Shaft alignment limitations

For design the allowable lateral deflection of the A-Frame structures under normal hoisting loads was limited to 50 mm and for combined wind and hoisting loads limited to H/700 to ensure adequate alignment for the operation of conveyances within the shaft. The allowable vertical deflection for flexural members was limited to L/300. 

Shafts should be aligned to within 0.050 in./ft, or 0.25 degrees for most single-strand roller chain drives and conveyors. That same limit applies to most silent chain drives up to 1-in. wide. A somewhat larger limit may be used for engineering steel drives. 

Where a significant lift is required, such as at an offshore facility, several options are available such as a shaft driven, hydraulic drive, or electrical submersible pumps. Shaft driven vertical turbine pumps historically have been used extensively offshore. Reliability improvements for electrical submersible pumps with hydraulically driven units have been used more often as they eliminate alignment concerns, topside weight is limited, and in some instances, are less complex than the right angle engine driven vertical line shaft pumps. Hydraulic calculations for offshore pump installations must remember to account for wave and tide fluctuation. 

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