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Coal Extraction
The Shearer(I)
Although there are many models, the shearer has several common basic components. A double-ended ranging-drum shearer(Fig.18.1), for example, consists of four major components: electric motors, gearheads, haulage unit (power pack), and the cutting drums.
The electric motor ranging form 300 to1000 horsepower (223~750kw) is the power source for the shearer.It provides power to run the hydraulic pumps in the haulage unit and the gearheads for the cutting drum. The large capacity shearers are generally equipped with two electric motors; one for the haulage unit and one gearhead and the other for the other gearhead and other ancillary equipment. The motors can be remotely controlled.
There are two gearheads, one on the left, and the other on the right-hand side of the shearer. Each gearhead consider of a gearhead, gearbox and ranging arm.
The cutting drum is laced with spiral vanes on which the cutting bits are mounted. Its diameter ranges form 34 to 72 in (0.86~1.83m) with rotational speeds form 30 to 105 rpm. The trends are toward fewer but larger bits and slower drum speed for better cutting efficiency and less coal dust production. The drums are also equipped with power cowl is usually located behind the cutting drum. For that reason, it can be rotated a full 180°
The electric motor, haulage unit and gearhead box combine to form the shearer’s body which is mounted on the underframe. The underframe has four sliding shoes. The face-side shoes. The face-side shoes are fitted and ride on the face side top guide of the face conveyor pan, and the other two gob-side sliding shoes are fitted on a guide tube to prevent derailment. The tramming speed of the shearer ranges form 19 to 46 ft/min (5.8~14.0m/min).
In addition, the shearer is equipped with auxiliary hydraulic pumps and control valves for operating the ranging arms and powers cowls, water spraying devices,cable, chain anchorage and tensioners and so on.
Types of Modern Shearers
Since its first appearance in 1954, the shearer has undergone continuous changes both in capability and structure. It is now types of shearers, single and double-drum. In the earlier models, the drum in the single-drum shearer is mounted on the shearer’s body and cannot be adjusted for height. Therefore it is not suitable for areas where are constant changes in seam thickness and floor undulation. Thus the single-ended fixed-drum shearer is used mostly for thin seams.
For the single-drum shearer with a ranging arm, the cutting drum is mounted at the very end of the ranging arm. The ranging arm can be raised up and down by hydraulic control to accommodate the changing seam thickness and floor undulation. (Fig.18.2)
But when the seam exceeds a certain thickness, the single-drum shearer can not cut the entire seam height in one cut and a return cutting trip is necessary to complete a full web cut. Furthermore, since the drum is located on the headentry side, it generally requires a niche in the tailentry side. A niche is a precut at face end, one web deep and a shearer’s length long. With a niche at the face end the shearer can turn around.
Nowadays, the double ranging-drum shearers are used predominantly. The shearer cuts the whole seam height in one trip. The two drums can be positioned to any required height (within the designed range) during cutting and lowered well below the floor level. The arrangement of the drums enables the whole seam to be cut in either direction of travel, thereby ensuring rapid face advance and shortening roof exposure time. There are various types of double ranging-drum shearers. Based on the location of the drums, there are two types: one with one with both drums mounted on one side of the machine. The former type is the most widely used. Its advantage is that with one drum on each side of the shearer, it can sump in either direction.
During the cutting trip, the leading drum cuts the upper 70% of the seam height while the rear drum cuts the lower 30% and cleans up the broken coal on the floor. The two drums are approximately 23~33ft (7~10m) apart. When the shearer is traveling in the opposite direction to that of the face conveyor, the coal cut by the leading drum has to pass under the shearer’s body, which increase the moving resistance of the shearer and the face conveyor and cause a “crowding” condition. If the broken coal is too large, it may block the shearer and stop the operation. In general, when the shearer and the face conveyor are traveling in the opposite directions, approximately 70% of the coal taken by the leading drum will pass under the shearer. But when they are traveling in the sane direction,the coal taken down by the rear drum together with the float coal from the floor constitute the approximately 30% of the coal that has to pass under the shearer. The former case consumes 25% more power than the latter. As compared to the single-ended shearer, the underframe of the double-ended shearer is higher, thereby ensuring a sufficient cross section for coal passage.
Based on the method of adjusting the height of the cutting drum, there are also two types of shearers: ranging-arm shearer and gearhead shearer (Fig 18.3).
The former one is commonly used, whereas the latter one is a recent development. The advantage of the gearhead shearer is that the haulage unit is located at the center of the shearer’s body and mounted on the underframe. On both sides of the haulage unit, there is gearhead. Each gearhead contains an electric motor and a speed-reduction unit. The gearhead is raised and lowered by an adjustable hydraulic ram. The adjustable range of cutting height is large. It can reach up to 4.6ft(1.4m).
采 煤
-----采煤機
盡管采煤機有很多模型,它們?nèi)匀挥幸恍┕餐幕窘M成部分。例如,雙端可調(diào)高滾筒采煤機由四個主要部分組成:電動機,傳動機頭,牽引部(動力裝置)和截割滾筒。
300至1000馬力(223至750千瓦)的電動機是采煤機的能量來源。它為截割滾筒在牽引部和傳動機頭中給液壓泵提供動力。大功率滾筒式采煤機一般裝有兩臺電動機;一臺帶動牽引部及一傳動機頭;另一臺帶動另一傳動機頭及其他輔助設備。電動機可以遠程控制。
采煤機上有兩個傳動機頭,一個在左邊,另一個在采煤機的右邊。每一個傳動機頭都由一個傳動機頭,一個齒輪箱和一個搖臂組成。
螺旋形的輪葉把截割滾筒束緊在安裝的截齒上。它的直徑為34至72(大約0.86至1.83米),轉(zhuǎn)速為30至105。其發(fā)展趨勢是采用數(shù)量少一些但大一點的截齒,并減低截割滾筒的轉(zhuǎn)速,一邊提高截割效率和減少煤塵的產(chǎn)生。截齒也裝有動力擋煤板,通常位于截割滾筒的后面 。因此,它可以旋轉(zhuǎn)180度。
電動機,牽引部和傳動機頭箱組合成采煤機的主體安裝在底座上。底座有四個滑瓦??拷ぷ髅嬉粋?cè)的滑瓦,安置在工作面輸送機槽的頂部導軌上,二靠近采空區(qū)一側(cè)的另外兩個滑瓦,則安置在導管上,以防脫軌。采煤機的牽引速度為每分鐘19至46英尺(約為每分鐘5.8至14.0米)。
除此之外,采煤機還裝有輔助的液壓泵和控制閥來操作搖臂,動力擋煤板,噴水裝置,牽引鏈錨固和拉進裝置,。
自從采煤機的第一次在1954年問世以來,它已經(jīng)在能力和結(jié)構(gòu)上經(jīng)歷了持續(xù)不斷的變化?,F(xiàn)在采煤機的種類有單滾筒采煤機和雙滾筒采煤機。在更早的模型里,單滾筒采煤機的滾筒是安裝在采煤機的主體部位而且不同適應它本身的高度。因此,它不適宜在有著不斷變化的煤層厚度和底板起伏不平的區(qū)域里。因而單端固定滾筒采煤機大多數(shù)情況下用于薄煤層。
單搖臂但滾筒采煤機的截割滾筒就安裝在該搖臂的末端。搖臂可以通過液壓控制來調(diào)節(jié)不斷變化的煤層厚度和底板起伏不平來升高降低。
但是當煤層超過一定的厚度,單滾筒采煤機就不能一次過截割整個煤層高度,所以是有必要來一次來回截割來完成一個完整的截割。此外,自從滾筒安裝在運輸順槽一邊,它通常需要在回風順槽有一個缺口。缺口是在工作面端頭預先開出的,其大小為一個截深和一臺采煤機機體的長度。有了工作面端頭的卻都,采煤機可以掉頭。
如今,雙滾筒采煤機占據(jù)主導地位。采煤機一次可以截割整一個煤層高度。兩個滾筒在截割過程中可以處于任何一種需要的高度(在設計的范圍內(nèi)),降低到地平線以下。滾筒的這種布置,使采煤機在每一次往返行程中均能進行整層截割,從而可保證工作面迅速推進并縮短頂板懸露時間。有不同類型的雙滾筒采煤機。根據(jù)滾筒的安裝位置,采煤機課分為兩類:一類是采煤機機身兩側(cè)各安一個滾筒;另一類是兩個滾筒都安在機身一側(cè)。大多數(shù)使用前一種,它的優(yōu)勢在于采煤機每一邊都有一個滾筒可以在任一個方向進刀。
在截割的過程中,前面的滾筒截割上部煤層高度的百分之七十,而后面的滾筒截割下部的百分之三十和清理地上損壞的煤渣。兩個滾筒相距23至33英尺(約7至10米)。當采煤機與工作面輸送機反向運行時,前滾筒采下的煤必須從采煤機機身下面通過,這就加大了采煤機及輸送機的運行阻力,并造成“堵塞”現(xiàn)象。如果壞掉的煤渣太大,它可能會阻礙采煤機,停止采煤機的運行??偟膩碚f,當采煤機和工作面輸送機在相反方面運行時,前滾筒采的大約百分之七十的煤會在采煤機底下通過。但是當它們在相同方向運行時,后滾筒采的煤和地上的浮煤組成的只有百分之三十的煤在采煤機地下通過。前者比后者多消耗了百分之二十五的能量。與單滾筒采煤機相比,雙滾筒采煤機的底座更高,因此能夠保證有效的橫截面運煤。
根據(jù)截割滾筒高度的調(diào)整,采煤機可分為兩類:搖臂采煤機和傳動機頭采煤機。
前者是經(jīng)常使用的,而后者是最近才發(fā)展運用的。傳動機頭采煤機的優(yōu)勢在于它的牽引部是安置在采煤機機身的中心和底座。在牽引部的兩邊都有一個傳動機頭。每一個傳動機頭都包含一個電動機和一個減速裝置。傳動機頭通過一個可調(diào)液壓千斤頂來升高和降低的。截割高度的調(diào)節(jié)范圍很大,它可以達到4.6英尺(1.4米)。