Case Study – How a TSHD dredged to 30cm accuracy

Strategic Dredging is assisting in the execution of this dredging project, which is still ongoing. In this Knowledge Update we share the most challenging aspect of this project.

The dredging project is part of a much larger project of constructing a new offshore windfarm project.

A completed offshore windfarm nearby

The dredging part consisted of clearing sand dunes along the proposed cable route. After dredging was completed a special large plough would come and bury the cable in the clay layers beneath the sand dunes.

The plough, even though it was big, could only handle small deviations to the sea bottom so the contractually agreed accuracy was a maximum over dredge of 30 cm. Imagine a TSHD in waves, dredging up to 15 m deep, with a draghead weighing dozens of tonnes and a width of about 7 m and you get the general gist of how challenging this accuracy was.

Preparation

Survey equipment suspended above the moonpool.

It was anticipated that when dredging closer and closer to the design a lot of high spots needed to be removed, instead of a steady layer across a large stretch. When trying to remove very small layer it becomes important to get feedback on the seabed after dredging as quick as possible. In addition, there was the potential for rough seas, so a small survey tender might not be able to perform accurate surveys. To solve both issues it was decided that the TSHD itself would be equipped with multibeam survey equipment. In that way the TSHD could dredge a high spot, survey directly afterwards and get almost immediate feedback on the new seabed level.

The second big preparation was coming up with a dredging plan, that would allow the vessel to get to the required design level, without over dredging more than 30 cm. It was decided that the dredging would be done in layers. First the bulk with a dredge level of design+75cm. Once that was (nearly) completed the next layer would be design+50cm and so on. This would ensure that any remaining high spots weren’t too high above the design, which would make it difficult the remove them later.

Other preparations included making sure enough bunkers and stores were available to last the entire anticipated dredge period, as bunkering would entail a lot of sailing time to and from a port.

Execution

The cable route was split in various Zones. The zones had been surveyed earlier, but because the sand dunes were moving on the seabed it was required to get a new survey done. This was first order of business.

The TSHD used on this project had a hopper capacity of more than 11,000 m3. A large TSHD like this can easily remove more than 50 cm of loose sand in one pass. If you try to dredge to 30cm accuracy that is a real challenge. So after the survey was done trials were performed to determine how to dredge without removing too much material in one pass. Parameters such as jet water use, mixture flow rate and draghead offset from the bottom were all tested to get the best possible outcome.

The last one might need a bit of explaining. By not placing the heel of the draghead on the sea bottom, but keeping it suspended 10-20cm above the seabed it would suck in a lot of false water. Normally you don’t want this, as it lowers your production. But in this case it helped a lot in making sure there was no over dredging.

Once the best working method was established the “bulk” dredging could commence. I put bulk in quotes, as you can hardly call it bulk dredging when you were still artificially limiting the production of the vessel. But we needed some way to distinguish between the two dredge phases, so this is what we used.

Over the next few weeks the dredging, punctuated by periods of surveying, took place.

Differential chart of the trench, showing high spots to be dredged.

Hand-Over

As expected the production was not even close to the capabilities of the vessel, but a necessary evil to get the required accuracy. Even with all the above it proved very difficult to get to the required accuracy. Luckily, in discussions between the client and the dredging contractor a practical approach was taken. After clearing some last spots which really weren’t maneuverable by the plough the dredged areas were accepted, even though not everywhere the tolerances were met.

This completed the first campaign. more campaigns were to follow in the coming months for other cable routes.

What did you learn from this case study? Let us know in the below comment section.

To your success,
Timon Vinke

How to get more projects

Dredging nowadays is a commodity. Meaning clients don’t select a dredging company based on expertise, your new shiny vessels, your nice head office, or the people you employ. They care about one thing only and that is price. There are rare exceptions but by and large this is how the industry now operates.

The conclusion is simple. The company that can dredge the cheapest and still make money will survive, thrive even. While the remaining companies will keep struggling.

The only reason that so many dredging companies are still alive today is that they all charge more or less the same price. No company has a clear advantage over the others.

On individual projects there might be quite a price discrepancy, where company A bids much lower than company B. But on the next project it can be the exact opposite, company B bids lower than A. This has more to do with how the companies estimate for the project, and their eagerness to get the project, than any structural advantage one has over the other.

Getting more projects is therefore quite simple, you bid the lowest price. The REAL question is, how can I bid the lowest and still make money? If you start losing money on projects the company will quickly be bankrupt.

So how do you ensure that you don’t lose money on the project?

  1. Estimate accurately, both production and financial.
  2. Bid above the estimate
  3. Execute the project as estimated

What if you estimate correctly, but then find your bid is too high? Two reasons can explain it. The first reason, which I hear quite often, is that your competitor is very eager to get the project, so he bids on or below cost price. This is not something you can control, and it won’t last if your competitor is actually bidding below cost price. After a few projects he will go out of business. If, however, your competitor does end up making a profit on the project, then this is not the real reason you lost the project.

Which brings us to reason number two, your competitor can dredge cheaper than you can. Estimates are typically based on previous experiences. If your competitors estimate is lower than yours than he had experienced a lower cost price on another project or even multiple projects. If he can sustain that, meaning he can still make a profit at these rates, then be warned! He has a competitive advantage over you and you need to reduce your cost of dredging. If you don’t address this issue you will go out of business.

When I say you need to dredge the cheapest, what do I mean by that? It seems simple, you charge the least amount of money for a certain project. This in essence means that your cost per cubic meter dredged is the lowest, which I call the unit rate. Conclusion, you need to lower the unit rate.

This can happen in three ways:

  1. You bring your costs down but keep the production equal.
  2. You increase your production but keep costs equal.
  3. You increase your costs but increase your production a lot more.

It is about finding the perfect balance in your total investment in your production. In the graph on the right this is shown.

 

Most companies focus on number 1, cutting costs. Few companies focus on number 2 and almost no company focuses on number 3. If you struggle in getting projects and keep losing bids on tenders it is time to start working on number 2 and 3. You need to increase your production, not cut more costs.

At Strategic Dredging we are experts at increasing productions. Contact us via this form to learn more.

How are you increasing your productions? Let us know in the below comment section.

To your success,
Timon Vinke

How to educate crew and staff with E-learning

How to educate crew and staff with E-learning

In many dredging companies there is a desire to educate the crew and project staff in depth on dredge related topics. Training these people result in higher productions and better maintenance, in short in higher profits for the company.

But I hear a lot of practical issues with training such as:

  • The training is not in our country. It is costly to send people abroad
  • We need our people to work, we can’t afford to send them to a week of training
  • They train for a week, but start to forget what they have learned a couple of weeks later

I am aware of these problems and have a solution to many of these problems: E-learning. Taking training over the internet.

Below are the major benefits of this type of training.

1. Accessible from everywhere, no travel required

When designed right E-learning can be accessed from any computer, laptop, tablet or even smartphone, anywhere on the planet.

Since the training is accessed through the internet you can train as long as you have an internet connection.

2. Train during the workweek

With E-learning you don’t have to train for a week at a time, you can train in bits and pieces. This allows the time spend on training to be spread out over a longer period.

So the employees can continue their regular work, minus for example one hour a week set aside for E-learning.

It also makes sure the training is not costing them their leave, which makes the employees more positive about the training.

3. Repetition

E-learning can be repeated as often as people want. Repetition makes people remember things better, we call that the retention.

The more a topic is repeated the better it stays in the memory of the students. And the better they remember what they learned, the better they can apply it.

4. Relevance

When designed right an E-learning course allows the student to quickly search for the information they need now, on the vessel, project and circumstances they experience now.

This makes the information very relevant, which enables the students to apply what they have learned right away.

This not only means quicker training results, but also reinforces the retention of the information even more.

5. Cost of training

A special training designed for your company and people is very costly. But with E-learning the development cost is spread over more people, making the cost per student lower than traditional classroom training, especially when you factor in travel time and cost.

 

There are many more reasons why E-learning is a great way to train people, especially in the dredging industry.

For that reason, we have launched Strategic Dredging Academy.

 

 

 

 

 

At the moment we have a Demo Course online, which you can access here: Demo

If you want to have the full experience of this course you can register for free here: Register

If you have questions or want to know more about Strategic Dredging Academy you can contact us here: Contact

What is your experience with E-learning? Let us know in the below comment section.

To your success,
Timon Vinke

Top 5 Factors That Determine Your Dredging Success

There are literally hundreds of companies that buy a small CSD and become dredging contractors. And a huge percentage of these companies fail, either on the first project or quickly after the first project.

One of the issues is the mentality of a Gold Digger, see this Knowledge Update.

But today I want to focus on what you can do to increase your chances of success in the dredging industry. Today we discuss the Top 5 Factors That Determine Your Dredging Success.

1. Crew

The quality of the crew will greatly impact the production you can achieve and the amount of uptime of the vessel.

The production difference between a good operator and a bad one can be more that ten percent. And a crew that is great at maintaining the vessel can keep doing that higher production for a much longer time.

2. Project staff

The dredger’s crew needs directions. What needs to be dredged and in what order? For this you need good project staff. Staff that understands the dredging process, can make a dredging plan and a planning.

The head of the staff, the project manager, also needs to understand the dredging contract and be able to communicate effectively with the client.

When these people are doing great a lot of problems on the project will be either prevented or quickly solved.

3. Office staff

Both the vessel and the project need support. This can be for the purchase of spare parts, to fix the cashflow of the project or to get specialised assistance. The latter can also be outside consultants, but it needs to be arranged by the head office.

In addition, the top management of the company needs to empower the project staff and provide the resources such that the project staff can properly execute the project.

Good office staff will make sure that the current project can be executed flawlessly, but also make sure there a new project to go after this one.

4. Good equipment

As a professional company you need professional equipment. Good equipment, whether it is the dredger or the support equipment, will earn itself back easily over the years.

I’ve worked with a few companies that bought cheap equipment, but when it arrived on site for the first time it took months to get it to dredge one cubic meter. This is the way dredging companies go bankrupt.

Invest in good equipment and you will never regret it.

5. Unit rate

Projects are awarded to the dredging companies that can offer the lowest unit rate. The unit rate is the combination of money and volume. Before you start saying, I need to cut costs to get a lower unit rate, think about the big four dredging contractors in the world.

They all have state of the art equipment, largely western crew, which is more expensive, and a western head office, which is also expensive. But they still get awarded project after project, often beating the local contractors.

They focus on production at least as much, maybe even more, than on cutting costs. They try to find the perfect balance in the unit rate.

 

These are the five top factors that determine your success in the dredging industry. There are many more smaller factors, but if you focus and start with these 5 you will be way ahead of the majority of dredging companies that are starting.

What factors do you think are important when starting a dredging company? Let us know in the below comment field.

To your success,
Timon Vinke

Top 5 Tips To Start A Project With A Bang

The nature of dredging projects is that they have a start and an end to the execution. But the start date is often known well in advance, so how can you use that time to make sure you start the project with a bang?

In today’s knowledge update I share with you 5 Top Tips to start a project with a bang.

1. Prepare well in advance

“By failing to prepare, you are preparing to fail.” A quote by Benjamin Franklin to which I wholeheartedly agree. Preparation will save you from so much agony when you actually start dredging, I find it amazing that many companies, and people for that matter, don’t do it thoroughly.

Prepare all aspects of a project. Think about the risks of the project, what could go wrong? How can you lower those risks now, by a good preparation? Preparation when there is no time pressure is so much more effective than having to solve a problem right then and there when it arises.

2. Have all equipment available on time

A true story. A client bought a CSD, which took several months to build and deliver. Then when it was at the project, ready to dredge, something was missing. The client didn’t buy floating hoses! They didn’t even order them.

Now this is a very large oversight which costed them tens of thousands of euros. But many companies are guilty of similar, although often smaller, oversights. This is where it also ties in to point number one, preparation. But with the added aspect of time. Make sure that any equipment that you need is readily available when the project is about to commence.

3. Start with the most difficult part

Although it seems contradictory to starting with a bang, it actually is complementary. Because when you finish the most difficult part of a project at the start it will be such a great relief to all people involved that the rest of the project almost feels like a breeze.

During the preparation you will have identified the most risky or difficult part of the project. Start with it immediately, or if that is not possible, work towards completing that part the soonest.

And in case this part does turn out to be even more difficult than expected you will have a lot more time to solve the issues.

4. Empower the project manager

In many dredging companies I see a certain reluctance to give the project manager a lot of decision power. I strongly object to this. Whenever a problem on the project occurs, who is more suited to solve it than the people already on site that know all the ins and outs of the project? Of course it also means the project manager has the capabilities to handle the responsibilities.

Give the Project Manager financial decision power to solve any issue on the project. Later on he of course must be able to defend his decisions to headquarters, but at least he and his team can act quickly.

5. Have sufficient spares

Once the first couple of weeks of dredging are done the first wear parts start to wear out and need replacing. The lead time of many spare parts can be months, so this means you need to have spare parts even before you start the project.

I have witnessed several cases where the project was doing well for the first couple weeks. But then the production lowered or even came to a complete halt, because there were no spare parts available.

This, to me, feels like such a big waste. It comes from the mentality of saving money. Don’t spend on spare parts when you don’t need them, is the argument for not having spares. But in the long run you will need almost all wear parts and not having them costs you much more in lost time and production.

 

When you take these 5 top tips to heart and actually implement them in your work, team and organization you will start every dredging project with a bang! This will create amazing results in your company.

What tips do you have to start a dredging project with a bang? Let us know in the below comments field.

To your success,
Timon Vinke

How to select the best cutterhead for the job

As with most things in life, having the right tools for a job makes the job much easier. With cutter dredgers this is not different. So today we discuss the best cutterhead and cutter teeth for the different soil types.

1. Cutting the soil with the right tool

When dredging it is important that you use the right tool for the job. Different types of cutterheads have been developed, depending on the soil characteristics. Roughly there are three types, although types somewhere in between and special purposes cutterheads also exist.

Rock

This material is the hardest to break. The cutterheads are very sturdy. The arms are very thick, and they are helix shaped. This means the arms are “twisted”.

 

 

 

 

 

Sand

Although we typically associate sand with a loose material it can also be quite compact and difficult to dredge although not as difficult as rock. For sand often so called multi-purpose cutterheads are used. The arms of these are a bit thinner, but they are still in a helix shape.

 

Clay

Clay is one of the most difficult materials to dredge as it can be very sticky and at the same time hard to cut.
In the last decade or so a new type of cutterhead has been developed to dredge this difficult material. The cutterhead has more arms, sometimes as much as eight. They are straight, and the teeth form an almost closed knife. On the right is a design from Royal IHC, although other designs are around as well.

2. Equip the tool with the right parts

Once you selected the right cutterhead you need to choose the right teeth to use. This again depends on the soil type

Rock

Use a pickpoint. These are very sharp and will break the rock the easiest. Depending on your cutterhead type there may be several sizes to chooses from. Trial and error is the best way to find out the best match for the material that you are dredging.

Sand

For soft sand use wide chisels. If the sand is too compacted for those, change to narrow chisels. And if the sand is even more compact, pickpoints can also be used.
You might think, since pickpoints can also be used, that you might as well always use pickpoints. When you do that for sand you will lose production and the cutterhead wears more, as it is less protected by the teeth.

Clay

When dredging clay you want to try to create more of a knife. You can do that by using the flared teeth. When aligned correctly the edges of the teeth will almost touch.
The idea of tis and the use of more arms in the cutterhead is that you cut very small layers of clay, which then get sucked into the suction mouth more easily.

 

So there you have it, a quick overview of the cutterhead and teeth types. Discussions with the equipment providers will provide more details for the exact choice, but at least you have a few pointers, so you understand the importance of the cutterhead selection.

Do you have a great story to share regarding cutterheads? Feel free to share in the below comment field.

To your success,
Timon Vinke

Top 5 Reasons why you need a vacuum sensor

Dredgers are equipped with various sensors and indicators. Some have very technical purposes like the temperature of the Main Engine.

But today I want to talk about the number one most important sensor for a good production, and the five top reasons why you definitely need it, the vacuum sensor.

1. Minimum requirement for Operators

An operator controls the dredging process by using the controls of the equipment, much like a car driver uses the pedals and steer to control the behavior of the car. The vacuum sensor is for an operator much like a speed indication on a car, the most basic and most important measure.

Without a good indicating vacuum sensor he will not be able to control the dredger in such a way that he can get the highest production.

2. Detect clogging

When a cutterhead or suction mouth gets clogged the vacuum sensor is the first indicator of problems. The vacuum will increase and subsequently stay high. This by itself is not an indication of clogging, but when the swingspeed has been reduced and the vacuum stays high there must be a clogging in the suction line. Without a vacuum sensor the clogging can only be detected once the pump starts cavitating heavily and you hear or feel it.

A clogging in the suction line inevitably leads to lower productions as more vacuum is used to get the slurry to the pump instead of achieving a high density.

3. Prevent Cavitation

When your process is suction limited you want to dredge with the highest vacuum possible, but you don’t want cavitation. Without the vacuum sensor the is no way to know whether you are close to the cavitation limit are still have a way to go.

Cavitation occurs all of a sudden, so the pump is either cavitating or not. Once you feel it you are too late with preventing it. Cavitation leads to high wear of the pump and all kinds of damages. Preventing it from happening should be number one priority, which means the vacuum sensor should be a number one priority.

4. Mixture Velocity Indication

With some preparation a vacuum sensor can be used as a crude, but effective, velocity meter. A dredger provider should be able to inform you of the vacuum reading at various mixture speeds, when pumping water, this is important. This only works when pumping water.

They can tell you if the vacuum is 60 kPa the velocity is 4 m/s, when it hits 70 kPa its 5 m/s, etcetera.

Then when you are on a project you can pump water for a while and compare the vacuum reading with the table. This gives you an upper limit of the mixture velocity. If the velocity is already down to 3 m/s you know you can’t really add sand to the mixture otherwise the pipe will clog.

A crude method, but it gives you some indication of where you are in terms of mixture velocity.

5. Production Indication

When pumping water for a while the vacuum will also stabilize around a certain value. Then when you start adding soil to the mixture the vacuum increases. The higher the vacuum reading the higher the production. Although it doesn’t give an exact figure it does give you an idea whether you are on the right track or not.

 

These are the top 5 reasons why you need a vacuum sensor. I’m always disappointed when I get onboard and the sensor is either not working or completely missing. It is such a cheap sensor and has such huge benefits.

I dare to say, if you are serious about production, you will make sure the vacuum sensor is always working 100%, which means regular calibrations as well.

What kind of benefits did you experience form the vacuum sensor? Let us know in the below comment section.

To your success,
Timon Vinke

Top 5 Biggest Problems with Gold Diggers in Dredging

There are companies or persons in dredging that think they can make quick money in dredging. They have zero experience or knowledge about dredging and don’t own any dredging equipment. Often, they have political ties that make them think, sometimes rightly so, that they can get a dredging project. They believe that dredging is easy, you only need a CSD and you become rich.

These companies and/or people are what I call Gold Diggers.

These Gold Diggers have a detrimental effect on the broad dredging market. In today’s Knowledge Update I share with you the Top 5 Biggest Problems with Gold Diggers in Dredging.

1. They ruin the price for dredging projects

Gold Diggers seriously underestimate the difficulties of dredging and have no idea how to prepare a production estimate. Hence their bids are more of a guess than an actual estimate.

Often, they guess a very low price and hence bid a low price and get the project awarded. All the while the experienced dredging contractor knows it often is not even possible to complete the project at that price, let alone make a profit. But in the end, they don’t get the project. The serious contractor is forced to lower prices or wait for a project in which the gold diggers are not interested.

2. They ruin the projects themselves

Since the Gold Diggers don’t know the first thing about dredging they often make the project more difficult to complete instead of easier.

They start dredging and if they encounter problems, move to another piece of the project until they find the easiest part and dredge that. Once only the problem areas are left they abandon the project leaving a mess for the serious contractor that needs to clean it up.

3. Clients will hate contractors

Due to their bad experiences with Gold Diggers they come to very much distrust and often outright detest working with dredging contractors. This results in more overhead work and stricter oversight for the serious contractor.

It is also reflected in contracts for new project that come up after the bad experiences of the clients. The contracts become more sided to the clients, instead of the being somewhere in the middle ground.

4. Suppliers grow wary

To get the business suppliers are often able to provide good payment terms and sometimes can assist in financing equipment. However, when they have too much bad experiences with Gold Diggers in an area they come to generally distrust contractors from that area. That means the terms for serious contractors also deteriorate. You will need to provide more security for the supplier, or simply pay higher prices, before they will even sell you a part.

5. Bad for employees

Employees of Gold Diggers are sometimes literally picked from the street. As such a genuine Dredger Operator or any other professional in dredging is not valued as much. The contracts are shorter, the terms are bad, and the salary is low. “Why pay more for an operator that has 5 years’ experience? This new guy is cheaper.” That is the line of thinking of a Gold Digger.

 

These were the Top 5 Biggest Problems with Gold Diggers in Dredging, but there are many more. But you might be thinking: “Ok, fine, I agree. But what can we do about it?”

The source of the issue lies in the qualification standards for bidding. Clients should consider only those contractors that already own at least one dredging vessel at the time of bidding. Gold Diggers only buy the equipment after they are awarded the project, as they don’t want the risk of having a dredger and no project.

Only serious contractors that already invested in a dredger have shown they are serious about the dredging industry.

What do yo think of my proposed solution? Do you have an idea for a solution to these companies?

To your success,
Timon Vinke

Top 7 Tips to Dredge Cheaper

Who doesn’t want to dredge a project cheaper? You will get more projects than a competitor and you will make more profit.

But they key is dredging a project cheaper. This doesn’t necessarily mean spending the least amount of money, it means finding the ideal balance between expenses and production, or in other words the lowest unit rate.

Not sure what I’m talking about? Have a look at this Knowledge Update.

Below are the top 7 ways to dredge cheaper.

1. Measure the unit rate

What you measure improves, this is a common phrase in management classes and it is true, I have experienced this myself. When you measure the unit rate yourself and your people will subconsciously think of and implement ways to improve it.

Measuring it is as easy of keeping track of the weekly production and the weekly project costs. No matter what the estimated unit rate is, you want the real unit rate to be as low as possible. Either to make more profits or reduce the losses on the project.

2. Prepare the project

A good preparation earns itself back tenfold. It shortens the time it takes to complete the project and allows you to start with a good production right from the start.

A good preparation entails knowing the soil you will encounter, having enough spares, having enough floating pipeline (Yes, I have experienced a dredging company that didn’t have ANY floating pipelines for his CSD), having the right people and much more.

3. Use the right equipment

Don’t bring a TSHD to a CSD project or vice versa. Not only will the unit rate be a lot higher, you might find you can’t even complete the project with the equipment. Bringing in another equipment is very expensive and will surely destroy your profits.

But not only the type of equipment, also the tools used onboard are very important. Using the right cutterhead and teeth for a CSD can make a major difference. For a TSHD a change in teeth can also make a difference, or perhaps you need a de-gassing installation?

4. Increase the production

Once the operation has started, increase the production with every turn. Most of the costs in dredging have a fixed weekly cost. When you increase the weekly production, you decrease the unit rate, which means you can finish the project with lower costs.

I have developed the DICE system to help you increase the production. You can find more about that system here.

5. Use the best people

The best people give the best results. You want people that are not necessarily already the best in their field, although if you can get them it would be the best. You want people that are motivated to become the best in their field.

This goes for all people in your organization: operators, superintendents, project managers, but also administrative people, head office managers and so on.

Remember that in the long run you get what you pay for. So don’t focus too much on the cost of the people, think about what they will earn for the company when you hire the best.

6. Buy quality equipment

What goes for people also goes for equipment. You want quality. That doesn’t necessarily mean getting the most expensive option, but it does mean that you consider not only the purchase price of the equipment you buy, but also the operating expense. That should include the costs of your dredger being idle when the equipment breaks down.

Mean time between failure is a good measurement to get an idea how often the equipment breaks. Subsequently also measure how long it takes to get back in operation when it fails, and you will have a fairly good picture of the real cost of the equipment.

7. Get help

Whenever you encounter problems in the operations, and in dredging you almost always do, get help. Don’t try to solve the problem with people that don’t really know the solution or don’t have a method of solving the problem.

Get expert help. We are here to help you with your production related problems, but there are many other experts in their respective fields.

 

These are the top 7 tips for dredging cheaper. When you take action on these tips you will reduce your dredging costs. If you want any help with implementing these, contact us here.

Did you ever take action that led to a lower unit rate and more profit? Let us know in the below comments section.

To your success,
Timon Vinke

Case Study – Increasing CSD production for channel dredging

Recently Strategic Dredging executed a consultancy project for one of our clients. The consultancy resulted in a 10% production increase and further improvements to be made soon.
Read below to find out what and how.

The situation

The project consisted of dredging an existing channel of about 11 km long. Luckily te discharge area was roughly in the middle, so that the discharge distance was a maximum of 6 km. Still a long distance, but manageable.

The project was tendered for with an expected progress of 120-150 m of channel per day of 12 hours. When they called us in they dredged a stretch of 70-80 m per day.

For a typical cross section of the channel during our visit, see the below figure.

The challenges

This project had several challenges, which weren’t identified during the estimating phase.

Gas in the soil

Some of the softer soil contained concentrations of gas. This was not anticipated and in fact the contractor was already in discussion with the client, because this has caused weeks of delays due to a needed modification of the vessel and reduced productions. By the time we arrived the issue was solved.

Slope dredging

As shown in the figure a slope of 1 in 4 needed to be dredged on either side of the channel. The dredger had manual controls, so the operator had to manually dredge these slopes. Technically not a problem, but it does cost production as you can’t swing as fast. This latter fact was not incorporated in the initial estimation.

Dense compacted fine sand on port side

Counter to many people’s expectation Fine Sand is more difficult to dredge than coarser sand. In this case the Fine Sand was quite densely packed, resulting in frequent stalling of the cutterhead if care wasn’t given to this area. The swingspeed was greatly reduced in this area.

The combination of dredging a slope and dredging of the dense fine sand resulted in a lower average swingspeed, which in turn resulted in less progress in the channel.

The improvements

After assessing the situation several improvements were made or suggested.

Larger step-size

Initially the CSD was making steps of 0.5 m, or 6 steps in a spudwagon. We tested making steps of 0.6 m. Because of this it was even harder to get through the Dense Fine Sand and that took more time. But the remainder of the swing where there was less soil we could still swing at full speed. Since we now only needed 5 swings per wagon the total result was less time needed to complete a spudwagon. This change alone resulted in a 10% production increase.

Increasing the maximum swing speed

The maximum speed of the side winches was 15 m/min. The maximum swingspeed was thus limited to about 15 m/min. Since this was a smaller CSD this wouldn’t be an issue under normal circumstances. But for this project a higher maximum swingspeed would result in less time needed during a large part of the swing, thereby increasing the overall production.

Slope dredging automation

The CSD is of a standardized variant, so changes are that the manufacturer has developed automation for this dredger. A slope dredging automation, technically a design dredging automation, will allow you to put the design into the CSD’s computer. Subsequently it will automatically operate the side winches and ladder winches to follow the design. It can do this more accurate than a human operator and in the case of this project it would mean the operator could focus more on dredging the Dense Fine Sand, which overall would reduce the amount of stalling of the cutterhead and thus time lost.

Hire professional production estimators

This is the first CSD for this client. Although the company employs experienced commercial estimators, they didn’t have experience with estimating productions of a CSD. Although hiring professional production estimators wouldn’t solve their current problems, it would have prevented many of the commercial challenges they now face.

For instance, dredging a stretch of 120 m per day was really at the maximum technical capabilities of the CSD. With the smallest problem the production would be less.

Having a realistic production estimate would either have resulted in an achievable planning and pricing or in the choice to not participate in this project. The latter would have saved the contractor thousands of euro’s as the project is now taking longer than planned, without compensation.

 

Our visit resulted in 10% higher productions and even further possible improvements after implementing our suggestions. This directly resulted in thousands of euro’s in reduced costs as they could complete the project faster.

What do you think of the client’s situation? Did you experience something similar? Please let us know in the below comment box.

To your success,
Timon Vinke