Mobil Oil, Beaumont, TX

Mobil Oil in Beaumont, TX has installed a PULSAIR for mixing six 8,000 gallon tanks and two 2,600 gallon tanks. They selected a PULSAIR PPC-8 Controller to handle the blending operation.

The 8,000 gallon tanks are rectangular; the 2,600 gallon tanks are square. The bracing to support the tanks is on the inside, which made mixing them using conventional mechanical mixers a real challenge. The larger tanks have eight accumulator plates connected to three injection valves, while the smaller tanks have 4 accumulator plates plumbed to two valves. An electro-pneumatic interface (EPI) receives control signals from the PPC for each pair of tanks.

Mobil had very little surplus compressed air for running the PULSAIR. Therefore, we programmed two new features into Mobil's PPC system. The first feature provides a link up to a remote PC so that the PPC can be switch on from the control room (the PPC is located out in the plant). Using the link up, the operator in the control room can switch on or off any one of the eight tanks for a specific length of time.

The second feature is a programmed on/off loop that sequentially mixes all eight tanks for a preset length of time. After the loop is completed, the system rests for a preset period and then restarts. Mobil selected a 2 minute mix time for each tank and a four hour rest period for their initial setting. The mixing was so thorough that they were able to turn the pressure down to 60 psi and still achieve superior mixing results. Finally, because of the loop programming, the system had no noticeable impact on the already strained air system.

When Mobil installed the system and started it for the first time, they used the dwell and injection time mixing parameters that we set during our quality assurance testing. The first thing Mobil did after start-up was to select the loop feature. The second thing they did was reduce the injection pressure to 60 psi because the system was mixing so well. Having made those two adjustments, the PULSAIR PPC continues to work well for them.