[SML] A question about scissor lift hour meters

[Dale Farmer]

On 12/6/2015 2:15 AM, Mt. Angel Performing Arts Center via Stagecraft wrote:
> Hi all,
>
> We are in the preliminary stages of looking for a used scissor lift in
> the 20' platform height variety and electric powered.
>
> There are several in area auctions coming up in the next several of
> weeks and we don't really need one until February.
>
> The auction listings have hour meter readings on 10-year old units in
> the 200-400 hour range.
>
> That doesn't seem like a lot of hours but the units, from the auction
> catalog photos, have obviously seen a fair amount of use.
>
> What is the hour meter measuring? Hours the pump is pumping, or hours
> the lift is switched on and powered, or something else?
>
> We figure we may be able to purchase a used unit for about what a 60-90
> day rental would cost but if not then renting makes more sense. It's an
> item that would be 'nice to have available' but we've gotten along
> swimmingly so far without actually owning one.
>
> Thanks in advance,
>
> Carla
>
> Fred's Bifurcate Law of Economic Independence: If you can't pay for it,
> don't buy it; and if you don't need it, don't buy it. Fred Reed - Fred
> on Everything
>
>
>
>
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>
I only ever seriously looked at one several years ago, and the hours 
meter was connected to the hydraulic pump.  But the hours meter is only 
one part of the story.

Scissor lifts are hydraulic machines, so the pump and valve manifold are 
the main wear items.  Their driving speed is slow and most of their 
motion is up and down.  The battery bank gets lots of use, and is 
probably the main maintenance item.  Their usage at construction sites 
is generally pretty hard, and maintenance is mostly just fix it when 
it's broke, so there probably are no maintenance records to look at. 
There should be some records of annual inspections by a recognized 
service company.  If this is from a construction equipment rental house 
then their in-house shop can be doing this.  Do they still have the 
manuals?  Read them.

So, assume the battery bank is mostly used up, and plan on replacing it 
in a fairly short time.  Depending on your usage of the thing, a mostly 
worn down battery bank may be perfectly fine for your needs.  Battery 
bank is pretty expensive, and depending on the model you have, may be 
ridiculously expensive.  Prices of lead acid batteries have more of less 
doubled in the last ten years, now that lead mines are unprofitable in 
countries with environmental and worker safety laws.

Check the hydraulic system.  Ideally by someone who has worked on them. 
  You are looking for leaks and signs of old leaks.  Check the fluid 
itself, and how much crap is in the filter and settled on the bottom of 
the tank. Also water contamination.  Fire up the pump and listen for 
abnormal sounds. Look at every flexible hose for cracks, chafing and 
leaks.  Carefully look at all the pistons at maximum extension.  Look 
for anything that is not clean bright smooth metal, and leaks at gaskets.

Check the electrical system.  Look for obvious problems, burn marks, 
damaged wires, etc.  Test the battery charger.  Make sure the service 
power outlet up on the platform still actually works when it is powered 
from the ground, all the way up and down.   Look at all flexible cables 
for cracks, crushes, chafing, any other damage.

Look at the structure.  Cracks, corrosion, bent metal, peeling paint are 
all bad signs.  Look at everything that has a grease fitting.  Does it 
look like the thing has been getting regular greasing? Any play in those 
joints? rust and wear?  Safety railings?  Push hard on them to find any 
inadequacies.   Fall arrest clip on points if any.  If there is a 
extending platform, can one person of normal strength operate it?

Wheels and tires.  Anything more than normal wear and tear?   Some 
models have outriggers that automatically deploy when the platform 
elevates.  Make sure they still work, this is a safety feature that is 
often disabled by workers so they can drive around while elevated.

Take the thing for a test drive, make sure that it will go up and down 
all the way.  Turns and drives correctly.  forward and reverse.  Test 
every control button while wiggling the cable on the control pendant. 
The cable of the control pendant is also a common failure point, 
intermittent opens a couple inches back from the control head usually. 
Drive it around for at least ten minutes, you are exercising the machine 
and also looking for a totally worn out battery bank.   Don't forget to 
test the second control point down at the bottom.  This may be anything 
from a full duplicate to just the emergency lowering valve.  Verify 
emergency stop button functionality.  When you have it at maximum 
altitude, start rocking the thing to see if it rattles or rocks 
excessively.

As soon as you have finished the test drive, recheck the hydraulic 
system for leaks and check the pump for hot spots.  It should be warm to 
the touch only.  If it is uncomfortably warm or hot enough to burn your 
fingers, then there is something wrong there that needs work.   If you 
have a thermal imaging camera, this is a good time to use it.  Also test 
the battery bank for hot spots, this could be a bad battery or 
electrical connection.

   As part of your purchase process, take it to whomever is going to be 
your usual factory authorized repair shop for full inspection and 
re-certification.  Make the purchase contingent on the thing passing 
this.  Even if the repair shop is the people you are buying it from. Get 
this in writing.

Good luck.

Dale