Usually when people hear that a mobile crane tipped over, they assume that it was due to the load weight. However, the truth is that loss of stability is inescapable when operators disregard the crane manufacturer’s guidelines concerning crane ratings. Simply put, the cause of a tipping accident is most likely the wrong boom angle or boom length.
A mobile crane is comprised of three basic components: the carrier (chassis), superstructure, and boom. The center of gravity of each component affects the center of gravity of the entire crane assembly. Preventing the crane from leaning too much to one side or tipping forward is the objective of two mechanisms: the counterweights and outriggers.
Counterweights are planted on the cab’s underside, on the back of the crane. The amount of weight needed for a specific operation depends on the load’s weight, the boom’s angle, and radius. Counterweights are removed when the crane is not performing a lift.
Outriggers use hydraulics to lift the whole truck (tires included) off of the ground. The outriggers are made up of the outrigger pad (also known as the “foot” or the “float), and the beam (the outrigger’s leg). Even when you’re working with loads that are under your crane’s lifting threshold, extending the outriggers properly is critical. Occasionally, mats (or wood floats) are lined up to form a base underneath the pad in order to evenly spread the weight over the ground surface, which can help preserve the pavement underneath the crane.
There is a special vocabulary when it comes to improving equipment stability with counterweights and outriggers. Below are a few of the terms you might come across while on the job:
Blocking- Also referred to as “pads”, “dunnage”, “mats”, or “cribbing”, blocking is used to support lattice boom sections and evenly distribute loads to the ground during disassembly and assembly.
Allowable Ground Bearing Pressure- The maximum amount of pressure approved on the supporting surface. The number is measured in Pascals (Pa) or pounds per square foot (psf).
Deflection- Bending of supporting materials as downforce is applied.
Crane Pad- An area of compressed concrete, mats, steel plates, or soil used to support a mobile crane during a lift.
Crush Rating- The amount of pressure that an outrigger is allowed and rated to carry. This depends upon the strength of the materials involved.
Displacement- The difference between the fully-loaded horizontal position of the outrigger pad and the unloaded horizontal positions of the outrigger pad.
Crane Mat- Used to lessen the ground bearing pressure from a crane’s crawler tracks, tires, or outriggers.
Ground Bearing Pressure (GBP)- The pressure that a crane pushes on the supporting surface, measured in Pascals (Pa) or pounds per square foot (psf).
Downforce- The pressure created from the outriggers onto the outrigger pads through the outrigger float.
Ground Load Rating (GLR)- The amount of weight that can be used on the outrigger pad based on the ground’s ability to support it.
Effective Bearing Area- The area underneath a crane mat that is sufficient in distributing the applied load to the underlying surface.
Ground Bearing Capacity (GBC)- The capability of the surface/ground to support a crane and its operation.
Outrigger Pad/Float/Foot- These help even out the load to the supporting surface by attaching to the outer part of a crane’s outrigger. As with several crane parts, they go by many names, typically depending on where you are. You may refer to them as “feet”, “outrigger floats”, “outrigger pans”, or simply “pads”.
Ground Conditions- How well the ground can hold up the crane and its load. These conditions include slope and soil compaction.
Maximum Outrigger Reaction Force- The maximum amount of weight that the equipment can exert through its outriggers.
Supporting Materials- These include cribbing, blocking, and mats, as described in OSHA 1926.1 OSHA 1926.1402(a)(2).
Regardless of how heavy your load is, you should always follow the correct setup procedures. Stick to your crane lift plan when the lift exceeds 75 percent of the crane’s rated capacity or demands the use of more than one derrick or crane to perform. Be sure to ask these questions prior to setting up your crane:
Have you ever been called or sent to take over a job that feels like you just jumped on board of a sinking ship? One that is either losing money, behind schedule or has quality issues? Then you need to try these three easy steps to help get it back on track quickly!
Clean The Job
More often than not an un-organized, messy job is usually behind schedule or poor on quality. If you want an efficient job, it needs to be clean and organized. By cleaning up the job, it not only makes it easier for the crews to work in and around so they can be more efficient, but it also shows progress and change. When you’re trying to change a job this will help with immediate results by changing the environment they work in from a messy, unsafe area to an area clear and free of materials and debris.
Supply Crews with the necessary: Materials, Tools, Equipment and Long Lead Items.
There is nothing more frustrating for a crew than to be waiting on information, tools, equipment or materials. The whole objective of a supervisor is to ensure all of this is taken care of before they even start work, clear a path for your crew to be successful. So don’t just look at the immediate needs, start looking ahead. Create a schedule with materials, tools and equipment needs for the activities. This will help ensure there will not be any hold ups.
Give them a reasonable objective to hit. If your behind and try giving them un-reachable goals, it will only add to the hate and discontent they have now. Start off with a couple of goals you know they can hit. Build up their confidence, then, start pushing once confidence is achieved. After that they will welcome a challenge and looking forward to what they can achieve now.
There could be many reasons a job starts going south, in order to fix the problem you need to first identify and remove the problem: this could be the wrong supervisor or foreman on the job or it could be a problem with the sequencing and logistics. Whatever it is, once you identify the problem and remove the cause, it is your responsibility to find a solution to get it back on track. The three listed above are just some general items to help you get the job organized.
Talk to the crews, contractors and sub contractors and get their opinion of why the job has not been performing like it should. Remember any feedback you receive can only help you identify the real problem so you can correct it.
Here are three steps to help you be successful with your next task.
Start with Planning:
Last but not least is to review.
This is how we become successful.
How important is organization on your job site? Have you ever thought about what it costs to be unorganized? Most all of us could use some improvement in this area. More jobs than not are in some serious need of organization. However, it doesn't stop there. Not only should a job be clean and organized, but efficient as well. I mean, what good is it to hurry and strip footings and place them in nice neat stacks where a crane or forklift can't get to them until after the backfill is complete. Sometimes it's a simple as stacking the material on one side or the other of a footing that can make all the difference.
Take a look at the pictures below, If this was your job what would you change? Are there any you feel you wouldn't change?
Just some things to look for:
Do work areas look ready
Are there too many or not enough people working in the work areas
This is a broad subject, it could be anything from logistics of the job to paperwork on your desk. Each area of organization could be costing your job money, if it takes you an extra 5 minutes to find the drawings you need then another 5 extra minutes to find paperwork for one of your crew members. That time can add up and is completely preventable! It might sound like much to worry about, but think about the whole jobs wasted time. If your logistics aren't planned out and organized we start talking about real money wasted. The construction industry as a whole wastes millions in double handling materials.
How well organized are your crews with tools and materials? It might be time to re-think the job logistics.
Hopefully you are noticing a reoccurring theme with a lot of the Constructorator blog posts, we can’t stress enough the importance of the planning portion of your job. As a supervisor it’s your responsibility to plan for all activities your crew will be performing and your crew is responsible for executing the plan.
I am not trying to sound like a broken record, but it’s the most important part that gets overlook the most often. The continuous planning is the first task to be neglected when we are feeling pressure either from schedule challenges or overrunning budgets. We feel the need to “jump in and help” or we just get caught up in moving from one fire to the next.
The first step always is to create the plan - schedule, manpower, materials, logistics. That part takes some serious effort, but if you slack off on your planning you will pay the price later. After you plan the work it's time to execute and maintain the plan. The continuous planning and plan maintenance are often not given the attention needed. We all know that in construction with so many moving parts and prerequisite work that needs to be completed before the next trade can start, we need to be flexible. This means we need contingency in our planning, nothing will ever go exactly as planned we need to be ready for a breakdown in the plan and react to it accordingly. You should always be adjusting the plan, don't let the hard work of creating the plan go to waste when a hiccup occurs.
I have a lot of carpenter's asking me how much time and men do they have to complete a certain task. So in this week's blog post we want to look at starting simple to figure how many men and how many hours for a certain task. Take an activity like spot footings, in the picture below there are twelve spot footings highlighted that we are going to use as an example today.
First, find the estimated/budgeted Man Hours for spot footings. (460man-hours)
Next, schedule duration for this activity, in this example there is 7 working days to complete the spot footing activity.
Now, take man-hours and divide by days - 460/7= 65
So you have 65 man-hours a day for a seven day duration to complete the footings.
Then you want to determine your crew size based of your daily man-hours
First take the daily hours 65 and divide by the crew size you would like to have, let's try 10 men. 65/10=6.5 if you have ten guys to stay in budget you could only work on spot footings for 6.5 hours a day, if you have 10 men for 8 hours a day for 7 days.- your total man-hours would be 560 (100 hours over budget)
Let's try a crew size of 8.
65/8.1= 8 so you could have a crew of 8 for eight hours a day for seven days- your total man-hours would be 448 (12 hours under budget).
There are many factors that come into play when determining crew size and it's easy to get over-whelmed. You have to break apart each task, understand the job flow, sequencing and schedule. But if you start with one task and work all the way through it then move to the next task and so forth, you start to create the data needed for an average crew. Maybe you only need 8 on spot footings but 10 on walls and four on columns, after you know your crew size you can double back to the schedule and see if the sequencing works out where you can get away with a crew size of 14 because of all the trade work or down time in-between activities or on pour days. The more you practice the easier it becomes.
The important part is that you learn and understand hours/cost on every activity you are part of, and it's never to late to start. In the case that you are not shown the budget or hours by your Foreman or Supervisor click here for a MH/Unit form that you can start tracking yourself. You want to become great at what you do, so empower yourself to learn, grow and excel above those who don't want to share the information.
After all the effort you put into the planning and sequencing, you put the plan into action and somehow the execution falls apart because something was out of sequence. Time, money and manpower was wasted because of a break in the link. If you’re a new foreman don’t overlook or dismiss it calling it, saying “that’s construction”, if you want to learn and grow get to the root of a problem by asking “WHY”.
For example, let's say you had a concrete pour that went ok, ask yourself:
Why was it just ok?
It took longer to pour out, then expected.
Why did it take longer than expected?
Because the finishers got behind; it took them a while to get the concrete placed.
Why were the finishers getting behind?
They concrete was stiff on the last half.
Because the trucks were starting to back up and the concrete was getting old.
Because we were still working on the slab prep (rebar placement, recess areas etc..) in the morning, while the pour was going on, which caused the finishers to wait on us at times.
Why were you still working on slab prep?
Because the area was not turned over until 3:00pm the night before.
Why was the area turned over late?
Because the dirt contractor was behind schedule.
Why were they behind schedule?
because he did not show up on Tuesday.
Why did they not show up, did someone forget to call them?
No, they were scheduled but decided another job was more important.
So after they were a no show what decisions were made as far as schedule and the pour date?
We had to make the pour, so we waited for them to show up the next day and went back to normal, just trying to get it done.
By asking “WHY” you can see that the pour production was subpar.
Because the finishers were not able to get the slab placed quickly with fresh concrete they had to work twice as hard to lay it down, because the carpenter crews were still placing rebar and fine grading the gravel, because the area was not turned over to them as scheduled because the dirt contractor did not finish on time because they were not on-site on the day they were supposed to begin the prep. So you can see one missed step cause a chain reaction of events to which caused the un-productive slab pour. If we focus on the problem at the first or second why we will never get to the route cause and will learn only half of our mistake. The problem is decisions not being made right then, whether it's changing sequence of flow (maybe focusing on one area, a certain section so that one half was completely ready for the finishers when they show up, instead of nothing being ready and work needing to be done in all areas).
Once a schedule disruption happens, an action item needs to be implemented.
It's like concrete trucks stacking during a big slab pour, you're trying to hurry and pump old, dry concrete before time expires. However, this will cause a chain reaction with stacked trucks behind the one currently being placed, whereas if you remove one of the old trucks from the lineup the next truck will be fresher with more time to place out and so forth down the line.
Flow is what we are trying to achieve to be productive. Every time there's a delay, well this disrupts the flow. So asking why allows us to find and get to the root of the problem. Why is a powerful word if asked continually it will only help you learn and grow.
Everyone wants a safe job, they also want to bring value to what they’re doing, in short they want to be productive.
So why wouldn’t all jobs be set up for safe productivity?
The two factors that would play part for having an unsafe and an unproductive job; cost and too much time. We hear it all the time “We don’t have time” “We don’t have money for that”.
So let’s start with money.
What is the cost of an extra ladder, barricades, trench box?
And what’s the cost of an accident, injury or even fatality?
How about time.
How long does it take?
Most of these can be done within a couple minutes, where we lose time is not planning for it so everyone thinks safety takes a lot of time for example, everyone goes up to the third floor after their morning meeting yet none of them take a retractable for a certain task that needs to be done. So once they all reach the third floor and realize they need a retractable they call on the radio and ask someone to bring it up, so now we have a whole crew broke down waiting for a retractable.
Another example let’s say your decking a slab and you get right up to the only access off the deck, if you would have planned ahead, you could have had someone put up a secondary access while you were decking and when you came to the point of needing the ladder moved so you could continue on it would have been done, instead you get right up to the ladder call on the radio and wait for someone to put up a secondary access so you can continue work. This happens all the time, I know, I know, but we are staying busy while they were working on moving the ladders, the problem is you were busy, but you were not productive. If you continued decking without waiting on access you would have been decked out today, instead you will finish tomorrow. But, you helped get the edge form guys caught up while you were waiting, now they are waiting on you to finish decking.
If you have a safe job more than likely you will have a productive job, one with clean work areas, proper access, lighting, tools and equipment.
Successor: thing that succeeds another
Predecessor: a thing that has been followed or replaced by another.
So, every project schedule has a successor and a predecessor. The goal is to have every activity in sync with the next, avoiding any gaps. Think of it like dominos lined up in a figure 8. The whole goal is to start one domino knocking the next continuously until they are all down. However, if there is one domino that misses or comes up short, it will disrupt the flow. They did not all go down in sync, therefore, no “domino effect”. Now it might be ok if it just happened once, but what if it took ten attempts to knock them all down. Well anyone that has ever set up dominos would set them up right the next time to make sure they all go down in one shot. Superintendents and foreman are the ones who set up the task and activities to start and finish on time. If you’re well planned out and organized, you will have all your dominos lined up and ready to go.
Here are some examples of how this can be achieved.
Planning and thinking through every process can help you mitigate any potential delay’s, cut out unnecessary steps and set you and your crew up to succeed.
Everything doesn’t go as planned 100% of the time, but if you have a good plan and follow through you will be miles ahead of those who don’t.
How many questions a day do you answer?
A Foreman’s responsibility is to answer questions, however, you could be answering more than needed. If you are doing nothing but answering questions all day long, either you’re a Foreman who needs to know all the answers therefore everyone comes to him for everything. Or you’re the nice guy, you know the one who does everything for everyone with a smile.
So how do you know if you are getting asked too many questions a day?
Tomorrow take note of every question you are asked, yes by the end of the day your list might be 10 pages long, it might be only half a page, but it’s data you need to see.
Next as you go through each question you were asked check it with a #1 (this is something you need to be asked), #2 (if someone else could answer it) and #3 (if the person asking the question could’ve resolved himself).
Let’s use some examples of a #1, #2 and #3 question below.
Q: Can we move a temperature PT Cable 1’ to the north- it interferes with an embed?
A number one is worth your time, it deals with a change to the contract documents and has a significant impact on the job, production and design.
Q: I need someone to help me with placing the form oil in the containment bin?
A number two could be avoided by the person asking the question to ask a fellow worker instead.
Q: Do we have saw blades?
A number one could be answered by himself if he knows the location of the tool trailer, gang box or wherever the saw blades are stored.
If you are continuously answering the #2 & #3 look at the overall planning and communication being done.
A number two can be avoided with planning; pre planning deliveries, order list, etc.
If your open to teamwork and set the expectation that we are all here to help when needed, then this one shouldn’t be a problem. But, if you’re over controlling then you will always be answering a number two question.
A number three can be avoided with a simple morning huddle meeting. Walking everyone through the site logistics, material, equipment and tools where they are stored and the procedure to note when something is low or needed. If everyone knows the storage locations and protocol for ordering this will save you a #3 question.
If you can limit yourself to number one questions only you’re managing and leading your team well. We can all improve and this is might seem small but time management is critical for your growth, you don’t want to get overwhelmed and you want to manage your time as efficiently as possible. Everyone wants to help, but, if you’re spending most of your day tracking down tools or materials leaving you with less time to focus on what you should be focusing on which is to run a safe and productive job.
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