BS 4409-3-1982 Screw conveyors Method for calculating drive power《螺旋输送机 第3部分 传动功率计算方法》.pdf

1、BRITISH STANDARD BS 4409-3: 1982 ISO 7119:1981 Screw conveyors Part 3: Method for calculating drive power ISO title: Continuous mechanical handling equipment for loose bulk materials Screw conveyors Design rules for drive power UDC 621.867.42 8BS4409-3:1982 This British Standard, having been prepare

2、d under the directionof the Mechanical Engineering Standards Committee, was published underthe authority of the BoardofBSI and comes intoeffecton 29October1982 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference MEE/128 Draft for comment 80/75221 DC ISBN

3、 0 580 13024 X Cooperating organizations The Mechanical Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: The organizations marked with an asterisk in the above list, together with the following, were directly r

4、epresented on the Technical Committee entrusted with the preparation of this British Standard: Associated Offices Technical Committee* Department of Trade (Marine Division) Association of Consulting Engineers* Department of Transport Association of Hydraulic Equipment Electricity Supply Industry in

5、England and Manufacturers Wales Association of Mining Electrical and Energy Industries Council Mechanical Engineers Engineering Equipment Users Association* British Compressed Air Society Federation of Manufacturers of Construction British Constructional Steelwork Association Equipment and Cranes Br

6、itish Electrical and Allied Manufacturers Health and Safety Executive* Association (BEAMA) Institution of Gas Engineers British Gas Corporation Institution of Mechanical Engineers* British Gear Manufacturers Association Institution of Plant Engineers British Internal Combustion Engine Institution of

7、 Production Engineers* Manufacturers Association Lloyds Register of Shipping British Pump Manufacturers Association London Transport Executive British Steel Corporation Machine Tool Industry Research Association British Steel Industry Ministry of Defence British Valve Manufacturers Association Ltd N

8、ational Coal Board* Chartered Institution of Building Services Oil Companies Materials Association Crown Agents for Oversea Governments and Process Plant Association Administrations Society of Motor Manufacturers and Traders Department of Industry (Mechanical Limited Engineering) Telecommunication E

9、ngineering attention is drawn especially to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, th

10、ey should be read as “British Standard”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations.

11、Cross-reference International Standard Corresponding British Standard ISO 2148:1974 BS 3810 Glossary of terms used in materials handling Part 2:1965 Terms used in connection with conveyors and elevators (excluding pneumatic and hydraulic handling) (Technically equivalent) Summary of pages This docum

12、ent comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS4409-3:1982

13、BSI 10-1999 1 1 Scope This International Standard establishes a method for the calculation of drive power of screw conveyors. 2 Field of application This International Standard only applies to a screw conveyor, used in a horizontal or inclined position (up to approximately20 ), for a regular, contro

14、lled and continual supply of the bulk materials. Excluded from this International Standard are the special screws for the following special uses: extracting screws calibrating screws mixing screws moistening screws inclined screw (above20 ) vertical screws 3 Reference ISO 2148, Continuous mechanical

15、 handling equipmentNomenclature. 4 Comments The necessary drive power and the rate of flow of the material which may be reached by a screw conveyor are interdependent. Nevertheless, they also depend upon the operating conditions, the nature of the product conveyed and the design parameters, the most

16、 important of which are considered in this International Standard which describes a relatively easy design method and therefore only reaches a limited accuracy which is however quite sufficient in most cases. A large number of less important parameters are not taken into account in the following for

17、mulae. Numerous factors in the formulae are empirical and result from long practical experience. 5 Symbols and units 6 Calculation of the capacity of a screw conveyor The nominal capacity to be considered is the capacity per hour of the maximum volume that may be reached by a screw conveyor. The vol

18、ume flow rate I Vis the product of: the working section of the screw conveyor in square metres by the conveying speed, in metres persecond from which results the equation: Symbol Designation Units A Working section of screw conveyor m 2 D Nominal screw diameter m F H Main resistances N F N Secondary

19、 resistances N F St Resistances due to inclination N g Acceleration due to gravity m/s 2 H Lifting height m I M Mass flow rate t/h I V Volume flow rate m 3 /h L Conveying length m n Number of screw r.p.m. r/min P Total power kW P H Power for material progress kW P N Power when operating at no load k

20、W P St Power due to inclination kW S Screw pitch m Linear speed of material movement m/s Trough filling coefficient Density of bulk material t/m 3 Progress resistance coefficient S n 60 - =BS4409-3:1982 2 BSI 10-1999 Selection of the trough filling coefficient In the following cases: materials that

21、do not flow normally, filling coefficient too high, there is a large difference between the actual and the theoretical conveying speed introduced into the equation The maximum filling coefficients depend upon the friction and adhering properties of the conveyed materials, on the screw pitch and the

22、inclination of the screw centreline. In general, the following are used: . 0,45 for screws without intermediate bearings and for materials which flow easily, scarcely abrasive (flour, cereals). . 0,3 for the most current bulk materials, with average abrasive properties, with a grading varying from g

23、rains to small lumps (salts, sand, coal). . 0,15 for heavy bulk materials, very abrasive, agressive (ash, gravel, minerals). These values should be reduced in the following cases: extremely large propeller pitch (normally S. 0,6 D to1,0 D) screw inclination (approximately2% per degree of inclination

24、 up to20 ) small diameter screws with cumbersome intermediate bearings. It should be pointed out that the diameter of a screw should not only be defined by the capacity but also by the dimensions of the largest lumps and their percentage. The peripheral speed of the screw should not be too high so a

25、s to prevent the material being thrown upwards which will spoil its transport. The peripheral speed should be chosen as a function of the screw diameter D, the physical properties of the material and the filling coefficient. 7 Resistances to the movement of the screw conveyor As a whole, the resista

26、nces to the movement of the screw conveyor, are composed of: Included in these three groups are all the resistances which the drive of a screw conveyor must overcome in order to surmount friction, the inclination, and the setting in motion of the material at the loading point. The resistance due to

27、the inclination does not exist in all the plants and it is a function of the path inclination. Out of all these resistances, only the resistance due to the slope may be calculated accurately. 8 Drive power of loaded screw The drive power of the loaded screw is given by the formula: P = P H + P N + P

28、 St in which: 8.1 Power necessary for the progress of the material, P H In practice, the capacity of a screw conveyor is expressed by the formula I M= I V For a length L of the screw conveyor, the power P Hin kilowatts will be the product of the capacity I Mby the length L and an artificial friction

29、 coefficient also called the progress resistance coefficient. This formula stresses factors that are involved in the power input, which, for a horizontal screw, is proportional to the mass flow rate and length of conveyance. Power is also proportional to the progress resistance of the material, . In

30、 addition, it should be noted that the sliding of the material particles against each other gives rise to internal frictions. Finally, other resistances due to the grading or the shape of the output show up. All this gives the parameter a higher value than that of the friction coefficients. Each mat

31、erial has its own coefficient. It is generally in the order of2 to4. The Annex indicates the values of for a few bulk materials. F H the main resistancesmaterial progress F N resistances due to operating at no-load F St resistances due to the inclination. P H power necessary for the progress of the

32、material; P N drive power of the screw conveyor at no load; P St power due to inclination.BS4409-3:1982 BSI 10-1999 3 8.2 Drive power of the screw conveyor at no load, P N The power P Nis very low compared to the power required for the progress of the material. This value is proportional to the diam

33、eter and the length of the screw. In practice it is given, in kilowatts, by the formula: 8.3 Power due to inclination, P St The power, in kilowatts, will be the product of the capacity I Mby the height H and by the acceleration due to gravity g,i.e.: The height H is positive in ascending screws and

34、will be negative in the formula for descending screws. 8.4 Total power necessary for the shaft of the screw conveyor The total power necessary is the sum of the various powers described above: BS4409-3:1982 4 BSI 10-1999 Annex Values for bulk density and progress resistance coefficient for a fewbulk

35、 materials (for information) Materials Bulk density in t/m 3 Progress resistance coefficient Ash and slag Lignite Ferrous hematite Heavy minerals (Cu-Pb) Light minerals Oats, barley Graphite Roasted lime Hydrated lime Potatoes Gravel Coke Ordinary Coal Classified Coal Clay, damp loam Flour Marl Mort

36、ar Maize, rye, rice Sand Wheat Cement 0,7to 1 1,1to 1,3 1,4 2to 2,5 1,25 to 2 0,5 0,4to 0,6 0,9 0,5 0,7 1,5to 1,8 0,5 0,8 0,9 1,8 0,6 1,6to 1,9 1,8to 2,1 0,5to 0,7 1,4to 1,7 0,8 1,0to 1,3 3 2,2 2,2 2,2 2,2 1,9 1,9 2,2 1,9 1,9 3 3 2,2 1,9 1,9 1,9 2,2 3 1,9 3 1,9 1,9BS4409-3:1982 BSI 10-1999 Publicati

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