Whether you rent a crane or purchase one new or used, the warning signs of immediate collapse remain the same. Ignoring the first signs of damage and deterioration will only lead to extensive property damage and injured or dead employees. Train everyone working on and around the crane to report these five warning signs of danger as soon as they notice any of them.
When a mobile or tower crane starts to lean and the tracks or tires start to leave the ground, tipping is very likely to occur. This is a sign that the crane is overloaded. Don't use base lifting as a way to test a crane to see how much load it can hold. Even if you retract the boom as soon as you notice any tilting or lifting, there's still a very good chance the crane will fall over. Overloading the equipment to the point of leaning also does permanent damage to the structural and lifting components. If a crane does start to lift or tip, have it inspected before using it again. Always stick to the load limits listed by the manufacturer, or call and ask the company renting you the crane when you're unsure how much it can handle.
Welding is good enough for assembling steel-framed buildings and pipelines, so most crane renters and owners assume it's also good for repairing damaged booms and structural supports. However, visible welds indicate that the work was completed by someone who is not familiar with proper crane repair techniques. Simply welding two broken pieces of steel back together will not restore the original strength of the metal, so a welded crane will always be compromised. Make sure that all mechanical and structural components are free from any signs of former damage, even if you know they were repaired in the past. If the crane doesn't look like new after being repaired, it's not safe enough to use.
Make sure there's at least one crew member who is keeping an eye on the ground around the base of the crane. Cranes must be completely supported by a level surface that can hold the entire weight of the equipment and the load. If the soil or other surface around the base of the crane starts to move or crack, it's a clear sign that the crane is in danger of tipping or sliding. Work should stop immediately so the crane can be moved to a more secure base, even if the load is nearly in place.
Cranes are fairly noisy when in operation, but crane operators and other construction site employees quickly figure out which noises are routine and which are unusual. When a crew reports that unusual sounds are emitting from the crane as they lift a load or move the boom, it's a clear warning sign that the equipment is not operating as it should. Unusual noises should warrant an immediate shutdown of the equipment and inspection by a professional. It may be just a simple case of vibration or a lack of lubrication, but taking the risk isn't worth it.
Finally, make sure the crane operator keeps an eye on the boom cable as it retracts after a load is released. Most employees are more relaxed at this point because the load is off the hook, but it's a prime time for spotting damage to the spooling mechanism or the crane. If the cable is not retracting smoothly and wrapping properly around the spool, there's something wrong with the crane. It may not seem like this problem is as serious as tipping or sliding, but a damaged cable or spool can result in a falling load.
If you notice any problems with your crane while it's in operation, be sure to have a qualified crane service technician inspect the crane to prevent any accidents.