By Mike Crabtree
As in many areas of the world, 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. It started business in 1999, and in 2002 it began working with another systems integrator in the water distribution and wastewater market. 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. In addition to providing consulting and integration services for water districts and municipalities, Forshock also provides training for all its products and services.
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 (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 upgrading pump station controls, frequent trips were required to check status. Remote monitoring has eliminated most of those visits, and the video surveillance system provides detailed information about pump station 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. This saves money and cuts downtime as compared to servicing equipment on a calendar basis or at failure.
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.