Conveyor Engineering Layouts and Formulas
Layouts and formulas
Chain rolling or sliding and material carried
The layouts on this page and page E-7 represent the most common conveyor arrangements. For layouts not shown, consult Rexnord Industrial Chain.
Layout A L
TAKE-UP
E
The symbols used in the formulas and layouts are: F = Friction factor, Tables 7 and 8 HP = Horsepower at head shaft L = Length of conveyor or elevator centers, feet M = Weight of material carried per foot of conveyor or elevator, pounds P = Chain pitch, inches PB = Pull due to digging material from elevator boot, pounds PC = Conveyor pull due to catenary tension, pounds (See page E-2 for formula.) PL = Conveyor or elevator pull on loaded run, pounds PO = Conveyor pull from other sources, pounds PR = Conveyor pull on return run, pounds PT = Total calculated chain pull per strand, pounds PCV = Total calculated conveyor pull, pounds PEL = Total calculated elevator pull, pounds PTU = Conveyor take-up pull, pounds R = Vertical rise of elevator or inclined portion of conveyor, feet S = Chain speed, feet per minute T = Number of teeth in drive sprocket W = Weight of chain and conveying member (slats, buckets, etc.), pounds per foot of conveyor Y = Horizontal length of inclined portion of conveyor or elevator, feet
Coefficients of friction The factors in Tables 7 and 8 refer to roller chains operating on smooth, flat, clean tracks at normal operating temperatures. The factors should be increased when tracks cannot be kept clean. The coefficients of sliding friction in Table 7 apply when the conveyed load is carried by the edges of the chain sidebars or by the top plates of flat-top roller chains. The coefficients of rolling friction in Table 8 apply when the conveyed load is carried by double-pitch conveyor chains with large diameter rollers. Chains with standard diameter rollers are not recommended for rolling conveyors since the rollers may not always turn due to the small ratio between outside and inside diameters.
E-6
DRIVE
TRAVEL
If the conveyor design involves both a horizontal and an inclined section, the total conveyor pull (PCV) is determined by calculating separate conveyor pulls for each section, using the formulas in Layouts A & B, and adding them together.
PCV
TRACK TRACK
Fig. 5068
Fig. 5068
The total conveyor pull is the sum of the following: Pull on loaded run PL = (W + M)LF Pull on return run PR = WLF Take-up pull ∆ PTU or PU Pull to operate tail sprocket PR × .1 Pull from other factors PO Total conveyor pull PCV Calculate the total chain pull per strand (PT) by dividing PCV by the number of strands taking the load. ∆ Usually, the takeup pull is known. If not, use 0.3% of the chain’s ultimate strength as a reasonable estimate. Horsepower required to operate the conveyor HP = (PCV – PTU or PC ) × 1.2 × S 33,000
Table 7 • Coefficient of sliding friction
(Conveyed load carried by chain sidebars or top plates)
Non-lubricated steel track
Lubricated steel track
.33
.24
Table 8 • Coefficient of rolling friction s
(Conveyed load carried by large diameter rollers)
Chain number C 2042 C 2052 C 2062H C 2082H C 2102H C 2122H
Non-lubricated Chain pitch, chain inches 1.000 1.250 1.500 2.000 2.500 3.000
.17 .16 .16 .15 .14 .14
Lubricated chain n
.12 .11 .11 .10 .09 .09
s When calculating the approximate chain pull, use a trial rolling friction factor of .17 for non-lubricated chains or .12 for lubricated chains. n These factors should be used only when an adequate oil film will be maintained between rollers and bushings. Otherwise, use the factors for non- lubricated chain.