TPT November 2011

A rticle

Dimensional tolerances lower than ½ of that specified by the Standards are achieved (Tables 3 to 5). The required standard tolerances EN 10219, EN10217, EN 10296, EN 10208, EN 10305-3 and API5L are adequately fulfilled. Besides, special products can be manufactured and special customers’ requirements met. The welding quality (Figure 9), which is decisively influenced by the forming section and the HF generator, allows the welding of critical sizes and grades. The tube quality is inspected directly downstream of the welding table, where the tube is submitted to a 100% check for welding defects on an ultrasonic tester (Figure 10). Another important and growing requirement to be satisfied by the product is the quality of the inside scarfing.

Figure 9 : HF-Welding: Ø 139.7 X 9.7 –S355

In addition to production quality and yield, the dimension changing time is an important factor regarding plant efficiency. At present, about ten wall thickness changes and two diameter changes (complete changes) per week are performed. On average, a wall thickness change takes from zero to 15 minutes, depending on the fact the tube is not inner scarfed. Presently a complete size change over take approx. 2½ hours with five operators assigned.

The nearest tolerance to: EN10219 – EN10208 – EN10217 – ISO3183 – API5L

Example 1 Ø 127. x 12. S355

Example 2 Ø 323.9 x 16. S355

EN10305-3 (max thick 6mm)

Characteristic

ASTM A450

Diameter (body + ends)

± 0.5% with a min: ± 0.5mm & max: ± 1.0mm ends: Ø ≤ 168.3 min: -0.4mm

Ø 101.6 ÷ 190.5: -0.64 / +0.38mm Ø 190.5 ÷ 228.6: -1.14 / +0.38mm

< Ø 120.: ±0.60 Ø 127. ÷ 139.7.: ±0.80 Ø 159. ÷ 193.7.: ±1.00

126.91 ÷ 127.42 = 0.51mm

323.90 ÷ 324.37 = 0.47mm

body ends

2%

In the tolerance of the diameter

Ovality

2%

0.4%

0.14%

1.5%

Straightness

1.5mm/mt on the total length & locally ≤ 3mm on 1mt

< 1.0mm/mt

< 1.0mm/mt

Table 3 : Dimensional tolerances of round products

Example 1 Ø 100. x 100. x8. S355

Example 2 Ø 300. x 150. x 14. S355

Example 3 Ø 250. x 250. x 12. 5 S355

EN10305-3 (sp max 4mm)

Characteristic

EN10219

ASTM A500

Ø ≤63.5: ±0.51mm 63.5<Ø≤88.9: ±0.64mm 88.9<Ø≤139.7: ±0.76mm Ø>139.7: ±1% of the greater dimension (tolerances for B=H & H<1.5*B) For: 1.5*B≤H≤3*B : 1.5 tolerance of B H>3*B : 2.0 tolerance of B

H,B<100mm ±1%

with min: ±.5mm ±0.65

100 ≤ H,B ≤ 200mm

99.74 ÷ 99.82 99.83 ÷ 100.20

Side dimension

±0.8%

±0.70

299.80 ÷ 300.20 149.35 ÷ 149.80

249.75 ÷ 250.10 249.4 ÷ 249.80

H,B>200mm ±0.6%

/

Concavity / convexity

±8.5% with min 0.5mm

Included into side dimension tolerances

Included into side dimension tolerances

0.40mm

0.20mm

0.30mm

Squareness of sides

90° ±1°

90°±1°

90°±2°

90°

90°

90°

T ≤ 6mm 1.6xT

17.3 ÷ 19.5 (16 ÷ 24)mm

Radius of corner

6

r≤2.2xT

r≤3.0xT

39.3 ÷ 40.5 (33.6 ÷ 50.4)

33 ÷ 36 (30 ÷ 45)

T>10mm 2.4xT

Straightness

1.5mm/mt on the total length & locally ≤ 3.0mm on 1 mt

10.4mm/5*L

< 1.0mm/mt

< 1.5mm/mt

< 1.5mm/mt

Twist

2.0 mm + 0.5mm/mt

Max 3mm/mt

Max 2 ÷ 3mm/mt

< 0.5mm/mt

<0.5mm/mt

<0.5mm/mt

Table 4 : Dimensional tolerances of square and rectangular products

102

N ovember 2011

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