Bulk Material Conveyor Install Tolerances

[ldeem]

I am wondering what other folks here use as overall installation tolerances for bulk material belt conveyors. I am familiar with CEMA standards of 1/8" over 40' straightness and +/- 1/4" of level. I have interpreted these in the past as overall tolerances from tail to head pulley relative to the design belt line but I am wondering if it is excessive. In the field I see belt alignments all over the place and they seem to work fine.

In particular the level tolerance on hanging conveyors. I see belts that look like undulating waves and they work fine. It seems that trying to maintain +/- 1/4" overall is to much.

 

[PersonalProfile]

My take follows: historically in AU conveyors were not installed to tolerances [or perhaps appropriate tolerances], and some people got "lucky", and the conveyor worked, though others were not lucky, and the conveyor did not work.
Consider the failures, a general trend occurred in the industry, to install conveyors according to tolerances [in my experience, tighter than you state] and the conveyors generally repeatably perform, and our industry has accepted this as standard practice for conveyor installation.

 

[racookpe1978]

The "real" tolerances (limits on missing assumed locations) are on the roller-roller total distances (which set belt tension and belt twisting), belt stretch limits, roller-bearing-steel support tolerances at both ends of the roller bearings, dust door limits and roller motor alignments to motor frames.
For example, belt 2 of 4 always breaks first - because the pulleys on belt 3 and 4 are too far apart. So belt 2 is too tight compared to 3 and 4, but all 4 belts are purchased the same length. Belt 1 is too loose, but doesn't break. Its motor runs hot though because the motor is slipping.