The law of physics upon which all ice rinks depend is that when a gas expands it drops in temperature much like when you put deodorant on in the morning (ever noticed how cold it can get). Using this principle to actually make ice upon which people can skate involves using a whole variety of differing gases, fluids, pumps, fans, pipes, compressors and heat exchangers which is often simplified down to one word, the "Plant". That's the easy bit, because the hard bit is actually operating the "Plant" efficiently and correctly to get the right type of ice surface at the right time for any particular skating activity.
At Murrayfield the ice pad is used for figure skating, ice hockey and public skating and the ice conditions required are different for all three. For instance the ice for a hockey match would not be acceptable for figure skating and is also different from that needed for public skating. A one degree change in indoor temperature can alter the quality of the ice and there is a considerable time lag between the Plant starting, achieving freezing mode and actually having an effect on the skating surface. Rink Management need to plan at least a day ahead to create the right type of ice when it is required taking into account the weather forecast, humidity, expected inside and outdoor temperature and the anticipated number of skaters and spectators. The Plant and ice surface conditions are both constantly monitored and recorded to keep in touch with changing conditions. The golden rule is plan for tomorrow today in order to get it right because you can't play catch up.
Once the plant has compressed and condensed the refrigerant back to liquid it then expands and cools through a heat exchanger known as a chiller to lower the temperature of the brine which is then pumped through the pipes which in turn freezes the water above the concrete floor.
There is a series of 2 inch bore plastic pipes containing brine, laid in 4 inches of concrete, running underneath the ice pad fed by steel header pipes located under the rubber matting at the south end of the rink. There are 274 pipes approximately 202 feet long resulting in a total of 55,400 feet, which is over 10 miles of plastic pipes!
During our refurbishment programme of 2012 our refrigeration plant was replaced by a chiller unit manufactured by Trane this unit allows us to comply with new regulations that will come into effect in January 2015 which will effectively make older plants using refrigerant gas R22 redundant as it will become illegal to add gas to these systems, so if they happen to leak there is no way to top them up,
as well as this there is many benefits in updating the plant in that it affords us more control over temperatures as well as increasing efficiency this put together with our installation of a new low-emissivity ceiling will reduce our carbon footprint by some 200 tonnes of CO2 per year.
Our Old Plant was manufactured and installed by Star Refrigeration in 1984. There were three compressors, one ten cylinder, two with eight cylinders which we use to compress the gas before it expands. Rarely all three were in operation at the same time. One or two are sufficient in the winter months but two were likely to be required over the summer months when the plant has to work harder due to the increased outdoor temperatures. Whilst this plant served the rink well as with almost everything else technology has marched on and our new system employs screw compressors which are a lot more efficient.
An Ice maintenance program has been adopted at Murrayfield to provide and maintain the best possible ice quality. When water is applied to an artificial surface it freezes from the bottom up therefore the greater the thickness of the ice the greater the insulation will be. Ice thickness therefore has a significant bearing on the ability of the plant to freeze the ice surface resulting in higher running costs. We try to keep the ice thickness at 2 inches.