Design Principles of Four Major Pipelines in Thermal Power Plants

Four major pipelines of thermal power plants

(1) Main steam pipe (high temperature and high pressure steam pipe from super heater outlet header to high pressure main steam valve connection)

(2) Hot reheat steam pipe (high temperature and high pressure from reheater outlet header to medium pressure main steam valve connection) steam pipe.

(3) Cold and reheat steam pipe (high-temperature and high-pressure steam pipe between the high-pressure cylinder steam outlet and the reheater inlet header connection)

(4) High-pressure water supply pipe (the feed pump outlet to the economizer inlet header connection) High-pressure boiler supply water pipeline, including feed water recirculation, superheater, reheater desuper heating water).

Design principles of the four major pipeline installations in power plants

   (1) The pipelines should be arranged in groups and rows, mainly to emphasize the aesthetics and ensure the economics of the pipeline supports and hangers.

   (2) The connection of pipeline equipment should be as short and straight as possible, especially for alloy steel pipelines. At the same time, there must be a certain degree of flexibility, and a flexible expansion joint is installed to reduce the force and moment generated by thermal expansion and displacement. When the elevation or direction of the pipeline is changed, it is necessary to prevent the pipeline from forming a dead angle where gas or liquid accumulates; if unavoidable, a gas valve at a high point, a liquid valve at a low point, and a corrugated expansion joint should be installed.

   (3) As the pipe flange is prone to leakage, in addition to flange connections for high temperature and high pressure pipelines, flange connections should be avoided. Welding connected pipes is the most economical way to ensure that the pipes are leak-free.

   (4) When the pipeline passes through the floor, platform and wall, waterproof casing protection shall be added. The diameter of the waterproof casing shall not hinder the thermal expansion of the pipeline and be larger than the diameter of the pipeline after insulation.

   (5) Minimize special-shaped fittings in the piping system. In the design of pipelines, the number of special-shaped pipe fittings such as pipes, bends, valves, compensators, expansion joints,and accessories should be reduced to a sufficient extent, and the processing volume connected to them should be reduced, and the costs of pipeline welding, installation and quality inspection should be reduced. The reduction of special-shaped pipe fittings can not only reduce investment in pipeline equipment, but more importantly, reduce the number of welded joints and improve the safety of the piping system.

   (6) The loss of pipeline pressure drop is required to be within the allowable range.