This standard specifies the product classification, technical requirements, test methods, inspection rules, packaging, storage and transportation of silicon carbide protection tubes for thermocouples. This standard applies to silicon carbide protection tubes for thermocouples with a maximum operating temperature below 1800°C. JB/T 8340-1996 Silicon carbide protection tubes for thermocouples JB/T8340-1996 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Silicon Carbide Protection Tube for Thermocouple
Subject Content and Scope of Application
JB/T8340--96
This standard specifies the product classification, technical requirements, test methods, inspection rules, packaging, storage and transportation of silicon carbide protection tubes for thermocouples.
This standard applies to silicon carbide protection tubes for thermocouples with a maximum operating temperature of less than 1800℃. 2 Reference standards
Packaging, storage and transportation pictorial symbols
Test methods for apparent porosity, water absorption, bulk density and true porosity of dense shaped refractory products GB 2997
JB3890
3 Product classification
3.2 Shape
Equal diameter silicon carbon rods
Silicon carbide
The appearance is shown in Figure 1:
3.3 Specifications
The basic dimensions shall comply with the provisions of Table 1.
Approved by the Ministry of Machinery Industry of the People's Republic of China on April 11, 1996, and sold on October 01, 1996
Outer diameter D
Inner diameter D
Length L
3.4 ​​Product marking example
JB/T8340—96
313,365,415.465,565
313,365.415,465,5 65.665,915.1165,1665.2165The shape should be arc-shaped, and its wall thickness should not be greater than 1/2 of the outer diameter of the tube. The silicon carbide protection tube for thermocouples with an inner diameter of 14mm, an outer diameter of 25mm and a length of 565mm is marked as: GBT25/14X565
4 Technical requirements
4.1 Appearance
The surface should be flat and free of defects such as cracks, hemp residue, and inner hole blockage. 4.2 Basic size limit deviation
Basic size limit deviation shall comply with the provisions of Table 2. Table 2
Basic size
Limit deviationbzxz.net
4.3 Straightness tolerance
20～25
Straightness tolerance shall comply with the provisions of Table 3.
>500～1000
>1000～1500
>1 500~~2 000
4.4 Physical properties
Outer diameter D
30～35
4.4.1 Thermal shock resistance: no cracking after three tests from 1400℃ to room temperature, 4.4.2 Porosity is not more than 30%.
4.4.3 Flexural strength at room temperature is not less than 30MPa, 5 Inspection method
5.1 Appearance inspection
5.1.1 Cracks, hemp residue, flatness, etc. are visually inspected. 40~50
Inner diameter D
Straightness tolerance
5.1.2 Inner hole blockage is inspected by placing a metal needle 0.3mm smaller than the lower limit of the hole diameter into the manhole. 5.2 Basic size inspection
Use a vernier caliper with an accuracy of 0.05mm to measure the diameter; use a steel ruler or tape measure with an accuracy of 0.5mm to measure the length. 5.3 Straightness measurement
Length L
313~2165
5.3.1 Place two V-shaped brackets of the same height on the platform, and adjust the distance between the two brackets according to the length of the protective tube to be inspected, so that it is not less than 98% of the total length of the tube to be inspected
JB/T 8340--96
5.3.2 Place the two ends of the inspected tube in the V-grooves of the two brackets so that the maximum bending point is at the minimum distance from the platform downward. Use a height gauge with an accuracy of 0.05mm to measure the height H1 from the maximum bending surface to the platform. Then rotate the protective tube 180° so that the maximum bending point is at the maximum distance from the platform upward. Use the same method to measure the height H1 from the maximum bending convex surface to the platform at the same position. Calculate the straightness tolerance using formula (1):
Where: 3—straightness tolerance, mm; H,—height value when the maximum bending point is downward, mm; H2—height value when the maximum bending point is upward, mm. 5.4 Thermal shock resistance test
(1)
Place the silicon carbide protection tube for the thermocouple in a 1400℃ furnace, insert it to a depth of 200mm, keep it warm for 10min, take it out and cool it to room temperature in the air, observe whether the tested tube has any bursting phenomenon, and repeat the above operation three times. 5.5 Porosity test
The porosity test shall be carried out in accordance with the provisions of GB2997. 5.6 Room temperature flexural strength test
The room temperature flexural strength test shall be carried out in accordance with Article 3.2 of JB3890. 6 Inspection rules
6.1 Appearance, basic dimensions and straightness tolerances shall be inspected one by one. 6.2 Thermal shock resistance, porosity and room temperature flexural strength are all random inspection items. 6.2.1 Random inspection cycle
Random inspection shall be carried out once every quarter.
6.2.2 Inspection method
Randomly select products from the inspection batch during inspection, and each inspection shall not be less than one specification. Three products of each specification shall be selected. 6.2.3 Result judgment principle
Inspect the samples one by one according to the inspection method specified in this standard, and the qualified rate of each inspection shall not be less than 90%. If the first inspection fails to meet the requirements, it is allowed to double the number for the second inspection. If it fails again, the batch of products shall be judged as unqualified. 7 Marking, packaging, purchase, storage, and transportation
7.1 The trademark must be clearly marked on one end of each product. 7.2 When packaging, the packaging box should be filled with soft and shockproof materials. The packaging box should have a certificate of conformity and indicate the product name, specification, quantity, factory name, and date of manufacture. The packaging box should have signs or words such as shockproof, moisture-proof, and handle with care. The signs should comply with the provisions of GB191. 7.3 It must be stored in a dry, ventilated, and shockproof warehouse. 7.4 Handle with care during transportation to prevent collision. Additional remarks:
This standard was proposed by the National Technical Committee for Standardization of Abrasives and Grinding Tools. This standard is under the jurisdiction of the Zhengzhou Abrasives and Grinding Research Institute of the Ministry of Machinery Industry. This standard was drafted by the Fifth Grinding Wheel Factory. The main drafters of this standard were Wu Wenjin and Sun Xiqin. 343
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