1、翻 译 部 分英文原文：Research on hydraulic-powered roof supports test problemsAbstract：The load-bearing characters of hydraulic-powered roof support with dual telescopic legs were analyzedWith a specific type hydraulic-powered roof support with dual telescopic legs for research object，the inside load test pr
2、oblems in factories was analyzed，and the correct test methods were given，which can enhance the test efficiency and make the factories away from the error design of hydraulic-powered roof supports and legs Keywords ：dual telescopic legs，hydraulic-powered roof support，load Introduction Dual telescopic
3、 leg has wide height adjustment and is easy to operate，which is extensively applied in the thin coal seam and high height hydraulic-powered roof supportsBased on the statistic data of China National Coal Mine Support Equipment Quality Supervision Test Center，there are about 40% of tested hydraulic-p
4、owered roof supports and about 61% of shield hydraulic-powered roof support using dual telescopic legs；therefore，the effective test of hydraulic-powered roof supports with dual telescopic legs is very importantDue to the limits of test technology and manufacturing cost，about more than 90% of hydraul
5、ic-powered roof supports and legs factories use inside load test devices for factory test and research test, according to the standards MT312-2000 General Specification for Powered Support and MT313-1992 Specification for Power Set Legs(China Coal Mine Standard,1996；ENl804-2,200 1)On one hand，the in
6、side load test devices have no function of infinitive height adjustment，and on the other hand，the dual telescopic legs and the hydraulic-powered roof supports with dual telescopic legs test should be kept to proper constraint condition or test rules to assure the test effectivityAt present，the metho
7、ds of inside load test of hydraulic-powered roof supported with dual telescopic legs in factories are seriously wrong, in which there is large deviation between the test load and standard load, and the largest deviation is about 50%The test results are seriously distorted，which may mislead the desig
8、n and manufacturing of hydraulic-powered roof supports，and as a result，their safety performance does not suit the practical work conditions and cause low productivityIn order to solve these problems，the ZY9000/25.5/55 high height shield hydraulic-powered roof support is taken for example for quantiz
9、ing analysisThe correct measures are given in this paper for the factories to test correctly 1 Load-bearing characters of hydraulic-powered roof support with two-stage legs The load-bearing procedure of hydraulic-powered roof supports used in integrated mechanized mining face mainly includes setting
10、 procedure, bearing procedure，and constant resistance procedureThe specific bearing characters are given as follows(Cheng and Cao,2002;Cheng and Su,2003;Jia et al，2010)： (1) During the setting procedure，as shown in Fig.1，a certain pressure first acts on the surface of the middle cylinder piston on t
11、he time that there are no resistance oil the leg，and the fluid pressure needed is very smallThe middle cylinder first lifts before the internal valve openingWhile the middle cylinder arrives at the boundary position，its piston presses the guide sleeveThe pressure of the fluid in inferior cavity (B c
12、avity) of the outside cylinder arises, and the internal valve is opened，which makes the fluid get into the inferior cavity(B cavity)The extension cylinder rises，and the roof is supported；the setting pressure(pc) is as follows (Liu,2007;Wang et al,2008;Rui et al.,2010)： Pc=3.14/4D22nPb103kNwhere，D2 i
13、s the extension cylinder diameter；n is the leg number；Pb is the pump pressure Fig.1 The middle cylinder compacting with guide sleeve ofhydraulic-powered roof support1-Middle cylinder piston；2-Intemal valve；3-Guide sleeve；4-Middle cylinder；5-Extensive cylinder；6-Canopy；7-Test bed mobile stage；8- Test
14、 bed base(2) Following the setting procedure，the roof gets convergent，which results in the fluid pressure of inferior cavity of the middle cylinder and inferior cavity of the outside cylinder rises，and the supporting pressure of the hydraulic-powered roof support rises too，which is late bearing (3)
15、During the constant resistance procedure，the roof force translates from canopy to extension cylinder as the roof force increasingBecause of the enclosing caused by internal valve，the extension cylinder could not retract，and the pressure of the inferior cavity of outside cylinder continues to rise un
16、til it gets to the safety valve setting pressure，when the safety valve opens and the pressure is releasedIf the roof force exceeds the setting pressure again，the safety valve acts subsequently，and the middle cylinder continue to refractIn time，the pressure of hydraulic-powered roof support supporting the roof becomes the working pressure，which is shown as follows： P=3.14/4D21nPa103kNwhere，D1 is
