Introduce Multi Lead Rifled Steel Tube
What is an internally multi-lead rifled steel boiler tube?
It is a seamless cold-drawn or cold-rolled steel tube with helical ribs on the inside surface. Designed to maintain nucleate boiling under high thermal loads, it prevents film boiling occurrence, thereby avoiding tube wall overheating and burnout, ultimately extending service life.
Main Applications:
- Water-cooled wall systems in large-capacity power station boilers
- High-pressure and ultra-high-pressure boilers
Function: To suppresses film boiling and delays heat transfer deterioration
The internal ribs induce rotational flow in the working fluid, enhancing turbulence near the tube wall. This sweeps steam bubbles generated on the inner wall upward via rotating liquid flow, while forcing water to adhere tightly to the ribbed surface along helical paths. Consequently, it prevents steam film formation caused by bubble accumulation on the tube wall, ensuring continuous cooling via water contact.
Available Tube Materials:
A106 Gr.B
A210 Gr.A1 & Gr.C
A213 T2, T11, T12, T22 & T23
Classifications of MLR Tubes:
Type A & B
Differences between type A and B:
|
Type |
Lead Angle |
Rib Side Angle |
Rib Width at Top (Longitudinal) |
|
A |
30° |
55° |
8.28 mm |
|
B |
30° |
50° |
5.59 mm |
Dimensional Display of Multi Lead Rifled Tubes
C——Major I.D. (C=D-1.11*Smin*2)
D——Tube O.D.
E——Minimum I.D.
G——Number of Ribs
I——Rib Width at Top (Circumferiential)
J——Rib Height
K——Rib Side Angle (Both Sides of the Rib)
M——Rib Pitch (M=N/G)
N——Lead
O——Rib Radius (Top and Bottom of Ribs)
Q——Lead Angle
S——Nominal Wall Thickness
T——Rib Width at Top (Longitudinal)
U——Groove Width (Longitudinal)
Tube O.D.: 28.58-76.2mm
Tube Length: 8000-12000mm
Size Tolerance of Multi Lead Rifled Tube
|
Parameter |
O.D. Range (mm) |
Tolerance (mm) |
|
|
Type A |
Type B |
||
|
Tube O.D. D |
OD≤38.1 |
±0.15 |
±0.15 |
|
38.1<OD<50.8 |
±0.2 |
±0.2 |
|
|
50.8≤OD<63.5 |
±0.25 |
±0.25 |
|
|
OD≥63.5 |
±0.3 |
±0.3 |
|
|
Major I.D. C |
OD≤38.1 |
±0.15 |
±0.15 |
|
38.1<OD<50.8 |
±0.2 |
±0.2 |
|
|
50.8≤OD<63.5 |
±0.25 |
±0.25 |
|
|
OD≥63.5 |
±0.3 |
±0.3 |
|
|
Minimum I.D. E |
- |
-0 |
-0 |
|
Minimum Wall Thickness Smin |
- |
+22% |
+22% |
|
Nominal Wall Thickness S |
- |
+10% |
+10% |
|
Rib Height J |
OD≤38.1 |
±0.2 |
±0.18 |
|
38.1<OD<50.8 |
±0.3 |
±0.2 |
|
|
50.8≤OD<63.5 |
±0.3 |
±0.23 |
|
|
OD≥63.5 |
±0.3 |
±0.28 |
|
|
Rib Side Angle K |
- |
±15° |
±15° |
|
Rib Pitch M |
- |
±3.2 |
±3.2 |
|
Lead N |
- |
±3.2 x G |
±3.2 x G |
|
Lead Angle Q |
- |
- |
- |
|
Rib Width at Top (longitudinal) T |
- |
±1.3 |
±1.3 |
Straightness: ≤1mm/m
Ovality: ≤80%OD tolerance
Eccentricity: ≤80%WT tolerance
Available Testing of High-Pressure Boiler Rifled Tubes
Flattening Test: The specimen shall show no visible delamination, flakes, or inclusions after testing.
Flaring Test: Conducted at room temperature with a 60° cone mandrel. The flared outer diameter shall meet specified expansion ratios. No cracks or splits shall occur after flaring.
Hydrostatic Test:
Performed tube-by-tube. Test pressure calculated by formula below (max. 20MPa). Maintain pressure for ≥10s. No leakage permitted in internally ribbed tubes.
P=2SR/D
P: Test pressure (MPa)
S: Nominal wall thickness (mm)
D: Outer diameter (mm)
R: Allowable stress (MPa)
Nondestructive Testing/Ultrasonic Examination
Decarburization Inspection:
For multi lead rifled tubes with OD ≤76mm:
- External surface total decarburization depth ≤0.2mm
- Internal surface total decarburization depth ≤0.3mm
- Sum of both ≤0.4mm
Theoretical Weight Formula (per meter):
Z=【π·(D-S)·S+G·J·[I+(tanQ/tank)·J]】*ρ/1000
ρ: Material Density (kg/dm³)
Z: Theoretical Weight per Meter (kg/m)
D: O.D. (mm)
S: Nominal Thickness/Average Thickness (mm)
G: Number of Ribs
I: Rib Width at Top (Circumferiential)
J: Rib Height
K: Rib Side Angle (Both Sides of the Rib)
Q: Lead Angle
Internally Rifled Boiler Tubes vs. Smooth Tubes
Compared to smooth tubes, the internal rib structure of multi-lead rifled (MLR) tubes:
- Enhances fluid turbulence
- Increases heat-exchange surface area concurrently improving heat transfer performance or reducing wall temperatures.