This standard specifies the method of conventional sealing test of general valve packing and the requirements for test equipment. This standard is applicable to the sealing performance test of valve packing with reciprocating valve stem movement. It can also be used as a reference for the sealing performance test of valve packing with spiral valve stem movement. JB/T 7760-1995 Valve Packing Sealing Test Specification JB/T7760-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T7760-95
Valve Packing Seal Test Specification
Published on June 16, 1995
Ministry of Machinery Industry of the People's Republic of China
Implementation on July 1, 1996
Mechanical Industry Standard of the People's Republic of China
Valve Packing Seal Test Specification
1 Subject Content and Scope of Application
This standard specifies the method of general valve packing seal test and the requirements for test equipment. JB/T7760-95www.bzxz.net
This standard is applicable to the valve packing seal performance test of valves with reciprocating stem motion, and the valve packing seal performance test of valves with spiral stem motion can also be used for reference.
2 Terminology
Packing test life: The cumulative number of times the valve stem is opened when the packing seal fails under the specified test conditions. Packing seal failure: Under the specified test conditions, tighten the packing gland, and the leakage rate still exceeds the specified value. b.
3 Test device
The sealing test is carried out on a special packing seal test device. The test device is mainly composed of a packing gland loading and measuring system, a valve stem reciprocating motion drive system, a medium setting and control system, a medium heating and control system, a measuring system and a simulated Langmen stuffing box. The schematic diagram of the device system is shown in Figure 1. The design and manufacture of the device shall comply with the following provisions. 1-Valve stem reciprocating motion drive system: 2, 5-Packing gland force loading and measuring system, 3-Medium heating and control system: 4-Simulated Langmen packing gland: 7-Medium setting system: 6.8-Humidity measuring system Figure 1 Packing seal test device system diagram
3.1 The measurement accuracy of the packing gland clamping force shall not be less than 1%. 3.2 The valve stem reciprocating motion drive system in the test device shall be able to ensure the smooth and uniform movement of the valve stem. 3.3 The test device should be equipped with a medium pressure stabilizing device to ensure that the medium pressure fluctuation value is within the range of ±2% of the specified value of the test medium pressure. Approved by the Ministry of Machinery Industry on June 16, 1995
Implementation on July 1, 1996
JB/T7760-95
3.4 ​​The medium heating system in the test device should be able to ensure that the medium temperature in the sealing chamber is stable and uniform, and can keep the medium temperature in the sealing chamber within the range of ±10℃ of the specified temperature of the test. 3.5 The test device should be equipped with a device for collecting and measuring the leaked medium. 3.6 The dimensional tolerance and surface roughness of the simulated valve stuffing box and valve stem in the test device shall comply with the provisions of the relevant valve standards. 4 Test parts
4.1 Test medium
The test medium is clean water. If there are special requirements, they will be negotiated separately. 4.2 Test medium pressure
The test medium pressure is recommended to adopt seven pressure levels: 1.6, 2.5, 4.0, 6.4, 10.0, 16.0, 25.0MPa. Special circumstances shall be agreed upon separately.
Test medium temperature
The test medium temperature is recommended to adopt six levels: room temperature, 150℃, 250℃, 350℃, 450℃, 550℃. Special circumstances shall be agreed upon separately. 4.4 Packing gland preload
The packing gland preload shall be determined according to the packing type, medium pressure and temperature. 4.5 Allowable leakage rate
The allowable leakage rate of packing is L≤5mL/h. If there are special circumstances, it can be agreed upon separately. 4.61
Valve stem opening frequency
The valve stem opening frequency shall not be less than twice per minute. 4.7 Valve stem movement stroke
The valve stem movement stroke is equal to the sum of the test packing heights in each figure. 5 Test procedure
5.1 Correctly install the packing into the clean packing box, and record the type, number of packing and the mass of the packing after baking. When installing in combination, the combination form should also be recorded.
5.2 Tighten the gland nut evenly and steadily so that the gland clamping force reaches the selected preload force. 5.3 Input the medium, turn on the medium heating device, and make the medium temperature and pressure reach the test selected value. 5.4 Start the valve stem reciprocating motion drive device to make the valve stem move quickly and smoothly, record the gland clamping force, medium temperature, medium pressure, and valve stem opening frequency at this time, and start counting the number of valve stem openings. 5.5 Record the gland clamping force, medium pressure, medium temperature, valve stem opening times and leakage rate during this period every 30 minutes. 5.6 When the medium leakage rate exceeds the specified value, tighten the gland nut, and measure the leakage rate during this period of time after 10 minutes. If the leakage rate does not exceed the specified value, continue the test according to Article 5.5, and restart the number of times the valve stem is opened. If the leakage rate exceeds the specified value, continue to tighten the gland nut until the leakage rate does not exceed the specified value. 5.7 When the packing seal fails, end the test and record the test data at this time. The recording items are the same as Article 5.5. 5.8 After the test, wait until the medium pressure and temperature drop to normal pressure and room temperature, carefully take out the packing, dry it and weigh it. 6 Test results and calculations
6.1 Determination of packing test life
6.1.1 The number of times the valve stem is opened when the leakage rate exceeds the specified value for the first time is the packing primary compression test life. 6.1.2 The number of times the valve stem is opened when the leakage rate exceeds the specified value for the second time is the packing secondary compression test life. And so on. 6.1.3 The packing test life is the sum of the compression test lives before the packing seal fails. 6.2 Packing wear is calculated by formula (1):
JB/T7760-95
Packing wear after the wide bar is opened N times·g: In the formula, W-
—Packing mass before the test, g:
Packing mass after the test, g.
Test report
The test report should include the following contents:
Indicate that it is carried out in accordance with this standard;
Stuffing box and rack dimensions:
Packing type, specification, brand, manufacturer, packing assembly structure:
Test conditions;
Test results (packing test life times, wear, gland clamping force when seal fails) test date, personnel.
Additional remarks:
This standard is proposed and managed by the Hefei General Machinery Research Institute of the Ministry of Machinery Industry, and this standard is drafted by the Hefei General Machinery Research Institute of the Ministry of Machinery Industry. The main drafter of this standard is Wang Qiang.
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