Sewage Pumps Offered with "No Flush" Design

Patterson Pump's Forceline® NCS Series and Type "F" sewage pumps are now offered with a sealing arrangement which requires no flush water, providing substantial savings in areas of maintenance and seal flush water.

This new technology features EnviroSeal's SpiralTrac™ throat bushing and the Chesterton® Model 442 split mechanical seal. With this unique design arrangement, no flush water is required, saving on the initial cost of the installation as well as long term costs associated with having to flush the stuffing box.

Ultimately, pump users benefit by having extended seal life, and maintenance can be performed to the seal and stuffing box without taking the pump out of service.

The SpiralTrac is a throat bushing that takes advantage of the natural circulation of process fluid inside a stuffing box. It is placed in the bottom of the stuffing box and used with a mechanical seal. Since the fluid in the stuffing box spins with shaft rotation, the SpiralTrac takes advantage of this action to expel solids and particles from the stuffing box during equipment operation. This increases seal life by leaving a cleaner fluid in the stuffing box for the mechanical seal.

Entrained air can collect in a stuffing box either from start-up as the pump is flooded or over time from the liquid being pumped. The air will surround the mechanical seal during equipment operation as the heavier liquid centrifuges to the stuffing box wall, resulting in higher seal heat and wear. The SpiralTrac releases this entrained air out of the stuffing box through a unique air vent in its top surface.

The Chesterton 442 Split Mechanical Seal's construction enables the seal to handle pressure 3½ times higher than conventional split seals. In addition, the 442 is the only split seal specially designed to withstand vacuum in the stuffing box. This makes it an ideal seal for non-clogging solids handling pumps.

The 442 provides the sealing capability of traditional mechanical seals without the need to disassemble and realign the pump. All parts are split to slip around the shaft and assemble in place. This feature allows for faster installation and rebuilds. Downtime is minimized and driver/equipment alignment is eliminated.

A prime example of a successful retrofit application took place at the Oconee County Sewer Commission in northwestern South Carolina.

The commission had experienced difficulties with traditional mechanical seals on its two 8x8x17 NCS V14 pumps, which had been installed and put into operation in early 1996.

Patterson recommended retrofitting one pump with the SpiralTrac throat bushing and Chesterton 442 split mechanical seal for a test period of several months.

Robert Winchester, General Superin-tendent at Oconee County, agreed to the test period. One pump was retrofitted and installed more than 18 months ago. The successful trial convinced Winchester to leave the retrofit in place.

"We had no problems at all since the retrofit," he said, "and we are now having the new technology installed in the second pump."

Booth 4547