This standard specifies the basic requirements for the manufacture, inspection, testing and acceptance of fusible alloy plugs. This standard applies to fusible plugs installed on gas cylinders. Fusible alloys used in gas cylinder valves should also comply with the provisions of this standard. GB 8337-1996 Fusible alloy plugs for gas cylinders GB8337-1996 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Fusible plug for gas cylinders
Fusible plug for gas cylinders1Subject content and scope of application
GB 8337-1996
Replaces GB8337--87
This standard specifies the basic requirements for the manufacture, inspection, testing and acceptance of fusible alloy plugs (hereinafter referred to as fusible plugs). This standard applies to fusible plugs installed on gas cylinders, and fusible alloys used in gas cylinder valves should also comply with the provisions of this standard. 2 Reference standards
GB469 Lead ingot
GB914 Cadmium ingot
GB 915
GB 7306
GB8335
3 Terms
3.1 Fusible plugbZxz.net
Pipe thread sealed with thread
Special thread for gas cylinder
A detachable pressure relief device that is activated by the flow or melting of the fusible alloy installed in the plug hole, cannot be closed again. Under normal circumstances, the plug hole is in a closed state; at a given temperature, the fusible alloy in the plug hole flows or melts, releasing the medium to relieve the pressure of the gas cylinder, so as to prevent accidents caused by overpressure of the medium in the gas cylinder due to temperature rise. 3.1.1 Plug body
A detachable component with a plug hole, the plug hole of which is used to inject fusible alloy. 3.1.2 Fusible alloy
A low melting point alloy composed of low melting point metal materials in weight ratio. 3.2 The flow temperature of fusible alloy
refers to the temperature of the glycerine bath when the fusible alloy sample melts when tested in accordance with the provisions of Article 5.2. 3.3 The action temperature of fusible plug
refers to the temperature of the glycerine bath when the fusible alloy in the fusible plug flows or melts to release the gas in the bottle when tested in accordance with the provisions of Article 5.3. 3.4 Batch
The number of fusible plugs of the same specification, the same fusible alloy formula, the same manufacturing process and the same furnace of fusible alloy continuously poured. 4 Technical requirements
4.1 The basic structure of fusible plug
The fusible plug consists of two parts: the plug body and the fusible alloy. Its basic structure is shown in Figure 1. Approved by the State Bureau of Technical Supervision on March 28, 1996 and implemented on November 1, 1996
4.2 Flow temperature of fusible alloy
GB8337---1996
Fusible alloy
Figure 1 Schematic diagram of the basic structure of fusible plug
The flow temperature of fusible alloy should be able to meet the requirements of the operating temperature of fusible plug. 4.3 Operating temperature of fusible plug
The operating temperature of fusible plug is divided into two types, 100±5℃ for dissolving acetylene cylinders; 70±℃ for other cylinders. 4.4 Plug body
4.4.1 Plug body material
4.4.1.1 The plug body material should have sufficient corrosion resistance and mechanical properties, and shall not react chemically with the medium contained in the cylinder. 4.4.1.2 The plug body material should be copper alloy, steel or other suitable metals. The plug body of the fusible plug used for dissolving acetylene gas cylinders shall be made of copper alloy with a copper content of no more than 70%.
4.4.1.3 The chemical composition and mechanical properties of the plug body material shall comply with the relevant technical standards and meet the requirements for manufacturing and use. 4.4.2 Basic type of plug body
4.4.2.1 The basic type of plug body is shown in Figure 2. Its structure shall ensure sufficient strength and no deformation during use. A
Step hole
Figure 2 Schematic diagram of basic type of plug body
Threaded hole
4.4.2.2 The outer thread of the plug body shall adopt the PZ27.8 or PZ19.2 tapered thread specified in GB8335 or the R1/4 or R1/8 tapered thread specified in GB7306.
4.5 Fusible alloy
4.5.1 The raw materials for preparing fusible alloy shall have a quality certificate. 4.5.2 Formula of fusible alloy
Fusible alloy shall be composed of bismuth, lead, tin and cadmium in different weight ratios, and shall be a eutectic alloy with a bismuth content of not less than 48%. For the formula, refer to Appendix A (reference).
4.5.3 Purity of raw materials of fusible alloy
Bismuth: shall not be lower than the requirements specified in Bi-2 of GB915; lead: shall not be lower than the requirements specified in Pb-2 of GB469; tin: shall not be lower than the requirements specified in Sn-2 of GB728; cadmium: shall not be lower than the requirements specified in Cd-3 of GB914. 4.5.4 Preparation of fusible alloy
4.5.4.1 After the formula of fusible alloy is determined, weigh it according to the proportion of the formula and melt it into liquid in the order of bismuth, lead, tin and cadmium. 564
GB8337-1996
4.5.4.2 During the mixing process of bismuth and lead, the temperature should not exceed 371℃; when adding tin and cadmium, the temperature should not exceed 260℃. 4.5.4.3 After the raw materials are melted, they should be cast into fusible alloy rods or ingots. 4.5.4.4 The casting of each furnace of fusible alloy should be carried out continuously in the same shift. During casting, the casting temperature should be higher than the flow temperature of the fusible alloy, and before each casting, the slag, dirt, metal oxides and other impurities floating on the surface of the liquid should be cleaned. 4.5.4.5 Each cast fusible alloy rod or ingot should have a permanent and obvious furnace number mark. 4.6 Pouring fusible alloy
4.6.1 Before pouring the fusible alloy, the plug body should be thoroughly cleaned to remove impurities such as oil and rust in the plug hole. 4.6.2 After the plug hole is cleaned, it is advisable to coat the surface of the plug hole first. Tin or tin-lead alloy is recommended as the coating material. 4.6.3 Use one of the following methods to pour the fusible alloy into the plug hole: 4.6.3.1 Heat the plug body to a certain temperature, which is slightly higher than the flow temperature of the fusible alloy, and then pour the melted fusible alloy into the plug hole.
4.6.3.2 Heat the plug body to a certain temperature, and then insert the fusible alloy rod into the plug hole to melt the fusible alloy in the plug hole. 4.6.3.3 Insert the fusible alloy rods of predetermined length or size into the plug hole, and then heat them to melt the fusible alloy. When using this method, the temperature must be strictly controlled to avoid overheating. 4.6.4 During the pouring process of the fusible alloy, the heating should be uniform and overheating should be avoided. 4.6.5 After pouring, the fusible alloy should fill the entire plug hole, and the excess should be removed. 5 Inspection and test methods and acceptance rules
5.1 Inspection of plug body outer threads
Use a gauge to inspect the plug body outer threads one by one. The plug body outer threads must comply with the provisions of Article 4.4.2.2. Plug bodies that fail the inspection shall not be poured with fusible alloys.
5.2 Fusible alloy flow temperature test
5.2.7 Two samples are selected from each furnace of fusible alloy for testing. The sample diameter is 6mm and the length is 50mm. 5.2.2 Support the sample horizontally on a knife edge at a distance of 25mm, with both ends extending 12.5mm outside the knife edge, and then pour it into the inner glycerin tank. The temperature is controlled by the outer glycerin tank. See Figure 3 for the test device. Thermometer
158688887
Heater
Effective alloy sample
Inner glycerin tank
Outer glycerin tank
Figure 3 Schematic diagram of the test device for the flow temperature of fusible alloy 5.2.3 The two samples should be tested at the same time. The thermometer used for temperature measurement is inserted into the glycerin bath and placed between the two samples. The bulb of the thermometer is kept at the same level as the sample. The heating rate of the glycerin bath shall not exceed 2℃/min. During the test, the glycerin should be stirred to make the temperature uniform. 5.2.4 The temperature at which the second fusible end of the four ends of the two samples melts is the flow temperature of the fusible alloy. 5.2.5 Acceptance rules
The flow temperature of the fusible alloy shall meet the requirements of Article 4.2. 565
5.3 Fusible plug test
GB8337--1996
5.3.1 Fusible plugs are produced in batches of no more than 3,000. 5.3.2 Select two samples from each batch of fusible plugs and test them in accordance with the provisions of 5.3.3 and 5.3.4. 5.3.3 Fusible plug anti-extrusion test
Apply compressed air to the end of the sample in contact with the internal medium of the gas cylinder, with a pressure of 3.4 MPa, and maintain it at a temperature not lower than 60°C for 24 hours, and then check the other end. It is qualified if there is no leakage and no visible extrusion of fusible alloy. 5.3.4 Fusible plug action temperature measurement test
See Figure 4 for the test device. Tighten the two test specimens that have passed the test in accordance with Article 5.3.3 on the support, with the end in contact with the internal medium of the gas cylinder facing downward, and pass compressed air into this end, the pressure of which shall not be less than 0.02MPa; at the same time, immerse the sample in a glycerin bath, with the thermometer as close as possible to the fusible plug, and the temperature of the glycerin bath shall be within 3°C below the specified minimum temperature. Maintain this pressure and temperature for 10 minutes, and there shall be no air seepage or spraying. Then, increase the temperature of the glycerin bath, the heating rate shall not exceed 2°C/min; at the same time, increase the pressure, the pressure shall not exceed 0.35MPa. When the fusible alloy in the sample is squeezed out to cause gas leakage, record the temperature of the glycerin bath at this time as the operating temperature of the fusible plug, which should meet the requirements of Article 4.3.
When conducting the above test, it is allowed to stir the glycerin to make the temperature uniform. 5.3.5 Acceptance rules
Both samples should meet the requirements of Articles 5.3.3 and 5.3.4, and the batch is qualified. Otherwise, four more samples should be selected from the same batch for testing. If any one of the four samples still fails to meet the requirements, the batch will be scrapped. Figure 4 Schematic diagram of fusible plug test device
1—fusible plug sample; 2-thermometer; 3-temperature measuring connecting hole; 4-heater: 5-glycerin tank; 6-heating test part; 7-air compression tank; 8-pressure gauge 5.4 Fusible plug air tightness test
Fusible plugs should be tested for air tightness one by one. The test pressure is the air tightness test pressure of the gas cylinder. The pressure holding time should not be less than the pressure holding time of the gas cylinder air tightness test. No leakage is qualified. 566
The inspection and test items of fusible plugs are shown in Table 1. Table 1
Inspection and test items
Plug external thread inspection
Fusible alloy flow temperature test
Fusible plug test
Fusible plug air tightness test
6 Marking
GB8337-1996
Table of inspection and test items for fusible plugs
Inspection one by one
Batch test
6.1 A permanent mark should be made on the end surface of the fusible plug that contacts the outside. The mark should be clear and firm. 6.2 Marking items include:
Nominal operating temperature of fusible plug: 70℃ or 100℃; production batch number;
Manufacturer code;
d. Year and month of manufacture.
Judgment basis
6.3 Marking sequence
The markings shall be arranged along the circumference, and the items shall be arranged clockwise in the order of a, b, c, d in 6.2. For example (see Figure 5): Production batch number
Nominal operating temperature of fusible plug
7 Batch quality certificate
Manufacturer code
Manufacture year and month
Each batch of fusible plugs shall have a quality certificate. The format of the batch quality certificate is shown in Appendix B (reference). 8 Others
8.1 Ventilation measures shall be taken during the preparation, casting and pouring of fusible alloys. 8.2 Safety protection measures shall be adopted when conducting fusible plug tests. 567
Alloy weight percentage, %
Actual operating temperature of fusible plug
Plug body material
Plug body outer thread type
Manufacturing year and month
Production batch number.
GB8337-1996
Appendix A
Fusible alloy formula
(reference)
Starting point
Appendix B
Melting zone temperature, C
Ending point
Batch quality certificate for fusible plugs
(reference)
×××××××××/
Batch quality certificate for fusible plugs
Plug hole type
This batch of fusible plugs has a total of,
After inspection and testing, this batch of fusible plugs meets the requirements of GB8337--1996. Inspection Section Chief (Seal)
Dead Weight Flow Point
Year/Month/Date
Additional Notes:
GB8337—1996
This standard was proposed by the Ministry of Labor of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Standardization of Gas Cylinders. The main drafters of this standard are Wu Hong, Qiu Changjian and Shi Jingyuan. 569
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