This standard specifies the general valve cleanliness index, sampling regulations, basic requirements and measurement methods. JB/T 7748-1995 Valve cleanliness and measurement methods JB/T7748-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Valve Cleanliness and Determination Method
Subject Content and Scope of Application
This standard specifies the general valve cleanliness index, sampling regulations, basic requirements and determination methods. This standard is applicable to the determination of the cleanliness of various valves. 2 Reference Standards
GB6004 Metal Wire Braided Square Hole Mesh for Test Sieve Solvent Oil for Rubber Industry
SH 0004
3 Terms
3.1 Cleanliness
JB/T 7748 --- 95
The degree of cleanliness of the inner cavity of the valve, which is measured by the amount of impurities and dirt attached to the surface of the valve inner cavity in contact with the medium (including all internal parts surfaces and blind holes).
3.2 Cleanliness Index
The maximum allowable amount of impurities and dirt contained in the inner cavity of the tested valve. 3.3 Constant
The object to be measured is dried and weighed repeatedly to make its mass reach a constant value. 3.4 Turbid liquid
Cleaning liquid containing impurities in the sampling part.
4 Cleanliness index
The cleanliness index is calculated according to formula (1):
G = S(DN/25)2
Where G-
The maximum allowable value of impurities and dirt, g:
Constant (selected according to Table 1);
Nominal diameter of the valve to be measured (when DN<25mm, calculate according to DN=25mm), mm. Table 1
Gate valve, stop valve, throttle valve, check valve, drain valve
Ball valve, butterfly valve, plug valve, plunger valve, cylinder valve, diaphragm valve, safety valve, pressure reducing valve, steam trap materials
Forged steel (including forging welding), forged copper
Cast steel (including plate welding), cast copper
Various materials
Approved by the Ministry of Machinery Industry of the People's Republic of China on June 2, 1995 676
Implementation on January 1, 1996
5 Sampling regulations
JB/T7748-95
The valves to be tested can be randomly selected from the qualified products at the end of the production line, or randomly selected from the finished product warehouse. 5.2
The minimum batch and sampling quantity for sampling shall be in accordance with the provisions of Table 2. Table 2
Nominal diameter DN, mm
50~200
250~350
100-600
650～1000
>1 000
Basic requirements
6.1 Measurement environment and measurement personnel
6.1.1 The measurement environment should be clean and meet the measurement requirements. Minimum batch
Sampling quantity
6.1.2 The measurement personnel should be familiar with the structure of the valve to be measured and master the cleanliness measurement technology. The measurement personnel's clothes, hats and hands should be clean during the measurement.
6.2 Measurement instruments, equipment, cleaning utensils and cleaning fluids 6.2.1 Cleaning utensils should be selected from clean basins, magnets, syringes, nylon brushes, paintbrushes, etc. (Cotton yarn and foam plastics that are difficult to dry are not allowed). After cleaning the cleaning tools, visual inspection and hand feel should be carried out to check if there are no foreign objects. 6.2.2 The filter should be a square hole screen specified in GB6004, and its model is SSW0.063/0.045 (equivalent to 235 mesh/inch). The oven should be a far infrared drying oven or an electric blast drying oven. 6.2.3
6.2.4 The sensitivity of the analytical balance for weighing is 1/10000g for valves DN<50mm and 1/100g for valves DN=50mm. 6.2.5 The cleaning fluid is kerosene, detergent or flux oil that meets the requirements of SH0004. Determination method
7.1 Preparation
7.1.1 The determination should be carried out in a dry and clean room. 7.1.2 Use SSW0.063/0.045 to clean the filter and filter the cleaning fluid. 7.1.3 Place the SSWO.063/0.045 filter in a clean cleaning solution for cleaning, take it out and place it in a 105C5C oven after the cleaning solution is slightly dry, take it out after 60 minutes, place it in a dryer to cool for 30 minutes and weigh it; repeat the drying and weighing until the difference between two consecutive weighings is no more than 4/10000g for valves with DN<50mm and no more than 1/100g for valves with DN=50mm. At this time, record the initial mass of the filter as G3.
7.1.4 The sampling location shall be in accordance with the provisions of Table 3.
Parts name
Valve body, valve cover
Shoulder and all parts in the inner cavity
7.2 Measurement steps
Sampling position
Inner surface and channel
Surface in the valve cavity
JB/T 7748 95
7.2.1 Wipe off dirt from non-sampling positions to prevent it from falling into the cleaning basin. 7.2.2 Disassemble the valve to be tested and take out all parts in the inner cavity. Press fittings and connectors that are not suitable for disassembly can be left unassembled. 7.2.3 According to the sampling position specified in Table 3, place the parts on the top of the cleaning basin and brush them repeatedly with nylon brushes, paintbrushes and syringes. After cleaning, the sampling position should be visually inspected and felt to be free of foreign matter. 7.2.4 Use a magnet to suck out iron filings at the bottom of the blocked hole, put them into the mixed liquid, and then rinse them clean. 7.2.5 Rinse the used nylon brushes, paintbrushes and basins with clean cleaning liquid, and pour all the impurities into the above turbid liquid. 7.2.6 Filter the above turbid liquid with a SSW0.063/0.045 constant weight filter to collect all impurities and dirt. 7.2.7 Bake the filter containing impurities and dirt in an oven at 105°C ± 5°C for 60 minutes, take it out, put it in a desiccator and cool it for 60 minutes, and then weigh it on a balance. Dry, cool and weigh the filter containing impurities and dirt several times until the difference between two consecutive weighings is no more than 4/10000g for a DN50mm valve and no more than 1/100 for a DN250mm valve. At this time, record the mass as G2: www.bzxz.net
7.3 Cleanliness
7.3.1 Cleanliness (mass of impurities and dirt) is calculated according to formula (2): G2 = G2 - G3
Where: G: —- Actual mass of impurities and dirt, g: \ —- Total mass of filter, impurities and dirt, g; G Initial mass of filter·g:
7.3.2 The result of cleanliness determination is expressed as the average value of the cleanliness of the samples taken. 7.4 Cleanliness determination report
Fill in the determination data in the report according to the contents of Appendix A (reference). 678
Product name
Product model, specification
Product number
Cleanliness index. Name
Conclusion and suggestion
Determination personnel
Additional instructions:
JB/T 7748 - 95
Appendix A
Valve cleanliness measurement report
(reference)
Initial quality of filter screen·g
Verifier
This standard is proposed by the National Technical Committee for Valve Standardization. Total quality of filter screen, impurities and dirt
This standard is under the jurisdiction of the Hefei General Machinery Research Institute of the Ministry of Machinery Industry. This standard was drafted by the Hefei General Machinery Research Institute of the Ministry of Machinery Industry. The main drafter of this standard is Yuan Tongzhen.
Filter element
Cleaning fluid
Cleanliness·&
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