1.4.2 Mechanical Tests of Tools for Live Working
Mechanical tests of tools for live working include static load test and dynamic load test under working load.Some tools for live working,such as insulating pulling plate(pole),hanging pole,etc.,shall only be subject to static load test;while some tools that may be impacted by loads,such as operating pole,tensioner,etc.,shall be subject to dynamic load test in addition to static load test.
1.Static Load Test
Static load test is a test to assess the ability of tools,devices and equipment for live working to withstand mechanical loads(tension,torsion,pressure,and bending force).Static load generally refers to the load applied in the rated test which is 2.5 times of the allowable service load of the tested object for 5min,after which if there is no permanent deformation on each part of the tested object,it shall be deemed as qualified.
The service load can be determined according to the following principles.
(1)For tightening,pulling,hoisting and supporting tools(including tractor and fixator),if they are products manufactured by manufacturers,the allowable working load marked on the nameplate shall be taken as the service load;or the maximum service load can be calculated according to the actual use.
(2)For tools used for loading people(including all kinds of ladders,hanging baskets,hanging wheels,etc.used by single person),the quality of people and tools carried by them shall be taken as the service load.
(3)For tools used for holding,hoisting and hooking insulators,the quality of a string of insulators shall be taken as the service load.
During the static load test,the loading method is:assemble the tool into working state and apply the test load by simulating stress condition on the spot.Fig.1-15 shows the static load test of tools and instruments for live working.(https://www.daowen.com)
Fig.1-15 Static Load Test of Tools and Instruments for Live Working
2.Dynamic Load Test
Dynamic load test is a test item to check whether the mechanism operation is flexible and reliable when the tested object is impacted.Therefore,the load applied shall not be too large.Generally,it is required to apply 1.5 times of service load to the test object assembled into working state,and operate movable parts of the test object(such as leading screw handle,hydraulic tightener handle and unloading valve,etc.)for three times,after which if there is no damage,failure and other abnormal phenomena,it shall be deemed as qualified.
Since the operating bar is often used to pull out cotter pin or spring pin,or wrest screw,it shall be subject to the impact and torsion resistance test with an impact torque of 500N·cm and a torque of 250N·cm.Fig.1-16 is the arrangement diagram of mechanical tests of insulator clamps.
Fig.1-16 Arrangement Diagram of Mechanical Tests of Insulator Clamps
1-fixed end;2-clamp;3-screw rod;4-insulator;5-dynamometer(sensor);6-tensile machine diagram