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6.1.2 The outlet pressure measurement point should be located downstream of the test valve, with a minimum distance of 10d from the valve.
6.2 A temperature measurement point should be placed downstream of the outlet pressure measurement point, and the distance between the two should not be less than 5d.
6.3 The flow measurement point should be positioned downstream of the temperature measurement point, with a minimum separation of 5d between them.
6.4 The tubing used must be straight, and the diameter of the holes in the axial direction should be consistent.
6.5 The size of the tubing and related fittings should match the inlet and outlet ports of the valve. The tubing should be installed as horizontally as possible to ensure accurate measurements.
6.6 Pressure Testing Hole
6.6.1 The diameter of the pressure testing hole must be at least 1mm and no more than 6mm.
6.6.2 The length of the pressure-measuring hole should be at least twice its diameter.
6.6.3 The centerline of the pressure measuring hole should be perpendicular to the centerline of the tubing. The intersection angle between the inner surface of the tubing and the pressure measuring hole should be sharp, with no burrs or rough edges.
6.6.4 The connection between the pressure measuring point and the measuring instrument pipe should have a diameter of at least 3mm.
6.6.5 When connecting the pressure measurement point to the measuring instrument, all air in the connecting pipe must be purged to avoid measurement errors.
7 Test Methods
7.1 Test Run
Under nominal pressure and rated flow conditions, the valve should undergo 20 consecutive switching operations, and it must meet the requirements specified in section 4.1.
7.2 Pressure Loss Test
7.2.1 Full Flow Range Pressure Loss Test
Adjust the test system so that the flow rate varies from zero to the rated flow. At least four points should be measured across this range to determine the pressure loss from the inlet to the outlet. A pressure loss versus flow curve should be plotted.
7.2.2 Pressure Loss Test at Rated Flow Rate
Measure the pressure loss across the valve at rated flow, including the pressure drop from the inlet to the working port and from the working port to the outlet.
Note: During the pressure loss test, the outlet pressure must be above 0.1MPa.
7.3 Internal Leak Test
Adjust the test system so that the inlet pressure is at the nominal pressure. Depending on the spool valve function and structure, internal leakage should be measured from both the working port and the return port under any operating position. The results must meet the requirements outlined in section 4.3.
Note:
â‘ During the internal leak test, the pressure on the outflow side must be atmospheric.
â‘¡ The pressure must be increased from atmospheric to the nominal pressure within 15 seconds.
7.4 Pressure Test
Block the working oil port and apply pressure to the valve’s inlet port while in the actuated position. If the nominal pressure is ≤16MPa, apply 1.5 times the nominal pressure; if it is >16MPa, apply 1.25 times the nominal pressure. Maintain the pressure for 3 minutes and check for oil leakage. The outlet pressure should remain at atmospheric. The test result must comply with the requirements in section 4.4.
7.5 Durability Test
Perform 100,000 continuous switching cycles on the sliding valve under nominal pressure and rated flow conditions. Afterward, evaluate the pressure loss and leakage performance.
8 Inspection Rules
8.1 Type Test
8.1.1 A type test refers to a comprehensive evaluation of the valve's quality and performance.
8.1.2 Type tests must be conducted under the following conditions:
a) For newly manufactured directional valves (including product conversions).
b) When changes occur in design, process, or materials that may affect the valve’s performance.
c) If previous type tests showed non-conformities in pilot valves.
d) Every three years for batch-produced valves.
Test items include: a) commissioning test; b) full flow range pressure loss test; c) internal leakage test; d) pressure test; e) durability test.
8.1.3 For type testing, at least three samples are required. One sample undergoes a full test, while the others are tested for specific performance aspects. If any item fails, the number of samples must be doubled for retesting. If the second test still fails, the type test is considered unsuccessful.
8.2 Factory Test
Factory tests must be completed before the product leaves the factory. The test items include: a) commissioning test; b) pressure loss test at rated flow; c) internal leakage test; d) pressure test.
8.3 Decision Criteria
8.3.1 The factory test items for the pilot valve must be divided into sub-tests and full tests, with sampling methods based on GB/T 2828.
8.3.2 The ordering party reserves the right to conduct a re-test of the reversing valve according to the factory test items and requirements. The re-sampling method follows GB/T 2828.
8.3.3 Special orders require joint development of test conditions and rules by the design, manufacturing, and user units.
9 Marking, Packaging, Transportation, and Storage
9.1 Identification
The reversing valve nameplate should be affixed to the product and include the following information:
a) Product name, model, and symbol.
b) Main technical parameters.
c) Manufacturer's name.
d) Manufacturing date.
9.2 Packaging
The valve should be packaged in moisture-proof materials. The packaging box must be sturdy and clearly marked with the following details:
a) Product name, type, and quantity.
b) Total mass (kg), net weight (kg).
c) Manufacturer's name, address, and destination station.
d) Packing date.
9.3 Transportation
During transportation, handle the reversing valve with care, and do not stack it higher than 1m. Ensure protection against moisture and rain.
9.4 Storage
Store the reversing valve in a dry, well-ventilated area. Avoid storing it with chemicals.
9.5 Accessories
The package should include the following:
a) Product certification.
b) User manual.
c) Spare seals and dust covers.
d) Packing list.
Additional Note: This standard was proposed by the State Bureau of Machinery Industry. It is managed by the National Automotive Standardization Technical Committee. The standard was drafted by Qingdao Special Purpose Vehicle Factory.