New Cold Weather Problems with Biodiesel Identified

New Cold Weather Problems with Biodiesel Identified

The recent bout of very cold weather in the northern tier states has shown new issues with biodiesel blends containing as little as 2% biodiesel.

We are seeing a significant number of customers that are having problems with the filters on their diesel fuel dispensers.

In nearly every case the customers are receiving a B2 to B5 blend.

In most of these cases they are not having vehicle or equipment problems, but rather problems getting the fuel from the storage tank to the vehicle tank. The dispenser filters seem to plug anywhere from a few hours to a few days of operation.

These filters when opened contain what at first appears to be wax. However when analyzed this material appears to be a glycerin type material. If you then bottom sample the storage tank, you generally find a material that resembles cottage cheese. There is often a layer that starts at the tank bottom and can be several inches thick of this material.

When this layer reaches the level of the pickup tube it can very quickly plug the dispenser filter.

This issue has several variations and we have identified several potential causal factors.

1. 
   Fuel that has a high level of dissolved water. This high water content seems to be a significant factor in all of these cases.
2. 
   Fuel derived from animal fats (including plant / animal blends of biodiesel) seems to be a factor in these problems.
3. 
   Long periods (more than 72 hours) of temperatures below 32 °F (the longer it is cold and the colder the average temperature the greater the problem).
   Above ground versus in-ground fuel storage.
4. 
   Use of additives – Some help, some make things worse.
   CP, CFPP, PP of the diesel portion of the blended fuel.
5. 
   Quality of the blend procedure and temperature at which the fuel and biodiesel are blended.
6. 
   Storage period.

Another factor in the rapid plugging of these dispenser filters is that as filter media starts to plug the filter actually begins to reduce the micron size of the media so that the filter picks more and more material that is smaller and smaller.

Also consider that a diesel engine tends to heat the fuel during the recirculation process whereas a dispenser provides no heat.

We offer some suggestions for users experiencing these problems.

1. 
   If you have this problem today you can go to a dispenser filter with a large micron size. There are winter filters available from Cim-Tek with a cleanable 144 micron stainless steel mesh.
2. 
   You can have the tank pumped from the bottom to remove this material. Depending upon your tank size, you may need to remove 50 to as much as 300 gallons to eliminate this problem.
3. 
   You can add certain types of additives that will break this material down and return it to solution.
4. 
   You can add kerosene (Note: if you have Ultra-Low Sulfur Diesel, you MUST use Ultra-Low Sulfur Kerosene). ULSD Kerosene is very expensive and it can take a lot of it to resolve this problem.
   Ask for your next two or three loads of diesel to be delivered with no biodiesel.
5. 
   Ask for biodiesel blends derived only from plant base oils during the fall and winter months.
6. 
   Additization with the correct products can help to prevent these problems.
   If you have access to biodiesel that has been through a distillation process, you will have far less problems.

Please let us know about your experiences with these problems

Cold Filter Plug Point versus Cloud Point

CFPP (Cold Filter Plug Point) vs. CP (Cloud Point)
Cold Weather Operability in Diesel Fuels including ULSD

Traditionally the two main considerations for diesel fuel have been Cloud Point (CP) and Cold Filter Plug Point (CFPP).

Let’s start by defining the terms:

Cloud Point (CP) ASTM D2500 – This test determines the point where wax becomes visible in a fuel sample. This wax first appears as a floating cloudiness in a transparent fuel.

Cold Filter Plug Point (CFPP) ASTM D6371 – This test is a more complicated procedure involving using a vacuum to draw a 20cc fuel sample through a 45 micron screen within a 60 seconds.

There is usually but not always a spread between CP and CFPP of 2°F to 8°F.

CP is a first indicator of cold weather operability temperatures for diesel fuels. It is a visible indication of paraffin wax in diesel fuels. Prior to the introduction of Ultra-Low Sulfur Diesel (ULSD, S-15) into the US market, the importance of CP was often discounted by many due to fact that diesel engines could generally successfully operate at temperatures many degrees below the CP.

Up until the introduction of ULSD many if not most operators used CFPP to provide a reference temperature for cold weather operability with diesel fuels. This is however a complicated and imperfect test. As mentioned above, CFPP uses a vacuum to draw a sample of the fuel through a 45 micron screen within a given time. The point at which the sample fails to go through the screen in 60 seconds is the CFPP.

The main issue is that up until recently most fuel filters used a 10 micron filtering media. The significant difference 10 microns and 45 microns caused a disparity between the test and real world operations. However many in the industry felt that this differential was consistent and that provided a reliable guide for cold weather operability.

For example if you had a CFPP of -30°F, you could feel reasonably confident that you could operate to -20°F.

However three new factors need to taken into account due to changes in fuels and engines.

1. The new ULSD fuel does not appear to provide the same consistent differential between CP and CFPP as we had come to expect with High-Sulfur Diesel (HSD, S-5000) and Low-Sulfur Diesel (LSD, S-500).

2. The new phenomenon of Wax Drop Out (WDO) where under periods of extended “Cold Soak” (48-72+ hours) the wax in the fuel suddenly drops out of the fuel can happen at temperatures that can be above the CP. This problem appears at this time to be independent of CP or CFPP.

3. As diesel engines have become more sophisticated there has been a rise in fuel injection pressures. In order to obtain these higher pressures OEM’s have had to manufacture pump and injector parts to ever closer tolerances. Today many injectors have tolerances in the 2 micron range. These tight tolerances and the very high cost of making and replacing these components have caused manufacturers to use fuel filters with smaller media to protect these components. Where in the past fuel filters typically were 10 microns, today we are seeing filters of 7, 5, and even 2 microns.

This makes the problems associated with ULSD even more difficult. Cloudy fuel that would easily pass through a 10 micron filter can often plug a 5 or 2 micron filter. This makes correcting the cold weather operability issues of ULSD like hitting a moving target. Today you need to adjust your fuel treatment to reflect the engines and filter arrangements in your fleet.

We are now suggesting a formula based on both CP and CFPP. Take the difference between CP and CFPP, divide by 1.5 and add to the CFPP to get a safe operability number.

Example: CP = 8°F, CFPP = 3°F

The difference between 8 and 3 = 5, 5 x .75 = 3.75, Take the CFPP of 3 and add the 3.75 to it equaling 6.75°F. You could expect to reliably operate that fuel in an engine with a 7 to 5 micron filter at 6-7°F.

For those operating 2 micron filters we suggest using the CP of the fuel.

For those still able to operate with 10+ micron filters, we are suggesting a number half way between CP and CFPP.

It is important to remember that the traditional method of using Kerosene or Jet A to “cut” or blend with HSD or LSD to lower the CFPP and Pour Point (PP) is not as effective or reliable as it was in the past when using the new ULSD #1 to cut or blend with ULSD #2.

Winter Problems with Ultra-Low Sulfur Diesel (ULSD)

Winter Problems with Ultra-Low Sulfur Diesel (ULSD)

Which One of these Filters Would You Rather Have on Your Vehicle?

The above image is from February 5th 2007, the first real winter weather while using the “new” Ultra Low Sulfur Diesel (ULSD). After being told by refiners and many distributors that ULSD would be the “be all, end all” magic problem solver for all diesel engines, this is what really happened when it finally got cold and stayed cold for 48+ hours.

The red colored filter on the left is the result of a fuel distributor using so much anti-gel additive that it actually saturated the fuel to the point of completely plugging THOUSANDS of fuel filters over several days.

The filter on the right shows paraffin wax plugging it. This customer used ULSD #1 (ULSD Kerosene) to “cut” the ULSD #2 fuel. However the “new” ULSD #1 doesn’t work the same way as the “old” LSD Kerosene (see more below)

The new ULSD gels 4°F to 5°F sooner than the “old” Low Sulfur Diesel (LSD). The new ULSD is harder to treat for cold weather than the “old” LSD. Many additives that you have been using for years no longer work on the “new” ULSD. The “new” ULSD holds more dissolved water than the “old” LSD, causing ice formation as the temperature drops below freezing.

When treating with a cold flow improver (anti-gel), using the recommended treatment ratio provides a certain level of protection, using twice the recommended ratio may improve the gel point a little, however if you go beyond that level it will actually raise or worsen the gel-point. At treatment levels beyond 3-4 times the recommended ratio, you will begin to saturate the fuel and can actually plug a filter full of anti-gel additive. This is generally indicated by a reddish or pink colored wax-like substance covering the filter as much as ¼” thick. This wax-like substance will not readily melt at room temperature unlike paraffin wax that melts above 32°F.

In the past the general “Rule of Thumb” regarding using Kerosene (#1D) to “cut” #2 diesel was that for every 10% kerosene added to #2 diesel you would lower the Cold Filter Plug Point (CFPP) by approximately 5°F. So for example a 50%-50% blend of #2D and Kerosene would have lowered CFPP by approximately 25°F. The “new” ULSD #1 is far less aromatic and has much less solvency than did the old Kerosene. As a result the new ULSD #1 will only lower CFPP by 2°F-3°F. This means that a 50%-50% blend will only lower CFPP by 10°F to maybe 15°F.

If you have any comments or related incidents or problems, please post to this blog.

Doctor Diesel

Biodiesel and Cold Weather Issues

We have recently seen a new cold weather problem related blended biodiesel fuels.
The problem has been seen with B5 and greater blends where the diesel portion has been treated with certain lubricity agents.
What is being seen is that when the stored fuel is cold (below 15F) for extended periods of time (generally 48 hours or more) the dispenser filters will plug with an orange colored material. When this fuel filter is removed and the fuel poured out into a container that will allow it to be viewed you see an orange cloud floating in the fuel. The colder it gets the more of this material is found in the filter.
This appears to be the result of the fuel becoming more viscous as it gets colder. As the fuel becomes thicker it will begin to reduce the pore size of the filter media. As the pore size gets smaller, the filter begins to filter out the lubricity additive and the filter will concentrate it until the restriction is such that little or no fuel will pass through the filter.
This is a separate issue from gelling. The fuel when tested can have a very good CFPP or LTFT number and still see this problem.
If anyone has seen this issue, please let me know and I can offer suggestions for how to deal with this problem.