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RE: Lifting system

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CMAA 70 is primarily for overhead electric cranes, but the prinicples are the same.  The safety factor depends on the load cycles and the component.  There are also some ASME documents and some DOE documents on rigging that are good.  But the CMAA 70 is the most straight forward for design.  There is also the UFC 3-320-07N Weight Handling Equipment that is a very good reference.
What you  are describing is very similar to the hoisting arm used for erecting towers.  The hoist drive is at grade level, but the hoist arm is connected to the tower and projects above the tower so that the sections can be lifted, rotated above the section below and the next higher section is set.  That is the way a 2,000 ft broadcast tower is erected. 
This is basically a rigging operation. 

Regards, Harold Sprague

Subject: Lifting system
Date: Tue, 17 Apr 2012 15:20:46 +0300
From: dcohen(--nospam--at)
To: seaint(--nospam--at)

Hi everybody

I'm designing a lifting system to ascend equipments from the ground to a building roof.

Due to some area problems, the winch has to be on the ground, and the arm-crane has to be in lower position by a normal day (same level of the roof), and has to raise itself above the roof about 4-5m, to lift the equipments (about 200kg), then to rotate and bring the equipments on their places.

By design the arm crane, I've taken a safety factor of 1.6 on the 200kg "live load", is anyone have experience with these kinds of structures? Is 1.6 is a sufficient safety factor for the structure bearing the equipments? Is there any code that I can justify the safety factor ?



David Cohen

Chief Engineering Manager






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