On Steam heating applications controlling the temperatures to set point avoids excess steam consumption.
Steam is used as a heating media in the processes. This may either be to heat the product as part of its manufacturing process, or may be used to generate hot water, or simply maintain the temperature of a media to facilitate its transport (e.g. Heavy oils, gels, etc.).
In any heating application temperature to be achieved in the process is an important parameter. In many such applications the end point temperature achieved is an estimate. In many others the temperature of the process is indicated on a display. In both these cases the operator manually throttles the steam valve to ensure the temperature is achieved.
Usually with this practice a 3-4 deg C of overshoot is common. While this may not seem alarming in, this over shoot leads to excess steam being consumption. Even 2 deg C of overshoot can lead to large quantities of excess steam being consumed. Thus, it is prudent to control the temperatures to set points with the help of temperature controllers and thus prevent excess steam consumption.
Consider a process vessel with operating capacity 50kl. Suppose we have to raise the temperature from ambient to 85 deg C by indirect steam heating with steam pressure of 3 kg/cm2. Now consider a 2 deg C overshoot. Thus
As seen in the above case 200kg/hr of excess steam is consumed if the temperature overshoots even by 2 deg C !