rail tank car mixing

The Pulsair rail tank car mixing process has been used for over 20-years to help accelerate the heating of liquids in rail tank car and to mix up settled slurries prior to unloading.   The Pulsair mixing process has also been used with great success blending in horizontal tanks of all lengths, diameters and capacities.  While the concept of actually blending in a rail tank car is not new for Pulsair customers, we want to share a success test that was done a few years ago at a large well known lubricant blending and manufacturing company.


A 23,000 gallon rail tank car was filled with 19,000 gallons of base oil.   To the base oil 300 gallons of liquid additive was introduced.  The viscosity of the base oil was 525 centistokes at 120 degrees C.  The viscosity of the additive was 656 centistokes at 120 degrees C.  The additive was pumped into the top of the rail car the night before the test.  By morning, the additive had settled along the bottom of the rail tank car.


A Pulsair rail car mixer was hooked up to the bottom discharge valve of the tank car using a Pulsair Rail Car Adpater.   The mixing gas used for the test was nitrogen.  When in operation the Pulsair mixer sends sequential pulses of compressed nitrogen through the bottom outlet of the car.  The injection pressure was at 55 psi and the pulse rate at 15 pulses per minute.  The blend time was arbitrarily set at 3 hours with product samples taken at 30 minute intervals.  When blended, the spec called for a target viscosity of 590 centistokes +/- 10 centistokes.

rail car tank mixing

By sequentially pulsing from below the liquid level in the car, the large Pulsair bubbles move vertically up through the liquid and vent out the top of the tank. A liquid circulation pattern is established in the car that extends all the way to ends of the rail car. The huge Pulsair bubbles pull large volumes of liquid up from the bottom of the car to the surface, while liquid from both ends along the bottom of the car are dragged toward the center to fill the void. By repeating this pulsing over and over on a timed basis, and by using large measured amounts of compressed gas, the Pulsair process quickly rotates the liquids in the car and blends them together.

At 30 minutes, a sample was taken from the center of the car through the center top hatch. Viscosity was 560 centistokes. Samples taken from the center of the car at 1 hour, 1-1/2 hours, 2 hours, 2-1/2 hours, and 3 hours ranged from 588 to 592 centistokes – on spec. To confirm that the ends of the rail car were mixed, a special sampling device was used. The device consisted of a 30ft long 3/8” SS tube that was lowered into the car and extended to within approximately 5 feet of the end of the car. The other end of the tube was attached to a vacuum flask and vacuum pump. Samples taken from the ends of the car were 598 to 599 centistokes. The test was halted as the material was considered “on spec” with regard to target viscosity and sample to sample repeatability.

The 3 hour blend time was arbitrarily chosen for the test. However, the goal of the test was to achieve “on spec” blends in 10 hours or less, which was the target time frame for making blending in a rail car an economically worthwhile endeavor. Pulsair easily met the goals of the test. Additionally, the test was done on what is considered the most difficult blending application at this facility, with the idea that if the test was successful with the most difficult blend, all other blends would be easier and take less time.

Learn more at rail.pulsair.com

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