Steam pipes fall into the category of "pressure pipes", which are defined in terms of the pressure that the pipe is subjected to and the characteristics of the conveying medium. Pressure pipeline refers to the pipeline that transports gas or liquid medium under a certain pressure. Steam pipeline is one of them, which is used to transport steam. This medium has a high temperature and pressure.

According to China's national standard GB/T 32167-2015 "Code for the Integrity Management of Oil and Gas Transmission Pipelines" and related pressure pipeline standards, pressure pipelines can be classified into several grades, among which steam pipelines are usually classified as thermal pipelines of GB2 grade. GB2 pipes are mainly used in heating, ventilation, air conditioning and industrial steam fields, and their medium can be hot water or steam.

Steam pipes, depending on their pressure and temperature, can be further subdivided into:

• Saturated steam pipeline: The pressure PN is less than or equal to 1.6 MPa.

• Superheated steam pipe: Pressure PN is less than or equal to 1.6 MPa and temperature t is less than 300 degrees Celsius.

These pipes are designed, manufactured, installed, inspected, and maintained with strict regulations to ensure safety and reliability. The welding and use of steam pipes need to comply with specific specifications, the welding personnel must be certified, and the pipe material is usually seamless steel pipe to adapt to the high temperature and high pressure working environment.

In addition, the part of the steam pipeline inside the boiler room, including the connection from the boiler to the sub-cylinders, is considered part of special equipment and is subject to strict supervision. While the part outside the boiler room, although not considered special equipment, is still a pressure pipeline and must be managed and maintained in accordance with relevant regulations.