QC/T 664-2019Automotive air conditioning refrigerant hoses (English PDF)

3.1 High pressure hose

A hose, which has a working pressure of not less than 3.5 MPa (marked as HP).

3.2 Low pressure hose

A hose, which has a working pressure not higher than 1.5 MPa (marked as LP).

5.8 Length change rate

Carry out the test, according to the test method specified in 6.9. During the test, under the action of the specified pressure, the length change rate of the hose shall be -4% ~ 2%.

5.9 Burst pressure

Carry out the test, according to the test method specified in 6.10. The minimum burst pressure of the hose, which has a nominal inner diameter not greater than 13.0 mm, shall be 14.7 MPa. The minimum burst pressure of the hose, which has a nominal inner diameter greater than 13.0 mm, shall be 12.0 MPa.

5.10 Pressure resistance

Carry out the test, according to the test method specified in 6.11. During the test, the hose shall be tested, according to the specified pressure and time. The abnormal phenomena, such as leakage, crack, sudden twisting of the hose, are not allowed.

5.11 Extractables content

Carry out the test, according to the test method specified in 6.12. After the test, the content of extractables, on the inner surface of the hose, shall not exceed 118 g/m².

5.12 Volume change rate of inner layer material

Carry out the test, according to the test method specified in 6.13. After the test, the volume change rate of the rubber material shall be -5% ~ 35%; the volume change rate of the thermoplastic material shall be -5% ~ 5%.

5.13 Ozone resistance

Carry out the test, according to the test method specified in 6.14. After the test, the outer rubber layer of the hose shall have no visible cracks, under an eight-fold magnifying glass.

5.14 Internal surface cleanliness

Carry out the test, according to the test method specified in 6.15. After the test, the impurity content shall not exceed 270 mg/m²; the size of the gas particles shall not exceed 0.5 mm x 1.0 mm.

6.2 Test medium

The test medium used in the test shall be a mixture of HFC-134a, which has a mass fraction of 90% or HFO-1234yf refrigerant and 10% refrigerating machine oil.

6.3 Dimensional measurement

6.3.1 Inner and outer diameters of hoses

The inner diameter of the hose shall be measured by a special measuring tool, such as a tapered plug gauge, expanding ball type or retractable meter, etc. The diameter is measured 3 times; the results are averaged.

6.3.2 Deviation of hose's wall thickness

The deviation of wall thickness of the hose shall be measured by a special meter, such as a caliper with a probe that can touch the inner wall of the hose. Measure the wall thickness of the cross section of the hose, at four points; take the difference between the maximum value and the minimum value measured. Make 3 measurements. Take the average of the results.

6.4 Permeation

Take 3 hoses. Fill the hoses with the specified test medium, according to the method in 6.5.3.1. Weigh the hoses and accessories. Then place the samples at a temperature of 100 °C ± 2 °C, for 24 hours. After taking out, weigh the mass of the hose and accessories again. Calculate the mass loss.

6.5 Refrigerant permeability

6.5.1 Test device

6.5.1.1 Accessories and fixtures

Accessories and clamps shall be sealed and leak-free, when subjected to the pressure in the hose.

6.5.1.2 Leak detector

The sensitivity of the leak detector shall be higher than 2 g/year (under the same volume and temperature conditions, the refrigerant's equivalent ratio HFC-134a:HFO-1234yf = 1:0.92).

6.5.1.3 Constant temperature chamber

The control accuracy of the constant temperature chamber shall be ±2 °C.

6.5.1.4 Balances

The measurement accuracy of the balance shall be 0.01 g.

6.5.2 Test conditions

For use of hoses at higher working pressures, the test temperature shall be 90 °C ± 2 °C or 100 °C ± 2 °C (high-pressure hose). For use of hoses at lower working pressures, the test temperature shall be 80 °C ± 2 °C (low-pressure hose).

6.5.3 Test method

6.5.3.1 Preparation before the test

Take 4 hoses, which have an exposed length of 1m, and accessories. Use seals to seal them at both ends. Three of them are used to measure the loss of refrigerant; the fourth one is connected with a joint, which is used as a comparison hose, to detect the change of the mass torsion of the hose itself. In the standard state, measure the exposed length of the hose (L1, L2), the accuracy is required to be ±1 mm. Weigh the mass of each hose and accessories (including joints), which is required to be accurate to ± 0.1 g. The hose assembly is filled with 0.6 mg of test medium per millimeter volume; the filling volume is accurate to ±5 g. The number of filled hoses is 3. Use a leak detector, to check that each hose is leaking.

Filling of refrigerant

Method 1:

Before filling the hoses and accessories, they must be kept in a low temperature chamber of -30 °C or lower, for 4 hours. Use the density of the test medium, at this temperature, to calculate the mass of the test medium to be filled. Keep the test medium and the hose at this temperature. Use an electronic balance, to weigh the test medium. Then fill the test medium into the hose. The filled hose and accessories are sealed at this temperature.

Method 2:

The hose and accessories are filled with the test medium, under a certain pressure, at ambient temperature. The device, to keep the test medium flowing, has a storage compressed air system, a piston pump, a device for controlling and measuring the flow.

6.5.3.2 Test procedure

First, place 3 test hoses, which are filled with refrigerant, AND 1 comparison hose, in a constant temperature chamber. Dry them for 30 minutes at the test temperature, to remove the moisture on the surface of the hose and accessories. Then use a leak detector to check for leaks. Weigh it.

6.7 Low-temperature resistance

Take 3 hoses and accessories, which have exposed length of 300 mm ~ 1000 mm. At room temperature, fill the sample with test medium to 70% of the volume of the hose, at room temperature. OR cool the hose, accessories and test medium to below -30 °C, for filling.

Place the filled hose and accessories, in a constant temperature chamber, at 70 °C ±2 °C. Keep it for 48 hours. Take it out and let it cool to room temperature. Put the hose in straight line state AND the mandrel which has a diameter 8 times the outer diameter of hose together, in a low temperature chamber, at -40 °C ± 2 °C, for 24 hours. Then bend the hoses and accessories, around the mandrel, at a uniform speed by 180°, within 4 s ~ 8 s, in the low temperature chamber. After removal, restore the specimen to room temperature. Carefully inspect the outer surface for defects, such as cracks visible to the naked eye. Then pour the test medium, which is filled in each hose and accessories, back into a suitable recovery container. Maintain the hose at hydrostatic pressure of 2.4 MPa (low-pressure hose) OR 3.5 MPa (high-pressure hose), for 5 minutes. Check the hose.

6.8 Vacuum resistance

Take hoses and accessories, which have a length of 600 mm ~ 1000 mm. Bend the hose into a U shape. The inner diameter of the U shape is 5 times the nominal outer diameter of the hose (the U-shaped inner diameter of hose, which has an inner diameter of more than 19 mm, is 6 times the nominal outer diameter of the hose). Measure the minimum outer diameter, on any plane, at the bottom of the U-shape, as the initial outer diameter (D0). Vacuum the hose to an absolute pressure of 81 kPa ± 3 kPa. Hold the pressure for 2 min. When the hose is still in a vacuum state, after the pressure holding, measure the minimum outer diameter (D1), on any plane, at the bottom of the U-shape again. Then calculate the collapse of the outer diameter of the hose, as follows:

Collapse of the outer diameter = D0 - D1 ....................... (2)

Where:

D0 - The outside diameter of hose, before test, mm;

D1 - The outside diameter of hose, after test, mm.

6.9 Length change rate

Take two hoses, which have an exposed length of 600 mm, and accessories.

6.12 Extractables content

Take the hose which have an exposed length of 450 mm ~ 1000 mm and its accessories.

Use isooctane solvent, to thoroughly clean the inner surface of the hose. Fill the hose to 70% of the hose capacity, by the liquid refrigerant, at room temperature. For convenience, the hose and refrigerant can be cooled to below -30 °C, so that the refrigerant is in a liquid state for easy filling. Put the hose and accessories in a constant temperature chamber, at 70 °C ± 2 °C, for 24 h. After aging, cool the hose to below -30 °C. Pour the refrigerant into a dried beaker, which was weighed as G0, to let it evaporate at room temperature. After evaporation, put the beaker in a 70 °C constant temperature chamber, for 1 hour. Take it out and cool it to room temperature. Weigh the beaker again, as G1. Calculate the extractables content of the hose, according to the following formula. Calculate the inner surface area of the hose, using the nominal inner diameter of the hose as the standard.

Extractables content = (G1 - G0)/S ....................... (4)

Where:

G0 - Beaker mass before test, g;

G1 - Beaker mass after test, g;

S - Inner surface area of hose, m².

6.13 Volume change rate of inner layer material

Carry out test, according to GB/T 1690. Take the material of the inner rubber layer of the hose as a specimen. Place it in a pressure container, that can withstand at least 10 MPa pressure. Cool it to below -30 °C. Make the specimen be completely immersed in the test medium. Seal the container. Place it in a constant temperature chamber, at 100 °C ± 2 °C for 70 h. After placing it, cool it to below -30 °C. Then take the specimen out of the test medium. Measure the volume change rate of the specimen, according to GB/T 1690.

6.14 Ozone resistance

Types A, C, D hoses must be tested. After bending the hose around a mandrel, which has a diameter of 8 times the nominal outer diameter of the hose, put it into an ozone test chamber, which has a test temperature of 40 °C ± 2 °C AND an ozone partial pressure of 50 MPa ± 5 MPa; the test time is 70 h ± 2 h. After the test, take out the hose.

Observe whether the outer rubber layer of the hose has cracks or fractures, under an 8X magnifying glass.

6.15 Internal surface cleanliness

Take the hose, which has an exposed length of more than 300 mm. The inner wall of the hose shall be dry. Bend the hose into a U shape; the lengths of both sides of the U shape are the same. Make the two ends of the hose stand upright. Use isooctane solvent to fill the hose. Then open the hose. Use the 0.8 µm filter paper, which was dried and weighed as G0, to filter the solvent into the filter device, which has the filter paper installed. Dry the filter paper at 70 °C ± 2 °C, for 30 min. Weigh the filter paper, after cooling to G1. Calculate the inner surface cleanliness of the hose, as follows:

Inner surface cleanliness = (G1 - G0)/S ........................ (5)

Where:

G0 - Filter paper mass before test, mg;

G1 - Filter paper mass after test, mg;

S - Inner surface area of hose, m².

6.16 Pulse fatigue resistance

Install at least two hoses and accessories on the hose pulse fatigue test device. For hoses, which have a nominal diameter less than or equal to 22 mm, bend it for 180°; the exposed length of hose = pi (r + d/2) + 2d (see Figure 5). For hoses, which have a nominal inner diameter greater than 22 mm, bend it for 90°; the exposed length of the hose = pi (r + d/2)/2 + 2d (see Figure 6). The minimum bending radius is 5 times the nominal outer diameter of the hose. Then according to the provisions in Figure 7, apply pulse pressure of (0.5 ± 0.5) MPa ~ (3.5 ± 0.175) MPa to high-pressure hose and accessories; apply pulse pressure of (0.5 ± 0.5) MPa ~ (2.6 ± 0.13) MPa to low-pressure hose and accessories; the frequency is 30 ~ 40 cycles per minute. The test liquid is refrigerating machine oil; the oil temperature is 40 °C ± 2 °C; the test is carried out, at an ambient temperature of 125 °C ± 2 °C. After a total of 150000 cycles, carefully observe the hose and accessories, for leaks and damage.