Winter Diesel Operability: Expect the Unexpected

Editor’s Note: With the recent extreme weather, we wanted to make sure you’re looking ahead and preparing for winter weather. Hurricanes make fuel supply tight, but cold weather can make your existing fuel completely unusable. Our winter program begins October 15, which is just around the corner; we’ve already seen snow storms this year in the northwest. This article from Q3 2016’s FN360° is as relevant as the day it was written. If you have any questions about winter fuel preparedness, email our winter fuel experts at arsenal@mansfieldoil.com or call Clint Hamlin at 678-450-2188.

From an unexpected blizzard in the South, to a crippling ice storm in the Midwest, to a surprising 70°F Christmas day in New York—last winter was unpredictable. The history books will remember it as setting the bar for the warmest winter on record for the lower 48 states, but another record for most snowfall in a single snowstorm in Philadelphia and New York. These bizarre patterns are indicative of the erratic temperature swings and weather events that fleets should prepare for every year.

This year, cold temperatures across the North are expected, with the ever-present potential for heavy snowfall in those areas. Across the southern states, the outlook is predictably rainy and mild. The past few years, however, have been defined by unexpected and unusual weather events. This trend of unpredictability calls into question the accuracy of any preseason forecast and makes it difficult to determine when to begin winterizing diesel fuel.

Volatile weather often leads to emergency situations. Taking a reactive approach to fuel winterization can lead to costly consequences. If this year sees the same 20°-in-24-hour temperature swings as last winter, unprepared fleets will rapidly fall victim to the cold weather operability dangers of diesel fuel.

 Winter Diesel Operability

Winterizing diesel fuel is a necessity in most parts of the U.S. due to the cold flow properties of ultra-low sulfur diesel. ULSD contains paraffin wax molecules that remain fully soluble at mild temperatures but crystalize and compound together to form sheets of wax as temperatures plummet.

These wax sheets then get drawn into the fuel filter, either at the fuel dispenser or in the fuel system of the engine. This wax buildup continues to compound until the filter is clogged and soluble fuel is unable to penetrate the filter. When this happens, it starves the nozzle or engine of fuel and shuts down operations.

Challenges with winter operability are compounded by the introduction of biodiesel, which is prone to premature wax fallout and gels at a higher temperature.

Emergency Preparedness

Emergency preparedness requires that fleet managers expect the unexpected.

Having onsite inventory of cold flow improver, emergency reliquifier, and water dispersant additives is a simple step consumers can take toward being prepared for sudden extreme temperatures. Preparedness also requires a current knowledge of the condition inside fuel storage tanks. A fuel testing program provides the insight needed to be proactive in protecting the fuel inside the tank from the onslaught of winter.

Cold Flow Improver Additive

Using a cold flow improver (CFI) ahead of an impending cold snap can greatly improve fuel performance during an extreme winter event. Ideally administered at the time of fuel delivery, CFI additives must be properly mixed into the fuel. When properly blended, CFI additives modify the structure of the waxy molecules in fuel, preventing them from glomming together and creating filter-plugging sheets.

Increasing the treat rate of CFIs may provide additional protection. However, anything above a double treat rate generally has significantly diminishing returns.

Emergency Reliquifier

Emergency reliquifier is a fuel additive that is administered directly into a vehicle that has already experienced—or is expected to experience—the effects of fuel gelling or icing. Reliquifier dissolves congealed fuel or ice and returns it to a liquid state, inhibiting further gelling or icing. The additive is supposed to be used as a reactive measure to ensure operability in extreme conditions and is not intended for consistent preventative treatment.

Water Dispersant

Water in diesel fuel, while fostering microbial growth and corrosion, can also be detrimental to winter operability. Water quickly freezes in the fuel lines and filters, causing filter plugging, fuel starvation, and ultimately, inoperability. A water dispersant additive, properly blended into the fuel, will rid diesel of entrained water that can lead to equipment failure if left untreated.

Fuel Testing

A comprehensive fuel testing program provides necessary insight as to the interior condition of a fuel storage tank. A testing program should include two basic types of analyses: a bottom sample test and a nozzle sample test.

Bottom samples are drawn using a device known as a fuel thief or bacon bomb.

Fuel samples taken from the bottom of the storage tank provide data on the extent of contaminants in fuel. A bottom sample is typically tested for water content, sediment accumulation, and microbial growth and should be tested right before winter to ensure such contaminants do not compound issues around winter operability.

Nozzle sample tests provide data on the cold flow properties of winter fuel. Taken from the dispenser, a nozzle sample provides key operational metrics such as cloud point, cold filter plug point, and water content—all of which are critical in terms of winter operability. Nozzle samples should be drawn and tested at least once a month during winter, and more frequently if operationally practical.

A Comprehensive Solution

While winter weather continues to be notoriously unpredictable, being prepared in the short-term requires constant weather tracking. Forecasts should be monitored up to two weeks out to allow adequate time for any preventative treatments or adjustments required. As a rule of thumb, a site should winterize its fuel for protection down to the tenth percentile of historical temperatures in that region. For any temperatures beyond that, emergency blending procedures should be incorporated.

An optimal blending program that leverages actionable insights gleaned from test results combined with the cold flow benefits of winter additives can achieve significant cost savings and ensure ongoing customer operability.