The following is taken from an article by Tom Pendley in Fire Rescue Magazine , August 2002 called Sky High Anchors.
"Overloading an aerial by lifting loads with
hydraulic systems could result in a
catastrophic boom collapse. Also, OSHA
regulations prohibit hoisting or swinging
people with a crane unless they ride inside a
certified personnel platform (a man basket).
OSHA 29 CFR 1910.180 (h) (3) (v) standard
for crawler, locomotive and truck cranes
states, "No hoisting, lowering, swinging, or
traveling shall be done while anyone is on the
load or hook." The standard speaks to the
hook and boom movement, not a manually
operated rope system attached to it."
I could not find any links to the article itself, I have a copy of it in a book from our state FA.
In our department , we do suspend Stokes from the buckets or ladder tips, via bridles for lowering off roofs.
I remember when this article was published; Tom has done some great work for the rope rescue community; but I must respectfully disagree with some of article.
One could argue that an aerial device does not fall under the OSHA requirement of a "crane". It is not a crane by definition, nor is it constructed like or function like a crane. It's primary mechanical function is not "crane-like" activity. You can't look at one sub-part of a standard and apply it; you have to look at the entire standard. I have delt with OSHA on many occassions and from my experience I would bet you would get 5 different answers from 5 different representatives.
When a load is attached to the tip of the ladder does it resemble the function of a crane? Somewhat. Does the equipment meet the definition of a crane? no.
I'd be just a BIT curious how you would "overload" an aerial device by lifting a Stokes with it assuming that: It was a minimum 250# tip load ladder, You were NOT at full extension horizontally,Had ONLY the Stokes attached,and your patient was of a NORMAL(300# MINUS)weight,that you PROPERLY attached lift points. With our Platform it is a NO CONTEST task. T.C.
Not disagreeing with you, the OP asked about an OSHA standard. I thought that might provide some insight for him.
Rescue 101 -Not in you situation, but, in some situations, it could happen. If the aerial was only used as a height advantage with a COD pulley on it, you can effectively place double the load weight on the tip with the deviation forces.
I TOW for a living. M/A is a fact of life(for me). Let me tell you a funny story somewhat related to this thread. We bought a 2.5 ton floor jack for the shop,BRAND NEW. About three weeks after we bought it,it wouldn't even lift a mid size sedan on one end. Being new,we sent it back under warranty. Company said we overloaded it and scored the piston. My question to them was;"Does this jack have a relief valve?" The answer: "Yes". " Then HOW is this possible,it should have gone into relief" Well,the Question was NEVER answered,the warranty was never honored, and we NEVER bought another piece of Blackhawk equipment.Same principle SHOULD apply to an Aerial. Having had an EARLY American Lafrance,I understand what you guys are saying. A VERY interesting and informative thread. T.C.
We use Seagrave tiller trucks with a 250# tip load for a high point. That tip load is for any extension / elevation combo. So it makes sense that this is for full extension straight off the side of the truck. It is a number based off of the operating pressures of the lifting cylinders.
Seagrave says the max operating pressure of those cylinders is 2500 psi. So, we are able to judge how close we are to our ladder's weight limits by keeping an eye on the cylinder pressure gauge. I'm not sure about other manufacturer's operating pressures.
We have a 60 ton rotating boom wrecker that does not have that pressure gauge and instead have to rely on weight estimates and a capacity chart on the wrecker. I've wondered why they don't have pressure gauge.
A LOT of wreckers DO,the gauges are in with the operating handles. Any that I'm aware of will do their rated capacity retracted and something in the 50% area extended. T.C.
so after much trial and error we've decided on a method and used it quite a bit in training now and are content with what it offers yet still provides a solution to our needs. Attached is a training document i put out showing 2 of the 3 configurations we are going to employ.
We went with 3 configurations:
1) fixed crane - litter attached to tip, full aerial function with package attached
2) reeved crane - ropes operated from turntable, over tip, dual tensioned mains, no traditional belay
3) high directional - fixed pulley at tip, no aerial function once operation has begun)
I received the blessing from the manufacturer on the first 2 configurations and i'm working on the 3rd with them, specifically looking at increasing tip loads if you eliminate the egress section of the aerial which carries the least rating in many positions. I'll post more once i complete that component.
Let me know what you think as i'm sure you all will...
Looks good, you've put a lot of research into it and got the manufacture involved. Like how the one person load on the non-fixed systems has been identified. How fast is it to set up? They look very intensive.
If possible, tag lines will help a lot in all the set-ups.
---section removed--- figured out the 3:1 system on the aerial.
How big is your bay? It looked like the one picture was an indoor training tower, or is that an optical illusion?
recently we had an evaluation involving a subject in a tank where the fixed crane evolution was selected as most effective. i'd say we had the stokes ready to raise within 10 minutes of setting the parking brake on the aerial.
tag lines are used on all setups, i guess i must have forgot that part. one thing i learned is to place the tagline on the end of the stokes that will keep tagline tender in visual contact with the aerial operator since they can serve both as spotter and tagline operator.
those pictures were taken at our indoor training facility. looks big but you don't have easy movement of the aerial in there. i should have taken a picture of the whole scene as i shoe-horned the truck in there between other rigs and had to be pretty careful not to take out hvac ducting and lights with the stick...
Mike, would love to see that if you ever get a chance.
Originally Posted by stickboy42
If I remember from when this started I was thinking that the fixed crane method was being used with a longer attachment, creating problems with keeping the high point above the pt. The short throw of the aztecs and the ability of the rescuer to adjust them would eliminate the problems I was envisioning. I also like the dual 3:1's (reeved crane) a lot the more I looked at it.
Interesting question I have. After reading here about useing the aerial as a hd if you attach a 3/1 or 4/1 M A to the tip of your 250# rated tip are you not setting the tip up for overload and or failure.
WHAT'S the LOAD? If it DOES NOT exceed 250# then NO you aren't. T.C.
Originally Posted by rescueraver
Rescueraver I see where your line of thought is coming from but, I think you are slightly left of center in your thinking. You have to remember by using a mechanical advantage system all that you are doing is lessening the input force used to move an object. 1:1 = 250#s force to move 250#s, 3:1 = 84.3#s force to move 250#s, 4:1 = 62.5#s to move 250#s, so on and so forth. Higher the MA, the lesser the input, the easier/less work involved in moving said object. The load does not change, just the input force, the load is almost always a fixed weight. Not many ways to lighten a load, some, but not many. You are still moving the same weight. In actuality you are lessening the strain on the structural members of the aerial since you will be pulling against the structure with less force to move the same weight. There will always be the same weight hanging from the aerial, just less force in certain directions when the system is being raised. Pure physics, don't let the idea of MA confuse you.
Great info. Noticed from the pics that you appear to be using Pierce's Lyfe Pulley Rescue System. Any experience in your testing using the system with the MA sewn off the tip in either a 2:1 or 4:1 configuration and anchored to the bottom square rung. I did some training with a local department with this system, neither they or I had much experience utilizing it, so it was a teach and learn for all of us. After researching the system, I've found that it can be rigged two ways, one supporting a maximum load of 500# with the main line anchored at the base of the aerial, and the other supporting a maximum load of 250# with the main line anchored to a separate anchor independant of the apparatus. Both ways can be utilized as a COD/High point or a crane type set-up. Correct me if I am wrong, however if the aerial has a 1000# tip load, wouldn't you be better off rigging the main 4 rungs back from the tip with a sling or webbing and maintaining the full use of the 1000# tip load?
Sorry I'm "coming late to the party" on this one but as I read through the post's here I think we're mixing apples & oranges in our discussion or we're overlooking some principles of physics. Also variations on the location of our working end, running end, and anchor points will result in drastically different scenarios.
Calculating the actual forces of the various way you should use & rig an aerial really gets into some pretty moderate physics and vector analysis so some of my examples will be greatly over simplified.
That being said, the first and main concern for placing any type of load on an aerial device is Dynamic Loading (often referred to as Shock Loading). Anyone who's ever had any training on working from aerial devices has surely been told not to routinely "jump on" the ladder when leaving the structure / working area (especially if the tip is unsupported). A 250# geared up firefighter that jumps / falls 6" onto an aerial device will generate an impact load of over 1,400# - the same physics apply if you "drop" a 250# load (combined load of Pt, stokes, rigging, etc) from the same 6" (say while trying to get them off a ledge or parapet).
Suddenly the tip load, design safety factor, and age/condition of the device are VERY important)
It should be noted that swinging a suspended load can also create shock loading of rotational forces which not only affect the aerial itself but also the torque box - after all the aerial is just a big lever and 250# of force on the tip of a 100' device is equal to 25,000lb/ft of torque at the base.
Now lets assume that we make every single move flawlessly and create absolutely Zero shock loads whatsoever and look at rigging.
A 250# load connected directly to the tip of the aerial device creates a 250# "load" or downward force on the tip - easy.
Assume you have the same load in a 1:1 mechanical advantage (MA) system (which is actually a misnomer since there is no advantage to the system rather just a change of direction) anchored at the tip of the aerial. You now have 250# downward force on the load side of the pulley plus an equal & opposite 250# downward force on the working side of the pulley which in turn translates to a 500# load on the tip of the aerial device where the pulley is anchored.
The only benefit of a true MA system (in terms of tip load only) is that you reduce the anchor force by reducing the required input force to hold/raise the loading force.
Or in math terms
A 2:1 MA system would still have the same 250# load but only require a 125# input force on the working end thus translating into a 375# load on the tip.
A 4:1 MA system would then be 250# load + 62.5# input force = 312.5# tip load
For the purist in the crowd these examples assume all force directions are parallel to one another and are therefore the maximum forces applied to the anchor for the given loads/forces. Once you begin pulling at angles, the anchor (tip) loading can decrease further based on the pulling geometry.
Now all this isn't meant to say you can't or shouldn't use an aerial device as any type of high point (or even a "crane" of sorts by rotating a suspended load) - but in addition to getting the device designers blessing on your intended usage, you should also request them to provide you with Working Load Limits (WLL) for those usages as well as yourself being able to adequately estimate your real life loads and stay within the given limits.
a little late here...but...
So if I get this, as soon as you hang a pulley and use the aerial as a high overhead COD, youve doubles the load because (if I think this correctly) the load exerts its exact weight on one side of the pulley, and your haul force exerts equal, or maybe a tad more due to inedfficiency, force on the other side of the pulley.
If this is the case, a rescuer, baslet, and load can easily add up to 700lbs, so youre looking at a 1400lb load with no shocking. Whats the answer here to avoid this dangerous predicament, if my assumption is correct?
I keep hearing from administration that it is an OSHA violation if you use the ladder as "a crane". Does anyone know what standard they are referring to? I cannot find which one they are basing this off of. I know one of the standards says something about using machinery and Im guessing this is what they are basing it off of. I want to be able to take something in writing and discuss the issue.
This is a great topic because it seems to have so many "what if's" and unknowns. I'm here in the firehouse working this easter reading through these posts and as always my creative and sometimes left-field juices get flowing.
The greatest focus and rightfully so seems to be on the tip load. So here comes a crazy idea and I'll again this is just an idea and no force loads have been measured with that being said.....
Why not connect a rope to the tip of the ladder and run it back to an anchor opposite the direction of the ladder. Once the load has been applied to the main line tension the line attached to tip going to the opposite anchor. In essence your back tying the anchor hoping to equalize some of that force. What are your thoughts? Do you think this will help the tip loading problem. I must also point out that the line used to back tie the overhead anchor (ladder tip) cannot come in contact with the ladder, if it did the load force would be placed back on the ladder defeating the purpose of back tying.
Over at another site(VES) there was a story about a dept using a stick to aid in lifting a large man out of a bath tub in a house. They cut a hole in the roof, etc and used the pulley as the one pictured on the end of the stick on page one as a COD and had their system down on the ground.. They were getting harrassed on overloading, etc but after contacting Pierce they were told that if they were right above it and no side load and the load indicator was still in the green. GO for it. The stick doesn't know where that force is comming from, just that it has weight pulling down on it.
Note: this was a tip rated 750lbs 105' stick.