Application of Over-Winding and Over-Falling Buffer Unit in Coal Mines of Datong Coal Group Company

Dec.2005J.China Univof Mining &Tech (English Edition)Vol 15 No 4Application of Over-Winding andOver-Falling buffer Unit in Coal Mines ofDatong Coal Group CompanyWANG Hong-qing WANG Jian-liDatong, Shanxi 037003, ChinResearch institute of Science and Technology, China University of Mining& Technology, Xuzhou, Jiangsu 221008, ChinAbstract: Dynamic force of Bs buffer unit in the enwinding hoisting system is calculated, and the buffer unit is in-stalled and tested. The result shows that this buffer unit is accurate in its regulated braking force and convenient in ad-justment and restoration. It can be repeatedly used as a bumper for both over-winding and over-falling without replacingany parts, providing an applicable device for safety operation in coal miningKey words: hoisting; over-winding; over-falling; buffer unitCLC number: TD 534. 21 IntroductionCoal Mines, issued in 2005 by the State Admini-stration of Safety Supervision for Coal Mines ofUp to now, Bs buffer units have been used in China, stipulates that a buffer unit with reliable per-some of the auxiliary shafts in coal mines of Datong formance must be installed within the over-windingCoal Group Company. Since 1995, no worker has or over-falling interval for hoisting. The buffer unitbeen hurt by over-winding or over-falling accident at should be able to quietly stop a cage or a balanceall in those auxiliary shafts where the bs buffer unit weight which is in a full-speed over-winding oris installed, achieving good social and economic ef- over-falling process so as to avoid a backward fallingfectdown or rebounding up. The buffer unit developed byAlthough there are many kinds of protective de- China University of mining technology has beenvices in hoisting systems, accidents hurting workers used in coal mines of Datong Coal Group Companyhoisting process still frequently take place. The for several years. The result shows that it can be usedreason for these accidents is that most of the protec- as a buffer for both over-winding and over-fallingtive devices are electric devices which are poor in operations and is less in maintenance, uniform inreliability, such as speed limitation protector of hoist, braking force, and is used in a closed form. So it canndicator, slowing down protector, meet the requirements stipulated by the Safety Regu-over-winding-proof protector, and slack rope protec- lations fortor. These protective devices need to be frequentlyFor convenient. we have the following assumichecked and maintained, resulting in a heavytions 21load, making oversight hard to avoid. Aiming at this1)The lateral vibration of hoisting cable is igproblem, the 397 item of the Safety Regulations for nored; 2)The中国煤化工 off in theReceived 25 Augst 2005; accepted 20 September 2005CNMHGCorrespondingauthorTel:+86-13952196261:E-mailaddressjianw623@hotmail.comJ. China Univ of Mining Tech(English Edition)Vol 15 No 4over-winding buffering process anno drivingSome researches show that the a value determoment exists; 3) No braking force is applied to the mined by maximum over-winding distance s isdamping brake of the hoist; 4) Braking force of the much smaller than 5 m/sbuffer unit is regarded as a constant; And 5) theTherefore, the interval of a isover-winding and over-falling buffer units are not(3)ynchronously laid out, which means the end ofover-falling is the beginning of over-windingwhere vo is the initial speed of cage in over- wind-g process(m/s)2 Calculation of Braking ForceSubstituting (2)and(3) into(1), we have theformula for calculating the braking force of21 Over-winding buffer unitover-winding buffer unit, which isBased on the above mentioned assumption, theand expressed as the following formula (3-y n as Fig.strained state of over-winding cage is showM+DH≤2S∑F≤5∑M∑m(gIn the left hand of formula(4), the mass of aempty cage should be substituted into >m, and inthe right hand, the overall mass of heavily loadedcage and should be substituted into∑2.2 Over-falling buffer unitThe strained state of over-winding cage is shownFig 1 Stress analysis of over-windingas Fig. 2, and its kinetic equation, as formula(5)∑ma1-∑F-∑mg=0,(1)here T is the tensile force at the joint betweenT,hoisting cable and the over-winding cage (N)∑F∑m, is the overall mass of the over-winding cage(kg), a, is the deceleration of the over-windingcage (m/s")∑Fs is the adjusted braking force ofIn,gover-winding buffer unit(N), and 8 is the gravity Fig. 2 Dynamic analysis of the cage in over-falling proces(9.18m/s2)According to the assumption, T can be cal72-∑m2a-∑F+∑mg=0(5)lated bywhere T2 is the tensile force at the joint between the∑hoisting cable and the cage(n)∑m, is the overallwhere∑M is the mass of the hoist system not inmass of over-falling cage(kg), a is the decelera-cluding the mass of its cage (kg), p is the unit tion of the cage(m/s),and >F is the regulatedlength weight of hoisting cable(N/m), and H is the braking force(Ndepth of shaft(m)The over-falling process includes three stages,According to the Safety Regulations for which are wire rope releasing, idle motion of fallingMines,for a heavily loaded hoist in its hoisting protector, and braking with the help of falling protecprocess, the deceleration must be equal to or smaller tor. Although, for the buffer unit, there is not an obthan 5 m/s when the safety brake works. It goes vious requiremH中国煤化工 ety regulawithout saying that the braking force of buffer unit tions for MinesCN MH Ghe cage. weshould be determined according to this requirementmay take the stipulation about the falling protector asWANG Hong-qing et alApplication of Over-Winding and Over- Falling Buffer Unit in Coal Mines ofa reference, which is a <5 gMaximum over-winding distance S=5mBased on our experiment, if the braking force ofwhich only the over-falling buffer unit functions 3.1 Calculation of braking force of over-widingalone is regulated to be in accord with the upper limitbuffer unitvalue stipulated by the Safety Regulations foow substitute the related data into formula (4)Mines, that is a<5 g, the over-falling velocity will It should be noted that in the left hand side of formulaeach its maximum value. At the moment that the (4), m, refers to the mass of light cage(withfalling protector begins its braking function, the cage only one person), while that in the right hand side,ithas already stopped falling or its falling velocity is refers to the fully loaded cage mass. By doing so, wesmaller than its creeping velocity(generally 0.5 m/s). obtain the interval of Fs(the braking force ofIn this process, even if the falling protector works inover-winding buffer unit of the cage on one side),braking, there will not have any damage to workerswhich isriding the cage because of a low velocity and a short∑5.525.5timeF≥45000×-(7134+75)9.81Suppose that, before buffering, the falling cage66.3×198=100339Nis in a uniform motion at a velocity of vo, the fallingandvelocity v of the falling protector after an idle moF≤5×45000(7134+4200)981-5)+tion time tk(generally tx-0.2 s) can be expressed∑66.3×198=183611N∑m2that is 100339N∑ m28 is the conditionif formula( 6) holdsLet v<0.5 m/s∑F calculated fromformula (6) can be used as the lower limit value ofbraking force of the over-falling buffer unit3 Case StudyFig 3 Lay-out of buffer unitThe auxiliary shaft of Yanzishan Mine uses adouble-cage and double-layer hoist, its main paranters are as followsThe safety factor should be corrected basedMaximum hoisting speed: vmax =vo=5.5 m/sonthe data calculated from the above formula. n>3 isMass of the cage ( including the grasperthe precondition to keep the wire rope unbroken inm=7134kg;over-winding processLoad capacity:2×28×75=4200kg3.2 Calculation of braking forceType of wire rope 6x19-043, its totalIn order to make the manned cage be more stabreaking force: P=1.19x10n, mass of unitble in over-falling process, a=3 g is usually usedIt is welllength: P=66.3N/m:Equivalent mass of the hoist system (not indeceleration i中国煤化工CNMHGcluding the cage )∑M=45000kgsituation theJ. China Univ of Mining Tech(English Edition)Vol 15 No 4∑F.≤f(134+75)0+3)×981=282881N. buffering test. 1.8 m is rushed upward after the cageroof has touched the buffer beam and then the brakeSubstitute this value directly into formula(6),webegins functioning. The steel guard bars are fully de-formed in this process, showing that the buffer unit282881WO√(7134+75)×252×10°The unhook method is used in over-falling buffsin arccos 1-7134+75981ering test. The disturbance resulted from falling pro282881tector is eliminated by jacking up its operating2828819810.2mechanism. The maximum test height for empty cageat the fastest hoisting speed in the unhook test is 1.5dv=-4.77ult shows that l )the buffer distance ofIt can be seen that if the above calculated valuethe cage is 0.62 m and the buffer deceleration iswas used as braking force of the buffer unit, the cage 2.42x981 m/s, 2)the overall braking force of thewould have stopped before the release of wire ropefour buffer units is 239 302 N, and 3 )the averageFrom calculation, if 2F.=150000N, v=0.13 braking force for a single buffer unit is 59 825 Nm/s, then 150000Ns2F. <282881 N, and the having an error of 6.1% to the designed value,whichaverage braking force F of each buffer iscan meet the design requirement37500N≤F2<70720NonclusionThe layout of over-falling buffer unit is the sameas that of over-winding buffer unit, and the differenceTheoretical analysis and case study show thatof them is in an opposite directionthe pre-determined braking force for buffer unit is3.3 Result and analysiscorrect. It is simple in regulation and can be repeatedAccording to the unhooking test, the average used without replacing any parts. It can be used forbraking forces of over-winding buffer and over-fal- not only over- falling buffering but also for over-ling buffer are Fs=39240N and Fr = 63765N, winding buffering, which has provided an applicablerespectivelysafety equipment for carrying out the Safety RegulaThe up-rush method is used for over-winding tions for Coal MinesReferences[1 State Administration of Safety Supervision for Coal Mines of China. Safety Regulations for Coal Mines. Beijing: Coal Industry Press, 2004.(In Chinese)2 Li J L. Research on Over-Winding and Protection of friction Hoist Container: [Ph D. dissertation]. Xuzhou: China Universityof Mining Technology, 1989.(In Chinese[3] Wang J L, Ge T L, Dynamic analysis of overwinding and overfalling of a drum winding hoist. Journal of China University ofMining Technology, 1997, 26(2): 103-106 (In Chinese[4] Hong X H Mine Conveyance and Hoist. Xuzhou: Chine University of Mining Technology Press, 2000. (In Chinese[5] Wang J L. Theoretical, Experimental, and applied Research on Over-Winding Buffer Unit of hoist Container: [ Ph D dissertation]. Xuzhou: China University of Mining Technology, 1995.(In Chinese)中国煤化工CNMHG