ASTM B111 C70600 Tube Size Chart

ASTM B111 C70600 tube is available from 1/4 inch (6.35mm) to 3 inches (76.2mm) outside diameter. 1/2 inch to 1 inch are the most common sizes for heat exchangers and condensers.

BWG numbers run backward： the larger the BWG number, the thinner the wall. BWG 22 is 0.71mm. BWG 10 is 3.40mm. Here is the full conversion chart.

Weight depends on OD, wall thickness, and density (8.94 g/cm³). Here are weights for common sizes. Use these for freight calculation and cost estimation.

Tolerances are tight because C70600 tubes are rolled into tube sheets. Loose tubes leak. Oversize tubes do not fit. Here are the standard tolerances.

OD tolerance：

Wall thickness tolerance：

±10% of nominal wall for all sizes

Length tolerance：

Cut lengths under 6m： +6mm / -0mm

Cut lengths over 6m： +10mm / -0mm

Random length (5-7m) ： within specified range

Q1： What is the most common C70600 tube size for heat exchangers?

3/4" OD x BWG 18 (19.05mm x 1.24mm wall) is the most common size. Many power plants and marine heat exchangers use this size. Second most common is 1" OD x BWG 16 (25.4mm x 1.65mm wall). If you are designing a new heat exchanger, start with these standard sizes.

Q2： What does BWG stand for in tube size?

BWG stands for Birmingham Wire Gauge. It is a standard for wire and tube wall thickness. For BWG, larger gauge number means thinner wall. BWG 22 is thin (0.71mm). BWG 10 is thick (3.40mm). Do not confuse with SWG (Standard Wire Gauge), which is slightly different. ASTM B111 uses BWG.

Q3： How do I convert BWG to mm?

Use the conversion chart above. For quick reference： BWG 18 = 1.24mm, BWG 16 = 1.65mm, BWG 14 = 2.11mm. The exact conversion formula is not linear. Always refer to a standard chart or ask your supplier for confirmation.

Q4： What is the tolerance on C70600 tube OD?

±0.004 inch (±0.10mm) for OD up to 1 inch. For larger ODs, tolerance increases slightly. This tolerance allows the tube to fit into a tube sheet hole. If your tube sheet has tighter holes, you may need to specify a custom OD tolerance, but expect higher cost.

Q5： Can I get C70600 tube with metric OD instead of inch?

Yes, metric OD sizes are available from many mills. Common metric ODs： 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 30mm, 35mm, 40mm, 50mm. However, inch sizes (1/2", 5/8", 3/4", 1") are more commonly stocked. Metric sizes may require production.

Q6： What is the difference between tube OD and tube ID?

OD is outside diameter. ID is inside diameter (OD minus 2 x wall thickness). For a 3/4" OD tube with BWG 18 wall (1.24mm), ID = 19.05mm - (2 x 1.24mm) = 16.57mm. For heat exchanger design, OD matters for tube sheet holes. ID matters for flow area.

Q7： Can I get C70600 tube longer than 6 meters?

Yes, up to 15 meters (49 feet) for most ODs. Longer tubes are possible for smaller ODs. However, longer tubes are harder to ship. Standard containers fit 6m tubes easily. Tubes over 6m need longer trucks or special containers. For most projects, 6m is standard.

Q8： What is the straightness tolerance for C70600 tube?

ASTM B111 does not specify a numerical straightness tolerance. Industry practice is 1.5mm per 3 meters. Tubes that are visibly bent can be rejected. For long tube bundles with many support plates, specify a straightness requirement on your PO. Mills can supply straightened tube at slight extra cost.

Q9： How do I calculate tube weight per meter?

Weight (kg/m) = (OD² - ID²) x π/4 x density ÷ 1,000,000. OD and ID in mm, density = 8.94 g/cm³. A simpler method： use the weight chart above or ask your supplier for a weight calculator. For rough estimate, C70600 tube weighs about 8.94 x wall x (OD - wall) x π / 1,000,000 in kg per meter.

Q10： What is the minimum wall thickness for C70600 tube under ASTM B111?

BWG 22 (0.71mm) is the thinnest standard wall. Some mills can go thinner by special agreement, but BWG 22 is the practical minimum. Thinner walls are difficult to draw without tearing and offer little corrosion allowance. Most engineers do not specify below BWG 20 (0.89mm).

Q11： Can I order C70600 tube in random lengths instead of cut lengths?

Yes, random length is usually 5 to 7 meters (16 to 23 feet). Random length costs less than exact cut length because the mill does not need to cut precisely. However, you will get tubes of varying lengths within the range. For heat exchanger bundles, exact cut length is recommended. For stock, random length is fine.

Raw material verification

Spectrometer test on every melt (ASTM E1473)

Ni must be 9-11%. Fe must be 1.0-1.8%. No exceptions.

Mechanical sample (one tube per heat)

Tensile pull： target 310 MPa minimum. We have seen 340-360 MPa typical.

Flatten test： squeeze a ring to 3x wall. Watch for cracks.

Flare test： expand the end with a 30° cone. Must not split.

100% non-destructive testing

Eddy current probe through every single tube (ASTM E243)

Any signal = reject. No patching. No second chance.

Final check before packing

Visual inspection of both ends

Cap plugs installed

Hydrostatic test upon request

Tube protection

Plastic end caps (both ends)

VCI paper between layers – stops condensation corrosion

Shrink wrap around each bundle – moisture barrier

Bundle securing

Steel straps – 4 to 6 straps per bundle

Wooden case for fragile sizes (small OD or cut lengths)

Steel bundle + wooden pallet for standard 6m tubes

Labeling

Waterproof label on each bundle

Grade, OD, wall, heat number, quantity clearly printed

Shipping

Container loading supervised by our warehouse team

Photos taken before container closes

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