JB/T 10373-2002 Hydraulic electro-hydraulic directional control valve and hydraulic directional control valve
Some standard content:
ICS23.100.30
Machinery Industry Standard of the People's Republic of China JB/T 10373—2002
Hydraulic fluid powerSolenoid actuated pilot operated directional controlvalve and hydraulic pilot operated directional control valve2002-12-27Promulgated
Implementation on 2003-04-01
Promulgated by the State Economic and Trade Commission of the People's Republic of ChinaForeword
Scope.
Normative references
Terms and definitionsbzxZ.net
Quantity, symbol and unit
Marking and basic parameters
5.1Marking..
Basic parameters
6 Technical requirements.
General requirements..
Performance requirements.
Assembly requirements
6.4 Appearance requirements,
Performance test methods
Test equipment,
Test conditions
Test items and test methods
Inspection of assembly and appearance
9 Inspection rules
Inspection classification
Judgment rules
10 Marking, packaging, transportation and storage
Quantitytt
Appendix A (Normative Appendix) Test circuit and characteristic curve test circuit||tt| |A.2 Characteristic curves
Principle diagram of test circuit..
Flow-pressure loss curve
Pressure-internal leakage curve.
Working range diagram,
Block diagram of test system
Valve core displacement-time transient response curve
Outlet pressure-time transient response curve…Quantity, symbol and unit..
Permissible variation range of average displayed value of controlled parameterTable 3 Permissible systematic error of measuring system
Table 4 Factory test items and test methods.
Type test items and test methods
Inspection methods for assembly and appearance
Europe
tt||Special electric power
JB/T 10373—2002
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Appendix A of this standard is a normative appendix.
This standard is proposed by China Machinery Industry Federation. Foreword
This standard is under the jurisdiction of the National Hydraulic and Pneumatic Standardization Technical Committee. JB/T10373—2002
The drafting units of this standard are: Beijing Huade Hydraulic Industry Group Co., Ltd. and Beijing Institute of Automation of Machinery Industry. The main drafters of this standard are: Zhou Weike and Liu Xinde. This standard is published for the first time.
1 Scope
Hydraulic electro-hydraulic directional control valve and hydraulic directional control valve JB/T 10373—2002
This standard specifies the basic parameters, technical requirements, test methods, inspection rules and marking, packaging and other requirements of hydraulic electro-hydraulic directional control valve and hydraulic directional control valve.
This standard is applicable to hydraulic electro-hydraulic directional control valve and hydraulic directional control valve with hydraulic oil or other liquids with equivalent performance as working medium 2 Normative reference documents
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard. GB/T786.1 Hydraulic and pneumatic graphic symbols (GB/T786.1-1993, eqvISO1219-1:1991, Fluid power systems and components-Graphic symbols and circuit diagrams—Part 1:Graphic symbols) GB/T2346 Hydraulic and pneumatic systems and components nominal pressure series GB/T2514 Four-port plate-type hydraulic directional control valves-mounting surfaces (GB/T2514—1993, eqvISO4401:1980, Hydraulic fluid power-four-port directional control valves-mounting surfaces )GB/T2828 Batch inspection counting sampling procedure and sampling table (applicable to inspection of continuous batches) GB/T2878 Types and sizes of threaded connection oil ports of hydraulic components GB/T7935 General technical conditions for hydraulic components GB/T14039-2002 Code for solid particle contamination level of hydraulic transmission oil (ISO4406:1999, MOD) GB/T17446 Terminology of fluid transmission system and components (GB/T17446-1998, idtISO5598:1985) GB/T17489 Hydraulic particle contamination analysis - Extracting liquid samples from working system pipelines (GB/T17489--1998, idtISO4021:1992) JB/T7858 Hydraulic component cleanliness assessment method and hydraulic component cleanliness index 3 Terms and definitions
The terms and definitions established in GB/T17446 and the following terms and definitions apply to this standard. 3.1
Nominal flow
Nominal flow
Nominal flow specified for hydraulic electro-hydraulic directional control valves and hydraulic directional control valves. 3.2
Test flow
The flow specified when testing the performance of the test valve. 4 Quantities, symbols and units
Quantities, symbols and units are shown in Table 1.
Table 1 Quantity, symbol and unit
Nominal diameter of valve
Volume flow
JB/T10373--2002
Inner diameter of pipe
Pressure, differential pressure
Oil density
Kinematic viscosity
Equivalent bulk elastic modulus
Note: M-
-Mass: L
Marking and basic parameters
5.1 Marking
Length: T
p, ap
Table 1 (continued)
Time: @
Temperature.
ML-IT-2
Pa (MPa)
s (min)
A clear and permanent mark or nameplate should be made at an appropriate and obvious position on the product. The content of the mark or nameplate shall comply with the provisions of GBT7935, and the graphic symbols used shall comply with the provisions of GB/T786.1. 5.2 Basic parameters
The basic parameters of hydraulic electro-hydraulic directional control valves and hydraulic directional control valves shall include: nominal pressure, nominal diameter, nominal flow, rated flow, slide valve function, and back pressure.
6 Technical requirements
6.1 General requirements
6.1.1 The nominal pressure series shall comply with the provisions of GB/T2346. 6.1.2 The plate connection installation surface shall comply with the provisions of GB/T2514. 6.1.3 The type and size of the threaded oil port shall comply with the provisions of GB/T2878, and 6.1.4 Other technical requirements shall comply with the provisions of GB/T7935. 6.1.5 The manufacturer shall specify the applicable conditions and environmental requirements of the product in the product samples and related materials. 6.2 Performance requirements
The performance requirements of electro-hydraulic directional control valves and hydraulic directional control valves shall include: switching performance:
Pressure loss;
Internal leakage:
Response time:
Minimum control pressure:
Sealing performance: Under rated working conditions, the static seals of electro-hydraulic directional control valves and hydraulic directional control valves shall not leak oil, and the dynamic seals shall not leak oil. No oil shall drip from the sealing part. Pressure resistance: Each pressure-bearing oil port of the hydraulic electro-hydraulic reversing valve and the hydraulic reversing valve shall be able to withstand 1.5 times the maximum working pressure of the oil port. There shall be no external leakage and parts damage. Durability: Under rated working conditions, the hydraulic electro-hydraulic reversing valve and the hydraulic reversing valve shall be able to withstand the specified number of actions, and its parts shall not have abnormal wear and other forms of damage. The decline of various performance indicators shall not exceed 10% of the specified value. 6.3 Assembly requirements
6.3.1 Assembly shall be in accordance with the provisions of GB/T7935. Internal cleanliness requirements shall be in accordance with the provisions of JB/T7858. 6.3.2
6.4 Appearance requirements
The appearance of the product shall be in accordance with the provisions of GB/r7935. 7 Performance test method
7.1 Test device
7.1.1 A test bench with a test circuit in accordance with Figure A.1. 7.1.2 Flow and pressure of oil source:
The flow of oil source should be adjustable and should be greater than the test flow of the valve under test. The pressure of oil source should be able to exceed the nominal pressure of the valve under test by 20% to 30% for a short time. JB/T10373-2002
7.1.3 It is allowed to add components to the given basic circuit to adjust pressure, flow or ensure the safe operation of the test system, but it should not affect the performance of the valve under test.
7.1.4 The inner diameter of the pipe and pipe joint connected to the valve under test should be consistent with the actual diameter of the valve under test. 7.1.5 Position of pressure measuring point.
7.1.5.1 Position of inlet pressure measuring point:
The inlet pressure measuring point should be set between the downstream of the disturbance source (such as valve, elbow, etc.) and the upstream of the valve under test, and the distance from the disturbance source should not be less than 10d (d is the inner diameter of the pipe). The distance from the valve under test should not be less than 5d. 7.1.5.2 Location of outlet pressure measuring point:
The outlet pressure measuring point should be set at least 10d downstream of the valve under test. 7.1.5.3 When testing according to Class C accuracy, the location of the pressure measuring point is allowed to be inconsistent with the above requirements, but the corresponding correction value should be given. 7.1.6 Pressure measuring hole:
The diameter of the pressure measuring hole should be no less than 1mm and no more than 6mm. 7.1.6.1
The length of the pressure measuring hole should be no less than 2 times the diameter of the pressure measuring hole. 7.1.6.2
The axis of the pressure measuring hole is perpendicular to the axis of the pipeline, and the intersection angle between the inner surface of the pipeline and the pressure measuring hole should maintain a sharp edge, but no burrs should be allowed. 7.1.6.3
The inner diameter of the connecting pipe between the pressure measuring point and the measuring instrument shall not be less than 3mm. When the pressure measuring point is connected to the measuring instrument, the air in the connecting pipe should be removed. 7.1.6.5
The temperature measurement point should be set at no more than 15d upstream of the inlet pressure measurement point of the tested valve. 7.1.8 The oil sampling point should be set in the test circuit and the liquid sample should be extracted in accordance with the provisions of GB/T17489. 7.2 Test conditions
7.2.1 Test medium
7.2.1.1 The test medium is general hydraulic oil. Temperature of test medium: Unless otherwise specified, type tests should be carried out at 50℃±2℃, and factory tests should be carried out at 50℃±4℃7.2.1.2
.
7.2.1.3 Viscosity of test medium: The kinematic viscosity at 40℃ is 42mm2/s~74mm2/s (special requirements shall be specified separately). Cleanliness of test medium: The solid particle contamination level of the test system oil shall not be higher than the level specified in GB/T14039-20027.2.1.4
—/19/16.
7.2.2 Steady-state condition
When the variation range of the average displayed value of the controlled parameter does not exceed the specified value in Table 2, it is regarded as a steady-state condition. The measured value of the test parameter shall be recorded under the steady-state condition7.2.2.1
Record the measured value of the test parameter under the steady-state condition.
Permissible variation range of the average displayed value of the controlled parameterTable 2
Permissible variation range of the average displayed value of the controlled parameter corresponding to each measurement accuracy levelControlled parameter
Pressure (%)
Flow (%)
Temperature ℃
Viscosity (%)
Measurement accuracy levelSee 7.2.5.
JB/T10373—2002
7.2.2.2 During the type test, the selection of the number of test parameter measurement readings and the distribution of the readings taken should be able to reflect the performance of the test valve in the entire range.
7.2.2.3 In order to ensure the repeatability of the test results, the test parameters should be measured at the specified time intervals. 7.2.3 Transient working conditions
7.2.3.1 The oil circuit volume from the output side of the test valve to the loading valve (including the oil circuit board connected to it) should be a closed volume at the beginning of the transient test, and this closed volume should be filled with oil before the test. The size of this closed volume and the cavity and pipeline materials should be recorded in the test report.
7.2.3.2 When the test valve is an externally controlled electro-hydraulic directional control valve or a hydraulic directional control valve, the pressure change rate of the control circuit shall enable the test valve to act quickly. The pressure change rate of the control circuit shall not be less than 700MPa/S. The pressure change rate of the control circuit refers to the ratio of the pressure change from 10% to 90% of the difference between the final steady-state pressure value and the initial steady-state pressure value to the corresponding time. 7.2.4 Test flow rate
7.2.4.1 When the specified rated flow rate of the test valve is less than or equal to 200L/min, the test flow rate is the rated flow rate. 7.2.4.2 When the specified rated flow rate of the test valve is greater than 200L/min, the test flow rate shall be allowed to be 200/min, but it must be evaluated under working conditions, and the performance indicators of the test valve shall be based on meeting the working conditions. 7.2.4.3 The factory test is allowed to be carried out at a reduced flow rate, but the corresponding correction value shall be given to the performance indicators. 7.2.5 Measurement accuracy level
The measurement accuracy level is divided into three levels: A, B and C. The type test should not be lower than level B, and the factory test should not be lower than level C. The allowable error of the measurement system corresponding to each level should comply with the provisions of Table 3. Table 3 Allowable system error of the measurement system
Parameters of measuring instruments and meters
Pressure (gauge pressure p<0.2MPa)
Pressure (gauge pressure p≥0.2MPa)
7.2.6 Electromagnet of the valve under test
Allowable error of the measurement system corresponding to each measurement accuracy levelB
During the factory test, the working voltage of the electromagnet should be 85% of its rated voltage. c
During the type test, the electromagnet should be continuously excited to its specified maximum stable temperature at the rated voltage of the electromagnet, and then the voltage of the electromagnet should be reduced to 85% of its rated voltage, and then the valve under test should be tested. 7.3 Test items and test methods
7.3.1 Factory test
Factory test items and test methods shall be as specified in Table 4. Table 4 Factory test items and test methods
Test items
Pressure resistance
Sliding valve function
Switching performance
Test method
Apply 1.5 times the maximum working pressure of each pressure-bearing oil port at a rate of 2% per second, and maintain the pressure for 5 minutes after reaching the pressure.
Switch and reset in sequence according to the function of the tested valve. At the same time, observe the oil flow of each oil port of the tested valve.
① Reversing test:
Adjust the relief valve 2-1 and the one-way throttle valve 6-1 (or 6-2) to make the pressure of the P port of the test valve 4 the nominal pressure, and then adjust the relief valve 2-2 to make the pressure of the T port of the test valve the specified back pressure value, and make the flow through the test valve 4 the test flow.
Test type
Test items
Reversing performance
Pressure loss
Internal leakage
Table 4 (continued)
Test method
When the test valve 4 is an electro-hydraulic reversing valve, make the solenoid of the test valve 4 meet 7.2.6, adjust the relief valve 2-3 so that the control pressure is the minimum control pressure of the test valve 4 (if the control oil is internal return oil, the control pressure is the minimum control pressure plus the specified back pressure value). Then energize and de-energize the electromagnet of the test valve, and continuously operate it for more than ten times to test the reversing and resetting (centering) of the test valve 4.
When the test valve 4 is a hydraulic reversing valve, adjust the relief valve 2-3 so that the control pressure is the minimum control pressure of the test valve, and then energize and de-energize the electromagnet of the solenoid valve 7, and continuously operate it for more than ten times to test the reversing and resetting (centering) of the test valve 4. ② Stay test
Under the test conditions, make the valve core of the test valve 4 stay in the original position and the reversing position for five minutes each. Then, the solenoid of the test valve 4 is energized and de-energized (for the test valve being an electro-hydraulic reversing valve), or the solenoid of the solenoid valve 7 is energized and de-energized (for the test valve being a hydraulic reversing valve), and the reversing and resetting (centering) of the test valve 4 are tested. The valve core of the test valve 4 is placed in each oil-passing position, and the flow through the test valve 4 is made the test flow. The pressure PP, PA, PB, and PT test pressure loss at each point are measured with pressure gauges 3-1, 3-2, 3-3, and 3-4 respectively.
For the two- and three-position four-way test valves: when the oil flow direction is PA, B→T, the pressure loss is △PP-A=PpPA, APB-T-PB-Pr, and when the oil flow direction is P→B, AT, the pressure loss is pP-B=pppB, △pA-T-pA-pr. For the three-position four-way valve with the middle position and the slide valve function with the oil flow direction of PT, a pressure loss test is required in the middle position, and the pressure loss is △pp·T-pp-Pr. For other slide valve functions, no test is performed in the middle position.
Adjust the relief valve 2-1 so that the pressure of the P port of the test valve 4 is the nominal pressure. According to the slide valve function and structure of the test valve 4, measure the internal leakage of the test valve 4 at different positions from port A (or port B) and port T respectively.
Before measuring the internal leakage: operate the test valve 4 continuously for more than ten times, and then measure the internal leakage after 30s.
For different slide valve functions, the internal leakage measurement diagram is as followsx
JB/T 10373—2002
Test type
JB/T103732002
Test items
Internal leakage
Package 4 (continued)
Test method
Test type remarks
Test items
Sealing
7.3.2 Type test
Table 4 (continued)
Test method
First, clean the valve to be tested. If some parts cannot be cleaned at one time and false leakage occurs after operation, it is allowed to be cleaned again. The inspection contents are divided into static seal and dynamic seal: (1) Static seal: Use clean absorbent paper to stick on the static seal and remove it at the end of the test. If there is oil stain on the absorbent paper, it is oil leakage.
(2) Dynamic seal: Place white paper under the dynamic seal until the end of the test. If there are oil drops, it is oil dripping.
Type test items and test methods shall be in accordance with the provisions of Table 5. Table 5 Type test items and test methods
Test items
Steady-state test
Test method
JB/T10373--2002
Test type
(1) According to the provisions of 7.3.1, test all items, and test and draw the characteristic curve diagram in the following method: a)
In the pressure loss test, cover the valve core of the test valve 4 at each oil-passing position, so that the flow rate through the test valve 4 gradually increases from zero to the test flow rate, and set several measurement points (the number of measurement points set should be sufficient to draw the flow-pressure loss curve), and use pressure gauges 3-1, 3-2, 3-3, and 3-4 to measure the pressure at each set point. Draw the flow-pressure loss curve shown in Figure A.2. During the internal leakage test, place the valve core of the test valve 4 in the specified measurement position, and gradually increase the pressure of the P oil port of the test valve 4 from zero to the nominal pressure. During this period, set several measurement points (the number of measurement points set should be sufficient to draw the pressure-internal leakage curve), and measure the internal leakage of each set point. Draw the pressure-internal leakage curve shown in Figure A.3.
(2) Working range test:
Make the solenoid of the test valve 4 meet the requirements of 7.2.6 (only for electro-hydraulic reversing valves), place the valve core of the test valve in a certain oil-passing position, fully open the one-way throttle valve 6-1 (or 6-2) and the relief valve 2-2, and make the indicated pressure of the pressure gauge 3-2 (or 3-3) the minimum load pressure. Then, gradually increase the flow through the test valve 4 from zero to a certain maximum set flow greater than the rated flow (this maximum set flow can be determined by each manufacturer according to the product level of the factory), set several flow points in the meantime, record the indicated pressure of the pressure gauge 3-1 corresponding to each flow point, draw the curve OD as shown in Figure A.4, adjust the relief valve 2-1 and the one-way throttle valve 6-1 (or 6-2) so that the indicated pressure of the pressure gauge 3-1 is the nominal pressure of the test valve 4. Gradually increase the flow through the test valve, and the test valve 4 should be able to reverse and reset (center) under the specified minimum control pressure. When the flow increases to a certain value and the test valve 4 cannot be reversed and reset under the specified minimum control pressure, adjust the relief valve 2-1 and the one-way throttle valve 6-1 (or 6-2) to reduce the indicated pressure of the pressure gauge 3-1 until the test valve 4 can be reversed and reset (center) under the specified minimum control pressure. According to this test method, until the maximum set flow. According to the data recorded in the above test, draw the curve ABC shown in Figure A4. The area contained by the curve ABCDO is the working range in which the test valve can normally change direction and reset (center), and the curve BC is the conversion area. Repeat the above test for no less than three times and draw the working range diagram shown in Figure A.4. a)
When the test valve is an electro-hydraulic directional control valve, it is assembled into an external control form, and the electromagnet of the test valve 4 meets the requirements of 7.2.6.
When the test valve is an electro-hydraulic directional control valve, if the control oil is internal return oil, the control pressure is the minimum control pressure plus the back pressure value of the oil port T of the test valve. For the test valves, which are electro-hydraulic directional control valves and hydraulic directional control valves, the change rate of the control pressure shall meet the following two conditions respectively, and the working range test shall be carried out respectively: Gradually increase the control pressure to the specified control pressure, and the control pressure change rate shall not exceed 0.02PN/s(a)
(p is the nominal pressure of the test valve):
Stepwise increase the control pressure to the specified control pressure, and the control pressure change rate shall not be less than 700MPa/s. 7
JB/T 10373—2002
Test items
Transient test:
a) Reversing
Time test:
Wrap 5 (continued)
Test method
The block diagram of the test system is shown in Figure A.5. The test method is as follows: Make the electromagnet of the test valve 4 meet the requirements of 7.2.6. Adjust the relief valve 2-1 and the one-way throttle valve 6-1 (or 6-2) to make the P oil port pressure of the test valve 4 the nominal pressure, and then adjust the relief valve 2-2 to make the T oil port pressure of the test valve 4 the specified back pressure value, and make the flow through the test valve the test flow or 80% of the flow qvB at point B in Figure A.4 (Note: (centering) time test. Durability test When 80%gvB is less than the test flow, the flow through the test valve is specified as the test flow: When 80%gve is greater than the test flow, the flow through the test valve is specified as the test flow and 80%qvB, where: the test flow is taken as the assessment flow, and 80%gv is taken as the flow reflecting the level). Then adjust the relief valve 2-3 to make the control pressure the minimum control pressure of the test valve (if the control oil is internal return oil, the control pressure is The minimum control pressure plus the specified back pressure value) and the maximum control pressure.
According to the above test conditions, the solenoid of the test valve 4 is energized and de-energized at the rated voltage (for the test electro-hydraulic directional control valve) or the solenoid of the solenoid valve 7 is energized and de-energized at the rated voltage (for the test hydraulic directional control valve) to make the test valve change and reset (center). The displacement sensor (displacement method) or pressure sensors 3-2, 3-3, 3-6, 3-7 (pressure removal) are used to record the change and reset (centering) of the test valve 4 with a recorder to obtain the change time, change lag time, reset (centering) time and reset (centering) lag time of the test valve 4. The transient response curve is shown in Figure A.6 and Figure A.7. a)
When the test valve is an electro-hydraulic directional control valve, it is assembled into an external control form. b)
The pressure change rate of the control circuit shall meet 7.2.3.2. Adjust the relief valve 2-1 and the one-way throttle valve 6-1 (or 6-2) to make the P oil port pressure of the test valve 4 the nominal pressure, then adjust the relief valve 2-2 to make the T oil port pressure of the test valve 4 the specified back pressure value, and make the flow through the test valve 4 the test flow, and then adjust the relief valve 2-3 to make the control circuit reach the appropriate control pressure. The test valve 4 is continuously reversed at a frequency of 60 times/min to test the number of reversals of the test valve 4. When the number of reversals specified in the durability index is reached, check the main parts and main performance indicators of the test valve 4. The tested electro-hydraulic directional valves are assembled into external control form for durability testing. 8 Inspection of assembly and appearance
Inspection methods of assembly and appearance shall be in accordance with the provisions of Table 6. Table 6 Inspection methods of assembly and appearance
Inspection rules
Inspection classification
Inspection items
Assembly quality
Internal cleanliness
Appearance quality
Product inspection is divided into factory inspection and type inspection. 9.1.1 Factory inspection
Inspection method
Visual inspection method,
In accordance with the provisions of JB/T7858
Visual inspection method.
Factory inspection refers to the various inspections that should be carried out when the product is delivered. Inspection type
Motor-shift
valves only test
switching
time and
(centering)
time.
The items and methods of performance inspection shall comply with the provisions of 7.3.1, and the performance requirements shall comply with the provisions of 6.2. The inspection methods for assembly and appearance shall comply with the provisions of Chapter 8, and the quality shall comply with the requirements of 6.3 and 6.4. 9.1.2 Type inspection
Type inspection refers to the comprehensive assessment of product quality, that is, comprehensive inspection according to the technical requirements specified in the standard. Type inspection shall be carried out in any of the following situations: 8
Trial production and identification of new products or old products transferred to the factory for production; a)
After formal production, if there are major changes in structure, materials, and processes that may affect product performance; b)
When the product is resumed after a long period of suspension; c
When the factory inspection results are significantly different from the previous type inspection results; d)
e) When the national quality supervision agency proposes a type inspection requirement. JB/T 10373—2002
The items and methods of performance inspection shall be in accordance with the provisions of 7.3.2, and the performance requirements shall comply with the provisions of 6.2: The inspection methods for assembly and appearance shall be in accordance with the provisions of Chapter 8, and the quality shall comply with the requirements of 6.3 and 6.4. 9.2 Sampling
The sampling plan for product inspection shall be in accordance with the provisions of GB/T2828 Note: Quality supervision inspection sampling shall be in accordance with relevant regulations. 9.2.1
Factory inspection sampling,
a) Qualified quality level (AQL value): 2.5; b) Sampling plan type: Normal inspection one-time sampling plan; c)
Inspection level: General inspection level II: The size of the pressure resistance test sample is 3/1000, but shall not be less than two units. 9.2.2
Type inspection sampling
Qualified quality level (AQL value): 2.5 [6.5]: a)
Sampling plan type: Normal inspection one-time sampling plan: b)
Sample size: 5 units [2 units]
Note: The values in square brackets are only applicable to durability tests. Internal cleanliness inspection sampling
Qualified quality level (AQL value): 2.5: a)
Sampling plan type: Normal inspection one-time sampling plan; b)
Inspection level: Special inspection level S-2.
9.3 Decision rules
According to GB/T2828.
Marking, packaging, transportation and storage
Marking, packaging, transportation and storage shall be in accordance with GB/T7935. Special requirements may be specified separately.
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