Steam distribution system has important relationship between steam generator and steam users. There are various methods for carrying steam from the central source to the point of use. Central source may be boiler room or expenditure of the cogeneration plant. Boilers can use primary fuel, or boiler that uses waste heat from the exhaust gas of high-temperature processes, machines or even the incinerator. Whatever the source, an efficient steam distribution system is very important to be designed so that the distribution of steam produced has good steam quality both pressure and temperature which are needed to all of equipment that use steam.
|Figure 1: Steam Distribution System|
Installation and maintenance of steam systems are important and should be considered to start design phase. Understanding of the basic steam circuits or 'loops and steam condensate' is very required. When the steam condenses in the process, the condensate must be distributed back into water supply pipes of boiler. Although the condensate has very small volume compared with steam, but can cause pressure steam flowing through the pipes down.
Steam generated in the boiler must be carried through the working pipe to the point where the heat energy is required. At first there were only one or more main pipes, or 'steam pipeline', which carries the steam from boiler towards plant that uses steam. The smaller branches pipes carry steam to the respective equipment. When the main isolation valve of boiler is opened, steam is immediately across from the boiler to steam pipe that has low pressure. The working pipe is initially colder than steam will be hotter when steam flows through pipe that has higher temperature. Heat transfer occurs from the steam to wall pipe, therefore pipe should be wrapped with insulation so as not to endanger the personnel who work around it.
Steam that contact with cooler pipes will begin to condenses. At start-up, the rate of condensation will have maximum value, this happens because the large difference of temperature between steam and pipe. The rate of condensation is usually called as 'initial load'. At the time temperature pipe rise to be hotter, the difference temperature between steam and pipe is minimal, but the condensation still occurred because pipe is still transferring heat to the surrounding air. The rate of condensation is called as ‘running load'. The result of condensation (condensate) falls down to the bottom of pipe due to gravity and is carried by the flow of steam. Condensate be trapped by the steam trap which has gradient angle of pipeline so that the flow of steam containing condensate will drop and then released into water pipe of boiler or disposal.