The size of the conveyor system required is determined by two factors, total chain pull, and the load to be carried on each trolley.

Plants with a large amount of overhead conveyors often use No. 458 systems instead of No. 348 for even the lightest loads, in order to standardize maintenance parts and permit future extension or combination of individual conveyors. The installed cost of No. 348 conveyor is not a great deal less than No. 458.

To calculate approximate chain pull, assume that the chain and trolley assembly weighs 10 lbs. per foot. Exact weights will be found in Table 3 when conveyor size and trolley spacing are known.

Measure the length of the conveyor on the layout and calculate approximate total weight of chain and trolleys. Add to this figure the total weight of empty and loaded carriers to determine total moving load. Multiply total moving load by factor indicated in Table 2 to find approximate chain pull. Choose a suitable chain from Table 4. Estimate the weight of a loaded carrier and consult Table 5 to make certain that the trolley corresponding to the chain size will not be overloaded.

 In some cases, calculated chain pull for a conveyor may exceed the allowable for a particular chain even though the trolley loads may be well within the capacity of rail and trolleys. Practice in such cases is to use two or more synchronized drive units. A more detailed discussion of this problem can be found in the Drive Unit Section of the Anchor Online Product Catalog.

Sometimes it may be found that unit load exceeds the single trolley capacity for a selected conveyor size even though the calculated chain pull is within the allowable limits.

This problem has two possible solutions:

• The next heavier conveyor can be selected.
• A multiple trolley and load bar arrangement can be used. This is more economical in certain applications.

In the case of 4-inch conveyors a third alternative is available.

A 6-inch trolley and rail utilizing a No. 458 chain, can sometimes prove a more satisfactory solution than the selection of either the 4-inch multiple trolley and load bar arrangement or the 6-inch trolley with No. 678 chain.