standardize the test process of fasteners used in the installation of steel pipe scaffolding, so as to effectively control the quality of test work.
1. Objective:
To standardize the test process of fasteners used in the installation of steel pipe scaffolding, so as to effectively control the quality of the test work.
2. Scope of application:
This work instruction is applicable to fasteners made of malleable cast iron or cast steel, such as scaffolding, derrick and formwork support with a nominal outer diameter of 48.3mm in construction projects, and also applicable to the inspection of fasteners used in municipal, water conservancy, chemical, metallurgical, coal and ship projects. Steel tube scaffold couplers with nominal outer diameter of 51mm and fasteners in use can also be implemented with reference to this work instruction.
3. Responsibilities:
The inspector in the fastener testing room is responsible for the concrete implementation of fastener testing. The person in charge of quality is responsible for the cooperation of testing.
4. Work requirements:
4.1 Implementation standard:
GB 15831—26 steel tube scaffold couplers
4.2 Fastener inspection:
4.2.1 Fasteners shall have no casting defects such as shrinkage porosity, slag inclusion and air holes in the main parts. Fasteners should be strictly shaped and closely contacted with the surface of steel pipe, and the anti-sliding and tensile properties of fasteners should be guaranteed.
4.2.2 the mechanical properties of the fastener and the base shall meet the requirements in table 1.
4.2.3 visual inspection of fasteners:
4.2.3.1 There should be no cracks in all parts of fasteners.
4.2.3.2 The opening distance between the cover plate and the seat shall not be less than 5mm；; When the nominal outer diameter of the steel pipe is 51 mm, it shall not be less than 55 mm.
4.2.3.3 There shall be no more than three sand holes on the surface of the fastener that are greater than 1mm2. And the accumulated area should not be greater than 5m2.
4.2.3.4 The accumulated sand sticking area on the fastener surface should not be greater than 15m2.
4.2.3.5 The misplaced box should not be greater than 1mm.
4.2.3.6 The height (or depth) of the convex (or concave) surface of the fastener should not be greater than 1mm.
4.
4.2.2.9 t-shaped bolts and nuts shall comply with the provisions of GB/T398.1 and GB/T398.2.
4.2.2.1 The moving parts should rotate flexibly, and the gap between the two rotating surfaces of the rotating fastener should be less than 1mm.
4.2.2.11 The model, trademark and production year number of the product should be cast in an eye-catching place, and the handwriting and pattern should be clear and complete.
4.2.2.12 The surface of fasteners should be rustproof (asphalt paint should not be used), and the paint should be uniform and beautiful, and there should be no pile of paint or exposed iron.
5. Test method:
5.1 Test conditions and methods
5.1.1 The steel pipe with a nominal outer diameter of 48.3mm and a wall thickness of 3.5mm in GB/T391 shall be used for the test, and the outer surface shall be uniformly coated with red lead paint and dried. Every time a test is done, the fastener should move to a fastening position.
5.1.2 The accuracy of hydraulic universal testing machine and dial gauge used in the test should be 1%, the accuracy of weight used in torsional stiffness test device should be 2%, the accuracy of fixed torque wrench should be 5%, and the accuracy of ring gauge and plug gauge should be 3.
5.1.3 T-bolts, nuts and washers of fasteners used for testing shall be unused and qualified products.
5.1.4 during the test, the opening between the cover plate and the seat of the right-angle fastener and the rotary fastener on the horizontal pipe should be upward.
5.1.5 When the fastener is tested, the torque of the fastening bolt should be 4N.m.
5.1.6 When the fastener is subjected to various load tests, the loading speed should be controlled at 3 N/s-4 N/s.
The total load in 5.1.7 test should include the preload.
5.2 mechanical performance test of right-angle fastener
5.2.1 anti-sliding performance test
When the fastener is doing anti-sliding performance test, when the vertical constant-speed increasing load p applied to the horizontal pipe (both sides of the fastener) reaches the specified value, measure the displacement values △1 and △2.
When the preload p is 1.kN, adjust the displacement measuring instrument to zero. When p increases to 7.kN, write down the value of △1; When p increases to 1.kN, write down the value of △2.
both arc surfaces of fasteners shall be tested.
5.2.2 Anti-destructive performance test
After anti-sliding performance test, undamaged fasteners can be used as anti-destructive performance test. At this time, an anti-slip support pad is attached to the lower part of the fastener. When p is 25.kN, all parts of the fastener shall not be damaged.
only one arc surface is made in the test.
5.2.3 Torsional stiffness performance test
Fasteners are installed on two perpendicular steel pipes. When the horizontal pipe is more than 2mm long, put a load P on the horizontal pipe at a distance of 1mm from the center, and measure the displacement of the horizontal pipe at a distance of 1mm from the center at the unloaded end? .
when the preload p is 2N, adjust the measuring instrument to zero. The first load is 8N, and then every 1N is added, and it is directly added to 9N. The measured values shall be recorded immediately under each load? .
5.3 Mechanical performance test of rotating fastener
5.3.1 Anti-sliding performance test
The test method should comply with the provisions in 5.2.1 of this instruction, and the preload p should be .2 kN. When p is increased to 7.kN, write down the value of △1; When p increases to 1.kN, write down the value of △2.
only one arc surface is made in the test.
5.3.2 destructive performance test
after the anti-sliding performance test, the destructive performance test is carried out. When p is 17.kN, all parts of the fastener shall not be damaged.
5.4 tensile performance test of the opposite fastener
The fastener bears the axial tension increasing at a constant speed, and the displacement value△ is measured. When the preload p is 1.kN, adjust the displacement measuring instrument to zero, and then continue to load. When p increases to 4.kN, write down the delta value.
5.5 compressive performance test of foundation
uniformly load at a speed of 1.kn/s. When p is 5.kN, the base shall not be damaged.
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