Some standard content:
National Standard of the People's Republic of China
Subject content and scope of application
Asbestos-rubber sheets
GB/T 3985—1995
Replaces GB3985—83
This standard specifies the product grades, specifications, technical requirements, test methods, inspection rules, marking, packaging, storage and transportation of asbestos rubber sheets. This standard is applicable to sealing gasket materials used in equipment and pipeline flange connections with water, steam and other media as the main media within the temperature range of 450℃ and pressure range of 6MPa.
Referenced Standards
GB541 Test method for tensile strength of asbestos rubber sheets GB544． Asbestos rubber sheet
Density test method
GB 2828
GB3986
GB 3987
GB3988
GB8170
Counting sampling procedure and sampling table for batch inspection (applicable to inspection of continuous batches) Test method for loss on ignition of asbestos rubber sheet
Test method for aging coefficient of asbestos rubber sheet
Test method for compression rate and rebound rate of asbestos rubber sheet Numerical rounding rules
GB/T 15520
Asbestos rubber sheet
3 Product brand and specification
Steam sealing performance test method
3.1 Product brand and color shall comply with the provisions of Table 1. Table 1
3.2 Product specifications:
3.2.1 The thickness and deviation of the product shall comply with the provisions of Table 2. Thickness
0. 5,0.6,0.8,1.0
3.0 and above
National Technical Supervision Week 1995-04-04 approved surface color
Applicable conditions
Temperature is 450℃, pressure is 6MPa
Temperature is 350℃, pressure is 4MPa
Temperature is 200℃, pressure is 1.5MPa
Thickness deviation between any two points 500 on the same piece of paper
Implementation on 1995-12-01
GB/T 3985—1995
3.2.2 The length and width of the product shall comply with the requirements of Table 3. Table 3
500,620
1000,1 260
1350,1500
Note: Other specifications can be agreed upon by both parties. 4
Technical requirements
500,620
1200,1260
Difference, %
4.1 The edges of the asbestos rubber sheet should be cut neatly and the surface should be smooth. No defects such as bubbles and delamination that may affect the use are allowed. 4.2 The surface of the asbestos rubber sheet can be coated with graphite as required and agreed by both parties. 4.3 The performance of the asbestos rubber sheet should comply with the requirements of Table 4. Table 4
Tensile strength, MPa
Aging coefficient
Loss on ignition, %
Density, g/cma
Compression, %
Rebound, %
Softness
Stress relaxation, %
Steam sealing
No cracks
Temperature is 440～450℃Pressure is
11~12MPaMaintain for 30minNo
Note:①Tensile strength test is not performed for thickness greater than 3.0mm. XB350bzxz.net
No cracks
Temperature is 340～350℃Pressure is
7 ~~8MPaMaintain for 30 minNo impact
②Thickness is 2.5mm or more (including 2.5mm)No multiplication softness test is performed. 5 Test methods
5. 1 Visual inspection.
No cracks
Temperature is 200～220℃, pressure is
2～3MPa, keep for 30min without impact
5.2 The length and width of the asbestos rubber sheet are measured with a steel tape measure or a meter ruler, and its thickness is measured at any three points with a dry ruler with a working surface diameter of 6~～10mm, the distance between points is more than 200mm, the measured value is accurate to 0.01mm, and the arithmetic mean of the three readings is taken as the thickness measurement result.
5.3 All physical and chemical performance test samples should be placed in a constant temperature box at 100±2℃ for 1h, placed in a desiccator to cool to room temperature, and then tested.
5.4 The tensile strength test of asbestos rubber sheet shall be carried out in accordance with GB541. 5.5 Softness test of asbestos rubber sheet:
5.5.1 Sample: Cut three longitudinal samples of 150mm×20mm. 5.5.2 Test steps: Bend the prepared sample 180° along a cylinder with a diameter 12 times the thickness of the test plate at room temperature, and the bending time shall not exceed 2s.
5.5.3 Test results: Observe the test bending part by visual inspection. 120
GB/T3985--1995
5.6 Density test of asbestos rubber sheet shall be carried out in accordance with GB544. 5.7 Loss on ignition test of asbestos rubber sheet shall be carried out in accordance with GB3986. 5.8 Aging coefficient test of asbestos rubber sheet shall be carried out in accordance with GB3987. 5.9 Compression rate and rebound rate test of asbestos rubber sheet shall be carried out in accordance with GB3988. 5.10 Stress relaxation test of asbestos rubber sheet shall be carried out in accordance with Appendix A. 5.11 The steam sealing performance test of asbestos rubber sheet shall be carried out in accordance with GB/T15520. 5.12 The test results of asbestos rubber sheet shall be rounded off in accordance with GB8170, and the numerical values shall be consistent with the technical indicators in Table 4. 6 Inspection rules
6.1 Asbestos rubber sheets of the same specification and brand are batched in 2000kg, and less than 2000kg are still counted as one batch. 6.2 The inspection of asbestos rubber sheet is divided into factory inspection and type inspection. The factory inspection items are: appearance, size and its deviation, compression rate, rebound rate, density, softness, tensile strength, loss on ignition, and aging coefficient. The type inspection items are all the items specified in the technical requirements. Type inspection should be carried out in the following circumstances.
The first batch or trial products,
After formal production, if there are major changes in structure, materials, and processes that may affect product performance; b.
During normal production, type inspection shall be carried out every six months, d. When the product is resumed after a long-term suspension of production; e.
When the factory inspection results are significantly different from the last type inspection; when the national quality supervision agency proposes a requirement for type inspection; when the user proposes a requirement for type inspection. 6.3 The inspection of the appearance and dimensional deviation of asbestos rubber sheets shall be carried out by random sampling according to GB2828, using a normal inspection one-time sampling plan, implementing inspection level II, and the qualified quality level is 6.5. The sampling quantity required for different batches shall be in accordance with Table 5 for the determination of qualified batches or unqualified batches. Table 5
90~150
Sample size
Number of qualified determinations
Number of unqualified determinations
6.4 The performance test of asbestos rubber sheets shall be carried out by random sampling, with at least one piece per batch, and shall be carried out according to the items in Table 4. The arithmetic mean of three samples shall be used as the measurement result for each test.
6.5 When any test result is unqualified, the index shall be doubled for re-inspection. If the re-test result is still unqualified, the batch of products shall be considered unqualified.
7 Marking, packaging, transportation and storage
7.1 Marking
7.1.1 Each asbestos rubber sheet shall be printed with the manufacturer's mark, product name and specifications. The trademark mark must be clear. 7.1.2 Each bag (bundle) shall be accompanied by a product qualification certificate, including: product name, brand, batch number, standard number and technical indicators, manufacturer name, and manufacturing date.
7.1.3 Each bag (bundle) shall be printed with the manufacturer's name, product name, specifications, batch number, net weight, manufacturing date, etc. 121
7.2 Packaging
GB/T3985—1995
7.2.1 Asbestos rubber sheets shall be bundled or bagged with moisture-proof paper. The net weight of each bag shall not exceed 110kg, and the net weight of each bundle shall not exceed 50kg. 7.2.2 Each bag (bundle) of asbestos rubber sheet is not allowed to have more than one sampling port, and one product of not less than 500mm×500mm is allowed. 7.3 Transportation
Asbestos rubber sheets should be transported by covered vehicles. 7.4 Storage
7.4.1 The storage of asbestos rubber sheets is calculated from the date of manufacture. The bundles should generally be stored upright, or their height should not exceed 1m when laid flat.
The product should be stored in a warehouse at 0-30℃, and protected from sunlight and 1m away from heat sources. 7.4.2
A1 Test equipment
A1.1 Stress relaxation testing machine (as shown in Figure A1). Dial gauge assembly
Micrometer
Measuring seat
Measuring rod
Flat circular plate
Specimen assembly
Clamping screw
GB/T3985--1995
Appendix A
Stress relaxation rate test method
(Supplement)
Bolt*
Figure A1 Test device
There is a gap between the specimens
Flat circular plate
Figure A2 Schematic diagram of specimen arrangement
Note: Calibration is required before the test. When it is loaded with 26.7kN, the elongation is 0.115~0.127mm. A1.2 Constant temperature drying oven.
A1.3 Dryer
A2 Test specimen
A2.1 Each specimen is 3.2±0.3mm long, 10±0.3mm wide and 1.5±0.15mm thick. A2.2 Each test requires 2 groups of specimens, each group of specimens consists of 4 pieces, and the thickness deviation between each piece of the same group of specimens is not more than 0.02mm. A2.3 The specimen is treated in a constant temperature drying oven at 100±2℃ for 1h, then taken out and cooled to room temperature in a dryer. A3 Test steps
A3.1 Clean the working surface of the flat circular plate and apply a small amount of lubricating oil on the threaded surface of the washer and bolt. A3.2 Clamp the prepared 4 specimens between the two flat circular plates according to the position shown in Figure A2, insert the bolt, put in the washer, and tighten the nut by hand. A3.3 Install the micrometer assembly on the bolt and tighten it by hand, and adjust the pointer of the micrometer to zero (reserve 2mm range). A3.4 Use a wrench to tighten the nut continuously, and make the reading of the dry gauge reach the bolt calibration elongation (D.) within 3s and keep it for 3s. A3.5 Remove the dry gauge assembly, put the sample assembly into a constant temperature drying oven at a temperature of 100±2℃, keep it for 22h, then take it out and cool it to room temperature in 123
air.
GB/T3985-—1995
A3.6 Install the dry gauge assembly again, tighten it by hand, and adjust the pointer of the dry gauge to zero. A3.7 Loosen the nut with a wrench, and then tighten the nut with finger force. The force scale is similar to that of A3.2. Note: The actions in this article should not affect the dry gauge assembly. A3.8 Read the thousandth value (Dt) and be accurate to 3 decimal places. A4 Calculation of test results
A4.1 The calculation of stress relaxation rate is carried out according to formula (A1). R
Where: R——stress relaxation rate, %,
D. ———elongation of bolts before heat treatment, mm; D. - D,
D——elongation of bolts after heat treatment and cooling, mm. A4.2 The test results are calculated to one decimal place. A4.3 The final test results are expressed as the average value of two groups of samples. Additional remarks:
This standard is proposed by the State Bureau of Building Materials Industry. This standard is under the jurisdiction of Weiyang Non-metallic Mineral Research Institute. X100
This standard was drafted by Changchun Asbestos Products Factory, and Shanghai Asbestos Products Factory participated in the drafting. The drafters of this standard are Cheng Yachun, Li Wangui and Gao Xia. 124
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