knowledge on tolorance in tolerance limit erection of structure.pptx

tolerance limit for fabrication

1. Fabrication and Erection Tolerances By Dr. Rakesh Ranjan

2. Fabrication And Erection Tolerances Fabrication Tolerances – Amount of deviation allowed in the nominal dimensions and geometry in fabrication activities, such as cutting to length, finishing of ends, cutting of bevel angles, etc. Erection Tolerances - Amount of deviation related to the plumbness, alignment, and level of the element as a whole in the erected position. The deviation are determined by considering the locations of the ends of the element.

3. Need For Tolerance There is no such thing as a perfect field-built structure. Not setting a tolerance in a critical area may render the part unusable according to the design intent, as each fabrication method comes with a certain level of inaccuracy. The behavior of the structure will not be as designed or expected, there will be a lack of fit. If tolerance is higher, it will cause secondary stresses in the structure which was not accounted for in the design. Everything measurable, from linear dimensions to weight, will always vary from part to part. When the design does not take the variation into account, components may not fit together or give too much slack, resulting in early failure.

4. Rolling Tolerance For Structural Steel Section Beam and Column (I section) Depth Width of flange Over (mm) Up to and including (mm) Tolerance (mm) - 200 ±2.0 200 400 ±3.0 400 600 ±4.0 Over (mm) Up to and including (mm) Tolerance (mm) - 100 ±2.0 125 150 ±2.5 150 250 ±4.0 “Measure twice and cut once.”

5. Flanges Out-of-Square or Out-of-Parallel Off-center of Web Width of Flange, B Over (mm) Up to and including (mm) Δ + Δ ’ (max) - 100 3.0 mm 100 250 3 percent of flange width Depth of Section Over (mm) Up to and including (mm) Off-Center of Web, e max (mm) - 300 3.0 300 450 4.0 450 600 5.0 Rolling Tolerance For Structural Steel Section

6. Camber Weight - tolerance on weight per meter shall be ±5 percent in the case of angles 3 mm in thickness and +5,-3 percent in the case of angles over 3 mm in thickness. Leg Length mm Camber Max, mm Less than 100 To be agreed between the manufacturer and the purchaser Including and over 100 0.2 percent of length Rolling Tolerance For Structural Steel Section

7. Out-of-Square – The flange shall be perpendicular to the web within a tolerance of 1 in 60. Camber – The maximum permissible camber and sweep shall be 0.20 percent of the length. Weight – tolerance on weight per meter shall be ± 2.5 percent. Rolling Tolerance For Structural Steel Section

8. Bulb Angle Depth Width of Flange (Length of the shorter leg) – The tolerance on the width of the flange up to and including 100 mm shall be ±2.0 mm. Out-of-Square – The legs of the bulb angles and angles with legs of unequal width and thickness shall be perpendicular to each other within a tolerance of ± 1.0 degree. Camber – The maximum permissible camber and sweep shall be 0.20 percent of the length. Weight – tolerance on weight per meter shall be ± 2.5 percent. Over (mm) Up to and including (mm) Tolerance (mm) Plus Minus - 125 2.5 1.5 125 200 3.0 2.0 200 400 3.5 2.5 Rolling Tolerance For Structural Steel Section

9. Rolling Tolerance For Flats Width – Thickness Over (mm) Up to and including (mm) Tolerance (mm) - 50 ±1.0 50 75 ±1.5 75 100 ±2.0 100 - ±2 percent subjected to max of 6.0 mm Over (mm) Up to and including (mm) Tolerance (mm) - 12 ±0.5 mm 12 - ±4 percent subjected to max of 1.5 mm

10. Rolling Tolerance For Flats Out-of-Square – The permissible tolerance for the out-of-squareness of the overall width in the case of parallelogram sections shall be as agreed to between the purchaser and the supplier. Weight Thickness of flat Tolerance (percent) 3 mm ±5 Over 3 mm +5 -3

11. Rolling And Cutting Tolerance For Plates Length Length (mm) Over (mm) up to and including Thickness (mm) Tolerance on length - 2200 Up to and including 20 -0 +10 mm Over 20 -0 +15 mm 2200 3000 Up to and including 20 -0 +0.5 percent Over 20 --0 +15 mm 3000 6300 Up to and including 20 -0 +0.5 percent Over 20 -0 +0.5 percent 6300 8000 Up to and including 20 --0 +35 mm 8000 - Over 20 --0 +40 mm

12. Rolling And Cutting Tolerance For Strips Width - tolerance on the width of strip with trimmed edge over (mm) Up to and including (mm) Tolerance (mm) - 160 ±1.25 160 250 ±1.50 250 400 ±1.75 400 500 ±2.25 500 750 [phone] [phone] [phone] +10 -0

13. Rolling And Cutting Tolerance For Strips Width - tolerance on the width of strip with as-rolled edge over (mm) Up to and including (mm) Tolerance (mm) - 250 [phone] [phone] [phone] [phone] [phone] +40 -0

14. Rolling And Cutting Tolerance For Sheets Width - tolerance on the width of strip with trimmed edge Width - tolerance on the width of strip with as-rolled edge shall be the same as strips. Width (mm) Tolerance Up to and including 1250 +6 -0 Over 1250 up to and including 1550 +0.5 percent -0 Over 1550 +0.6 percent -0

15. Rolling And Cutting Tolerance For Sheets Thickness – The thickness shall be measured at the following points: One at each corner of the plate One in the middle of the width One in the middle of the length These measurements shall be 25 mm away from the edge at points randomly chosen Thickness (mm) Tolerance (mm) Thickness (mm) Tolerance (mm) 0.40 ±0.06 1.25 ±0.13 0.50 ±0.07 2.0 ±0.18 0.63 ±0.09 2.50 ±0.20 0.80 ±0.10 3.15 ±0.22 0.90 ±0.11 3.55 ±0.24 1.0 ±0.12 4.0 ±0.25 1.12 ±0.12 4.67 ±0.27

16. Cutting Tolerance Cutting tolerance for all lengths of hot rolled steel products except plate, strip, and sheet shall be (+100 -0 )mm.

17. Built-Up Section The width of gap S between the ends of members connected by rivets or bolts shall not exceed 1.5 mm for depth of sections up to 1000 mm and 3 mm for sections over 1000 mm depth.

18. Flange Angles The out-of-square between flange and web measured as the difference between the diagonals of nominal length L shall not be greater than 0.001 L.

19. Deviation In Straightness Of Girders With the bottom laid on the ground the deviation y 1 in the horizontal plane from the straightness of solid web girders and members of lattice girder shall not exceed 0.001 L subject to a max. of 10 mm. In the vertical plane no concavity shall be allowed, and the convexity y 2 shall not exceed 5 mm.

20. Column Tolerance On Height And Straightness The deviation Δ in the heights of the column measured from the bottom of the base plate or support shall be as specified in Table 5.

21. Deviations In The Alignment Of Beams The lateral deviation Δ 1 in the alignment of the nodal points of the lattice beams perpendicular to their axial plane measured after the fabrication in the shop or after trial assembly, shall be limited to ± 0.001 L where ‘L’ represents the span of the beam, subject to a maximum of ± 10 mm. However, the lateral deviation Δ 2 ( non-alignment ) measured between any two consecutive nodal points shall not be more than the values specified below:

22. Crane Gantry Girders The curvature of crane girders in the horizontal plane shall not exceed 3 mm in the 12 m length of the girder. Flange of gantry girders shall, for a distance of 500 mm from the ends, be free from any curvature and shall be normal to the web. The camber of the girder in the vertical plane shall not exceed 3 mm in 12 m length. The horizontal misalignment of the crane rail shall not exceed 3 mm. Crane rails shall be centered on crane girders as far as possible. However, in no case, the rail eccentricity exceeds half the thickness of the web of the girder.

23. Deviation In The Internal Dimensions Of Opening Unless otherwise specified in technical drawings the tolerance on the internal dimensions of openings for the erection of equipment (openings on the floor, on crave bridges, etc ) shall be +3 -0 mm.

24. Permissible Deviations In Bearing The permissible deviations for cast steel bearings for steel structural works of groups B and C shall be as given below: The permissible deviations of the length and width of the base Plate of a sliding bearing or the seating plate of a fixed bearing shall be +- 1 mm. The permissible deviations of the overall height of the bearing shall be +-2 mm. The relative difference in height at both ends of the assembled bearings in the transverse direction shall be limited to 1 mm.

25. Deviations On Dimensions Of Holes For Riveting And Bolting

26. Deviations On Dimensions Of Holes For Riveting And Bolting

27. Deviations On Dimensions Of Holes For Riveting And Bolting

28. Pre-Erection Requirements Before erection, Inspection and segregation of damaged structures should be done and should be brought to the notice of the person in command. Then it is decided whether the structure should be rectified or rejected. Any damage to the painted surfaces shall be repaired beforehand.

29. Steel Trusses

30. Steel Crane Girders And Rails

31. Thank you