Warm Up/ Starting Loads
During start up the steam pipework is cooler than the steam. This leads to heat transfer from the steam to the pipe and because the air surrounding the pipes is also cooler than the steam, heat transfer between the pipework and surrounding air also occurs. At the same time steam that is contact with cooler pipes will being to condense. The rate of condensation is at its maximum during start-up owing to the fact that the temperature difference between steam and the pipework is at its greatest. This condensation rate is called “starting load”.
Once the pipework is warm the temperature difference between the steam and the pipework will naturally reduce. However some condensation will continue to occur since the pipework radiates heat to its surroundings. This condensation rate is called “running load”. Condensate that falls at the bottom of the pipe is carried along by steam and also by gravity to specific points from where it is drained.
The same process occurs once steam flows from the distribution network into the utilization section. The energy of the steam is used in warming up the equipment and product, heat transfer continues even after temperature is achieved. Because condensate forms due to heat transfer it must be removed from both the distribution network and the utilization section. This condensate is an energy source and can be re-used as hot boiler feed water. Not recovering this condensate is simply a waste of energy and hence it is recommended to recover all the condensate to the boiler feed water tank and complete the steam and condensate loop.