Seamless tubes with internal riffling

Seamless tubes with internal riffling are made by cold drawing. The starting material used for this is semi-finished seamless drawn tubes. Tubes with internal riffling are used as boiler tubes or heat exchanger tubes. Compared with tubes that have a smooth internal surface, it offers the customer many advantages: (a) the degree of the heat transfer is improved even at the higher share of steam, (b) the degree of heat transfer is very good and preserved even at a lower flow of the media, (c) temperature in the tube walls is being lowered therefore the risk of the wall failure is lowered too, (d) at the same time the space is created for an improved heat transfer by a suitable optimization of the riffle geometry.

Dimensions of the tubes with internal riffling

Dimensional assortment of the tubes with internal riffling is shown in a separate table

The types of steel for the tubes with internal riffling

The tubes are supplied in grades according to EN 10216: P235GH, 16Mo3; JIS G3461: STB340, STB410, STB510; JIS G3462: STBA12; ASTM, ASME A/SA 192, 209 210 A 213 and other corresponding grades.

From the dimensional and weight point of view, the tubes with internal riffling are characterized with its parameters shown in the table below. In the table there are basic dimensional limits shown. The specific parameters are subject of an agreement between the supplier and customer.

Symbol
Parameter
Range
mm
inch
OD
Outside diameter
18 - 72
.750 - 3.000
WT
Wall thickness
1 - 6,5
.047 - .250
Number of rifflings
6 - 8
h
Height of riffling
0,3 - 1,0
.016 - .047
f
With of riffling (cross section)
3 - 8
.125 - .313
ß
Angle of riffling flank
30°
r
Radius of riffling
0,1 - 0,15
.004 - .006
a
Lead angle of riffling
25° - 35°
Lead length of riffling (360°)
depending on outside diameter
Center-to-center spacing of riffling in longit. direction
upon agreement
s
Top width of riffling (longitudinal section)
upon agreement
Top width of span between rifflings (longit. section)
upon agreement
Inside circumference of tube
upon agreement
Cross diameter of tube
upon agreement
Weight of tube
kg/m
lb/ft
Length of tube
upon agreement

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