Pressure reducing valves (PRVs) are used throughout water distribution
systems to reduce pipeline pressure to a predetermined set point. This
decreases water loss and prevents pipe breaks.
Over time, PRVs wear
and lose their calibration settings. Telog's PRV monitor offers early detection of the valve’s
improper operation so proactive steps can be taken to ensure pressures are maintained
throughout the system under all flow conditions.
Wireless PRV monitoring is achieved using Telog's high performance RTU to monitor PRVs, providing historic performance data, real-time alarms and computation of flow through the valve.
Telog’s PRV monitoring solution includes a submersible Ru-33 RTU with two pressure sensor/transmitters. The pressure sensors provide ¼ NPT fittings for convenient attachment to the PRV’s inlet and outlet pressure ports.
Since the Ru-33 is a data recorder, it can sample pressure frequently (e.g., every 5 seconds), compute and store interval statistics (e.g., minimum, average and maximum pressure) at user defined intervals (e.g., every 5 minutes, hourly, etc.) and push this data up to the user’s host application infrequently (e.g., once per hour, daily, etc.). The RTU can also initiate calls to the host server immediately in response to high/low pressure alarm events.
Once the data is received by the host application—Telogers for Windows or Telog Enterprise—the data is stored in a database for web site viewing, system reports or sharing with other software applications such as modeling, SCADA, etc.
The Telog Ru-33 runs on user-replaceable batteries and consumes very little power, permitting operation for extended time periods with no maintenance. Power use is kept at a minimum by pulse-exciting the pressure transducers for very short periods whenever a measurement is made. Data calls are initiated infrequently by the RTU, so the cellular radio shuts down between calls, greatly reducing energy consumed for communications.
By contrast, SCADA system RTUs are typically configured to receive incoming queries for data, so they must power their radios or communication modems continuously. The energy consumption of the Telog RTU typically consumes two orders of magnitude less energy than SCADA system RTUs.
The standard Ru-33 is powered by a single 6-volt lantern battery. Telog also offers an extended body enclosure that will accommodate a custom alkaline battery pack, which will increase battery life by a factor of 4 to 5.
The Telog Ru-33 RTU is rated NEMA 6 (IP-68) and can operate submerged underwater. All material that comes into contact with the environment is either plastic or 316 stainless steel, permitting many years of trouble-free service in harsh environments.
Telog also offers a variety of cellular antennas, including a burial antenna that may be installed in the street below the asphalt. This results in a completely underground, battery powered wireless system that is easy and inexpensive to install and maintain.
The Telog Ru-33 can also monitor the valve stem position sensor if supplied with the PRV. This sensor provides a measure of the valve open position, or % open. Many PRV manufacturers characterize their valves for flow as a function of differential pressure and valve position.
The Telog RTU can compute differential pressure across the valve from the two pressure sensors (inlet and outlet), measure the valve open position, and then compute flow through the PRV using the valve manufacturer’s algorithm and calibration data. Since the computation is performed in the RTU, interval flow totals at user-defined intervals may also be performed in the RTU.
This flow computation approach is much more accurate than performing the computation in a SCADA host application from infrequently sampled data (every few minutes, for example). Flow is computed and stored as interval data in the RTU, so alarm calls can be generated on high/low flow as well as pressure conditions.