1. Purpose
During the process of product assembly and equipment maintenance, the assembly work of bolts and nuts shall be standardized to prevent related losses caused by inconsistent assembly methods and torques. In order to ensure assembly quality, these regulations are formulated.
2. Scope
Applicable to process management of product assembly and equipment maintenance of Shandong Changlin Agricultural Equipment Co., Ltd.
3. Responsibilities
1, the technical department is responsible for determining the applicable bolts, nuts and other standard parts for the product. Provide guidance on technical issues;
2, the production department process team is responsible for the formulation, specification and guidance of assembly methods;
3, each workshop of the production department is responsible for the standardized operation of the assembly process and the strict control of data parameters;
4 and the quality department are responsible for supervising and inspecting the assembly work. The data complies with the specifications of each parameter and provide timely feedback on relevant situations.
4. Definition
1, torque: is the force that causes an object to rotate. In this rule, it refers to the rotational force applied to the bolts and nuts when they are tightened after the bolts are assembled.
2, 5, 4, 1 rules for bolted connections:
Forces in thread tightening: clamping force, friction between the thread pair, friction between the inner surface of the bolt end and the connected parts. Usually, in a threaded connection, only about 10% of the energy consumed when turning the fastener is converted into clamping force, and the remaining 90% is lost by the friction of the thread pair and the friction between the connecting piece and the inner surface of the bolt end. The maximum distribution ratio is 4:5, each accounting for 40% and 50%. This is the so-called 5, 4, 1 rule.
5. Assembly specifications
1. Before assembly, visually inspect the bolts, nuts or wire holes of the connected parts. There should be no bumps or scratches and they should comply with the drawings or relevant standards;
2. During the assembly process, the threaded part of the bolt must not be damaged.
3. The head of the bolt and the end face of the nut should be in uniform contact with the plane of the fastened part. They should not be tilted. It is also not allowed to hit the two planes with a hammer to make the two planes contact. There should be no bending deformation of the screw.
4, the connected parts should be evenly pressed, fit closely to each other, and the connection should be firm.
5 It is strictly prohibited to use inappropriate wrenches and sockets when tightening bolts and nuts.
6, the fasteners are assembled strictly in accordance with the grade specified in the drawings or process documents. In principle, it is not allowed to replace high-performance fasteners with low-performance fasteners or replace low-performance fasteners with high-performance fasteners.
7. When applying thread locking sealant (such as anaerobic adhesive, etc.) to the external thread, it should be applied within a length of 15mm from the end of the thread.
8. Generally, when assembling bolts and screws, the thread pitch should be greater than 2 to 3 by hand, and then tightened with a wrench or pneumatic tool. In particular, when the thread diameter is large (usually ≥M14) and the tightening position is important, a torque wrench needs to be used to confirm the torque value and ensure accuracy.
Special note: The pneumatic air trigger cannot be used as the final tightening tool (because its power is tightened by the continuous impact of the hammer, the torque fluctuation range is too large. It is also affected by the air source pressure, air trigger model, air trigger wear degree, impact time, etc.)
9 When assembling bolts, screws and nuts, pay attention to the protection of the paint film, coating, etc. of the connected parts. Pay attention to the protection of the bolts, nut heads, screw slots, etc., and do not damage them.
10. When the thread hole needs to be threaded, a suitable tap must be used and the axis of the thread hole must be perpendicular to the surface of the connecting piece.
11. After the nut is tightened, the heads of the bolts and screws should expose 2 to 3 thread pitches on the end face of the nut. When the nut and flat washer are assembled together or the nut is assembled alone, the nut and washer are both facing away from the connected body. (The side with the words on the nut is the front, and the round side of the washer is the front)
12. After the countersunk head screw is tightened, the countersunk head must not be higher than the end face of the countersunk hole.
13, stud assembly
(1) It should be ensured that the double-ended studs and the machine body threads have sufficient tightness to ensure that there is no loosening during the process of assembling and disassembling the nuts.
(2) The axis line of the double-ended stud must be perpendicular to the surface of the machine body. During assembly, a right-square ruler can be used for inspection.
(3) When installing double-headed studs, they must be lubricated with oil to avoid seizing when screwing in and to facilitate subsequent disassembly.
When tightening 14, set of bolts and nuts, they should be tightened in a certain order according to the shape of the connected parts and the distribution of the bolts (generally 2 to 3 times).
When tightening a group of bolts or nuts arranged in a rectangular shape, start from the middle and gradually expand symmetrically to both sides). Groups of bolts or nuts arranged in a circular or square manner should be tightened symmetrically). If there are locating pins, start tightening from the bolts closest to the locating pins.
15, paint mark after bolt tightening
Purpose: 1) To prevent missing bolts during tightening. 2) makes it easy to detect whether the bolts are loose during use.
Mark location:
The mark is usually marked with paint (red) at the contact point between the bolt and the nut. The color can be changed according to the place of use, but the color must be clearly distinguishable.
Appendix 1: Threaded connection tightening torque value (unit: N.m)
(Source: Internet)