By Mike Crabtree
Water districts and municipalities in California must meet growing demand with limited supply, putting more stress on the water distribution infrastructure. Response to these challenges has resulted in a complex maze of supply systems for getting water to local communities.
Southern California in particular places a high priority on investments in maintaining and upgrading water supply infrastructures, due in part to its desert climate. Automation is a necessary part of that investment because it enables water districts to lower costs, reduce energy use, operate more reliably, reduce maintenance and cut downtime.
Forshock (www.forshock.com) is a systems integrator working with water districts and municipalities in Southern California to implement water monitoring and control systems. Its primary customers are small water districts. Using its experience from interface design and development, Forshock created an HMI system for water and wastewater applications.
Although different water districts have different requirements, typical systems do have several things in common.
For example, most of the installations require only one PLC per remote site. Also, most systems connect back to a control center, usually located in the production department or operations building. The system usually uses a master-slave configuration, which enables simplified maintenance and emergency recovery.
The master or central control system generally contains PC-based HMI software or an operator interface touch panel. Most systems use UHF-licensed radios to provide reliable connectivity to remote sites. For non-PLC systems, some districts use simple, seven-day timer modules that are set based on expected demand. Using this method, operators run the risk of either not keeping up with demand or producing too much, which could cause property damage to nearby parcels if storage tanks overflow.
On a Mission
Mission Springs Water District, one of Forshock's recent clients, provides water to Desert Hot Springs, located just north of Palm Springs and built on a natural hot mineral water aquifer. Mission Springs upgraded its pump station and reservoir controls at multiple sites to meet energy and reporting requirements. "The PLCs provide control for our video surveillance systems to monitor intrusion and security events," says Richard Johnson, water production supervisor at Mission Springs Water District. The PLCs are supplied by AutomationDirect (www.automationdirect.com), either the DL05 or the DL06 depending on the site.
The water district doesn't use HMIs at the remote sites, but instead connects each site to the central station HMI via MDS's (www.microwavedata.com) UHF-licensed radios. At the central station, this HMI is used for display and reporting purposes.
Flexibility, security and reporting are important features for Mission Springs Water District. "Having the ability to remotely control and monitor VFDs allows us to adjust settings to maintain operation pressures and setpoints," notes Johnson. "The inclusion of on-site intrusion detection allows us to monitor potential threats to our customers' water supply. The HMI provides reporting features that we use to properly schedule maintenance of our motors and controls."
Before the pump station controls were upgraded, frequent trips were required to check status. Remote monitoring has eliminated most of those visits, and the video surveillance system provides detailed information about conditions and operation, further reducing required trips to the site.
Constant monitoring of pump station components allows maintenance to be performed proactively on a planned basis, saving money and cutting downtime.
When the control system is located at a remote facility, reliability is an especially important consideration. "To date, we've had no failures directly related to the control system," recounts Johnson. "The HMI alarm software notifies our operators of potential problems quickly via text messaging and email. The latest versions include basic communications failure control based on duration of the outage and time of the day."
To clarify, in the current DL06 DirectLogic software, the real-time clock is used to measure the time since the last update from the central master station HMI. Should the time be longer than the configured delay at the site, the PLC at the site will enter into a local-control mode, operating independently of the central station HMI.
Back at the Ranch
Located just 10 miles from Forshock's Victorville, Calif., headquarters is Mariana Ranchos County Water District, which serves the community of Apple Valley. With an average annual high desert-rainfall of less than six inches, water conservation is an important component of life there.
The water district's recent water supply infrastructure investments included changes to its automation equipment, including upgrades to its existing pump station controls. Cost, efficiency and convenience were the primary reasons for upgrading the pump station controls, according to James Hansen, general manager of Mariana Ranchos County Water District.
One of the three pump stations uses a VFD, and the other two use conventional motor control circuits. Both boosters use conventional motor control circuits. The booster and pumping station PLCs communicate with the central station HMI via MDS UHF-licensed radios.
The water district controls and monitors the three pump stations and two booster stations with AutomationDirect Model DL06 PLCs. The HMI runs Forshock's SCADAspire software on a PC.
Time-of-use is one of the most important SCADA features for pump station applications at the water district. "Without this one feature, we would be spending three times as much on our electric bill," Hansen notes. "We can control by time or by level. This offers the ultimate in convenience when trying to customize a particular location. You can match each tank or reservoir to each pump station with great flexibility."
The time-of-use feature uses the system's internal real-time clock to allow water district operators to create schedules for weekdays and/or weekends to prevent pumps from operating during preset times. This lowers the risk of accidental start-ups, which can incur additional costs if pumps operate during peak local electrical utility demand hours.
As with all of the local control system features, time-of-use can be controlled and monitored remotely from the central station HMI. This cuts travel costs to the sites and encourages system optimization, further lowering operating costs.
Efficiency, low cost and ease of operation are features that water districts seek when upgrading their control systems. However, reliability is extremely important too. "In over two years, we haven't had a single hardware-related problem," says Hansen of Mariana Ranchos. "Forshock's 24-hour/7-day-a-week service has always been above reproach. Dedication to service after the sale has been a driving factor in keeping Forshock at the top of our provider list. We know that any problem we experience is usually taken care of with a simple phone call."
Johnson reports that there have been no control system failures at Mission Springs Water District as well. "The service has been amazing," he said. "The ability to talk directly to the developer of the system at any time of the day certainly inspires confidence."
Editor's note: A version of this story appears at ww.controlglobal.com/articles/2010/WaterAutomation1012.html.
Mike Crabtree is president of Forshock.