Today let’s continue to discuss the tolerance of the structural tubing on the Specification.
- Permissible Variations in Dimensions.
- Outside Dimensions:
- Round Structural Tubing-the outside diameter shall not vary more than ±0.5%, the measurement shall be made at positions at least 2 in. (5cm) from the ends of the tubing;
- Square and Rectangular Structural Tubing-the outside dimensions shall according to table 3,
when OD is 2 1/2 in. (65mm) or under, the tolerance is ±0.02in. (0.5mm)
When OD is over 2 1/2in. to 3 1/2in.(65-90mm), the tolerance is ±0.025in. (0.6mm)
When OD is over 3 1/2in. to 5 1/2in.(90-140mm), the tolerance is ±0.03in. (0.8mm)
When OD is over 5 1/2in.(140mm), the tolerance is ±0.01in.
The measurement shall be made at positions at least 2 in. (5mm) from the ends of the tubing.
- Wall Thickness:
The minimum wall thickness at any point of measurement on the tubing shall be not more than 10% less than the specified wall thickness. The maximum wall thickness, excluding the weld seam of welded tubing, shall be not more than 10% greater than the specified wall thickness. For the square and rectangular tubing’s wall thickness measurement shall apply only to the centers of the flats.
Structural tubing is normally produced in random length 5 ft (1.5m), multiple lengths, and in specific lengths. When the length is 22ft (6.5m) and under, the tolerance is -13/+6mm, when the length over 22ft (6.5m), the tolerance is -19/+6mm, but if the purchase list has other requirements for this, that need to the purchaser and supplier negotiation.
- Straightness – The tolerance of the unit pipe is: 1/8in. times the number of feet of total length divided by 5 (10mm times the number of meters, and divided by 5). For example, the structural tubing unit length is 6m, the straightness is 10*6/5=12mm.
- Squareness of sides – This is for square and rectangular structural tubing, adjacent sides shall be square (90°), with a permissible variation of ±2° max.
- The radius of Corners – For Square and rectangular structural tubing, the radius of each outside comer of the section shall not exceed three times the specified wall thickness.
- Twist – For square and rectangular structural tubing, the twist of each meter from 1.3mm to 2.8mm according to different sizes.