Cold Weather Diesel Problems

In cold weather certain components of diesel fuel start to come out of solution as waxes. People use the term gelling for diesel fuel in cold weather, meaning that enough wax comes our of solution to make the diesel fuel a gel consistency. The temperature at which this happens in the pour point – the point at which diesel fuel will not readily flow through valves and devices.

The pour point would be approximately +0 to -10 degrees F for #2 diesel fuel and -25 to -30 degrees F for #1 diesel fuel.

Generally we are more concerned with a higher temperature known as the cloud point – the temperature at which wax starts to come out of solution. The reason is that the wax can clog filters that would block flow to the generators.

The cloud point would be approximately +5 to +10 degrees F for #2 diesel fuel and -10 to -30 degrees F for #1 diesel fuel.

A winter blend is a mixture of #1 and #2 diesel fuel to provide a cloud point below the expected minimum ambient temperature. Winter blend is a standard fuel delivery in cold climates during winter months. For new generator placed in service during the summer, a winter blend can be ordered throughout the year form most fuel suppliers.

Tnak heaters are available for heating of aboveground tanks in cold climates. However, many aboveground tanks are not heated if a winter blend of fuel is used.

Part of the thinking in not heating the aboveground tank is that the fuel will rise in temperature before it reaches the generator by: (a) movement through a pump, (b) movement through heat traced and insulated piping if used, and (c) storage within a day tank if the day tank is located within a heated room or enclosure.

In cold weather climates there is a concern for maintaining the functionality of critical fuel systems in freezng weather. In general a winter blend of #1 and #2 diesel fuel will lower the cloud point to about -10 degrees F and the pour point to minus 30. However this may be borderline for many users, and for that reason exterior piping is often heat traced and insulated.

The problem with cold weather performance is often not the fuel itself, but any water that may be present in trace amounts in the fuel. This water can accumulate within the cavities of valves and other equipment, so it is important that these devices also be heat traced and insulated, or located within heated enclosures.

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