New Control System Delivers Clean Water to Growing Idaho Community
Post Falls, Idaho is a small town that has been growing up. This small community of 19,000 people, located near the Idaho/Washington border, has experienced incredible population growth in the last 10 years or so.
Along with this growth has come the need for water - lots of it. Ross Point Water District has the responsibility of providing water for the ever-increasing demand. A prior control system at Ross Point Water consisted of four wells and one reservoir tied together with long distance solid-state relays from BW Controls. The relays were used to transmit signals via telephone wire for on/off states, such as sensing the level of the reservoirs and turning pumps on and off. The lines belonged to the phone company, who had to be contacted for repairs if something went wrong. If the lease lines were at fault, the telephone company was not usually able to show up at a job site on short notice and the repair time could be lengthy. For instance, if the probe leads from the reservoir were damaged and disabled the BW relays, the level would have to be maintained manually. This made for long nights for district water employees.
Working together with Empire Control and Automation, Ross Point Water put together a control system that is both reliable and practical, using the latest technology. They decided to implement a PLC/radio communication system that makes the district less dependant on the phone company for its daily operation.
The new water system is made up of five AutomationDirect PLCs (DL05 and DL06 models), five radios, an autodialer, and two AutomationDirect operator touch screens and three operator text panels. " AutomationDirect offered the best of all worlds - quality, dependability, and affordability", says Dan Seldon of Ross Point Water.
The system monitors and controls water level, pressures, room temperature, well pump operation, auto-manual settings and power water valve operations to provide clean water to customers. The Primrose well, which is also the main office location, has a 75 HP vertical shaft turbine pump and a DL06 PLC coupled to it, along with an operator touch panel. Another well at the 20 th St. location, about a mile north of Primrose, has a 125 HP vertical pump, a DL06, and an operator panel. To the West of 20 th St. is the Syringa well site, which includes a 100 HP well pump with a DL05 PLC and an operator text panel. The final well, Horsehaven, has a new 250 HP pump, paired with a DL05 PLC and an operator text panel.
When the system is in automatic mode, all pumps are started and stopped by PLC outputs connected to a relay timing system, which integrates with a valve attached to the pump discharge line. The valve allows air, which fills the well casing when the pump is not running, to exit the piping system at startup. This system prevents "water hammer", a condition that can break large pipes and cause much damage to homes.
The PLCs monitor the operation of the valve, shut down the system in case of failures, and notify operators of alarms through the autodialer system. Each site has several alarm sensing inputs. Each PLC is programmed to shut down its associated pump motor depending on the type of alarm activated. An alarm can be acknowledged from any touch or text panel location at any of the sites.
Northern Idaho outdoor temperatures can get down to -20 degrees in the winter and over 100 degrees in the summer. Freezing pipes are a concern in cold weather and overheating electric motors are a concern in the summer, so all well house buildings are monitored for ambient temperature. The PLC monitors the room temperature and sends an alarm to the autodialer if the pre-set limits are reached. The PLC also monitors control voltage in the event of a power failure. If control power is lost, a backup UPS installed at each location ensures that an alarm gets sent to the autodialer. Each UPS has a special circuit added, which sends signals to the PLC in the event of UPS failure.
The electric motors at each well have been converted from "across the line" starters to soft starters. The soft starters have auxiliary contacts that close if any one of five failures is detected by the starter. These include loss of phase, shorted SCRs, over current, over speed, over voltage and under voltage. The PLCs will send an alarm signal to the autodialer in the event of a soft starter fault. Any significant drop in pressure in the system while the pump is running will activate a timer in the PLC and will shut down the pump if pressure remains low.
The five sites are linked by radio transmission and each radio is connected to the PLC's serial port. Constant communication between all sites enabled the use of extensive failure alarms, which is a valuable feature. Even if a pump is not being used, its radio system is still being monitored for functionality. These alarm and shut down features are vital to the continued operation of the water system and also protect expensive equipment from damage, thus saving the water district money compared to prior repair expenses.
The radio system has helped save money on phone lines too. With the old system, when a "no water" alarm was necessary, all sites except the 20 th St. location had a Motorola bag phone (cell phone) connected as a dialer for the alarm. 20 th St. is now the only site that has a cell connection for dialing out, eliminating several phones at the other sites. A new autodialer was also added at the 20 th St. site, with 40 input capability. These inputs are integrated with the outputs of the DL06 at the 20 th St. well site. All alarm conditions that are monitored by AutomationDirect PLCs are sent via radio transmission to 20 th St. The PLC at 20 th St. then activates the appropriate autodialer input, which has been voice recorded to dial out to emergency personnel. The voice recording tells the person on the phone what kind of alarm has been activated, such as "soft start fault failure at Syringa" so employees may respond accordingly.
At the reservoir, a pressure transducer has been installed and the pressure is converted into feet of water by the PLC. This information is then displayed on the three touch screens. The previous system had sensor probes that dipped into the reservoir tank and connected to the leased lines, eventually making relay contact back to Primrose. With this type of system, it was not possible to know the reservoir levels or control them. The DL05 and DL06 PLCs with 4-20ma analog option cards proved to be an excellent alternative to the probes. Now the reservoir level can be monitored at a touch screen display and the set point levels can be adjusted from the office. Reservoir high level and low level setpoints can also be adjusted from the touch panels.
Three reservoir booster pumps, one 5 HP and two 10 HP, supply water to specific areas because the terrain in those areas make it impractical to supply water by gravity feed from the reservoir. A fire pump is also installed at the site to supply large amounts of water to hydrants if needed. The water system must be online and monitored at all times, especially when one considers life and property may be at stake. Each booster pump can be placed in manual or auto mode. The water supply line from the booster pumps also has a pressure transducer connected to the analog card on the DL06. When pressure drops, booster pumps turn on to meet the demand.
Since water demand goes up dramatically in the summer, more pumps need to be online during that time. In the past, it was necessary to travel to the sites to place a well into auto or manual mode. With the new system, this is now accomplished with the touch of a button on the touch panel at the Primrose location.
All in all, the system has been very successful. "We are now saving $350 per month on cell phone and lease line bills and have seen an increase in uptime due to continued operation without breakdown", says Seldon. That kind of savings and increased efficiency not only makes the system a success for the Water District, but also for their customers, who benefit from outstanding service.
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