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Common Pipes for Ultra Supercritical Power Plants

Attention:     Issuing time:2019-10-09 15:57
Common Pipes for Thermal Instruments in Ultra Supercritical Power Plants
According to NDGJ16-89, when the measured medium pressure is 17 MPa 25.4 MPa and the temperature is 500℃- 566℃, the material of the primary pressure tapping short pipe and conduit in the steam-water system is 12CrlMoV or the same material as the main pipe. Although the steam parameters of ultra-supercritical units are far beyond the prescribed pressure and temperature range, the content is not applicable, but the standard of the same material as the main pipe is still applicable.
(1) Material of steel pipes for main steam and hot reheat instrumentation conduits
The temperature of the primary front pipe of the main steam and reheat pipeline instrument is the same as that of the medium of the main process pipeline. In the current domestic practice, the same material is mostly used as that of the main process pipeline. In this respect, the advantages of these new heat-resistant steels can be enjoyed. At the same time, the welding of dissimilar steels at the high temperature of the instrument pipeline in the construction site can be reduced and the welding treatment can be avoided. Undue waiting for risk. Therefore, P92 pipes are used in the main steam and hot reheat piping instruments of ultra-supercritical units. P92 steel is a new type of steel developed on the basis of P91 steel. It has low linear expansion coefficient, high ambient temperature strength and high temperature strength. Its weld crack sensitivity is lower than that of traditional ferrite heat-resistant steel. It can be used as header and steam pipe material under extremely harsh steam conditions. At present, P92 pipes can be purchased in the market, but small caliber pipes need to be ordered in advance. Compared with P92, TP316H stainless steel has higher carbon content and better decarbonization resistance, so it is suitable for use under high temperature conditions. In addition, TP316H has better yield strength and toughness. The use temperature of austenitic stainless steel such as TP316H can also reach 620. With mature technical conditions, it is relatively easy to purchase. It is widely used in instrument conduits in foreign power plants. Therefore, TP316H pipes are selected for the main steam and hot reheat instrument primary valve rear conduit.
(2) Material of steel pipe used in instrument conduit of high pressure water supply pipeline
The material of main process pipeline for high pressure water supply of ultra supercritical unit is WB36. According to the principle of the same material as the main pipeline, the material of WB36 can be selected for the duct. WB36, formerly known as 15NiCuMoNb5 according to German standard, is a Nb microalloyed bainite Ni-Cu-Mo steel. It is mainly used in water supply pipelines and headers of power plants. It has a history of more than 30 years. It has good high strength performance below 450 . The service temperature is 280℃-320 . The maximum service pressure does not exceed 450 and 530 bar. In addition, although the feed water pressure is high, but the temperature is not high, so stainless steel pipes can also be used. TP316 can be used for all the instrumentation pipes before and after the primary door, and 12CrlMoV pipes are used for some projects. Which material is better to use should be chosen according to the actual situation.
Material and Specification of High Temperature and High Pressure Instrument Conduit

Material (Grade) Specifications Elbow radius (R)
Main steam Design parameters P≤35.04 MPa , T≤610℃
A335 P92 33.7*9.09mm ≥3Do
A213 TP316H 18*4.5mm ≥4Do
One heat reheat Design parameters P≤13.71MPa , T≤618℃
A335 P92 33.7*9.09mm ≥3Do
A213 TP316H 18*4.5mm ≥4Do
Secondary reheating Design parameters P≤4.32MPa , T≤618℃
A335 P92 33.7*9.09mm ≥3Do
A213 TP316H 18*4.5mm ≥4Do
A cold reheat Design parameters P≤13.71MPa , T≤457℃
12CrlMoVG 17*3mm ≥3Do
16*3mm ≥3Do
A213 TP316 17*3mm ≥3Do
16*3mm ≥3Do
High pressure water supply (in front of valve) Design parameters P≤50MPa , T≤200℃
A213 TP316 25*6mm ≥4Do
18*4mm ≥4Do
High pressure water supply (behind valve) Design parameters P≤44MPa , T≤335℃
A213 TP316 25*6mm ≥4Do
18*4mm ≥4Do
Boiler steam-water separator Design parameters P≤36.9MPa , T≤500℃
A213 TP316 18*4mm ≥4Do
Boiler and boiler water recycling Design parameters P≤37.41MPa , T≤380℃
A213 TP316 18*4mm ≥3Do


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