Scale in a hot water boiler
Company: Südbad, Stadtwerke München, Munich, Germany
About the customer:
Stadtwerke München is supplying greater Munich with water, energy and operating several city owned estates. The water they are supplying is coming from the Alps, to produce electricity they are operating their own power plants, supplying hot water for district heating and of course electricity. The area they are supplying is covering the city of Munich itself and the surrounding counties, all together approximately 8 Million people. The actual case is a big public indoor swimming pool owned by the city of Munich and operated by the customer. MERUS has done for SWM a row of projects in both outdoor and indoor swimming pools.
The actual application in the "Südbad", an indoor swimming pool with sauna, are the hot water boilers. The storage capacity of hot water in the boilers is rather high, in order to meet requirements of peak consumption times. All together there are 4 boilers each with a capacity of 3.000 liters, they have to feed more then 30 showers.
The temperature in the boiler has to be 60°C, to avoid a possible growth of legionella in the water system. Also at days, where there are fewer customers in the pool using the showers. At such days there is only little flow in the boiler. As a result the heat bundle has a high tendency of scaling. The raw water is chemically not treated, due to cost reasons.
The 4 pieces 3.000 liter boilers are all in one room, very close to each other, so we have installed only one 3" MERUS Ring at the common feed pipe for the 4 hot water boilers.
The monitoring could be done only visual, during shut down at planned service times. The heat bundles have been removed from the boilers, and the result can be seen at the two pictures on this page. There was still some scale found on the heat bundle, but it could be observed the scale was only building at the upper side and the scale is very soft. As can be seen in the right the scale was so soft and loose. There have been big junks of scale, but not sticking to the heat-pipes as before, but loose on top. These junks are coming of during normal operation and fall down, either collected on the lower end of the bundle or at the bottom of the boiler.