long Island's 10th percentile temperature in December is -14 degrees C. For Alabama in December, it's -6 degrees C. 

As a user, you want to start considering cold weather treatment when the temperature starts coming within 5 degrees of your fuel's cloud point. This means, if you're tracking the ambient temperatures for your area when the forecast starts projecting lows that approach 10 degrees above the normal 10th percentile minimum ambient temperature, that is the time for you to get your cold flow improver into the fuel.

Administering Anti-Gel

Preventive maintenance is the name of the game to keep this from happening. Treating the diesel with a cold flow agent is the only effective way to eliminate these costly gelling incidents and cold flow problems.  Cold flow fuel treatment is a relatively low fixed cost that can be factored into the budget with ease. Keep in mind that, to be most effective, cold flow treatment of the fuel needs to be done before the fuel gets cold enough to get.  Cold flow agents keep fuel wax dispersed, but they don’t reverse fuel that’s already been gelled.

What About Kerosene?

Kerosene is a more traditional solution for lowering diesel's cold filter plug point, working on the principle of dilution of the paraffin. It does work, but you need to keep some things in mind if you elect to go this route vs. using a cold flow improver.

The biggest performance difference with kerosene vs. an anti-gel is that kerosene provides less of a drop in temperature. A typical fuel anti-gel should be able to drop a fuel's cold filter plug point by, say, 15 degrees. It does depend on the fuel's characteristics, but 15 is a reasonable expectation.

Kerosene dilution works off the rule of thumb that you can expect about a 3-degree drop for every 10% kerosene you use. So if you needed to drop your diesel's gelling temperature by 15 degrees, you'd need to use a 50-50 blend of ULSD and kerosene. At such sizeable amounts, you'd also have to factor in the loss of mileage you'd be getting with kerosene, which has less energy than #2 diesel and therefore will give you less mileage. 

So yes, kerosene will work, but you need to be realistic in accounting for how much you'll need to use to get you where you want to be.

Is there anything to be done for an agency’s fuel that has already gelled to the point where it’s shutting engines down? In these cases, there are "quick thaw" rescue treatments that typically function to melt gelled fuel in a fuel system.  These emergency treatments are fairly inexpensive and can be included in a preventive maintenance budget without creating too much pressure.

You may be interested in these other posts on cold flow problems:

• Diesel fuel lubricity trends for fleet and business
• How to Prevent Diesel Fuel Contamination
• Prevent Your Diesel Fuel from Gelling in Cold Temperatures