畢業(yè)設計---振動篩外文翻譯

1、 第 1 頁 Screening Vibrating screensPrinciples --Vibrating screens save space and weight and operate on little power because the screening surface may be actuated b

2、y vibrating, gyrating or pulsating movement of small amplitude, but at frequencies that normally exceed 3,000/min. Selection of Proper Vibration Sereen --Be sure the screen supplier knows all details of the application.

3、 The centrifugal force factor, or combination of frequency of vibration (speed) and amplitude (throw), may affect performance of any vibrating screen. Also, a correct combination of slope and direction of mechanism rota

4、tion is vital for inclined screens. Usually, the larger the opening, the greater the amplitude needed for a screen. If the throw is too small, the material may clog or wedge in the openings. Increasing the throw beyond

5、what is required to prevent blinding or plugging does not necessarily increase the life of the bearings and reduce screening efficiency. Increased rate of travel permits more tonnage to be passed over the screen per unit

6、 of time. For a given tonnage, a faster rate of travel results in a thinner bed of material and high screening efficiency. Maximum slope is reached when the material travels too fast for the fines to penetrate the ribbon

7、 of material and reach the apertures in the screen cloth. At this point an excessive amount of fine material passes over the screen with the oversize, resulting in poor efficiency. When an existing screen is to be used f

8、or an application other than that for which it was originally intended, check with the Supplier to see if any of the operating characteristics need modification and if the the screen is structurally suitable for the new

9、 application. The operator can get the correct vibrating screen by providing the supplier with the following information: ? Maximum tons per hour to be screened, including any circulating load or any surges in the feed

10、 rate. ? A complete size consist or sieve analysis of the material or, if available, an estimated analysis. ? Type of material and weight per cubic foot in broken state. ? Separations desired on each deck. ? Surface moi

11、sture carried by the material if screening is to be dry or amount of water with feed if wet. ? Special operating requirements or conditions such as temperature, abrasiveness, corrosiveness or other physical characteris

12、tics of the feed, warm, dry screen wire versus cold, damp material can be maintained economically through transformer control settings. With every opening in the heated screen mesh protected against blinding, there is no

13、 guesswork about what size particle will be delivered. A uniform, unvarying quality to meet tough specifications comes through day after day, no matter what the weather. (High humidity makes trouble with unheated screen

14、s.) Plants operating heated screens will have no trouble with excessive amounts of fine, dusty material that formerly sifted through reduced meshes on clogged screens. Service life of screen cloth is greatly increased w

15、hen electric heating ends the punishment of old-fashioned cleaning methods, such as rough pounding or brushing. Blowtorch flames put too much heat in one spot and bouncing chains added to wear and tear. But, screens kep

16、t clean and open with electric heating reportedly are seldom mistreated and last up to eight times as long. Heated decks end the threat of pile ups and strains that can break the mesh. Economical operation of electric he

17、ating for screens requires one transformer for installations of up to three panels of screen cloth (maximum area 4- x 12-ft). Two transformers are used on longer decks. Any deck (top, center or bottom) can be heated. El

18、ectric heating is most desirable of all where a screen surface is hard to get at. Changing heated screens does not involve more unbolting than needed for ordinary screens. In specifying screens to deliver a uniform parti

19、cle through heated mesh, the first thing to consider is weight per square foot of the wire cloth needed to set up appropriate resistance. Most calculations are based on square openings. Slotted openings must be identifie

20、d as to width of clear opening, diameter of wire and number of wires per inch before weight per square foot can be found in any screen cloth manufacturer's catalog. Having determined the usable weight per square foo

21、t of screen cloth, the next step is to select the size of clear opening needed, making no allowance for reduction in this size as formerly was the case when material stuck to the wires. Heated wires will maintain the c

22、lear opening at all times, making it possible to screen finer without blinding. From a wire catalog, select a mesh weighing no more per square foot (can weigh less) than determined using the method above with the clear

23、 opening characteristics desired. This often turns out to be a more efficient screen because the wire diameter will be smaller and the percentage of the open area will be greater. For example, where a 1/8-in. clear open