Even the smallest rental company has a few scissor lifts in its fleet. For those jobs where a ladder just won't get the job done, a scissor lift • when used properly • can be the safest and most productive way to accomplish the project. Because scissor lifts are such basic machines • they go up, down, and back and forth • they should be relatively easy to inspect, right? Well, yes and no.
At the heart of scissor lift is its scissor stack. The biggest problem with scissor lifts is that this most important part of the machine is the hardest to inspect. But if you know what to look for, it's possible to determine the condition and future life of the unit. Before you begin, make sure you look for any overhead obstructions or power lines that might interfere with your ascent as well as any hazards that could be in your way when you drive the machine. Here's a basic outline for more effective electric scissor lift inspections:
Walk around - it's good exercise
Always start the inspection with a walk around the machine. Check for bent rails, missing guardrail pins, loose wheel lug nuts, and leaks. This article covers electric scissor lifts; for internal combustion units, use the same rule of thumb discussed on any of my previous articles on IC machine engine compartments. (See A Closer Look at Telescopic Handlers [http://www.industrialliftandhoist.com/index.php?id=804] and Boom Lift Inspection Basics [http://www.industrialliftandhoist.com/index.php?id=622])
Locate the hydraulic manifold compartment and inspect the hoses and fittings for wear or leaks. Also open the battery tray (if so equipped) and inspect the condition of the batteries. Using gloves, open the battery plugs and make sure the battery has adequate water levels.
There are many areas that could be covered in a walk-around inspection, but factors affecting safety, as always, should be the primary focus.
Structure
The most commonly manufactured scissor lifts are truly scissor lifts, as opposed to Z-arm lifts. A scissor lift consists of a platform mounted on top of a scissor stack, attached to a motorized base. It's the force of lifting the platform load that causes the pins, bushings, and scissor arm ends to wear out and/or crack. Careful attention must be paid to this area on the machine.
While the unit is in the lowered position, inspect the arms on the stack and any pivot points. Look for any cracks or rusted areas around the pins and bushings - even in the metal surrounding the welds where the pins and bushings are mounted. Look carefully for any signs of abnormal wear such as metal shavings, elongated pins, or bushings. The tolerances must be tight, and there shouldn't be any unusual gapping where the two meet.
Lower controls
Using the lower controls, raise the platform a few feet. Don't forget to use the scissor stack-locking device (refer to the manual) to keep the stack from unexpectedly dropping. Now look at the place where the stack rides in the frame of the machine. Does the unit use rollers or sliders to accomplish the smooth operation of the stack rising?
Check the area where the scissor stack connects to the platform to make sure it is tightly fastened and shows no signs of cracking or damage. Look for even spacing on both sides of the machine stack. Again, check the pins and bushings on the inside for cracks, rust, or any other noticeable metal fatigue.
Safety devices
Many late model scissor lifts are equipped with pot-hole protection. It's a safety feature that will not allow the deck or stack to rise without the protection bar deploying. It's almost like having training wheels and keeps the machine from being accidentally driven into a hole and overturning. Make sure this safety feature is in good working order.
Remove the scissor stack-locking device. Now locate the emergency lowering device (usually located on the base of the machine) and confirm that it works properly by lowering the scissor lift. Refer to the manual (that should be attached to the machine) to determine where any other safety features, such as limit switches, might be located.
Controls
Last, mount the lift to check all the functions from the upper control box. First, determine if the steering works properly, moving from left, right, and back to center.
On a level surface, raise the machine. Listen for any groaning or whining of the hydraulics. Now drive the unit forward and backward. The machine should cutout from high drive to low speed (in the drive mode) after raising the platform a few feet. When coming back down to terra firma, make sure there is no binding or creaking coming from the scissor stack.
Ready to go
When done with the inspection, you should always plug in the machine so it receives the proper charge. Most new model battery chargers make this operation painless, and an idiot light will come on to tell you the machine is charging properly.
Basic attention to detail on these very common labor savers will result in a machine that will last through a number of cycles (up and down) and will ensure your investment for many years to come.
Lift & Access is part of the Catalyst Communications Network publication family.
