Тексты по специальности ТЭС / Boilers

Boilers

Boilers hang from reinforced steel joists in the boiler house which are like big hollow boxes. The boiler house can be 220 m long, 60m high, and 55m wide. The boiler walls are formed by 53 kilometres of 6.25cm bore tubing. Inside these tubes, extremely pure water is converted by heat into steam at high pressure. The steam is then super-heated to 568 degrees Celsius A modern 500 MW boiler can consume over 200 tones of coal per hour and is capable of delivering l,522,727 kgs of steam per hour at a pressure of 1967 x 10-4 Pascal's.

To transfer large quantities of steam from the boiler to the

turbine, the steam must travel at very high speeds (200-300 Km/hr), In the case of problems the steam flow must be halted immediately. This is done by placing a valve close to the

turbine. The valve's hydraulic systems ensure that it can close in a fraction of a second, ensuring that the turbine does not over speed.

As temperatures rise and fall so the pipes expand and contract 5 and therefore cannot be too solidly enclosed. To allow expansion, pipes must be shaped so that internal stresses do not cause buckling. This can be done by providing loops in the pipe. The amount by which a pipe expands depends on it's length. A 100 m pipe, having it's temperature increased by 500 ' would expand by approximately 5 metre (1/200th of its length).