Valuable valves examined

The agenda began with a welcome to the members, all of whom had made a very early start to make the flight up to Glasgow. A history of thermostatic control valves, which Horne began to manufacture in 1909, was described as was the development of the earliest thermostatic mixing valves (TMVs) in the early 1920s. Early TMVs were used to control the temperature of water in hospitals, poorhouses, bathhouses and other institutions so that users of the baths were not exposed to excessively high water temperatures. It was pointed out that, as such, TMVs have always primarily been a safety device and were developed by Horne to address the danger of scalding.

The presentation then focused on how regulations relating to the control of legionella in healthcare establishments had a radical impact on the design and application of thermostatic mixing valves. Examined was the current trend to use multiple small valves close to the point of use to deliver water that is both safe from scalding but also safe from legionella.

Demonstrated was a TMV working on a test rig built to the NHS Model Engineering Specification DO8 Thermostatic Mixing Valves (Healthcare Premises). One test replicated a heater control failure where the valve was supplied with hot water which rose over a period of several minutes from a starting point of 60ºC up to 100ºC and then gradually reverted to 60ºC. It was seen that at no time during the test did water pass from the TMV at a temperature that would be unsafe to the user. A second test showed a TMV working with water supply pressure reversals and differentials. Subsequent to this, there was a demonstration of a thermostatic control valve working to heat water in a tank with steam as the heating medium. This was of particular interest to some of the more senior members of the Institute who associate HORNE with this type of control valve as well as TMVs.

There was also a presentation of a new product, currently under development, which the Horne design engineers wanted to show to Institute members for comment. Horne has always supplied directly to hospitals and recognise the importance of addressing the needs and preferences of end users and maintenance personnel.

Horne is very keen to arrange similar factory visits for other IHEEM branches.