Scissor Lift on Grating
Scissor Lift on Grating
(OP)
Hello everyone.
We're trying to calculate if we can safely use a scissor lift over a grating.
We've calculated the uniform and concentrated load capacity of the grating, but I'm not sure if the wheel load will translate the same way. The gross weight + load of the lift is approximately 3500 lbs. The maximum wheel load of the scissor lift is 1200 lb as per the manufacturer but is that a straight shot comparison with the concentrated load capacity of the grating?
Also, the maximum tire pressure is listed at 133 psi. Wheels are 12x4.5x8 inches. It seems rather high and I'm not sure if that will cause any special localized effects on the grating.
Any idea on what the procedure should be? Thank you in advance.
We're trying to calculate if we can safely use a scissor lift over a grating.
We've calculated the uniform and concentrated load capacity of the grating, but I'm not sure if the wheel load will translate the same way. The gross weight + load of the lift is approximately 3500 lbs. The maximum wheel load of the scissor lift is 1200 lb as per the manufacturer but is that a straight shot comparison with the concentrated load capacity of the grating?
Also, the maximum tire pressure is listed at 133 psi. Wheels are 12x4.5x8 inches. It seems rather high and I'm not sure if that will cause any special localized effects on the grating.
Any idea on what the procedure should be? Thank you in advance.






RE: Scissor Lift on Grating
"Look for 3 things in a person intelligence, energy and integrity. If they don't have the last one, don't even bother with the first 2. W. Buffet
RE: Scissor Lift on Grating
RE: Scissor Lift on Grating
Remember to look at actual bearing bars activated by the tires (not a 12" strip). Make sure you know how many continuous spans you have (probably a simple span). Check shear with the wheel(s) next to the support. The news may not be all that good for the contractor.
RE: Scissor Lift on Grating
Most grating has a capacity well above that. Study the manufacturer's load table for the grating depth and span specified. Then as other's have noted, you can check the allowable grating plate point load by using the maximum uniform load in the design table x the span, and then half it.
RE: Scissor Lift on Grating
RE: Scissor Lift on Grating
Note that grating can hold a smaller fork lift than you think.
RE: Scissor Lift on Grating
Divide that into 4 wheels = 900 lbs per wheel.
You are considering using 1200 lbs/wheel from the scissor lift manufacturer. Apparently "conservative" but not unreasonable on the surface: This would assume the 3600 lb total weight load is on 3 wheels, and one wheel is in the "air". Since three wheels is the "only" stable configuration if the scissor lift is not rocking back and forth (which NOBODY is going to ride and work in!) that is a 1.0 safety margin.
That final 1.0 safety margin is NOT conservative though!
The 1200 lbs IS concentrated not on a square foot, but on 1/4 of one foot area (the thin rods and bars actually touching the bottom of the tire.) You cannot use a "per square foot" loading table but need to consider the "point load" values of 1200 lb/(1/4 sq foot) or 4800 lbs/ft rating problem.
A thick (stiff!) steel plate under the wheels will divide the load out to manageable lbs/sq ft basis. A thin steel plate will do nothing but camouflage the bending and yielding when it happens.
RE: Scissor Lift on Grating
On one project, we analyzed the man-lift load on grating in an empty state for the case where it is being moved around the floor by remote. Then once the workers reached the location to do their work, we had them lay down plates under each wheel to distribute the loaded man-lift wheel loads out over a larger area.
RE: Scissor Lift on Grating
The problem would be simplified if we had the manufacturer grating information available but I should have mentioned that we don't.
The grating and the supporting steel is in good shape but about 20 years old, so I used a different manufacturer's data (McNichols) to get a feel for the capacity based on the bearing bar spacing and size.
Comes to about 1100 psf for floor loading and 2500 lbs. for concentrated loads. Will check other manufacturer data also. Can't just use those values, so the issue is the appropriate reduction of those given values. Demand is about 300 psf and 1200 lbs. wheel load. It's a simply supported 4'6" span.
There was a guide from that I used to calculate the capacity but not sure if that's an airtight reference. http://www.indianagratingsinc.com/PDFs/metal_bar_g...
To clarify what racookpe1978 and PMR06 stated regarding the tire contact area; the tires are sized at 12.4.5x8. For a 12" diameter, and 4.5" width do I determine the grating area in contact with the tire and then use the 1200 lb point load to calculate the psf loading and determine if it's adequate? Is that the procedure you outlined?
RE: Scissor Lift on Grating
If I need more bearing bars I will call for a steel plate overlay.
RE: Scissor Lift on Grating
Dik