CHAIN DRIVE SELECTION Heavy Series Chains
BRITISH STANDARD CHAIN DRIVE SELECTION
Table 4: ANSI Roller Chain Selection Table
1. The following must be considered when selecting roller chain: a. Source of Power b. Driven machine c. HP to be transmitted d. RPM of drive and driven shafts e. Diameter of shafts f. Center distance of shafts 2. Use Table 1 to obtain the service factor. 3. Multiply the horsepower value by the service factor to obtain the design horsepower value. 4. Use Table 4 on page 255 to obtain the chain number and the number of teeth for small sprockets. Refer to the number of revolutions of the high speed shaft (the driving shaft when the speed is reduced; the driven shaft when the speed is increased) and the design horsepower value. For smoother chain drive, a smaller pitch chain is suggested. If a single strand chain does not satisfy the requirements, use a multi-strand chain. If space is limited, a smaller pitch, multi-strand roller chain can be used. 5. After determining the number of teeth for the small sprocket, refer to the sprocket section to check if the sprocket diameter satisfies the space limitations. 6. The number of teeth for the large sprocket is determined by multiplying the number of teeth for the small sprocket by the speed ratio. More than 15 teeth on the small sprocket is suggested. The number of teeth for the small sprocket should be less than 120. By reducing the number of teeth for the small sprocket, the number of teeth for the large sprocket can be reduced. 7. For temperatures below 15°F, see the environmental temperatures and points of concern table on page 262.
Generally Super Series chains are suggested when the chain speed is less than 160 ft./min and where the roller chain or the ASME/ANSI Heavy Series chains are not strong enough to meet application requirements. 1) Tentatively select the chain and sprocket with the same size and number of teeth as used in the “Selection for Slow Speed. ” 2) Calculate the chain speed from the number of teeth of the driving sprocket using equation (A) and check whether the speed is less than 160 ft./min. 3) Calculate the chain tension necessary for the above drive from equation (B). 4) Select the same service factor and the chain speed coefficient from Tables 1 and 2. 5) Select the suitable chain and verify that the chain satisfies equation (C).
P × N × n 12
S =
! !
(Ft/min)
33,000 × HP S
T =
= ( LBS )
T x Service Factor x Chain Speed Coefficient ≤ or = to MAL ………..(C)
S: Chain speed (ft/min) P: Chain pitch (inches) N: Drive sprocket teeth No. n: RPM of drive sprocket T: Chain tensions (lbs)
Table 1: Service Factor Type of Impact
Service Factor
Smooth
1.0 1.3 1.5
Some Impact Large Impact
Table 1: Service Factor
Source of Power
Type of Impact
Machines
Internal Combustion Engine
Electric Motor or Turbine
With Hydraulic Drive
Without Hydraulic Drive
Table 2: Service Factor Chain Speed
Speed Coefficient
Belt conveyors with small load fluctuation, chain conveyors, centrifugal blowers, general textile machines, machines with small load fluctuation. Centrifugal compressors, marine engines, conveyors with some load fluctuation, automatic furnaces, dryers, pulverizers, general machine tools, compressors, general work machines, general paper mills. Press, contruction or mining machines, vibration machines, oil well rigs, rubber mixers, rolls, general machines with reverse or large impact loads.
Smooth
1.0
1.0
1.2
Less than 50 ft/min
1.0 1.2 1.4
50-100 ft/min 100-160 ft/min
How to use this table:
Some Impact
2 – Horsepower lines of 20, 24, and 30-tooth sprockets are shown only in the high speed range on the right hands side of the above chart. When checking with the horsepower line of these sprockets, make a line parallel to the other lines on the left hands side of the dotted line for a size 50, 24-tooth sprocket. 3 – When the chain speed is less than 160 ft./min, it is more economical to select the right roller chain by the selection method for slow speed drives (page 252).
1 – Example – Design horsepower 7hp a) Assume that the RPM of the small sprocket is 100. Judging from the inter- section point pf the design horsepower’s value of 7 hp and the RPM value of 100, size 80 roller chain and a subsequent sprocket with 17 or 18 teeth can be selected. Sprockets with 17 teeth are more economical than those with 18 teeth. b) Assume that the RPM of the small sprocket is 300. A size 60, 15-tooth sprocket is appropriate from the intersection point in the same manner as above. The line for a size 50 chain, 24-tooth sprocket can also be seen as near the intersection of 7 hp and 300 RPM. Therefore, either a size 60 chain, 15-tooth or a size 50 chain, 24-tooth sprocket can be selected. This table is used to make a tentative selection. The Horsepower Rating Tables should be used to determine the most appropriate chain and sprocket.
1.3
1.2
1.4
Large Impact
1.5
1.4
1.7
253
254
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