This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of magnesia concrete backboards, trench covers and coal retaining plates. This standard applies to magnesia concrete backboards, trench covers and coal retaining plates for underground belt conveyors used in mines. MT/T 375.4-1994 Technical conditions for backboards, trench covers and retaining plates of magnesia concrete products for mines MT/T375.4-1994 Standard download decompression password: www.bzxz.net

Coal Industry Standard of the People's Republic of China
Mine Magnesium Concrete Products
Technical Conditions for Back Plates, Trench Covers and Coal Baffles 1 Subject Content and Scope of Application
MT/T375.4—94
This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of magnesia concrete back plates, trench covers and coal baffles.
This standard applies to magnesia concrete back plates, trench covers and coal baffles for underground belt conveyors in mines. 2 Reference StandardsWww.bzxZ.net
MT/T375.1 General Technical Conditions for Magnesium Oxychloride Concrete Products for Mining MT/T375.2 Technical Conditions for Ladder Brackets of Magnesium Oxychloride Concrete Products for Mining 3 Terminology
3.1 Magnesium Oxychloride Concrete Back Plates Magnesium oxychloride concrete lagging is made of reinforced magnesia concrete and is a plate-type product used for tunnel support and side guards. 3.2 Magnesium oxychloride concrete drain cover is made of reinforced magnesia concrete and is a plate product used to cover the tunnel ditch. 3.3 Magnesium oxychloride concrete cowl is made of reinforced magnesia concrete and is a plate product used to prevent coal from sliding down in underground belt conveyors. 4 Technical requirements
4.1 The product shall comply with the requirements of this standard and shall be manufactured according to the drawings and technical documents approved by the prescribed procedures. 4.2 The raw materials shall comply with the provisions of Article 4.1 of MT/T375.1. 4.3 The dimensional deviations of the back plate, drain cover and coal retaining plate shall comply with the following provisions: length: ±5mm,
width: ±4mm;
thickness: ±3mm.
4.4 Appearance quality
4.4.1 The surface of magnesia concrete backboard, trench cover and coal retaining board shall be flat, the edges shall be neat, the thickness shall be uniform, the depth of pits shall not exceed 3mm, and the area shall not exceed 5% of the surface area. 4.4.2 There shall be no penetrating needle holes, the reinforcement shall not be exposed, the board surface shall not have salt return phenomenon, and its appearance defects shall not exceed the requirements of Table 1. Approved by the Ministry of Coal Industry of the People's Republic of China on November 16, 1994, 194
Implemented on December 1, 1994
Appearance defects
Length of missing edges
MT/T375.4—94
Magnesium concrete backboard
Magnesium concrete trench cover and coal retaining board
No more than one, the length of the corner drop shall not exceed 20 shall not exceed 30
No more than 5
4.5 The compressive strength of magnesia concrete shall comply with the provisions of Article 4.2 of MT/T375.1. 4.6 The durability of magnesia concrete shall comply with the provisions of Article 4.3 of MT/T375.1. 4.7
The water resistance of magnesia concrete shall comply with the provisions of Article 4.4 of MT/T375.1. The apparent density of magnesia concrete shall comply with the provisions of Article 4.5 of MT/T375.1. 4.8
Shall not exceed 20
After the impact resistance test, cracks larger than 0.5mm shall not appear on the magnesite concrete backboard, trench cover and coal retaining plate. After the bending failure load test, the magnesite concrete backboard, trench cover and coal retaining plate shall comply with the provisions of Table 2. 4.10
Product category
Ditch cover
Coal retaining plate
Bending failure load
The standard test piece with a span of 800mm, a width of 200mm and a thickness of 50mm shall not be less than 8The standard test piece with a span of 500mm, a width of 350mm and a thickness of 50mm shall not be less than 14The standard test piece with a span of 800mm, a width of 500mm and a thickness of 50mm shall not be less than 6Note: If the span of the test backboard, trench cover and coal retaining plate is different from that listed in Table 2, the failure load is allowed to be calculated according to the bending moment equivalent principle. 5 Test methods
5.1 Appearance quality shall be checked in accordance with 5.1 of MT/T375.2. 5.2 Dimensional deviation shall be measured in accordance with 5.2 of MT/T375.2. 5.3 Compressive strength shall be measured in accordance with 5.2 of MT/T375.1. 5.4 Durability shall be measured in accordance with 5.2 of MT/T375.1. 5.5 Water resistance shall be measured in accordance with 5.3 of MT/T375.1. 5.6 Apparent density shall be measured in accordance with 5.4 of MT/T375.1. 5.7
Test method for impact resistance
Put the back plate (or trench cover plate, or coal retaining plate) flat on the ground, 200mm above the ground, and the distance between the two ends of the support points is as specified in Table 2. Use a sandbag with a mass of 20kg (or 25kg, or 10kg) to fall freely from a height of 1000mm, impact the middle of the component 15 times, and measure the crack width with a ruler.
5.8 Bending failure load test
5.8.1 Instrument
Universal material testing machine or hydraulic pulsation fatigue testing machine: the maximum loading capacity is greater than 100kN, or other loading devices with equivalent functions. Magnifying glass: the magnification is not less than 5 times. 5.8.2 Test pieces
MT/T375.4—94
Test pieces that have been cured for 28 days according to the provisions of Article 5.1.2 of MT/T375.1 and have qualified dimensional deviation and appearance quality should be selected for testing. 5.8.3 Test steps
5.8.3.1 Back plate
5.8.3.1.1 Load the back plate centrally as shown in Figure 1. 5.8.3.1.2 The arithmetic mean of the failure load values ​​of the two back plates is taken as the failure load of the batch of back plates. 5.8.3.1.3 Load grading Take 10% of the estimated failure load and load step by step. Each load level lasts for 3 minutes until the limit state is reached. 5.8.3.2 Trench cover
5.8.3.2.1 Load the trench cover centrally as shown in Figure 2. 5.8.3.2.2 The calculation of results is the same as that of Article 5.8.3.1.2 of this standard. 5.8.3.2.3 The load level is the same as that of Article 5.8.3.1.3 of this standard. 5.8.3.3 Coal retaining plate
5.8.3.3.1 The loading method is the same as Figure 1.
5.8.3.3.2 The calculation of results is the same as that of Article 5.8.3.1.2 of this standard. 5.8.3.3.3 The load level is the same as that of Article 5.8.3.1.3 of this standard. L/3
L= 500
5.8.4 When the bending failure load test is carried out on the universal material testing machine, the loading speed is 0.05~~0.08MPa/s. 6 Inspection rules
6.1 Factory inspection
MT/T375.4—94
6.1.1 The product self-inspection shall be carried out by the quality inspection department of the manufacturer, and the product can be shipped only after passing the inspection and issuing the certificate of conformity. 6.1.2 The items of factory inspection are shown in Table 3.
6.2 Type inspection
The quality supervision and inspection agency of the Ministry of Coal Industry shall be responsible for sampling and inspection from the qualified products in appearance and size inspection. 6.2.1
Product type inspection shall be carried out in the following situations: trial production and identification of new products or old products transferred to the factory for production, when there are major changes in structure, materials, formula and process after formal production, which may affect product performance; in normal production, it shall be carried out once a year, and in products with an annual output of more than 1000m, it shall be carried out once every six months, when the product is stopped and production is resumed;
When the factory inspection results are significantly different from the last type inspection; when the quality supervision agency proposes the requirement of type inspection. Table 3
Inspection category
Inspection items
Dimensional deviation
Appearance quality
Compressive strength
Durability
Water resistance
Apparent density
Impact resistance
Bending failure load
Technical requirements
4.4.1, 4.4.2
Note: ① If the test environment conditions do not meet the requirements of this standard, the test results are only for reference and should be noted in the report. ② "V" means inspection, "-" means no inspection. 6.3 Batching and sampling
6.3.1 Products
For products of the same variety and specification, 1,000 pieces are considered a batch. Two pieces are randomly selected from each batch for bending failure load test, and two pieces are randomly selected from each batch for impact resistance test. 6.3.2 Test pieces
Test pieces shall be made according to the provisions of 5.1.3.1 and 5.1.3.2 of MT/T375.1, and the compressive strength, durability, water resistance and apparent density tests shall be carried out according to the corresponding provisions.
6.4 Judgment rules
6.4.1 When the test results do not meet the technical requirements of any of 4.5, 4.6, 4.7, 4.8, 4.9 and 4.10, double the number of test pieces shall be drawn for re-inspection. If one piece is found to be unqualified, the batch of products shall be judged to be unqualified. 6.4.2 The test results do not meet the requirements of 4.3, 4.4.1 and 4.4.When any two of the two technical requirements are met, the test pieces should be doubled and re-tested. If one item is found to be unqualified, the batch of products shall be judged to be unqualified. 7 Marking, packaging, transportation, storage
7.1 Each back plate, trench cover and coal retaining plate shall be marked with a non-fading mark indicating the manufacturer's name, product specifications and production date. 7.2 The products can be packaged in bundles.
7.3 During loading, unloading and transportation, they shall not be thrown.
MT/T375.4—94
7.4 The site for product storage should be solid and flat. Products of different specifications should be stacked separately or cross-stacked, and the stack height should not exceed 2m. Additional notes:
This standard was proposed by the Standardization Technical Committee for Coal Mine Special Equipment of the Ministry of Coal Industry. This standard is under the jurisdiction of the Mine Equipment Branch of the Standardization Technical Committee for Coal Mine Special Equipment of the Ministry of Coal Industry. This standard was drafted by the Beijing Mine Construction Research Institute of the China Coal Research Institute. The main drafters of this standard are Tu Linan, Wang Huiyun, Guo Aimin and Guo Jianming. The Beijing Well Construction Research Institute of the China Coal Research Institute is responsible for the interpretation of this standard.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.