11.02.2022
On the hook
We have been sent a series of photographs of a team of arborists in the UK removing a series of pine trees. They look very professional and have a wide range of kit to do the job, including an aluminium boomed trailer crane.
The crane - a Böcker - is being used to remove the tree trunks, lifting modest-sized sections in a safe and efficient manner. The road is properly cordoned off and outrigger mats used.
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Bosuns chair or abseiler’s sling?
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A safe form of access?
However, some of the photographs show the crane being used to lift a tree worker into the tree to attach the slings with a sling-type Bosun’s chair. While many powered access professionals frown on this form of access, with good reason, they have their place. BUT... that very much depends on the device itself - this one looks like an abseilers' sling - and the lifting machine used.
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Assuming that the ‘chair’ itself is kosher, the next focus is on the crane. In many jurisdictions machines used for lifting persons need to have a full formal Thorough Inspection every six months, while cranes or other machines used to lift loads only require an annual inspection. Most trailer cranes are designed to take a full EN280 work platform attachment and so have the additional required safety features required for a dedicated work platform.
Finally, one photograph seems to show the man, having been lifted into the tree, attaching the sling. The question is does he then climb down, or did he ride with the load - the tree section?
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So does he ride the load or climb down?
So, is this one for our Death Wish series?
Certainly, at first glance it looks like it is, but to be definitive more information would be required.
What do you think? Let us Know, either via a comment or my email
[email protected].
Have a safe weekend.
emailed comment
With all due respect and in response to both short comments re man baskets I would say that the respondents are probably involved in other industries and not professional tree workers or they would know that it is virtually impossible to gain access to a tree crown from a man basket swinging from a crane. Without getting close enough would the tree surgeon be expected to climb out of the basket to cut the tree?
What if the falling cut section snags on the basket with the resultant dynamic forces throwing the person out or possibly damaging the basket or crane. This by the way is also a common cause of overturns with aerial work platforms used in tree work.
The tree surgeon’s harness and climbing equipment is tested under LOLER and more importantly is carefully checked by the tree surgeon as he uses it throughout the day. Being lowered into the tree he can avoid branches etc and get to the exact location he needs to safely carry out his cuts. Also all climbing systems now use two attachments points so that at no stage is the tree surgeon free or unsupported.
One respondent suggests it is a cost saving measure so that two cranes don't have to be used. We all know the increased risk of using two cranes close together particularly on a very restricted site which is often the case in tree surgery jobs. Of course there would still be the same problem of access to the crown and the risk of the cut section of tree snagging the basket which the tree surgeon is in. I can assure him or her that crane cost is very unlikely to be the main consideration by professional people carrying out this highly skilled work.
While man baskets are really good for certain work they are not ideal for tree work if there are safe alternate options to use.
Regarding the emailed comment I would reinforce that person’s comment on estimated weights as once the tree is cut there is no letting go if it’s too heavy! Probably the most common cause of crane overturns in tree work. Our rule of thumb is also to overestimate weights by a factor of 2-3.
Sent my the MD of a large tree care company and equipment supplier
A lot safer than being lifted in a Man Basket ?
I don't agree and would like to know why you would think it was not as safe .
Safer than being lifted in a Man Basket ??. Come on Chief !
A lot cheaper i would say as you'd need Two Cranes.
emailed comment
Obviously, I have nothing to do with this job whatsoever, however I have had to deal with similar situations, as you say the guys look very professional for starters.
I would say that I avoid using the Bockers for any tree work, purely as any estimated weights we are given I double then put an extra 20% safety factor on top!
Access to the tree is never easy , if they use a platform, they will need to climb out of it to access the tree especially whilst using a chainsaw. Then a bosuns chair means they can't tie themselves to the tree to sling it because they can't get out of it.
So, the way that it is done, considering that these guys are fully trained and highly skilled is as you see and as you describe in equipment more than capable to support them. However, as they are lowered into the tree, they fix a rope to the top and climb down it. On route they sling the piece to be cut and are no longer then attached to the crane, they then loop a rope round the tree below the cut to support them reposition the safety rope lean back make the cut and the crane takes the piece away.
I don't think it would be possible for them to ride the crane whilst the timber is attached!
The one thing I would say as you have Identified is the Crane would need to have been inspected and identified in a six-monthly scheme for lifting persons. Not just inspected in the last six months.
And assuming a full risk assessment has been carried out It might well have been identified as both the safest and most practical way to do the job.
Chief
I have been involved in tree work for 52 years and at one time employed over 50 Arborists with our own cranes and MEWPs. This is one of the most heavily regulated industries I know and the safety practices (used by professional companies) exceed most other industries. The photos show a commonly used method of removing trees in sections and is perfectly safe if used correctly. The climber is using a tree surgeon's harness (not a Bosuns chair) and a lifeline both of which will have breaking strains of about 3 tonnes so even allowing for wear and tear will still have a substantial safety margin. The standard practice is to be lifted into the tree and attach the cranes chain or sling before attaching their lifeline to the tree and detaching from the crane. When safely attached to the tree the section to be removed is cut before the tree surgeon uses his lifeline to descend safely out of the way. The crane can then safely lower the cut section to the ground. I know ill informed people will say its not safe lifting a person this way but it is certainly much safer than someone climbing up a tree from the ground which is far from easy and a lot safer the being lifted in a man basket which is common in other industries. It is also exhausting and can compromise the tree surgeons ability to carry on working safely. I'm sure the usual cry will go up to use a MEWP and most tree surgeons do if it is practical. Often it's not because of access not only on to the site but also getting into the tree crown its self.
Finally we should look at the figures for tree work injuries and fatalities using MEWPs as apposed to climbing equipment. You may be surprised.