Legionella-safe hot water beats risk of scalding
Extensive monitoring and control of the temperature of domestic hot water at Dover Docks controls the risk of legionella and delivers water at a safe temperature.
A large-scale system for monitoring the temperature of hot water and storing data at the Port of Dover is designed to protect against the risk of legionella. The system is based on Eurotherm 5000B data recorders and monitors water temperatures at around 1000 taps and shower fittings throughout the Eastern and Western Dock sites, as well as about 150 hot-water storage tanks. Real-time temperatures can be monitored on line, and the collected data can be stored in a tamper proof format for up to six years — far exceeding the requirements of current UK and international health-and-safety guidelines. Dover’s solution sends temperature data to a central monitoring point via a fibre-optic data bus. This enables staff to monitor temperatures accurately on line, with both visual and audible alarms for out-of-tolerance or faulty readings. This information ensures high levels of protection against legionella infection and assists with tasks such as routine maintenance, general system diagnostics and precise location of faults The system is based on ensuring that stored water temperatures always exceed 65ºC, so that legionella bacteria are killed. This temperature, however, would risk scalding at taps and showers, so hot water is mixed with cold using a thermoscopic mixing valve just before being delivered to tap outlets at 45°C. The temperature of the hot water as it enters the valve, and the temperature of the water fed to the tap outlet are monitored by independent thermocouple probes in the pipes, the signals being fed back to a Eurotherm 5000B in the vicinity. 6- or 12-channel 5000Bs are used depending on the number of points monitored. The probes were designed to be easily inserted or removed from pipes using push-fit plumbing fittings, and ensure that the probe is positioned centrally within the feed pipes. To monitor the higher temperatures in cylinders and tanks, probes are fitted at the top and bottom of each tank. The temperatures at each location are recorded into an on-board 13 MB non-volatile flash memory in each 5000B; this batch data is downloaded to the central monitoring station every hour These 5000Bs have no permanently connected user interface; instead, they are configured and operated remotely over an Ethernet link using remote operation software to provide a connection to a PC anywhere in the world. This facility is used for monitoring individual probes and calibrating on site via a hand held PDA (Personal Digital Assistant) operating Bridge 5000 software. Connection between the PDA and the system, is either via an Ethernet lead or wireless link. The PDA also has a bar-code reader, which automatically identifies precise probe location from bar codes mounted near to each tap outlet or storage cylinder. Colin Dobson, building manager for The Port of Dover, believes that remote monitoring systems will become an ‘industry standard’ for legionella protection. He comments: ‘Facing the challenge of meeting our legal obligations within such a geographically widespread and technically demanding site, meant that we had to come up with what is a pretty advanced solution. With help from Eurotherm engineers and a great deal of “lateral thinking”, we now have what I consider to be an archetype system which will set the pattern for other legionella monitoring solutions across a range of industries. email@example.com