Thermal Expansion
When screw conveyors are required to convey hot or cold materials it is necessary to recognize that the conveyor will change length slightly from the original ambient temperature length.

The recommended general practice is to provide supports for the trough which will allow movement of the trough end feet during the trough expansion or contraction when handling hot or cold materials. The drive end of the conveyor is usually fixed, allowing the remainder of the trough to expand or contract. In the event there are intermediate inlets or discharge spouts that cannot move, then expansion type troughs are required.

The screw and the trough may also expand or contract at different rates. In this case expansion hangers are generally recommended. The trough end opposite the drive should incorporate an expansion type ball or roller bearing which will safely provide sufficient movement.

The change in screw conveyor length may be calculated using the following formula:
r L = L (t1 - t2) C
Where
r L = Increment of change in length (inches)
L = Overall conveyor length (inches)
t1 = Upper limit of temperature (F)
t2 = Lower limit of temperature (F)
C = Coefficient of linear expansion, per (F)

The coefficient of expansion is as follows by material type:

Hot rolled carbon steel = 6.5 x 10-6/F
Stainless Steel (304SS/316SS) = 9.9 x 10-6/F
Aluminum = 12.8 x 10-6/F

Example: A stainless steel conveyor 45 feet long is subjected to a rise in temperature of 200 ºF, reaching a temperature of 260 ºF from an original metal temperature of 60 ºF.

r L = (540") (200 ºF) (9.9 x 10-6/F) = 1.07 inches

In the above example sufficient means should be used to accomodate the expected change in length of 1.07 inches.