Hitachi

Conveyor Chain Selection Example #2: Inclined Scraper Flight Conveyor Step 2: Calculate Conveyor Pull Supplied Information: Bulk Material Bituminous Coal - slack dry. Conveyor Capacity: 150 Tons/hr Operating Speed: 100 ft/min Total Lift: 30 ft Sprocket Centers: 50 ft Infrequent Moderate Shock Loading. 24 Hour Operation in Dirty Conditions Steel Trough Width: 24 inches Average depth of Coal: 6 inches Scraper Flights: 5/16" x 12" x 23" long, 22.8 lbs. ea We now use the Conveyor Pull formula for the incline conveyor on the preceding pages as follows: P=[(Mf)cosu+(Wf)cosu+Msinu+Wsinu]C + [(Wf)cosu-Wsinu]C+J J = (C x H ) / R From Table 7 we note that R = 14 for coal and thus: J = (50 x 6 x 6 ) / 14 J = 129 lbs. Now we determine P P = [(50)(.5)(.8)+(50)(.14)(.8)+(50)(.6)+(50)(.6)] (50)+ [(50)(.14)(.8)-(50)(.6)] (50)+129 P = [20 + 5.6 + 30 + 30] (50) + [5.6-30] (50) + 129 P = 4,280 - 1,220 + 129 P = 3,189 Step 1: Determine Basic Requirements An appropriate chain type for a scrapper flight incline conveyor when the chain does not run in the material might be 2 strands of a Roller Conveyor Chain with G-19 or G-29 scraper flight attachments. Since we are traveling up an incline the roller type chain will help reduce the power required. Dirty conditions may prevent the use of effective lubrication so we will base our selection assuming no lubrication for the chain. Finally, we note that in this bulk material conveyor the chain does not directly carry the conveyed load, therefore, there will be no need to check the allowable roller/bushing bearing pressure. G-19 attachments are available in 9"-24" pitch chains. G-29 attachments are available in 4" or 6" pitch chains. If we tentatively select a 9" pitch 925R chain we can calculate the estimated weight of the chain attachments and flights as follows: Chain and attachments = 9.8 lbs/ft. x 2 strands = 19.6 lbs/ft. Scraper flights weigh 22.8 x (12/9) = 30.4 W = 19.6 + 30.4 = 50.4 lbs/ft Material weight (M) is determined by: M = [33.3 x Capacity (tons/hr)] / conveyor speed (ft/min) M = (33.3 x 150) / 100 M = 50 lbs/ft We estimate the rolling friction coefficient to be fr = .14 since 925R has a 3 inch diameter roller which will not be lubricated (see Table 3 page 25). The sliding friction coefficient for bituminous coal in a steel trough from Table 4 (page 25) is fs=.50 From Table 10 (page 27) we find the Service factor by: SF = 1.0 x 1.2 x 1.4 x 1.2 SF = 2.02 From Table 9 (page 27) if we specify a 12 tooth sprocket we determine the speed correction factor as: SC = .99 From Table 8 (page 26) since we are using 2 strands of chain we determine the number of strands factor as: NS = 1.2 Since the conveyor is inclined it will be useful to determine the sine and cosine of the incline angle: sinu = 30 /50 cosu = 40 / 50 sinu = .6 cosu = .8 Step 3: Calculate Design Conveyor Pull The Design Conveyor Pull (DP) is given by: DP = P x SF x SC x NS DP = 3,189 x 2.02 x .99 x 1.2 DP = 7,653 lbs. Step 4: Calculate Chain Tension The calculated Chain Tension (T) is given by: T = DP / Total Number of Chain Strands T = 7,653 / 2 T = 3,827 lbs Step 5: Select Chain, Recalculate Chain Tension (T) From the dimensional tables we note that our tentative selection of 925R has rated working load of 4,150 lbs. which is greater than the calculated value of 3,827 lbs. so that 925 is a satisfactory selection. If we determined that the sprocket is too large for this application and that a 6 inch pitch chain with an 11 Tooth sprocket was required we can check the suitability of 1131R with G-29 attachments every 6 inches as follows: W=((12.5 + 2.7) x 2) + (22.8 x (12 / 6)) W = 30.4 + 45.6 W = 76 lbs / ft M = 50 lbs/ft;SF=2.02;SC=1.03(see Table 10) and NS=1.2 P = [(50)(.5)(.8)+(76)(1.4)(.8) + (50)(.6)+(76)(.6)](50)+ [(76)(.14)(.8) - (76)(.6)] + 129 P = [20 + 8.5 +30 + 45.6](50) + [8.5-45.6](50) + 129 P = [5,205 - 1,855 + 129] P = 3,221 lbs. DP = 3,221 x 2.02 x 1.03 x 1.2 = 8,042 lbs T = 8,042 / 2 = 4,021 lbs. Since the calculated chain tension (4,021 lbs) is less than the rated working load (5,900 lbs) for 1131R, this chain is suitable. We note that we could select a lighter 6 inch pitch chain such as 625R without additional calculation since it's rated working load is 4,150 lbs. The scrapper flight attachment is not standard, but can be designed. 29

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