DL/T 5054-2016Code for design of steam water piping in thermal power plant (English PDF)

1.0.1

This code is formulated with the view to standardizing the design of stream/water piping of fossil-fired power plant and ensuring safe, full-capacity, economical and continuous operation of fossil-fired power plant.

1.0.2

This code is applicable to the design of steam/water metal piping within the scope of fossil-fired power plant, it is not applicable to the design of water supply and drainage piping, fire-fighting water piping and large-caliber thin-wall exhaust piping of direct air-cooled unit.

1.0.3

The design of stream/water piping of fossil-fired power plant shall comply with this code and the requirements of relevant current standards of the nation.

2.1 Terminologies

2.1.1 Piping

It consists of piping components and pipe supports and hangers, etc. and is used for conveying, distributing, mixing, separating, discharging, measuring or controlling fluid flow.

2.1.2 Piping components

Elements used to connect or assemble piping, including pipes, pipe fittings, flanges, gaskets, fasteners, valves, filter screen and compensator, etc.

2.1.3 Pipe or tube

The piping component with round cross section and used for conveying fluid.

2.1.4 Pipe fittings

A category of piping components, including bend or elbow, tee, stub tube, reducer and end cap, etc.

2.1.5 Pipe supports and hangers

The generic term of various assemblies or devices bearing piping load, restraining piping displacement and controlling piping vibration, and transferring load to support structures, but excluding the civil structures.

2.1.6 Guides

The device used to guide piping to displace along the predetermined direction instead of other directions. The guiding device used for horizontal piping may also bear the dead load of piping.

2.1.7 Restraints

The device used to restrain or partially restrict the displacement of piping system in a certain or several directions at the hanging and supporting point. Generally, it doesn't bear the dead load of piping.

2.1.8 Vibration reducing device brace

The device used for controlling low-frequency and high-amplitude shaking or high-frequency and low-amplitude vibration of piping, but having certain restriction on thermal expansion or cold shrinkage of piping system.

2.1.9 Snubbers

The device used for bearing seismic load or impact load of piping, controlling high-speed vibration displacement of piping system, meanwhile allowing free expansion and contraction of piping system.

2.1.10 Set pressure

The preset pressure of safety valve started under operating conditions, it is the gauge pressure measured at valve inlet. Under this pressure, the force generated by medium pressure under specified operating conditions to open valve is balanced to the force that keeps valve clack on valve seat.

2.1.11 Relieving pressure

The static pressure at the inlet of safety valve when the safety valve clack reaches specified opening height, which is also known as full opening pressure. It is equal to the set pressure plus the pressure increment exceeding the set pressure, which is generally expressed in the percentage of the set pressure.

2.1.12 Reseating pressure

The static pressure at the inlet of safety valve when the valve lift is zero and medium stops flowing out due to recontact of valve clack and valve seat, with the fall of system pressure after safety valve relieves.

2.1.13 Blowdown

The difference between set pressure and reseating pressure of relief valve, which is generally expressed in the percentage of the set pressure.

2.1.14 Rupture disk device

The pressure relief device that is composed of such assemblies as rupture disk (or rupture disk assemblies) and clamp holder or support ring. The rupture disk will act, crack or fall off immediately and then discharge the pressure medium when the pressure difference between both sides of the rupture disk reaches the preset value at the preset temperature.

2.1.15 Steady pressure pipe blowing scheme of boiler

The pipe blowing mode of boiler where the pressure of boiler vaporization system is constant during pipe blowing. It is a relatively steady state process to boiler system, during this process, boiler maintains energy balance between input energy and energy output and the mass balance between water supply quantity and evaporation capacity.

2.1.16 Energy storage reduced pressure pipe blowing scheme of boiler

It is a kind of pipe blowing mode using the heat storage of boiler as well as the additional vaporization capacity generated during fast pressure drop process of boiler to obtain relatively large steam flow in short time, so as to achieve pipe blowing by relying on the effective pipe blowing time and accumulation where the blowing coefficient is larger than 1 during pipe blowing.

2.1.17 Target and target holder assembly

Target is the test metal plate produced according to the material and dimension specified by relevant standards and used for inspecting the cleanliness of the pipe blown. Target holder assembly is the device used for fixing target.

2.1.18 Collector

Collector is also known as slag trap, which is the device collecting the relatively large sundries previously blown from the steam piping during pipe blowing, so as to prevent the sundries from being blown into reheater.

2.1.19 Blowing control valve

The main valve used for controlling blowing steam, it is an important part affecting the blowing procedure.

2.1.20 Temporary parts

The generic term of parts replacing the valve core of main steam valve, temporary medium-pressure steam valve and high-pressure bypass valve and parts such as piping temporary baffle, etc.

2.1.21 Temporary pipe

It includes the temporary connecting piping between the original systems and the temporary pipe exhausting blowing steam to the atmosphere.

2.2 Symbols