Internally rifled boiler tube

Introduction

 

Boiler tubes design is crucial for efficiency of power generation in thermal power plant. As important component of heating surface, internally rifled tube is widely used to build waterwall for subcritical boiler, supercritical boiler, sliding pressure once-through boiler or heat recovery steam generator (HRSG). It is also named multi lead rifle tube (MLR tube). Due to its internal ribs of helical pattern, internally rifled boiler tube could suppress heat transfer deterioration by increasing turbulence of two phase flow: liquid water and steam vapor in mixture inside waterwall tube. This special waterwall tube is designed for high pressure, high temperature application in modern large utility boilers.

 

Material

 

20G, SA210C, SA210A1, 15CrMoG, 12Cr1MoVG, T2, T12, T22, T23, T91, etc.

 

Technical standard

 

Seamless internally rifled tube for high pressure boiler not only needs to meet the general requirement for bare tube, but also keeps in accordance with national standard for rifled tube.

 

GB5310-2008
GB/T 20409-2006
ASME SA-210M-2015
ASME SA-213M-2015

 

Specification

 

Outer diameter: 22 to 82.6mm

Wall thickness: 4.0 to 16.0mm

Length: normally within 12m, in special case up to 20m.

 

Benefits

 

• Due to internal ribbings, mixture of water and steam would rise in spiral inside tubes. Steam bubbles created on inner wall of tubes will be moved away in time, and liquid water is forced against tube wall to promote cooling performance. This greatly increases safety margin to avoid boiler tube rupture caused by overheating.
• Internal ribbings create about 20~30% more surface area inside tubes to enhance heat exchange.
• Gaps and peaks of internal ribs could cause turbulence flow to break boundary layer and make liquid water and steam bubble evenly mixed.

 

Chemical composition (%)

Grade	C	Mn	Si	Cr	Mo	S	P
20G	0.17~0.23	0.35~0.65	0.17~0.37	--	--	≤0.020	≤0.025
20MnG	0.17~0.23	0.70~1.00	0.17~0.37	--	--	≤0.020	≤0.025
25MnG	0.22~0.29	0.70~1.00	0.17~0.37	--	--	≤0.020	≤0.025
12CrMoG	0.08~0.15	0.40~0.70	0.17~0.37	0.40~0.70	0.40~0.55	≤0.020	≤0.025
15CrMoG	0.12~0.18	0.40~0.70	0.17~0.37	0.80~1.10	0.40~0.55	≤0.020	≤0.025
SA-210A1	≤0.27	≤0.93	≥0.10	--	--	≤0.035	≤0.035
SA-210C	≤0.35	0.29~1.06	≥0.10	--	--	≤0.035	≤0.035
SA-213T2	0.10~0.20	0.30~0.61	0.10~0.30	0.50~0.81	0.44~0.65	≤0.025	≤0.025
SA-213T12	0.05~0.15	0.30~0.61	≤0.50	0.80~1.25	0.44~0.65	≤0.025	≤0.025

Physical properties

Grade	Tensile strength (MPa)	Yield strength (MPa)	Elongation (%)	Hardness
20G	410~550	≥245	≥24	--
20MnG	≥415	≥240	≥22	--
25MnG	≥485	≥275	≥20	--
12CrMoG	410~560	≥205	≥21	--
15CrMoG	440~640	≥235	≥21	--
SA-210C	≥415	≥255	≥30	≤143HBW
SA-210A1	≥485	≥275	≥30	≤179HBW
SA-213T2	≥415	≥205	≥30	≤163HBW
SA-213T12	≥415	≥220	≥30	≤163HBW