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Avoiding Pump Failures for Non-Fouling Solution


False Measurements Due to Equipment Malfunction: In Newport News, Virginia, several restaurants were built in an area serviced by the same municipal wastewater lift stations. The introduction of heavy grease content to the wastewater caused the existing level measurement equipment to foul, and fail.

In wastewater measurement, accurate readings are essential to ensure proper pump operation. Failures in this area result in unhygienic liquid waste overflow and costly repairs to pump mechanisms.

Prior to the development of the commercial district, the Newport News Waterworks and the Hampton Roads Sanitation District relied on a combination of mechanical floats and traditional submersible level transmitters. Once the restaurants were in operation, the increased volume of grease would cling to both instruments and, as a result, both the primary and redundant level measurement failed to properly transmit level data to the pump controller. 

The accumulation of grease to the submersible level transmitter clogged the pressure ports, which blocked the free flow of liquid, making a proper application of hydrostatic pressure to the sensing diaphragm impossible. On the redundant float switch, whose purpose was to trigger the pump in the event of a failed level transmitter, the accumulation of grease blocked the mechanical operation of the float ball. With the level transmitter and backup system inoperable, the affected lift stations would fail, either reading too much wastewater, or too little, which caused the pumps to run continuously or not at all.

Several instrumentation companies offer non-fouling products, which offer only minor variations of their existing and unsuitable solutions. These instruments use a Teflon-coated elastomer diaphragm that is relatively weak and prone to puncture. Their answer is to employ a bulky protective cage, consisting of a shield mounted on bolts and standoffs. However, these shields can collect rags, grease and biosolids from the wastewater, which leads to erroneous readings. 

Newport News officials contacted KELLER, whose 36 XKY, also known in the U.S. as the LevelRat, provided a unique approach to wastewater level measurement. The tougher Kynar i diaphragm employed on the 36 XKY provides superior abrasion and puncture resistance relative to other “non-fouling” solutions. This design also minimizes the 36XKY profile, creating a sleeker design without the need for bulky shields, resulting in a truly non-fouling instrument.

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