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Cold water is pumped from the municipal mains to a 100 000l tank on the roof ( seventeenth floor ) from where it is fed down into the calorifier in the basement . From here , the hot water is fed up to a ring main on the sixteenth floor and fed down in branches to connect on the first floor ring main .
The hot water system heats the water to 80 ° C , a temperature that can be reached after only an hour and a half if the system had been off completely .
Inside the plant room , pipes have been colour-coded to mark each feed : green for cold , yellow for steam , double yellow for condensate , red for hot , and double red for the hot water return .
The water is heated by the coil of steam at five bar pressure ( about 158 ° C ) so the steam cools , creating condensate . This condensate is still high in heat energy and as the water used for the steam has been chemically treated for corrosion control , it makes the contents of this liquid valuable . This condensate is pumped back to the boiler house about 1km away , to be reused in the steam generation system .
Challenges The biggest challenge on this project was the high pressure needed to get the water up to the sixteenth floor . Almost six bar pressure is needed to achieve this , which meant that the entire system had to be built to cope with this — from the pipes to the fittings to the valves .
Another challenge was the fact that the steam can never be turned off or it shuts off the entire hospital — it has to run 24 / 7 .
Steam generation The operation requires a large amount of energy to run and as such , the hospital has its own central boiler room system that creates steam from natural gas and feeds it to the various buildings as needed . It transfers the heat from the gas to the steam . The municipality would simply not be able to provide all the energy required and if it could , it would very expensive .
The steam is used for various applications around the hospital , from the industrial kitchen , laundry , hot water systems to sterilisation in the autoclaves .
This steam is supplied at 10-bar pressure from the boiler house and reduced at each plant room to the required pressure .
As steam pressure and temperature are directly related , this is an easy way to control the temperature required for each application .
“ Steam is a lot more efficient than using electrical elements in installations such as these ,” explained Franco Habib of Allsteam Engineering who did the installation . “ However , it ’ s only really feasible for quite large installations as there is a high start-up cost .”
Another challenge was the fact that the steam can never be turned off or it shuts off the entire hospital — it has to run 24 / 7 .
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www . plumbingafrica . co . za March 2017 Volume 23 I Number 1