A manufacturer of nylon intermediates, the DuPont Sabine River Works Site increased throughput and improved product quality at its Orange, Texas, plant with the installation of two gas seals and centrifugal pumps.
In one application, the plant had been using canned pumps, which required a lot of maintenance and adversely affected unit operation. In the three years since the new pumps and seals were installed, maintenance costs were trimmed by more than $47,000 dollars. Additional gas seals have been installed in other applications at the plant.
The canned pumps were used to pump the tails of a distillation column at 187 Degrees C to the next column in the process. The pumps originally were selected to prevent any air from entering the process and to eliminate any possibility of leakage. Unfortunately, the canned pumps could not handle the process upsets that would occur throughout the year. These upsets included pressure swings in the distillation column and clogging of the in-line suction screen, resulting in frequent canned pump overhauls.
The canned pump overhauls were performed outside the plant because of the specialized nature of the equipment. Unfortunately, the pump overhauls were both expensive and time consuming. As a result, spare canned pumps had to be stored on-site for installation in the unit, adding to the company's inventory and warehouse space.
DuPont investigated its sealing options with conventional centrifugal pumps, looking at single seals, dual seals and gas seals. Ultimately, the company opted for gas seals.
Gas seals would operate on plant nitrogen common in the unit. The gas seals would not fail in the absence of process fluid lubrication. Even if the pump ran dry, the gas seals would remain unaffected.
The 4400 model gas seal works well in both normal operation and process upsets at the plant.
