There is nothing like putting a 50 tonne crane into overload at 9.30 in the morning to really get your day started.
But let us rewind back to the beginning…
We took down two Lombardy poplars last week, hollow at the base, with a considerable girth. The crane we were using was a Liebherr MK80, which is well suited to the urban environment we usually operate in, with very limited space, narrow roads and tallish buildings. The crane can get into pretty tight spaces, is affordable and fast to set up.
We were lifting the two trees over a building to a space in which we could further process the wood. The reach from the position of the crane to the trees was about 38 meters, allowing for a maximum weight of 2 tonnes at the furthest point.
We started the morning with a site safety briefing, discussing with all on site and the crane operator how we were going to run the job, who was going to take care of which task, how we were going to communicate, what the emergency plan was etc. As usual, the crane picks would be documented, we make a note of the number of picks, the estimated and effective load and also the orientation of the limb.
The weight we were aiming for at the outmost point was around one and a half tonnes.
Lombardies are not entirely straight-forward to rig. Especially at this time of year, when water is already being transported into the limbs, making these very heavy, so you are presented with trunk sections with long, heavy limbs attached. To avoid tipping and keeping it in the same orientation, you need to add quite a bit of trunk weight to the lower part of the section. Yet to operate within the defined weight range, there is a limit to how big you can go. We were attaching the chains low, adding an attachment point higher up to the limb to prevent tipping. Judging the centre of gravity correctly on picks like this is essential, as otherwise you can really get into trouble.
An issue we came up against was the fact that these trees were obviously drought stressed. In such trees, the water distribution is very uneven, leading to sections being very heavy and waterlogged, whereas others are dry and light – this makes is very difficult to estimate the weight of the section correctly.
On pick four or five, when I had started to get a handle on the kind of weights we were lifting (I thought), I attached a section of stem with some long limbs on it, got everything ready, communicated the estimated weight to the crane operator, about 1.8 tonnes, got him to pre-tension to chains to 1.5 tonnes, got myself in position… to then decided that it did not feel right, too heavy, so I went up and removed the chains off one of the limbs I had integrated, repositioned and got cutting.
I always agree prior to the lift with the crane operator how much tension he can put on the chains before we reassess the situation, this is to prevent too much tension being applied, when actually the problem is not the weight but that the cut is not all the way through, a couple of fibres can be all it takes to prevent a section from being lifted off. This is potentially a very hazardous situation as the fibres might suddenly break, resulting in the piece taking off, to then dunk down next to the climber. This is obviously a scenario you want to avoid at any cost!
When the crane attempted to lift the section, there was minimal movement, when I heard an ominous whistling starting up from the other side of the building. Argh, overload! Not good.
Not good, but it sounds worse than it is. Even when overloaded, these machines still have a safety margin, not massive and nothing I would speculate on, mind you. I was confident though that we were only marginally over the threshold, yet still, situations like this certainly get the adrenalin pumping. In such a case, a modern crane will go into safety mode and shut down until the load is decreased. I asked the operator to keep the piece exactly where it was, sitting on the stub.
Ok, Mark, you got this, deep breath, work your plan. Yes, thank you, inner dialogue, I am working on it! Not just hanging around looking – more or less – pretty.
I have a rule of never going on a crane job without packing rigging gear, because… you never know. Well, I was certainly glad for that foresight in this instance, as we broke out the rigging gear, attaching a Port-a-Wrap to the base of the tree and rigged a couple of the longer limbs off the section attached to the waiting crane. After we had thus removed two stems, I could see a bit of movement and we were then able to lift the section off the stub, towards the crane, where it could then be lifted over the building.
The piece was waterlogged and weighted in at 2.2 tonnes, minus the two limbs we had removed.
What this situation demonstrated to me was how it is essential to reflect your actions step by step. Move forwards one step, review what has happened so far. Does this feel right? If not, systematically identify and address the issues until it does. Expect the unexpected: When something unexpected does happen, again, be systematic and methodical, work through the issues and identify solutions. Have a range of options ready in your head – as well as physically a range of tools on site to sort problems with as they pop up.
Whilst the situation I described above was not pleasant, it was actually that big a deal, we had it sorted out within 10 minutes, I apologised to the crane operator, who was actually fine with it (I think people operating large machinery tend to have heart rates like a blue whale, e.g. veeeeeeeery slow) and we moved on to the next section. Having said that, with a less experienced team, who decides to simply bosh it out and to go for it, for instance by sliding the section off the stub, things might have turned out a lot less well.
I believe the other important point to bear in mind in situations such as this is to have confidence in your abilities and competence, the procedures you have put in place and the team around you. Do not be over-confident and cocky, but also do not allow yourself to become paralysed by terrible things that might happen. If I start to radiate insecurity and fear, it is likely to have a domino effect into the team, which is not helpful. Remaining focused and confident is more conducive to finding a solution, sometimes it is merely a matter of identifying the way forwards and putting the plan into action.
Oh, that was a total of twenty tonnes of wood we removed from that site. Not to mention the other two trees we removed on that day. I was tired afterwards.