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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.
Continued on page 44 >>
www. plumbingafrica. co. za March 2017 Volume 23 I Number 1