[SML] A question about scissor lift hour meters

Sun Dec 6 15:39:16 UTC 2015

On 12/6/2015 6:41 AM, Dale Farmer via Stagecraft wrote:
> 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
>

Dale,

Thank you for an excellent tutorial - I shall do as much of what you 
recommend as is possible and modulate our bids/offers proportionally.

Some of the machines we are looking at are offered at auction and 
pre-testing and inspection will be rather limited - but we do have lots 
of time to make a deal on other machines - or just bag it and rent from 
a trusted supplier.

Thanks again,

Carla