Flow Monitor Meets Challenge of Sewer Pipe Measurement

Accusonic Technologies Inc. has developed a new flow monitor, the IntelliFlow IF30.

The IF30s processor, communication and power components are packaged in a unit that measures 15 inches high and weighs 15 pounds - less than half of traditional units.

The key to weight and size reduction is the adoption of a single PC board assembly. System electronics are surface mounted on the assembly, which is barely seven inches in diameter. Aside from the space reduction, surface mount technology is robust and should result in lower maintenance costs.

While the processor is the brain of the system, the eyes and ears of the IF30 are the pipe-mounted sensors. In a standard manhole installation, cables feed from the logger to two sensors attached to a stainless steel ring that hugs the diameter of the host pipe. At the top of the installation ring, an ultrasonic depth sensor; at the bottom of the ring, an ultrasonic velocity sensor teamed with a pressure transducer.

The ultrasonic sensor consists of three crystals residing in a narrow PVC shell. Protected by a Teflon? coating, these crystals form a total of six different paired transmit and receive combinations to maximize measurement uptime.

Accusonic engineers developed a novel backup depth measurement system after listening to customer complaints about the cost and extra maintenance required to service traditional desiccant tubing designs. Their approach is unique: the IF30 measures pressure in the flow and at the logger with separate pressure transducers. The resulting pressure differential is converted to flow depth and is recorded in the logger.

IntelliFlows velocity/pressure sensor is the smallest in the industry, an important factor in reducing fouling and clogging. Like its collaborating ultrasonic sensor, the bottom-mounted velocity/pressure sensor is housed in PVC to withstand harsh sewer flow.

As the sensors communicate with the logger during the split second measurement sequence, the loggers computing function takes over. Because sewer flow acoustic measurement is tricky, engineers focused on isolating the sensors analog inputs from digital signal processing.

"In essence, we separated the analog and digital functions which greatly reduces electrical noise. The result is improved sensitivity of the sensors under a wider range of conditions," said Steve Wright, Accusonic lead engineer on the project.

The IF30 fully automates data quality and integrity checking. All sensor readings are analyzed and incoming signals adjusted for signal strength. The intelligent firmware determines measured variable quality factors for a "good reading."

Power to operate the IF30 is provided by two standard lantern batteries. The units packaging segregates the batteries from the electronic compartment so field crews replacing batteries do not have to worry about breaching the electronic nerve center of the system.

Bringing readings above ground for analysis is accomplished through standard telemetry techniques. Or data can be collected at the manhole using a laptop computer. In either case, to query an IF30, Accusonic software engineers developed a PC software called IntelliSite to configure, collect and store individual sensor, diagnostic and final flow values.