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Fluid conduction · Copper tube

TECHNICAL DATA SHEET

FT-TC-TUB-CUFLEX-001

Issue date: July 22, 2026 · Rev. 001

Check the current version

SKU VT-156450 · seamless flexible copper tube, annealed temper, 15 m (49.2 ft) coil · 9 sizes by actual OD (1/8″–7/8″)

1. TECHNICAL SPECIFICATIONS

Flexible copper tube is seamless tube in annealed (soft) temper, supplied in 15 m (49.2 ft) coils and designated by its actual outside diameter, from 1/8″ to 7/8″ (ACR pattern). It serves refrigeration and air conditioning, fuel gas and water connections; it bends by hand or with a bender and joins with 45° flare connections.

Dimensions and allowable pressure by size (coil, annealed temper)

¹ Allowable internal pressure of annealed coil tube per CDA, Copper Tube Handbook, Table 3e, computed with the ASME B31 code formula (see calculation section). Dimensions and weights: CDA, Table 2e (ACR tube, annealed temper). It is not a certified rating for any given lot: read the calculation basis and the technical notice. Note that 3/4″ takes less pressure than 7/8″: its standard coil wall (0.89 mm) is proportionally thinner than the 7/8″ wall (1.14 mm).

General specifications

2. ENGINEERING CALCULATIONS

The allowable internal pressure of copper tube is calculated with the ASME B31 code formula for thin-walled cylinders, as applied by the Copper Development Association (CDA) in the Copper Tube Handbook. Because of copper's corrosion resistance, the B31 code permits the corrosion allowance C = 0, and the formula becomes:

P = 2 · S · t_min / (D_max − 0.8 · t_min)

All values used are declared below — nothing is assumed silently:

Worked example — 1/4″ OD (annealed coil, ≤38 °C)

1. Nominal wall 0.030 in; t_min = 0.027 in. OD 0.250 in; D_max = 0.252 in (the calculation is done in inch-pound units, the declared standard units of ASTM B88-22 and of the CDA tables).
2. P = 2 × 6,000 × 0.027 / (0.252 − 0.8 × 0.027) = 324 / 0.2304 = 1,406 psi.
3. Conversion: 1,406 psi ≈ 96.9 bar ≈ 9.69 MPa — matching the value published by CDA in Table 3e (annealed coils, 100 °F).

Why soft tube takes less pressure than hard tube

The answer is in S: temper sets the allowable stress. Annealed (soft, coiled) copper works at S = 41.4 MPa (6,000 psi); the same copper in drawn temper (hard, straight lengths) works at S = 71.0 MPa (10,300 psi) at ≤38 °C. At equal diameter and wall, annealed tube takes 42% less pressure — that is the structural difference between this coil and rigid K/L/M tube, not a product defect. Furthermore, when hard tube is joined by brazing, the heat anneals the joint zone: CDA directs that such systems be evaluated with the annealed rating. In soft-soldered systems, the joint rating often governs the design over the tube rating (CDA, Copper Tube Handbook).

Temperature derating — S for annealed temper (CDA, ASME B31 basis)

Allowable pressure scales in direct proportion to S: at 93 °C, each value in the specifications table is multiplied by 0.817. Example: 1/4″ OD at 93 °C → 1,406 × 0.817 ≈ 1,148 psi (79 bar).

3. B88 VS B280: WHICH STANDARD COVERS SOFT COPPER TUBE

What is the difference between ASTM B88 and ASTM B280 copper tube?

The difference is the service and how the size is designated: ASTM B88 is water tube, designated by nominal size (actual OD is nominal size + 1/8″), in types K, L and M by wall thickness; ASTM B280 is ACR tube for air-conditioning and refrigeration field service, designated by actual OD, and additionally delivered cleaned, dehydrated and with both ends sealed to protect the refrigerant circuit from moisture. Both standards cover the same alloys (C10200, C12000, C12200) and both exist in annealed (coil) and drawn (straight-length) tempers.

• This product is designated by actual OD (1/8″–7/8″) and sold as annealed coil: the ACR dimensional pattern of ASTM B280. The certified standard of each lot (B280, NTC 4128 or annealed B88 K/L) is stated in the manufacturer's certificate and confirmed on quotation.
• For fuel gas, NTC 2505 accepts flexible copper tube certified under any of three routes: NTC 4128, ASTM B280 or ASTM B88 type K or L (clause 4.1.2) — see the gas section.
• For refrigeration, the B280 condition (dehydrated bore and sealed ends) is what matters: a coil opened and exposed to moisture must not go into a refrigerant circuit without an evacuation/dehydration process.
• There is also ASTM B68 (bright annealed seamless copper tube), used where internal surface cleanliness is critical.

Quick rule: for refrigerant systems specify B280; for water or general connections annealed B88 complies; for residential gas in Colombia any of the three NTC 2505 routes works with a certificate.

4. BEND RADII AND THERMAL EXPANSION

Minimum bend radius (annealed temper, with bender)

The practical limit of soft tube is bending it without collapsing the section. CDA publishes minimum bend radii for annealed tube with mechanical bending equipment (Copper Tube Handbook, Table 13); the CDA table is expressed by nominal K/L size, restated here by the actual OD used to designate this product:

• The radii are minimums with mechanical bending equipment (note in Table 13 itself); freehand, without a tool, use larger radii to avoid ovalizing or kinking the wall.
• For 1/8″, 3/16″, 1/4″, 5/16″ and 3/4″ OD, CDA publishes no minimum radius: use the bender die matching that OD, per the tool manufacturer.
• A CDA data point in favor of well-made bends: tests show the bursting strength of a bent copper tube can actually be greater than before bending (Copper Tube Handbook, Bending section).

Thermal expansion

The average coefficient of linear expansion of copper tube is 9.4 × 10⁻⁶ in/(in·°F) between 70 and 212 °F (CDA, Copper Tube Handbook), equivalent to 16.9 × 10⁻⁶ m/(m·°C).

• CDA example: 100 ft of tube heated +100 °F expands 1.128 in (30.5 m with ΔT = 55.6 °C → 28.7 mm).
• Example with this coil: 15 m with ΔT = 40 °C → ΔL = 16.9 × 10⁻⁶ × 15,000 mm × 40 = 10.1 mm.
• On long runs, absorb the movement with expansion loops or changes of direction — the annealed temper itself makes them easy to form.

5. FUEL GAS IN COLOMBIA (NTC 2505)

Seamless flexible copper tube is expressly accepted for residential and commercial fuel gas supply installations in Colombia: NTC 2505:2006 (fourth update), clause 4.1.2, item b), requires it to comply with NTC 4128, ASTM B280, ASTM B88 type K or L, or ASTM B88M type A or B.

NTC 2505 conditions that apply to this product

Scope note: NTC 2505 governs the design and construction of the installation; responsibility for the gas installation lies with the certified installer and the inspection required by current regulation. This sheet provides the tube data; it does not replace that certification.

6. Application notes

7. Technical notice and limitation of liability