Caterpillar in Joliet, Illinois had five existing wet bed scrubbers servicing five ventilation systems.  These systems could not meet the federal MACT mandate for chrome emissions of .015 mg/dscm, so Caterpillar asked for bids to replace two of the five scrubbers.  A large scrubber manufacturer from the midwest received the contract, and installed two large vertical, 3-stage composite mesh pad systems with periodic wash down.  Each vessel consisted of three composite mesh pads housed in a cartridge which slid into a drawer section in the chrome separator.  The middle stage was designed to coalesce particles and was constructed of two course pads and 20 ultra fine pads.

Both systems passed the emissions mandate, but within one month the two vessels exceeded the 1" pressure drop increase allowed by regulations, forcing Caterpillar to shut down the process to clean the pads.  This high maintenance chore became a major nightmare - causing a loss of three shifts!  The large cartridges were very difficult and heavy to remove, and the pads had to be cut open to allow the fibers in the center to be cleaned.

Caterpillar continually contacted the scrubber manufacturer for assistance.  The vendor sent representatives to the plant who told Caterpillar engineers that "at least the system had passed the difficult MACT mandate" and Caterpillar needed to expect that "a filter system is high maintenance" and that this vendor's system was "the best technology available".  After one year, Caterpillar proceeded to purchase the third (of five) chrome separators required, and asked ScrubAir to quote on the project along with the other scrubber manufacturers.  ScrubAir proposed their unique gradual step down system, guaranteeing that it would not have the plugging problem Caterpillar experienced with the other two coalescent scrubbers.  ScrubAir also promised Caterpillar that they could expect to go one full year before the ScrubAir system would require cleaning of the composite mesh pads.

After receiving the purchase order from Caterpillar, ScrubAir installed an 18,000 CFM horizontal 3-stage composite mesh pad unit with a PLC control panel.  Six months later, the system had only increased 2/10 of an inch (well below the 1" pressure drop allowed).  Stack testing proved that the emissions were well below the MACT mandate at .003 mg/dscm.

Caterpillar had become convinced that the ScrubAir technology really worked, and proceeded to issue an order to replace the two composite mesh pad systems they had just purchased 1 ½ years before with two new ScrubAir gradual step down vessels.  These two new units also operated one full year before Caterpillar pulled the pads for cleaning! Caterpillar then requested ScrubAir to quote a price to replace the final two wet-bed scrubbers.  ScrubAir was awarded this contract, and fabricated and installed two more Chrome Separators.

Today, all five systems at Caterpillar are ScrubAir gradual step down composite mesh pad systems. These units have proven to require very little maintenance, and use a minimal amount of water for the rinse down cycle.