HG/T 2718-1995 Rubber and plastic hoses and hose assemblies for automotive air conditioners
Some standard content:
Chemical Industry Standard of the People's Republic of China
Rubber and plastic hoses and hose assemblies for automobile air conditioning
1 Subject content and scope of application
HG/T2718-1995
This standard specifies the categories, dimensions, structures, technical requirements and test methods of rubber or plastic hoses and hose assemblies for automobile air conditioning systems.
This standard is applicable to rubber and plastic hoses and tube assemblies for conveying circulating liquid and gaseous mononitrogen difluoromethane (refrigerant R12) in automobile air conditioning systems.
The hose can be used in the temperature range of -3 ℃ to +125 ℃. 2 Reference standards GB/T1690 Test method for resistance of vulcanized rubber GB/T 2941 Standard temperature, humidity and time for environmental conditioning and testing of rubber specimens Test method for liquid pressure on rubber and plastic hoses and hose assemblies CB/T 5563 Non-flexion hydraulic impulse test for rubber, plastic hoses and hose assemblies GB/T 5568 Evaluation of oxygen resistance of rubber and plastic hoses under static conditions GB/T 9571 GB/T 9576 Guide for selection, storage, use and maintenance of rubber and plastic hoses and hose assemblies GB/T 9577
Rules for marking, packaging and transportation of rubber, plastic hoses and hose fittings 3 Product classification
3.1 Type and structure
3.1.1 Type A1 and A2 fabric-reinforced rubber hoses The hose shall consist of a seamless, oil-resistant synthetic rubber inner layer, a fabric reinforcement layer that is well bonded to the inner layer and the outer layer, and a heat-resistant and ozone-resistant synthetic rubber outer layer. The outer layer can be needle-punched. Type A1 hoses shall have: a fiber fabric braided reinforcement layer. Type A2 hoses shall have two fiber fabric braided reinforcement layers. 3.1.2 Type B1 and B2 steel wire reinforced rubber hoses The hose shall consist of a seamless, oil-resistant synthetic rubber inner layer, a steel wire reinforcement layer bonded to the inner layer, and a heat-resistant fabric outer layer impregnated with synthetic glue.
3.1.3 Type C fabric-reinforced thermoplastic hose The hose shall consist of an inner layer of thermoplastic material, a suitable fabric reinforcement layer and an outer layer of heat-resistant and ozone-resistant thermoplastic plastic. The outer layer can be needle-punched.
3.1.4 Type I fabric-reinforced thermoplastic hose The hose shall consist of an inner layer of thermoplastic plastic, a fabric reinforcement layer that can be bonded to the inner and outer layers, and an outer layer of heat-resistant and ozone-resistant synthetic rubber. The outer layer can be needle-punched. 3.2 Dimensions
3. 2. 1 The dimensions of the hose shall comply with the requirements of Table 1. Inner
Nominal size
A1, A2.B1 type
HG/T2718—1995
Table 1 Hose size
B2, D type
Maximum value Minimum value Maximum value Minimum value Maximum value Minimum value Maximum value Minimum value Maximum value Minimum value 5-1
1) 4. 8 mm Specification inner diameter Maximum and minimum values do not apply to D type 3.2.2
Soft Coaxiality: Measure the pipe wall thickness at different parts of the
-section, and the tolerance value shall not exceed the value specified in Table 2. Table 2 Soft deaf coaxiality
A1, A2, B1, B2 and D type
Nominal size
4. 8~ 6. 4
3.3 Product marking
Maximum axiality
Nominal size
Maximum coaxiality
Marking content: Manufacturer name (trademark) Product name, model, specification, standard number, manufacturing year, season Marking example:
××××(××） Automobile air conditioning soft replacement A 10 GB/T ×××× —×× ××××X
One year
Standard number
Product name
Manufacturer name (trademark)
4 Technical requirements
HG/T 27181995
4.1.2 Under the test pressure of 6MPa, the hose should be free of leakage, bubbling, cracking and other abnormal phenomena when maintained for 30～3008. 4.1.3 When the hose is subjected to the test pressure of 2.1MPa, the change in its length should not exceed -4%～+2%. 4.2 Leakage resistance
When the hose and the soft temporary assembly filled with refrigerant are subjected to the leakage test at the specified temperature, the mass loss rate of the refrigerant (R12) shall not exceed the provisions of Table 3.
Table 3 Refrigerant mass loss rate
Test temperature
Reference pressure
1) Hoses and hose assemblies intended for use at high pressure are tested at (100±2)°C; 2) Hoses and hose assemblies intended for use at low pressure are tested at (80±2)°C; 3) Calculated based on the inner surface area of the hose
4.3 Overall performance
Refrigerant mass loss rate"
kg/m**a. Small
Type A Type L||t t||Type C and D
After the hose filled with refrigerant is conditioned at (107+2)℃ for 24 hours, the inner rubber layer of the hose should be free of cracks, damage and other abnormal phenomena. 4.4 Low temperature resistance
After the low temperature test, the hose filled with refrigerant has no cracks or leakage. 4.5 Hot air aging performance
After the hot air aging test, the outer surface of the hose should be free of cracks. When the hydraulic test is carried out, there should be no liquid leakage. 4.6 Vacuum resistance
The hose should be resistant to vacuum test. During the test, the external diameter shall not exceed 20%. 4.7 Liquid resistance
4.7.1 The inner rubber layer of the hose is immersed in No. 3 standard oil at a temperature of (100-2)°C for 70 hours, and the volume change rate is measured within 5 minutes after being taken out: the volume change rate should be -5% to -35%.
4.7.2 The inner plastic layer of the hose is immersed in No. 3 standard oil at a temperature of (100+2)°C for 70 hours, and the volume change rate is measured within 5 minutes after being taken out: the volume change rate should be -35% to +5%.
|4.8 Ozone resistance
Except for Type B hoses, when the hose is kept at an ozone concentration of (50±5)×10-\ and a temperature of (102)℃ for 70 hours, observe the outer layer of the hose with a double magnifying glass and no color cracks shall be found. 4.9 Refrigerant extraction performance of the inner layer
The amount of oily or greasy matter extracted from the inner layer of the hose by refrigerant R12 shall not exceed 118g/m2. 4.10 Internal cleanliness
The amount of foreign matter on the inner surface of the hose shall not exceed 270mg/m2. 4.11 Pulse resistance performance
At least two hose samples should be tested. The hose should be subjected to pulse test at a frequency of 30 to 40 cycles/min at a temperature of (107 ± 2)°C and a pressure of (0.17 ± 2.6 MPa) ± 0.17 MPa, with a medium viscosity of 5.0 to -10.0 cs1 at (107 ± 2). After 150,000 pulse tests, no leakage or damage should occur. During the test, the minimum bend of type A, type B and type D hoses The bending radius should be 5 times the outer diameter of the hose: The minimum bending radius of the C-type hose should comply with the provisions of Table B1 in Appendix B.
HG/T2718—1995
The pull-off force required to separate the hose from the pipe joint shall not be less than the provisions of Table 4. Table 4 Pull-off force of hose fittings
Inner diameter/mm
5 Test method
5.1 Hydraulic test shall be carried out in accordance with GB/T5563. 5.2 Leakage test and overall test shall be carried out in accordance with Appendix A. A, CD type
The overall test can be carried out separately or with (107±2) for 24 h frequency adjustment during the leakage test. The number of samples is three. 5.3 Hot air aging test shall be carried out in accordance with the following conditions and methods. Take a 300mm1000tmt long hose sample, wrap it around a mandrel of the size specified in F, and place it in an air aging box at (12512)℃. After keeping it for 168h, take it out and cool it to air temperature. Then loosen the hose to a straight state, check whether the hose sample has cracks, cracks or other defects, and then subject the hose sample to 2.4MPa hydraulic pressure for 5min to observe whether there is liquid leakage or loss.
Thin shaft diameter:
Type A, B, and D hoses: 8 times the outer diameter of the corresponding hoses: Type C hose: 2 times the minimum bending radius of Type C hose in Table B1 of Appendix B of this standard. 5.4 The low temperature resistance test shall be carried out in accordance with the provisions of Appendix B, and 5.5 The vacuum resistance test method shall be carried out in the following way. Take a hose sample of 610mm~1000mm in length. Bend the hose sample into a U shape, and the inner radius of the semicircle at the bottom of the U shape shall be 5 times the nominal inner diameter of the hose. Evacuate the hose to 81 kPa.Bend for 2 min. Measure the outer diameter of the U-shaped bottom hose, determine the outer diameter value at the minimum point, and calculate the collapse rate according to formula (1).
Outer diameter collapse rate:
Initial outer diameter value - minimum outer diameter value
Initial outer diameter value
5.6 The inner layer liquid resistance test shall be carried out in accordance with GB/T1690. 5.7 The ozone resistance test shall be carried out in accordance with GB/T 9571. (1
The hose sample should be wound on a mandrel that is 8 times the outer diameter of the hose, and the length of the sample should be about 250mm longer than the circumference of the mandrel. 5.8 The inner layer resistance to cold extraction test shall be carried out in accordance with the provisions of Appendix C. 5.9 The internal cleanliness test shall be carried out as follows. Bend the hose sample into a U shape; the lengths of both sides are equal, place it vertically to the horizontal plane, and fill the hose with trichlorotrifluoroethane (refrigerant TF). Then use a weighed Gustav worm, sintered glass or 0.4μ filter to filter the trifluoroethane in the hose through the filter.
HG/T2718—1995
The filter and the filtrate are dried at 70°C for 20 minutes and then weighed. The amount of foreign matter on the inner surface of the hose is calculated by the differential weight method. Per square meter The number of milligrams on the inner surface of the hose per cubic meter is expressed as (mg/m\): 5.10 The impulse test shall be carried out in accordance with the provisions of GB/T5568. 5.11 The pull-off test shall be carried out in the following manner. Install special pipe head clamps with screw holes on both ends of the hose assembly sample and clamp them on the upper and lower clamps of the tensile testing machine. Use a traction speed of (2515mm/min to carry out the pull-off test, and measure the pull-off force when the hose assembly pipe joint is separated from the hose. The free length of the hose is at least 300mm.
6 Inspection rules
6.1 The hose shall be inspected in batches by the inspection department of the manufacturer! Each batch of hose products must have a quality certificate when leaving the factory. 6.2 Hoses of the same model shall be classified as one batch, and the quantity of each batch shall not exceed 50,000m: 6.3 The specifications and sizes of the hose shall be determined one by one Root inspection.
6.4 For each batch of hoses, select one specification to conduct various performance tests. If there are less than one batch, the inspection should not be less than times every six months. 6.5 For each batch of hoses, each specification is subject to permeability test and assembly pull-off test. If there are unqualified ones after the test, double samples should be taken from the batch of hoses for retesting of the unqualified items. If ～~ indicators are unqualified after the retest, the batch of hoses is unqualified. 7 Marking, packaging, transportation, storage, selection, use and maintenance 7.1 The marking, packaging and transportation of hoses shall comply with the requirements of GB/T9577. 7.2 The storage, selection, use and maintenance of hoses shall comply with the requirements of GB/T9576. Appendix A
Refrigerant loss determination test
(Supplement)|| tt||A1 Scope
This appendix specifies the method for determining the rate of refrigerant loss in automobile air conditioning hoses. A2 Principle
The diffusion rate of refrigerant through the hose wall is determined according to the principle of mass change. A3 Apparatus
43.1 A metal container with an internal volume of 475cm~525cm and a minimum bursting pressure of 21MPa, and a pipe joint for connecting the hose assembly sample.
A3.2 A hose joint that can ensure that the refrigerant under pressure in the hose does not lose any refrigerant at the connection between the hose and the pipe joint. A3.3 A halogen detector with a sensitivity of 11g per year. A3.4 An air oven that can maintain a uniform test temperature during the test. A3.5 A weighing balance with an accuracy of 0.1g. A4 Samples
Take four hose assembly samples with a length of 1m, three of which are used to determine the refrigerant loss, and the fourth is used as a reference test to determine the mass change of the hose body alone. A5 Operating Procedure
HG/T 2718—1995
A5.1 Measure the free length of each hose assembly at atmospheric pressure (accurate to 1mm). Connect the four hose assemblies including the end plugs to the metal container respectively, measure the total mass of each test device (accurate to 0.1g), and charge the three test devices with refrigerant at a ratio of 0.6mg refrigerant per 1mm2 volume, with a tolerance of ±5g. Check the charged test devices with a halogen detector to ensure that there is no leakage. Any method that can safely charge the refrigerant can be used. It is recommended to use the methods in A5.2 and A5.3. A5.2 Method—1
Place the test device in a refrigerator at a temperature below the boiling point of the refrigerant. After conditioning and cooling for at least 4h, the test device can be smoothly charged with refrigerant.
According to the density of the refrigerant at the conditioned temperature, the corresponding charge weight of the refrigerant can be calculated using the volume at that temperature. Keep the refrigerant hose at the regulated temperature, use a graduated cylinder to measure the calculated volume of refrigerant, and fill it. Cover the refrigerant-filled test device at the regulated temperature, but remove it from the refrigerator and tighten it to ensure complete sealing.
A5.3 Method 2:
The refrigerant can be transferred under pressure through suitable valves and connectors at room temperature to fill the test device with refrigerant. Suitable instruments for this purpose are a refrigerant cylinder, a pressure storage type compressed air system, a piston pump and a metering control device. A5.4 Place the three filled test devices and a reference test device in an air oven at the specified test temperature for (30+5) minutes to eliminate surface moisture. Do not bend the hose in the oven into a curve with a diameter less than 20 times the outer diameter of the hose. Check the filled test device for leakage, remove the test device from the oven, and weigh the mass of the test device within a time greater than 15min and less than 30min. Record the weighed mass as the initial mass. Return the test device to the air oven at the specified temperature and condition for 24 hours. After these 24 hours, remove the test device, weigh it as described above and return it to the oven. If there is a loss of more than 20%, stop the test, check for leaks and repeat the test. Consider the first 24 hours as the pre-conditioning time. In the final calculation, the mass loss during this period can be ignored. After weighing during the pre-conditioning period, condition it in the oven for another 72 hours. Remove the test device and weigh it again under the same conditions as above to obtain the final mass. A6 Calculation
Calculate the refrigerant mass loss rate of the charging test device according to formula (A1): R
[AB C- E]
Wherein: R--: refrigerant mass loss rate, kg/m·a; A--: initial mass of the charged test device after pre-adjustment, denoted by: B--: final mass of the charged test device after 72 h, denoted by: C
: initial mass of the reference test device after pre-adjustment, denoted by: D--: nominal inner diameter of the hose, mm;
: final mass of the reference test device after 72 h, g; free length of the hose in the charging test device, denoted by:; free length of the hose in the reference test device, m#38.7, is the belt number.
A7 Test report
The test report shall include the following contents:
) Reference to this standard number,
h) Model and specification of the test hose;
c) Test results obtained;
d) Any events that may affect the test results, B1 Scopewww.bzxz.net
HG/T 2718—1995
Appendix B
Low temperature test
(Supplement)
This appendix specifies the method for evaluating the performance of automobile air conditioning hoses at low temperatures (·30C). B2 Principle
A hose sample filled with liquid refrigerant is first aged at 70℃ for 48 hours, then frozen at -30℃ for 24 hours, then bent 180° on a mandrel at low temperature, and then subjected to a 2.4 MPa hydraulic test at ambient temperature for 5 minutes. No refrigerant leakage shall occur.
B3 Specimen
The length of the hose specimen should be between 450mm and 1000mm. B4 Procedure
Fill the hose specimen with liquid refrigerant in an amount of 70% of its capacity at room temperature (for convenience, the hose assembly and refrigerant can be cooled to below the boiling point of the refrigerant to ensure that the refrigerant is filled in the liquid state). Place the hose specimen in an air oven at 70℃ for 48 hours, and then cool it to room temperature.
Put the hose straight and in a (-30±2)℃ freezer for 24 hours. The freezer should contain uniform cold air or a mixture of air and carbon dioxide to ensure that the specified temperature is reached. Without removing the hose specimen from the freezer, bend the hose specimen 180° on a mandrel of suitable diameter (the mandrel should also be pre-frozen to (-30±2)℃) within 4 to 8 hours. For type A, type B and type ID hose specimens,The mandrel diameter should be 8 times the nominal outer diameter of the hose; for C-type hose specimens, the mandrel diameter should be 2 times the minimum bending radius specified in B1. Table BIC-type hose minimum bending radius
Standard inner diameter size
Raise the hose specimen temperature to ambient temperature and pour out the liquid refrigerant. Minimum bending radius
The hose is then subjected to a 2.4MPa hydraulic test and maintained for 5Ini. Observe for leakage or liquid loss due to the presence of a leak. B5 Test report
The test report should include the following:
a) Reference to this standard number;
b) Model and specification of the test hose;
c) Test results obtained:
d) Any events that may affect the test results. HG/T 2718 : 1995
Appendix C
Liquid refrigerant extraction test
(Supplement)
C1 Scope
This appendix specifies the test method for the resistance of the inner layer material of the hose assembly for air conditioning to liquid refrigerant extraction. C2 Principle
Inject the liquid refrigerant into the hose assembly and keep it at 70℃ for 24 hours to complete the extraction test. C3 Sample
The free length of the hose assembly sample is between 450 mm and 1 000 mm. C4 Procedure
Fill the hose sample with chlorotrifluoroethane (refrigerant TF) and then immediately pour it out to remove any surface impurities. At room temperature, fill the hose sample with 70% of its capacity of the specified body refrigerant. For ease of operation, the hose assembly and the refrigerant can be cooled to a temperature below the boiling point of the liquid refrigerant so that they can be handled in a liquid state. The hose assembly filled with refrigerant is placed in an air oven at a temperature of (70 ± 2) ° C and kept for 24 hours before being taken out. Bring to a temperature of -34 ° C or lower, then pour the liquid refrigerant into a weighed beaker and allow it to evaporate at room temperature. After the liquid refrigerant evaporates, place the beaker at 70 ° C for 1 hour to eliminate condensed water vapor and then weigh it.
C5 Result Expression
The test results are expressed in grams per square meter of the hose inner surface area, that is, g/m*. The inner surface area of the hose is calculated based on the nominal inner diameter of the hose. Additional Notes:
This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Rubber Hose Sub-Technical Committee of the National Rubber and Rubber Products Standard Promotion Technical Committee. This standard was drafted by the Shenyang Rubber Industrial Products Research Institute of the Ministry of Chemical Industry. The participating drafting units include Shanghai Rubber General Factory, Nanjing 7425 Factory, Taizhou Rubber General Factory, and Zhengzhou Rubber Second Factory. The initiators of this standard are: Wang Baozhu, Ji Wencai, Liu Yixian, Zhang Weixiang, and Li Xiaoxue.
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