【 Weak current College 】 stage machinery safety design (2)

2. safety equipment
Device security refers to the stage machinery equipment in working condition long-term use no accident; in the event of a temporary failure could reduce the technical parameters after working capacity; stage machinery equipment on non-functional State of perception, ability to display and alarm. This capability or performance are usually mechanical design itself and completed with electric control; consider performance stage machinery cannot be ruled out as soon as possible of a temporary failure of the stage machinery of the failure as possible without affecting the performance of the work.
Involves device security to a number of factors, mainly has following several aspects:
1. adequate factor of safety
All mechanical parts of the selection and design must guarantee at rated load and inertia loads under the combined action, be reliable and have certain security reserve, i.e. sufficient safety factor. Safety factor is defined as: all the materials of the ultimate stress and part of the maximum operating stress ratio. Part of the working conditions should consider maximum static load and dynamic load (emergency braking, collision, and so on reboot inertial load) under stress. For example: hanging weights or traction wire rope, the safety coefficient should be greater than or equal to 10; lifting chain of safety should be greater than or equal to 12; transmission chain of safety should be greater than or equal to 10; all parts of the transmission system in the selection should be able to withstand two times the load rating; initial brief calculations, transmission parts and mechanical parts of the safety coefficient should be greater than or equal to 6, precise calculation of the safety coefficient should be consistent with the relevant standards or specifications on the part of the class.
2. appropriate stiffness
The stage machinery of major force widget should have appropriate stiffness in order to adapt to the needs ofthe stage performance. Typically, the provisions in force in the Member deflection should be less than the widget span of 1/1000 ~ 1/800, sometimes also the absolute value of the deflection, these components must meet both requirements. Transmission parts of torsional rigidity, stability, etc. compressed should comply with the standard norms. On the platform, in order to obtain sufficient lateral rigidity, which calculates the horizontal load of not less than the vertical movement of the load of 1/20.
3. reasonable structure and the dimensional parameters
To avoid or reduce certain structural dimensions of machine parts as unreasonable and excessive additional stress or premature fatigue failure, the design-time structure should be given enough attention. Winch system parts typical, such as: winch drive drum diameter should be greater than the diameter of the wire rope and pulley diameter 18 times larger than the diameter of the wire rope 20 times, friction drive (traction transmission) of the driving wheel diameter should be greater than 40 times the diameter of the wire rope, etc., all of the accessories are ropes and wire rope diameter to be matched, rope connector can only use those delivery loads greater than 80% of the wire rope breaking load of the coupling type, such as: splicing connector, alloy cast casing joints, wedge-shaped connectors, extruded aluminium alloy casing and comply with the requirements and proper use of steel wire rope clips, etc. Drum flange height should be greater than 2 times the diameter of the wire rope, single-layer winding of the drum, leaving at least two ring friction fixed ring, steel rope and reel or pulley of deflection angle should be less than 4 °.
4. reliable security appliance
The stage machinery and equipment must have better security protection devices to ensure the safety of the operation of equipment. General devices are equipped with stroke limit switches and hyper-limit switch. Similar to the boom winchor supposes, winch rope protection, job hopping or composite rope protection, overload protection and speed (over current) protection and other security measures and in the very context display and alarm in the event of a dangerous situation, the control system only allows devices to reduce the dangerous movement. When the device returns to normal status in order to continue the original campaign. For security purposes, the stage machinery of the brake must be: two independently controlled brakes (or hydraulic lock), or institutions self-locking (including reducer self-locking) together with a brake. Moreover, each actuator is take all the transmission torque. In a two-stage brake when one is working brakes, another is the safety brake.