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Welded tubes of large diameters
Published:2013-07-07 15:18:57    Text Size:【BIG】【MEDIUM】【SMALL

The starting material for the production of welded tubes is rolled sheet. Sheets are cut to required size and by planing the edges bevel is made for the weld. The sheet is twisted into a tube shape and longitudinally welded. The tubes are arc welded, welds on both sides, by automated flux. To achieve the desired length it is possible to weld tubes by transverse circumferential welds. Longitudinally welded tubes are manufactured in dimensions, outer diameter 324 - 2220 mm and wall thickness of 5-22 mm.

According to the use, welded tubes of large diameters are supplied as follows:

Tubes for structural use

- of standard steels - list of standards 
(EN 10219-1: S235JRH, S275JOH, S275J2H, S355JOH, S355J2H)
- of fine grain steels - list of standards
(EN 10219-1: S275, S355, S460 NH, NLH, MH, MLH)

Tubes for machine construction and general use list of standards

(EN 10296-1: E155, E185, E235, E275, E355)

Tubes for pressure pipelines

- for ambient temperature - list of standards
(EN 10217-1: P195, P235, P265 - TR1, TR2) 
- for higher temperatures (boiler type) - list of standards
(EN 10217-5: P235 GH, P265 GH, 16Mo3) 
- of fine grain steels - list of standards
(EN 10217-3: P275, P355, P460 NL1, NL2 a P355, P460 N, NH) 
- for low temperatures - list of standards
(EN 10217-6: P215 NL a P265 NL) 

Tubes for water delivery pipelines - list of standards

(EN 10224: L 235, L275 a L355) 

Tubes for transport of flammable media - list of standards

(EN 10208-1: L210GA, L235GA, L245GA, L290GA, L360GA) 
(EN 10208-2: L245NB, L290NB, L360NB, L245MB, L360MB) 

Dimensions of welded tubes

Dimensions of the tubes are shown in the tables according to GOST 20295, according to DIN 2458, according to EN 10220, according to API 5L.

Dimensional tolerances of welded tubes and weld

Values below are informative, are not applicable to all standards.
Outside diameter

Outside diameterr (mm) Maximum deviation of diameter (mm)
324 - 1 020 (1 000) ± (0,5 % OD + 1)
1 220 - 2 220 ± 6 (5)

Ovality of tube ends (circularity)
Ratio OD/WT Ovality
OD/WT < max. 1,4 %
50 <= OD/WT <= 100 1,4 - 2 %
OD/WT > 100 Ovality is not guaranteed


Wall thickness
Wall thickness Maximum deviation
WT <= 5 mm - 0.25 / + 0.30 mm
5 mm < WT <= 10 mm - 0.35 / + 0,45 mm
WT > 10 mm - 0.50 mm / upper limit is limited by the allowed deviation of the theoretical weight

Perpendicularity of the cut
Outside diameter (mm) Deviation of the perpendicularity of the cut (mm)
324 - 630 2
720 - 1 020 3
1 220 - 1 620 4
1 820 - 2 220 5

Camber of the welded seam
Wall thickness (mm) Deviation (mm)
t <= 8 <= 2.5
8 < t <= 14 <= 3.0
14 < t <= 40 <= 4.0

Lengths and its tolerances

Tubes with outside diameter 324 – 1220 mm - max. length 12 m.
Tubes with outside diameter above 1220 mm - max. length 6 m.
Types of supplied lengths of the: (a) production, (b) approximated - ± 500 mm, (c) exact – tolerances agreed upon when ordering. To achieve the desired length, the tubes are cross welded. The maximum length of one section is 3 m. 

Straightness of welded tubes

The tubes are visually straight. Straightness deviation is 2 mm per 1 m length (0.002 x L). The total deviation is the product of permitted value and the length of pipe, the value must not exceed: (a) at length d 6 m, 10 mm, (b) at length 6 - 9 m, 15 mm, (c) at length 9 - 12 m, 20 mm

The weld

The tubes are welded by double-sided weld beneath the flux (longitudinal weld). Coefficient of weld v = 0.75 – 1.

Surface treatment of welded tubes

Tubes are delivered:
- without surface treatment 
- with surface treatment: (a) standard asphalt coating, (b) asphalt + fiberglass mat ( 20 kV ), (c) asphalt + reinforced fiberglass mat (25 kV), (d) asphalt + impregnated paper + fiberglass mat ( 25 kV ), (e) asphalt + PVC + fiberglass mat ( 35 kV ), (f) surface according to DIN 30672 standard, (g) painting, (h) extruded polyethylene (in cooperation).

Marking of welded tubes

The tube is marked with data: manufacturer, dimensions: outside diameter x wall thickness, steel grade, heat number, serial number of the tube, mark of the technical inspection, mark of the welder.

Testing of welded tubes

The tubes are tested according to the requirements of relevant standards. The following tests are performed: visual inspection of the weld and surface, control of dimensions, mechanical testing of the base material and weld (tensile test, Charpy V – notch test and brittleness), hydrostatic test, nondestructive testing of weld and insulation testing. Other tests can be arranged.

Certificates for welded tubes

Certificates are issued according to the following standards:
• DIN 50049
• EN 10204
• ASTM A 530
• API 5L

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