Selecting appropriate access equipment

[Junior8]

One of the reasons I stopped visiting this site was the continuous repetition of the same questions. Yes we used to move tallescopes and towers around with people on board and now we can't. That doesn't mean you don't use 'em you just use 'em properly. If this is an issue you have to apply some lateral thinking. You say you have between 16 & 40 lanterns rigged here for every show in a 200 seater venue. (Goodness me back in the day I'd have had to sling half of these away before starting!) The answer is to fix 30 of these in a basic rig and give yourself a maximum of 10 to visit. The last time I had responsibility for a venue and was on my own I had to do something like this. It's good discipline.

[Jivemaster]

A safe system of work does NOT include telling HSE that they are wrong or elevating a digit at the approved codes of practise. Training with access equipment is important but doesn't need to be at post doctoral level.

 

Go and design a rig that suits 90% of your shows, then you only need to do 10% of the WAH -risk and hazard reduced. Train several people to use the Tallescope so that you can place it, check it and use it, then dismount and move it and another person can climb it in the next position.

 

Sadly sending students out into the real world believing that the rules are wrong is very poor for a college, sending them out brokenby accident is even poorer. You need to find a safe system of work and t=you need to enforce it and budget for it. ALSO remember that the cost of safety is usually orders of magnitude less than the cost of an accident.

[OllieDuff]

OK, there seems to have been some miscommunication on several sides:

 

The training issue seems to have arisen from a well-meaning individual who sold me on the idea that "every user is trained and competent to use powered access" meant "every user has a PAL for that class of MEWP", which I have since discovered isn't the case. In practical terms, our users need only be trained on that specific machine in our venue, because that's the level of "sufficient training and experience, or knowledge and other qualities" (I'm paraphrasing slightly) that they require to carry out the work. Therefore, MEWPs are back on the table as an option, and it's probably the one I'm going to pursue - many thanks to Bryson and Mumbles for suggesting a vertical mast lift, that looks about right as it fulfils the same role as a tallescope but without all that ladder climbing.

 

I am very aware that one cannot move an occupied tallescope other than in the manner detailed in ABTT COP011. I am also aware that the guys I work with don't feel comfortable with running up and down the 'scope all day long, which is why I'm looking for options that aren't tallescopes.

 

I'm not trying to flip the bird to the HSE. I am explicitly trying to come up with a system of work which is in line with industry practices, which is why I'm considering a very wide range of solutions in the first instance and asking questions which I'm sure seem elementary to the more experienced users on this forum, for which I apologise profusely.

[gibbothegreat]

If I could... find a sufficiently light MEWP, I'd get a MEWP.

Hi Ollie,

 

I think you may be making unnecessary problems for yourself with this: as S&L said in another thread, good data is everything in the context of H&S decisions. You reckon the sprung floor won't take the weight, but unless you know its loading specifications, then you can't really judge that.

 

As it happens, I had a similar issue in making a choice of access equipment, and what I discovered is that a MEWP will exert rather less of load on a floor than say, a beefy male dancer doing a leap and landing on one foot. A sprung floor would be rather pointless if it wasn't strong enough for the latter, so your assertion that it wouldn't be strong enough for a MEWP is, IMHO, unlikely to be the case. I'm tall, heavily built and somewhat overweight, and if I stood on tiptoe on one foot I'd be exerting a greater point load than the genie (an AWP30S) we use .

 

Our floor was designed to a loading of 4.5kN/300mm² point load and 7.5kN/1m² distributed load, and the engineers (Arups, who one might reasonably expect to know a thing or two about this) tell me that's been a standard for theatre stages for some while. So to be clear, it's specced for a greater point load over 300mm x 300mm than the entire weight of a MEWP, which in practise will always be supported by at least four points.

 

 

BTW, if you do get a MEWP and should you want training at your venue, any provider worth their salt will want a precise statement of your floor's loading specs before they'll do it there

 

 

[charl.ie]

The training issue seems to have arisen from a well-meaning individual who sold me on the idea that "every user is trained and competent to use powered access" meant "every user has a PAL for that class of MEWP", which I have since discovered isn't the case. In practical terms, our users need only be trained on that specific machine in our venue, because that's the level of "sufficient training and experience, or knowledge and other qualities" (I'm paraphrasing slightly) that they require to carry out the work.

Can you provide more detail on this - I'm facing a similar issue at the moment.

[adamharman]

Our floor was designed to a loading of 4.5kN/300mm² point load and 7.5kN/1m² distributed load, and the engineers (Arups, who one might reasonably expect to know a thing or two about this) tell me that's been a standard for theatre stages for some while. So to be clear, it's specced for a greater point load over 300mm x 300mm than the entire weight of a MEWP, which in practise will always be supported by at least four points.

 

Ah, but there's a difference between the design loading for the floor structure, and the pressure required to damage the surface or punch a small hole through it.

 

Whilst I agree that the total weight of a MEWP is unlikely to cause an issue, they do tend to have quite solid tyres and therefore exert a fairly high pressure on a small area of floor. As the floor apparently dents when you look at it too hard, this could potentially be a problem.

[gibbothegreat]

Ah, but there's a difference between the design loading for the floor structure, and the pressure required to damage the surface or punch a small hole through it.

Is there a difference? I would have thought that's precisely what the point load figure is referring to. It's pretty meaningless otherwise.

 

Whilst I agree that the total weight of a MEWP is unlikely to cause an issue, they do tend to have quite solid tyres and therefore exert a fairly high pressure on a small area of floor. As the floor apparently dents when you look at it too hard, this could potentially be a problem.

Yet those solid tyres, or the pads on the outrigger, don't exert as much pressure as, say, a beefy male dancer (say 75Kgs) leaping and landing from height on the ball of one foot, or carrying a ballerina on his shoulders and walking using a dancer's walk (weight applied to the ball of the foot only.) Being dynamic loads, those would seem to me to be rather a greater challenge for the floor than the generally static load of a MEWP, and if the floor can take the former, it can most certainly take the latter. If it can't, then it's rather failing to serve its purpose as a sprung floor.

 

Furthermore, I would guess that the ground contact surface area of the MEWP tyres (certainly for the Genie which we possess) is well over double that of the tallescope with its much smaller wheels. Given the tallescope's weight of 127Kg, and the fact that the outriggers on a scope don't take significant weight, as opposed to those of the MEWP, these are likely to exert quite as much if not a greater pressure on the stage floor than the Genie.

[adamharman]

Is there a difference? I would have thought that's precisely what the point load figure is referring to. It's pretty meaningless otherwise.

 

It's all to do with bending of the structural beams and allowable deflection. A 3kn load on a 30cm section of a beam will cause more deflection than 3kn spread over a metre. The 30cm square (which is an odd size) may well come from the spacing of something in the structure - if you load an area 30cm square there's a fair chance that almost the entire load will be taken by one beam whereas over a square metre it would be spread over 3 or 4.

 

Yet those solid tyres, or the pads on the outrigger, don't exert as much pressure as, say, a beefy male dancer (say 75Kgs) leaping and landing from height on the ball of one foot, or carrying a ballerina on his shoulders and walking using a dancer's walk (weight applied to the ball of the foot only.) Being dynamic loads, those would seem to me to be rather a greater challenge for the floor than the generally static load of a MEWP, and if the floor can take the former, it can most certainly take the latter. If it can't, then it's rather failing to serve its purpose as a sprung floor.

 

Furthermore, I would guess that the ground contact surface area of the MEWP tyres (certainly for the Genie which we possess) is well over double that of the tallescope with its much smaller wheels. Given the tallescope's weight of 127Kg, and the fact that the outriggers on a scope don't take significant weight, as opposed to those of the MEWP, these are likely to exert quite as much if not a greater pressure on the stage floor than the Genie.

 

I'm not saying you're wrong, and I'm not familiar with the equipment in question, just that if the surface is as soft as we're told then it's something to watch out for. Not so much that it could go through the floor, more that it could damage the surface.

 

Out of interest, how hard does a dancer land? I would assume they're quite careful to control it as much as possible otherwise they could have a fairly short career before they destroy their knees.

[alistermorton]

The 30cm square (which is an odd size)

 

About a foot square - still seem odd?

 

 

 

[adamharman]

About a foot square - still seem odd?

 

I don't mean it's an odd size generally as it clearly is about a foot, just unusual to find it in a building context which is why I suggested it relates to the spacing of something underneath.

 

There's no set spacing for joists in timber floors but the vast majority are 400mm. If your boards won't take the required load at 400 spacing, or you're tight on height and want to use more, smaller, joists then you'd reduce it.

[gibbothegreat]

It's all to do with bending of the structural beams and allowable deflection. A 3kn load on a 30cm section of a beam will cause more deflection than 3kn spread over a metre. The 30cm square (which is an odd size) may well come from the spacing of something in the structure - if you load an area 30cm square there's a fair chance that almost the entire load will be taken by one beam whereas over a square metre it would be spread over 3 or 4.

 

Wouldn't that be the difference between point and distributed loadings, alluded to in the 2 different figures I gave?

 

I'm not saying you're wrong, and I'm not familiar with the equipment in question, just that if the surface is as soft as we're told then it's something to watch out for. Not so much that it could go through the floor, more that it could damage the surface.

 

Out of interest, how hard does a dancer land? I would assume they're quite careful to control it as much as possible otherwise they could have a fairly short career before they destroy their knees.

You'd be astonished about how much there is on the web about this! As you rightly say, it's a difficult thing to model, because of the complicated dynamics of a jeté, but one set of measurements from an 'average' sized male dancer measured a high of about 3.4kN and a low of around 2 kN, all within a time of much less than a tenth of a second. Even the lowest of those is substantially higher than an outrigger pad of a MEWP, even if it's loaded to its full permitted extent and assuming the wheels are entirely lifted off the floor.

 

EDIT** to say that this was a professional male dancer, so presumably possesssed of a reasonable landing technique

 

The 30cm square (which is an odd size)

About a foot square - still seem odd?

It is odd, in that many things that exert point loads are likely to be considerably smaller than this, but it is what the chaps from Arups told me has been a standard for theatre for a fair old while.

[adamharman]

It is odd, in that many things that exert point loads are likely to be considerably smaller than this, but it is what the chaps from Arups told me has been a standard for theatre for a fair old while.

 

Could be some degree of arse covering involved? "we didn't give you a spec for loading an area smaller that a square foot so it's not our fault you went through it"

[jonathanhill]

Did we not use foot/pounds as the measure of force, before we all went metrified and starting using Newton/metres?

[kerry davies]

Probably not at all A-covering, metrication often used older and accepted "norms" like pounds per square foot and converted from what people were comfortable with and for which we had endless charts in "old money".

 

The Met office still measures snowfall in 2.5cms gradations. Be interesting to find and log all these anomalies but there must be dozens like MPG while we sell petrol in litres.

[alistermorton]

Did we not use foot/pounds as the measure of force, before we all went metrified and starting using Newton/metres?

 

My point, in a nutshell. Old measures converted.