PIME: accurate pile installation

In pursuit of accuracy
Ensuring the accuracy of pile straightness is becoming more and more important for the installation of foundation piles, particularly monopiles for the offshore wind industry. In order to measure the inclination of monopiles during installation, IHC IQIP has developed PIME (pile inclination measuring equipment). IHC Insight takes a look at this innovative technology, and the advantages it has for the industry.

IHC IQIP supplies innovative equipment and smart solutions for foundation, installation and decommissioning projects in the oil and gas, offshore wind, and coastal and civil markets. Combining experience and expertise with a passion for service and innovation makes IHC IQIP ideally positioned to meet the demands of its broad customer base, which includes offshore wind farm developers, installation contractors, design companies and government authorities. 

With offshore wind construction projects such as new wind farms seeing an increase in size and complexity, company’s operating in this evolving field are becoming more aware of the importance of maintaining an accurate installation from the ground up. It’s vital to ensure accuracy – but this often has implications for time and money. 

As monopiles for wind turbines are constructed from a number of connected sections, the key is to guarantee a level top section, which will in turn ensure optimum performance for the wind turbine itself. IHC IQIP’s PIME has been designed to measure piles during installation from inside the sleeve, monitoring and calculating the angle and inclination of the top section.

An instant success
In 2012, IHC first developed a concept for a new inclination measuring system that would offer a faster, swifter and more effective solution than others on the market. “We very quickly made a design featuring two beams, with one sensor in each beam,” explains Robin Nagtzaam, project leader responsible for PIME. “On the first project using the equipment, the technology was an instant success and everybody involved was very pleased with the outcome.”

During the project, and those that have followed, the team was given the opportunity to assess some critical feedback from service colleagues and customers, and saw where improvements had to be made. So, in 2013, the design was progressed. “We made it more robust, and added one extra sensor per beam so the system is able to do a self-checking routine,” adds Robin. “With just one sensor, it’s impossible to accurately check if a certain value is 100% correct or not. With two, each sensor is able to constantly check the other in order to confirm values. In that regard, PIME is self-checking.”

In 2014-15, over 300 monopiles were installed using the PIME system. Each was completed within a stated tolerance of 0.05 degrees, achieving 95% operational reliability for the equipment. The system was able to diagnose any minor problems so that other solutions could be easily presented to ensure a 100% accurate installation. “During these projects, the system proved to be very reliable,” says Griedo Bel, Project Engineer for PIME at IHC IQIP. “It’s an excellent tool for installation purposes.”

Feedback from the field
To date, all feedback from the field has been positive, with customers reporting that the PIME system offers an effective solution for accurate pile driving. “The only issues reported were those related to the human element,” explains Robin. “Due to the complexity of the equipment, we have improved the workflow of the system to ensure that operators must follow the correct procedures – it’s now difficult to make mistakes or rush the process.”

Close cooperation with customers is vital to understanding where improvements can be made to the system in order to maximise its potential. Griedo has worked on five offshore projects using the equipment, each time helping to train the service engineers while ensuring the PIME technology worked correctly. “The feedback from these projects has been integrated into the latest designs,” he explains. “And IHC IQIP’s training facility ensures operators arrive on site with the knowledge required to carry out their jobs using the equipment correctly.”

“Our relationship with customers is defined by their willingness to trust us,” continues Robin. “And they only trust us when they see evidence that our equipment is measuring data correctly. When PIME has been tested against older, more expensive methods, it has been found to be highly accurate. Once a customer trusts us, they’re happy to use our single system instead of two, three or four separate pieces of equipment!”

Operational principles
Griedo summarises the operational principle of the equipment: “We carry out a calibration on the sensors before the hammer is used in order to ensure a correct readout and process without any sensor deviations. Once any necessary adjustments have been made, we pile for one metre, then we take another inclination measurement. The process is then repeated at regular intervals to ensure the pile is driven correctly and within installation tolerance.”

The first PIME design featured only a vertical system. It was soon discovered that this was not the optimum approach for certain monopile constructions, because some elements – such as rough welded surfaces – led to a miscalculation of the inclination. “For monopiles with top flanges, we prefer to use a horizontal system,” explains Robin. “With this technique, we take measurements against our own anvil, which is always perfectly aligned with the top flange’s surface.”

In horizontal configuration, two beams on top of the sleeve are used to measure the surface of the anvil, which is in the same horizontal orientation as the monopile’s top surface. In vertical orientation, the beams are mounted on the side of the sleeve, directly measuring the pile wall’s surface.

Two types of data are combined during the measurement process. Since PIME’s sensors use the gravity-based horizon as a reference point, each beam determines the absolute angle (X and Y), while the software combines several measurements in order to determine the final inclination, or relative angle.

All measurement data is reported directly to an IHC IQIP laptop, which is installed inside the control cabin along with the hammer controls, camera monitors, survey information, and other useful equipment. Specialised software immediately calculates the current angle and orientation of the monopile, providing a detailed and accurate report to the end user.

The software also acts as a reliable diagnostics tool. An additional benefit of using two sensors is that the system is able to quickly identify any problems, and relay this information to the end user, which also results in reduced downtime. “It’s very important that the system is working as well as it possibly can,” says Robin. “The inclination of the monopile can only be adjusted until it reaches a depth of around 10m, after that it’s set, and it cannot be corrected without major reworks.”

A successful track record
“The key thing, and one of the main advantages of PIME, is that you are able to measure directly at the top section of the pile in order to guarantee reliability,” says Robin. “PIME is the best interface for consistently measuring the straightness during the piling process.

“Another way to do it would be to retract the hammer when piling, and use a different set of tools such as a water level to measure these readings. But this takes up so much time, and every hour of operational time comes at a major cost. PIME is able to save both time and money, as well as decreased hoisting operations thanks to a more integrated approach.”

An example of these benefits can be found in the 2015 installation of monopiles for the Gemini offshore wind farm, one of the largest projects of its kind in the world. In total, the work involved the installation of 150 4MW-capacity turbines, and the spread also included IHC’s S-2000 hammer with 5.5m sleeve.

“The first pile took 11 hours to install using other measuring systems beside the PIME,” says Griedo. “But by the end, once we had refined the process using the PIME system, this was reduced to an average of just two hours. Other inclination measurement systems were simply not necessary anymore or were not operational. At one point, we installed six monopiles in just one week.”

Examples of successful installations can also be found in earlier North Sea projects, including the Westermeerwind offshore wind farm, in which 48 3MW turbines were installed using IHC’s S-800 hammer with a 5m sleeve, and a similar project with 97 6MW turbine installations also testing the new equipment – with positive results.

Future applications
PIME is also capable of taking measurements underwater, making the system well suited to all types of piling operations – on- and offshore. While the standard PIME set-up can be easily installed on sleeves ranging from 108” and upwards, it can also be adapted for smaller sleeves.

“Using PIME, we will also be able to measure the inclination of anchor piles and jackets, which are used extensively in the oil and gas industry,” Robin predicts. There is a lot of potential in the future for using PIME across a number of different applications, and each would offer the customers the same effective results.”