Iowachild said:
ULSD is coming right off the treating unit at our refinery with a cloud of -16 degrees F and a pour point of -34 degrees. The "all weather diesel", treated with among other things a pour point improver, had a pour point of -44 degrees F yesterday. BTW we have a terminal in Rochester, NY.
That may be very true but not all ULSD that is hitting the pumps has a pour point that low. If the fuel you are talking about comes from PA crude it is naturally lower in paraffin's and higher in aromatic's which lead to lower pour points. However, not everything that is being dispensed is that good. The horrible problems some people are having with temps in above 0 degree F. weather this last weak is proof of that.
Local bus fleet's in Carroll County Maryland had some problems this week and the temp was only down to around +7 or +8 degree's F, and on top of that it is even a winter blend fuel. Around Westminster they cut the winter blend fuel with ULSK 1 (ultra low sulfur kerosene #1) instead of ULSD 1.
One thing I think we need to clear up is some of the terms being thrown around.
Pour Point = The pour point of a fuel is typically 5 degrees F above the temperature at which the fuel fails to flow and turns solid (CFPP). This is also the lowest temperature that the fuel will flow sufficiently to be pumped or transferred.
Gel Point / Cold Filter Plug Point (CFPP) = This is the temperature at which the paraffin waxes in the fuel actually turn solid and clump up.
Pour Point Depressant / Anti-Gel = This is a additive you add to your fuel that lowers the pour point. On the microscopic scale wax molecules are long slender molecules. When they reach the gel point they start to align into clumps that evenly align and start to form microscopic sheets of wax crystals. These clumps are to large to pass through fuel filter media and in severe cases can even form solid clumps in fuel lines. A pour depressant modify's the size and shape of the wax crystals and keeps them from combining with one another to form a gel.
Now, everybody's big question. Do I need a pour point depressant in my fuel? No way of telling without testing your fuel to tell what it's CFPP is. If it's been cold where you are and have not had any problems then your fuel supplier is probably adding a healthy dose of pour point depressants and cutting the fuel with enough ULSK 1 or ULSD 1 to lower the CFPP. If like many you have been having problems I suggest buying some pour point depressant (anti-gel) additive and having it on hand to add to your fuel BEFORE it gel's up. Just keep a eye on the weather reports and when you see a cold spell coming treat your fuel.