Have you ever wondered why you have so many problems with your crane? After over a decade servicing cranes, I’ve seen it all. Frequent crane issues can be caused by age, use (or perhaps abuse) of the crane, and even environmental factors. Establishing good practices with your overhead crane goes a long way; allowing you to increase your production by reducing downtime, service call volume, and repair bills.
Perhaps the best thing you can do for your cranes is to have your operators successfully complete a certified Crane Operator Training course. Crane Operator Training provides your operators more knowledge about the crane and an increased awareness while running your equipment. A proper crane operator training course serves to educate and correct some of the poor practices of novice operators; reducing incidents that could damage the crane and actions that accelerate component wear.
It may be easy to gloss over the importance of taking a few minutes to complete a pre-use check on the crane at the beginning of a shift or before the first use of the crane on each shift. Numerous issues can be caught on a pre-use inspection and dealt with immediately before they become problems. Completing a pre-use check may allow you to catch a malfunction in the crane before it breaks down with a load stuck in the air. An issue picked up on a pre-use inspection could be a quick, inexpensive repair now, before it becomes a lengthy and expensive repair after your valuable load falls to the floor.
Regular maintenance on your crane keeps your equipment in good condition for long, reliable production. Replacing oil before it gets too old, dirty, or contaminated will help reduce damage to the gearboxes. Periodic cleaning and adjustment of the brakes will prevent breakdowns due to drifting loads and motors running through the brakes causing them to wear out very quickly. Properly scheduled inspections can catch component wear or damage that can be repaired during an opportune window before it becomes a larger problem impeding your production schedule.
Now seems as good a time as any to get into the do-nots.
Side loading causes the wire rope or load chain to rub along the guide, causing wear and damage. It will result in replacing parts much quicker, accelerated wear on the wire rope or load chain, or even outright damage to the wire rope in the form of kinks or broken wires. Side-loading can also dislodge the trolley, allowing unexpected motion or even a swinging load.
Dragging a load with your crane will damage and/or prematurely wear your equipment. Dragging loads with your crane causes the same problems as side-loading along with the possibility of dislodging the hoist and trolley right off the bridge and down to the floor.
Over my career, I have seen many, many operators just mash a function button all the way down, jogging the crane with frequent short bursts of motion in high speed. As AC motors get a very large burst of current when they initially start, jogging causes a large amount of these bursts in a short period of time, generating large amounts of heat in the motor. Excessive use of this technique can cause not only motor damage – resulting in lengthy downtime and expensive repairs – but can even trip the motors thermal overload protection; stopping the crane completely and generating a service call.
So what is the proper technique? When you approach the target in high speed, then switch to low speed when near the target (unless the equipment is single speed of course). Once you are very close to the target, jog the crane in LOW speed if necessary, to complete your task.
Whether your hoist is on a push/pull system or a jib crane, pulling your hoist by the pendant will inevitably result in the pendant drop cable pulling out of either the pendant or the hoist. Always get in the practice of pulling your hoist around by the hook or the load. You can also attach a tag line to the hoist or to the end of the jib beam and use that to move the equipment.
All operators should pay attention when they are moving the cranes around; not just at eye level, but above as well. Watch for the equipment nearing its end of travel -- reaching this point stops the trolley or the bridge but it does not stop the wheels. The wheels will just keep spinning, wearing the treads and rubbing divots into the rails. Eventually, these divots will need to be filled because when they get deep enough the wheels will not be able to get out of them. Suddenly stopping an overhead crane when reaching end of travel at speed can also impart significant swing to the load; never a desirable outcome.
Your crane’s service life will also improve if you ensure your operators know the specifics of the equipment they are using and monitoring.
Hoist Specifics Example
Say your chain hoist does not have a lower limit switch, but your daily pre-use inspection requests a “Lower Limit” check. Checking the lower limit repeatedly in this circumstance will cause the hoist to run through the load limit clutch. Over time, the clutch will wear and the hoist capacity will be reduced.
Crane Specifics Example
Do your cranes have an anti-collision system installed? If not, you should ensure your operators pay greater attention while approaching other cranes. Two cranes colliding in high speed may result in damage to the structure and/or electrical components.
Building Specifics Example
Are your operators aware of the location of the heaters in the building? Parking the crane under a heater for a significant amount of time could melt the electrical cables, cook the gearbox oil, or even damage the motors.
The great outdoors is always rough on overhead cranes. Rain causes rust which can weaken the structure over time. Water can get into the gearboxes and contaminate the oil. Wet brakes can seize up when they dry. Many of the issues caused by rain can be prevented by covering the brakes and gearboxes on cranes that go outside.
Cold weather, especially here in Canada, can freeze the oil and cause it to gum up and stop coating the gears. Heaters can be installed on the gearboxes to maintain the oil’s viscosity.
Extreme cold can also cause frost to build up on the power conductors. Frost can then build up between the conductors and the contact shoes, isolating the crane from power. If this is a frequent issue you see, investing in special wire-brush contact shoes (self-cleaning contact shoes) will clean off the conductors to prevent the buildup of frost and other elements.
Exposure to the elements can also dry off the lubrication on the wire rope and drum, resulting in chattering or even damage to the rope guide. If your crane spends a great deal of time outside, I recommend more frequent applications of grease and oil.
But when it comes to protecting your crane from the weather, I recommend doing whatever possible to keep your crane inside. If parking your crane inside overnight is not an option, even covering your crane at night will go a long way towards preventing many weather-related issues.
Throughout this article, I’ve highlighted several things you can do to get more life out of your cranes. Some are simple solutions that can be easily and cheaply implemented; some are things that will cost you a little money now but will undoubtedly save you a lot of money later. Putting these strategies to work for you will give you a more reliable crane that lasts longer, improving production and reducing downtime. After all, that's what we all want, isn't it?
The Crane Tech
