ASTM B395 U-Bend Tubes|Copper Alloy Heat Exchanger Tubes

Products Description

ASTM B395—Standard specification for U-Bend Seamless Copper and Copper Alloy Heat Exchanger and Condenser Tubes

What is ASTM B395 Standard?

ASTM B395 is a standard for U-shaped tubes for seamless copper and copper alloy heat exchangers and condensers developed by the American Society of Testing Materials (ASTM). It provides the chemical composition, mechanical qualities, dimensions, process requirements, and appropriate testing techniques for the applicable copper alloys.

Structural Design of U-Bend tubes

The main feature of U-bend tubes is that the curved component in the middle of the tube forms a U-shaped structure, which can aid in transferring fluids or altering the direction of the tube in a short space without the need for elbows or other pipe connections.

U-bend tubes are commonly employed as tube bundles in heat exchangers, condensers, and evaporators. They are typically constructed of numerous U-bend tubes organized in a specified pattern and welded to the tube sheet. The U-tubes in a U-bend tube bundle typically have multiple bending radii in order to fit more tubes into the smallest space and improve heat exchange efficiency.

How tube bundle works?

Usually, fluid is introduced into the inner tube of the U-tube, and the fluid exchanges heat with the medium on the tubes surface. Under the action of high-temperature fluid, the outer surface of the U-tube transfers heat to the surrounding cooling medium or vice versa, transferring external heat to the internal fluid.

Specifications of B395 U-Bend Tubes

⚑ Type: Seamless+U shape

⚑ Material: Copper and copper alloy

⚑ Outside diameter: ≤2 in.(50mm)

⚑ Usages: Condenser, evaporator, heat exchanger

Copper Alloy Common Grades & Chemical Composition

Grade

Cu^①

Ni+Co

其他元素

C10200^①②

≥99.95

O:≤10ppm

C10300^①

≥99.95^③

0.001-0.005

C10800^①

≥99.95^③

0.005-0.012

C12000^①

≥99.9^③

0.004-0.012

C12200^①

≥99.9

0.015-0.04

C14200^①

≥99.4

0.15-0.5

0.015-0.04

C19200^④

≥98.5

0.8-1.2

≤0.2

0.01-0.04

C23000^④

84-86

0.05

≤0.05

Rest

C44300^⑤

70-73

0.9-1.2

0.07

≤0.06

Rest

0.02-0.06

C44400^⑤

70-73

0.9-1.2

0.07

≤0.06

Rest

0.02-0.1

C44500^⑤

70-73

0.9-1.2

0.07

≤0.06

Rest

0.02-0.1

C60800^①⑥

Rest

5-6.5

0.1

≤0.1

0.02-0.35

C68700^①⑥

76-79

1.8-2.5

0.07

≤0.06

Rest

0.02-0.06

C70400^①⑥

Rest

4.8-6.2

0.05

1.3-1.7

≤1

0.3-0.8

C70600^①⑥

Rest

9-11

0.05^⑦

1-1.8

≤1^⑦

C70620^①⑥

≥86.5

9-11

0.02

1-1.8

≤0.5

≤1

≤0.02

C:≤0.05

S:≤0.02

C71000^①⑥

Rest

19-23

0.05^⑦

≤1

≤1^⑦

⑦

C71500^①⑥

Rest

29-33

0.05^⑦

0.4-1

≤1^⑦

≤1

③

C71520^①⑥

≥65

29-33

0.02

0.4-1

≤0.5

≤1

≤0.02

C:≤0.05

S:≤0.02

C72200^①④

Rest

15-18

0.05^⑦

0.5-1

≤1^⑦

≤1

⑦

0.3-0.7

⑦⑧

Note:

① Copper content includes silver

② High conductivity copper, minimum copper conductivity 100% in the annealed state

③ Contains P

④ The sum of copper and all listed elements shall not be less than 99.8%

⑤ The sum of copper and all listed elements shall not be less than 99.6%

⑥ The sum of copper and all listed elements shall not be less than 99.5%

⑦ When the product is subsequently used for welding purposes and specified by the purchaser, zinc should be ≤0.50%, lead should be ≤0.02%, soda should be ≤0.02%, carbon should be ≤0.05%

⑧ Silicon should be ≤0.03%, titanium should be ≤0.03%

Tension Properties of ASTM B395 Common Grades

✔ O61: annealed

✔ H55: light drawn

✔ HR50: stress-relieved+drawn

Grade	Temper	Tensile Strength, ksi [MPa]	Yield Strength, ksi [MPa]	Elongation in 2 in.
C10200 C10300 C10800 C12000 C12200 C14200	H55	≥36 [250]	≥30 [205]	-
C19200	H55	≥40 [275]	≥35 [240]	-
C19200	O61	≥38 [26]	≥12 [85]	-
C23000	O61	≥40 [275]	≥12 [85]	-
C44300 C44400 C44500	O61	≥45 [310]	≥15 [105]	-
C60800	O61	≥50 [345]	≥19 [130]	-
C68700	O61	≥50 [345]	≥18 [125]	-
C70400	O61	≥38 [260]	≥12 [85]	-
C70400	H55	≥40 [275]	≥30 [205]	-
C70600 C70620	O61	≥40 [275]	≥15 [105]	-
C70600 C70620	H55	≥45 [310]	≥35 [2400]	-
C71000	O61	≥45 [310]	≥16 [110]	-
C71500 C71520	O61	≥52 [360]	≥18 [125]	-
WT≤0.048in. (1.22mm)	HR50	≥72 [495]	≥50 [345]	≥12%
WT>0.048in. (1.22mm)	HR50	≥72 [495]	≥50 [345]	≥15%
C72200	O61	≥45 [310]	≥16 [110]	-
C72200	H55	≥50 [345]	≥45 [310]	-

Dimensions & Tolerance of ASTM B395 Seamless U-Bend Tubes

Outside Diameter tolerance

Outside Diameter		Wall Thickness
Outside Diameter		in.	mm	in.	mm	in.	mm	in.	mm
in.	mm	0.032	0.813	0.035	0.889	0.042	1.07	≥0.049	≥1.24
≤0.5	≤12	±0.0025	±0.064	±0.0025	±0.064	±0.0025	±0.064	±0.0025	±0.064
0.5<D≤0.74	12<D≤18	±0.004	±0.1	±0.004	±0.1	±0.0035	±0.089	±0.003	±0.076
0.74<D≤1	18<D≤25	±0.006	±0.15	±0.005	±0.13	±0.0045	±0.11	±0.004	±0.1
1<D≤1.25	25<D≤32	±0.009	±0.23	±0.008	±0.2	±0.006	±0.15	±0.0045	±0.11
1.25<D≤1.375	32<D≤35	-	-	-	-	±0.008	±0.2	±0.005	±0.13
1.375<D≤2	35<D≤50	-	-	-	-	-	-	±0.006	±0.15

Wall Thickness Tolerance

Wall Thickness		Outside Diameter
Wall Thickness		in.	mm	in.	mm	in.	mm
in.	mm	1/8<D≤5/8	3<D≤16	5/8<D≤1	16<D≤25	1<D≤2	25<D≤50
0.032≤T<0.035	0.816≤T<0.889	±0.003	±0.076	±0.003	±0.076	±0.004	±0.1
0.035≤T<0.058	0.889≤T<1.47	±0.004	±0.1	±0.0045	±0.11	±0.0045	±0.11
0.058≤T<0.083	1.47≤T<2.11	±0.0045	±0.11	±0.005	±0.16	±0.005	±0.13
0.083≤T<0.12	2.11≤T<3.05	±0.005	±0.13	±0.0065	±0.17	±0.0065	±0.17
0.12≤T<0.134	3.05≤T<3.4	±0.007	±0.18	±0.007	±0.18	±0.0075	±0.19

Tube Leg Length Tolerance

Length		Tolerance
ft	mm	in.	mm
L≤20	L≤6000	+1/8	+3.2
20<L≤30	6000<L≤9000	+5/22	+4
30<L≤60	9000<L≤18000	+1/4	+6.4
L>60	L>18000	+3/8	+9.5

Properties of ASTM B395 U-Bend Copper and Copper Alloy Tubes

✔ Excellent thermal conductivity

Copper is an excellent thermal conductor. Copper alloy U-tubes can effectively transfer heat. Their high thermal conductivity ensures that the equipment can maintain high efficiency when handling high-temperature fluids, reduce energy loss, and improve the overall efficiency of the system.

✔ Excellent corrosion resistance

Copper alloys have good corrosion resistance, especially copper-nickel alloys and naval brass, which perform well in marine environments or other highly corrosive media and are therefore widely used in seawater cooling systems, ships, and offshore platforms.

✔ Good antibacterial properties

Copper is a natural metal element that can kill microorganisms and algae aquatic organisms in water. In 2008, the U.S. Environmental Protection Agency (EPA) confirmed that copper can kill harmful and potentially fatal pathogens. Therefore, copper alloy U-tubes have unique advantages in the food and drinking water treatment industry.

✔ Good machinability and weldability

Copper alloy U-tubes have good machinability and weldability and can easily achieve welding, cutting, and other processes during installation.

✔ Higher strength and hardness

They are highly hard and have good wear resistance. They can withstand high pressure and impact and are not easy to deform or break.

ASTM B395 Copper and Copper Alloy U-Bend Tubes

Production Process of ASTM B395 U-Bend Tubes

Processing method: generally cold-worked

Processing process: first cut the tube into a suitable length, then put it into the tube bending machine and bend it into a U shape.

Before bending, the copper and copper alloy tubes should be in the following conditions:

O61: C19200, C23000, C44300, C44400, C44500, C60800, C68700, C70400, C70600, C70620, C71000, C71500, C71520, C72200

H55: C10200, C10300, C10800, C12000, C12200, C14200, C19200

C70400, C70600, C70620, C72200 (if required)

HR50+drawn: C71500, C71520 (If required)

Tempers after bending

Because in a corrosive environment, the tensile stress formed by straightening may cause stress corrosion cracking, so for some copper alloy grades of U-tubes, it is necessary to perform stress relief heat treatment on the bent part after bending and straightening.

HR: Stress relief state → C23000, C44300, C44400, C44500, C60800, C68700

If required, the bent part of the following grades of copper alloy U-tubes should also be in HR state:

C70400, C70600, C70620, C71000, C71500, C71520, C72200

Surface Quality Requirements

O61: clean and smooth; inner and outer surfaces can have a superficial dull iridescent film

Drawn-temper: clean and smooth, inner and outer surfaces can have a drawing lubricant surface.

HR: Inner and outer surfaces can have a light oxide scale

Applicable Tests

✔ Dimensional inspection

✔ Chemical composition analysis: The chemical composition of the finished product should comply with the ASTM B395 standard or the chemical composition specified in the purchase order

✔ Grain size

✔ Tensile performance test

✔ Expansion test: After the sample tube is expanded according to the specified expansion rate, there are no cracks or other defects on the surface by the naked eye

✔ Flattening test: The sample tube is flattened according to the specified test method. There should be no cracks in the flattened area, but defects that do not affect its applicability are acceptable

✔ Mercurous nitrate or ammonia vapor test: This test is only performed on the following brands of tubes → C23000, C44300, C44400, C44500, C60800, C68700

✔ Non-destructive tests:

- Eddy current test: Each pipe must be subjected to an eddy current test before bending

- Hydraulic pressure test

- Air pressure test

ASTM B395 U Bend Tubes|Copper Alloy Condenser Tubes

Products Description

What is ASTM B395 Standard?

Structural Design of U-Bend tubes

How tube bundle works?

Specifications of B395 U-Bend Tubes

Copper Alloy Common Grades & Chemical Composition

Tension Properties of ASTM B395 Common Grades

Dimensions & Tolerance of ASTM B395 Seamless U-Bend Tubes

Properties of ASTM B395 U-Bend Copper and Copper Alloy Tubes

ASTM B395 Copper and Copper Alloy U-Bend Tubes

Production Process of ASTM B395 U-Bend Tubes