Just in! Cranes that have internal expanding friction
clutches and Lattice Booms were commonly referred to as “Friction cranes” by
the Standard writers and the Manufacture themselves. Nowadays, the Clutch type
drums on the new lattice boom cranes are being replaced with Hydraulic Winches.
So, these crane types are currently being named “Conventional cranes” (I wonder
what an un-conventional crane is).
A hydraulic winch on lattice boom crane is nothing new; I
worked on one in 1962 at Cape Canaveral, a 100 ton Bucyrus Erie with a
hydraulic winch and a Triangular boom. But, with the demands of modern cranes
the hydraulic winch has advantages, one thing, less moving parts subject to
fatigue.
The photos following show a broken friction shoe on the main
hoist of a Link Belt crane. This is the “power down side”, and if you think
about it is actually being “pulled” when working due to its job of slowly
lowering a weight against gravity.
When it failed the load was still controlled because the
other side was engaged but, the operator recognized something went wrong by the
vibration he felt in the crane. He set the load on the ground and went back to
look and this is what he found!
Inspection of the Frictions clutches is as follows;
- Lining thickness
- Contamination from oil or water
- Evenness of drum surface and contamination
- Proper adjustment
- Observe operation for smooth engagement
- Visible damage or cracking of shoes
- All pins, springs and keepers in place
- Evidence of overheating of any component
- Other noticed problem observed during operating under functional load test
Well this one got away, but now I look closer at this area of the shoe for “hammering” and cracking, so should you?
