Technical conditions:
1.Heat treatment: Stress relive annealing of U-tubes after bending
2.Dimensional tolerances U-tubes acc. to TEMA R.C.B.
3.Length of straight part -0/+5 mm
4.Flattening (also called “ovality”) at the bend shall not exceed 10% of the nominal tube outside diameter.
5.Wall thickness in bending part acc. to TEMA RCB 2.31
6.Minimum tube wall thickness in the bend part (T min)
T(min) ≥ (SW × (2×R + D))/( 2× (R+D)
where: SW=smallest wall thickness, D=Nominal outside diameter,R=radius
7.Radius tolerance 1) for R 100 mm +/- 3 mm, 2) for R ≥ 100 mm +/- 5 mm
8.Straightness tolerance max. 1,5 mm per 1 m
9.U-Tube ends: plain, vertically cut to the tube axis
10.Repairs by welding: prohibited
11. Surface condition Finished U-tubes shall be free of scale, without scratches after bending,
12. Delivery Condition: Passivation and oiled, Black paint or varnish, Bright Annealed
13. Packing:Plastic plugs in both ends, bundles of max. 3,000kg with several steel strips, Two tags on each bundle, Wrapped in waterproof paper packed in wooden case
Main Testing Items and Procedure:
3. Chemical Composition Analysis Test With 100% PMI and One tube from each heat by Direct Reading Spectrometer
4. Visual inspection for waviness and cracks by Dye Penetrant Test. and Endoscope Test for Surface Quality Test:
5. 100% Hydrostatic Test: Minimum:10 Mpa-25Mpa and 100% Eddy Current Test before U bend Formed
6. Ultrasonic Test before U bend Formed subject to the MPS (Material Purchase Specification)
7. Mechanical Tests includes Tension Test, Flattening Test, FlaringTest, Hardness Test
8. Impact Test subject to Standard request
9. Grain Size Test and Intergranular Corrosion Test
10. Ultrasonic measuring of Wall Thickness
11. Stress Relieve Annealing on U bend Parts after bending
12.Air Under Water Test After Bending
