Using the steam produced by the boiler to slowly warm up the steam pipe by means of the bypass valve of main steam and to heat the steam pipe to the approach its working temperature is called warming-up the pipe. The purpose of warming-up the pipe is to slowly heat the pipe and accessories (valves, flange) to make their temperature evenly rise, to prevent occurrence of a larger temperature difference stress, and to make the water be smoothly drained and to prevent water hammer phenomenon.

 During warming-up the pipe, if the temperature speed is too fast, the pipe and accessories will have a larger temperature difference, resulting in a larger additional stress. In addition, if the temperature rises too fast during warming-up the pipe, the water in the pipe will not be drained in time, thus causing serious water hammer , which will endanger the safety of the pipe,  pipe fittings and support.   （lsh）