GB/T 26291-2020Seamless copper-nickel alloys tube for ships (English PDF)

3.1 Nominal size

The size identification of a combination of letters and numbers used for piping system components consists of the letter DN followed by a dimensionless integer number.

Note 1. This dimensionless number is directly related to the characteristic dimensions such as the aperture or outer diameter (in mm) of the end connector.

Note 2. Unless otherwise specified in the relevant standards, the dimensionless numbers following DN do not represent measured values and should not be used in calculations. [GB/T 1047-2019, definition 2.1]

5.4 Process performance

5.4.1 Flaring test

Tubes with an outer diameter of not more than 108mm can be flared test. During the test, the top core angle is 45°, and the expansion rate is not less than 30%.

There should be no visible cracks or damage to the rear pipe.

5.4.2 Flattening test

The pipe should be subjected to a flattening test. During the test, it should be flattened until the distance between the two walls is equal to the wall thickness. After the test, there should be no visible cracks or damaged.

5.4.3 Two-way bending test

Pipes with an outer diameter greater than 108mm should be subjected to a two-way bending test. During the test, both ends of the sample should be bent 180°, and there should be no appearance after bending. Cracks or breakage visible to the naked eye.

5.5 Grain size

The average grain size of the pipe is 0.010mm~0.045mm.

5.6 Non-destructive test

5.6.1 Eddy current flaw detection

For pipes with an outer diameter of not more than 160mm, eddy current testing shall be carried out. When the pipe is inspected by eddy current testing, the signal of the eddy current testing equipment Straight pipes that do not send out an alarm signal on the device shall be regarded as pipes that meet this standard. The coil should be printed at the defect position not less than 300mm long For the dark mark, the allowable number of defects is determined by the supplier and the buyer through negotiation. The standard artificial defect should be a through hole, and its drill diameter should comply with GB/T 5248 Provisions.

5.6.2 Water pressure test

The maximum working pressure of the pipe is calculated according to formula (1).

When the pipe is subjected to hydraulic test, the test pressure is calculated according to formula (2). The maximum test pressure does not exceed 6.9MPa, under this pressure, continuous After 10s~15s, the pipe should be free of leakage and permanent deformation.

Where:

P - Maximum working pressure, in megapascals (MPa);

S - Material allowable stress, in megapascals (MPa). At room temperature, take the corresponding grade and state Rp0.2 minimum value in Table 8 50% of;

t - The nominal wall thickness of the pipe, in millimeters (mm);

D - The nominal outer diameter of the pipe, in millimeters (mm).

Where:

Pt - test pressure, in megapascals (MPa);

n - safety factor, usually 1.50~1.65;

P - Maximum working pressure, in megapascals (MPa).

5.7 Electrochemical corrosion performance

The pipe can be tested for electrochemical corrosion performance, and the potential difference between the inside and outside of the pipe is deltaE<=0.07V.

5.8 Surface quality

The inner and outer surfaces of the pipe should be smooth and clean, and there should be no defects that affect the use.

6.1 Chemical composition

The analysis of the chemical composition of the pipe shall be carried out in accordance with the provisions of GB/T 5121 or YS/T 482, YS/T 483, and the arbitration shall be carried out in accordance with GB/T 5121 Regulations proceed.

6.2 Dimensions and allowable deviation

The external dimensions of the pipe and its allowable deviation are measured in accordance with the provisions of GB/T 26303.1.

6.3 Mechanical properties

The room temperature mechanical performance test of the pipe is carried out according to the regulations of GB/T 34505-2017, and the hardness test is carried out according to the regulations of GB/T 4340.1 get on.

The types of tensile specimens are shown in Table 9, and the specific requirements should meet the requirements of Table 13 in GB/T 34505-2017.

6.4 Process performance

6.4.1 The flaring test of the pipe shall be carried out in accordance with the provisions of GB/T 242.

6.4.2 The flattening test of the pipe shall be carried out according to the provisions of GB/T 246.

6.4.3 The two-way bending test of the pipe shall be carried out according to the following regulations.

Take a longitudinal arc sample along the center of the pipe, the length is not less than 300mm, and the wall thickness is the original wall thickness of the pipe.

The two ends are bent 180° in opposite directions, as shown in Figure 1 after bending.

6.5 Grain size

The inspection of grain size shall be carried out in accordance with the provisions of YS/T 347.

6.6 Non-destructive test

6.6.1 The eddy current flaw detection of pipes shall be carried out in accordance with the provisions of GB/T 5248.

6.6.2 The hydraulic test of the pipe shall be carried out in accordance with the provisions of GB/T 241.

6.7 Electrochemical corrosion performance

Refer to Appendix A for the electrochemical corrosion performance test of the pipe.

6.8 Surface quality

The surface quality of the pipe shall be inspected visually.

7.1 Inspection and acceptance

7.1.1 The pipe material shall be inspected by the supplier's technical supervision department to ensure that the product quality meets the requirements of this standard, and fill in the material quality assurance certificate.

7.1.2 The purchaser shall inspect the received products in accordance with the provisions of this standard, and the inspection results are not consistent with the provisions of this standard and the contract (or purchase order). It should be submitted to the supplier in written form, and the supplier and demander shall negotiate and resolve. The objection that belongs to the surface quality and dimensional deviation should be Submitted within one month from the date of the product. Objections to other properties should be raised within three months from the date of receipt of the product. If arbitration is required, This should be done jointly by both the supplier and the buyer.

7.2 Batch

Pipes should be submitted for acceptance in batches, and each batch should be composed of pipes of the same brand, specification and condition. The weight of each batch does not exceed 5000kg.

7.3 Inspection items

7.3.1 Pipe inspection items shall be carried out in accordance with Table 10.

7.5 Judgment of inspection results

7.5.1 Numerical rounding and judgment of the test results shall be carried out in accordance with the provisions of GB/T 8170, and the rounding value comparison method shall be used for judgment.

7.5.2 When the chemical composition is unqualified, the batch of pipes shall be deemed unqualified.

7.5.3 When the outer dimensions of the pipe and its allowable deviation or the surface quality is unqualified, the root (or plate) is judged to be unqualified. Number of unqualified pieces in each batch If the quality limit is exceeded, the whole batch will be judged as unqualified, or the supplier will be inspected one by one (or plate), and the qualified will be delivered.

7.5.4 When there are unqualified samples in the test results of mechanical properties, process performance, grain size, and electrochemical corrosion, the batch of pipe materials (including acceptance Take another double number of samples from the unqualified pipe (or plate) to repeat the test. If all the repeated tests are qualified, the entire batch of pipes will be judged qualified. If the repeated test results still have unqualified samples, the entire batch of pipes shall be deemed unqualified, or the supplier shall inspect one by one (or plate), and the qualified delivery.

7.5.5 If the non-destructive test fails to pass the inspection, a single (or coil) pipe shall be deemed as unqualified.

7.5.6 When other defects occur, the batch of pipes shall be resolved through negotiation between the supplier and the buyer.

A.1 Method summary

Fill the sample with potassium chloride (KCl) solution, use a potentiometer to measure the potential of the inner and outer surfaces of the pipe, and calculate the potential of the inner and outer surfaces of the pipe Poor, to determine the corrosion resistance of the pipe.

A.2 Reagents

Potassium chloride (KCl) solution. 0.02mol/L.

A.3 Sample

Intercept 200mm~300mm pipes from the samples to be tested, sand the outer wall of the pipes under circulating water with sandpaper to remove the oxide film (avoid The high temperature caused by friction oxidizes again).

A.4 Instruments

Potentiometer [reference input impedance. >1014ohm (parallel capacitance 1pF)].

A.5 Test procedure

A.5.1 Sample cleaning

Using absorbent cotton, combined with acetone, carefully wipe off the grease on the inner surface of the copper pipe until the inner wall is clean.

A.5.2 Filling with potassium chloride (KCl) solution

One end of the tube is sealed with rubber, placed upright with the opening facing upward, and the tube is filled with KCl solution. Reference electrode [saturated KCl solution Mercury chloride electrode (SCE)] is placed in the sample tube. Keep 10mm~20mm long pipes that are not wetted by the test liquid.

A.5.3 Determination of the internal surface potential of the pipe (corrosion potential E1)

When measuring the inner surface potential of the pipe, the pipe is connected to the positive electrode (red) of the voltmeter, and the reference electrode is connected to the negative electrode (black ground), which is stable 10min, wait for the metal corrosion potential to stabilize before measuring.

A.5.4 Measurement of the external surface potential of the pipe (corrosion potential E2)

When the external surface potential of the pipe is measured, the pipe and the reference electrode are both placed in a beaker containing 0.02mol/L KCl solution.

A.6 Test data processing

The potential difference deltaE between the inner and outer surfaces of the pipe is calculated by formula (A.1).