One of the major parameters in the performance of EOT Cranes is the RAIL Allignment. I perfectly aligned crane rail is a must for the satisfactory performance, life and prevent fatal accidents (like derailing of the crane and falling of the crane) The Crane Rails have to be parallel, straight, level, and at a proper elevation. The rails allignment should be checked in these parameters

• Span of the crane rails
• Level with the other one
• Parallel to the other one
• Up/down
• Left/right

BS 466 defines the tolerances, abstract from the same is as under

Span of the crane rails – (refer fig 4) a) max tolerance 3mm for span < 12m b) 3+0.25(s-12) mm for span (s) more than 12m Track straightness – horizontal plane (refer fig 5) a) Max in total bay length 10mm from the datum b) Locally 1mm per 1M

Track Elevation tolerance (refer fig 4) a) Tolerance max is 0.001*span b) Max 10mm — in the total bay length Please read the below abstract from BS466 - for more clarity