At the end of 2023, the contract with Cranemaster AS was signed: We were to engineer and produce the largest unit we had ever made.
– We thought we had broken the scale for how large a hydraulic shock absorber could be in 2016 with a capacity to absorb 1,100 tons. In 2025, we are now delivering one that can absorb 3,000 tons, says Raymond Sæther, Head of Technical at Servi Group
We couldn't design this in the same way as before. We had to find several new solutions, especially to handle the large forces.
On Monday, March 10, 2025, the shock absorber was picked up by a ship in Rissa and transported to its destination.
Even though we have done this many times before, special adaptations were still necessary when we were to make such a large shock absorber. Aage Dahle, Head of Sales and customer manager for Cranemaster AS, lists:
A new production hall was expedited, new manifold solutions for accumulators had to be designed and made, the road from the production hall to the port had to be reinforced, and an assembly bench had to be designed and made.
Cranemaster AS is a Norwegian company specializing in the development and production of shock absorbers and heave compensators for offshore lifting operations. The company is known for improving the operational weather window and reducing operational risk. By using their crane shock absorbers, dynamic forces and loads that can occur during lifting operations at sea are reduced.
For over 30 years, Servi has been developing hydraulic shock absorbers – and CEO of Cranemaster AS, Espen B. Johansen, sees a trend towards increasingly larger hydraulic shock absorbers in the energy sector:
Moving day, the shock absorber, with a specific weight of 220 tons, will be moved out of the production hall in Rissa
- With increasing demands for energy production and infrastructure, more robust and efficient damping systems are required. At the same time, we see that the development of larger and more complex machines and equipment, such as wind turbines in offshore wind and large underwater installations in oil and gas, requires stronger shock absorbers to ensure stability and safety, says B. Johansen.
Hydraulic shock absorber manufactured for Cranemaster on its way out of Servi Group's production hall in Rissa, March 2025
It sure is a milestone to achieve, Tom-Arne Solhaug, CEO of Servi Group confirms.
– This project demonstrates our ability to innovate and deliver solutions that meet the most demanding needs in the energy sector. It is a testament to our commitment to advancing technology that contributes to a more sustainable and efficient future, says Solhaug.
Espen B. Johansen, CEO at Cranemaster agree.
– We felt confident that this was a job Servi Group could handle, as they have solved demanding and complex deliveries for us for several decades. At the same time, we are particularly pleased that the project succeeded so well, as this required a new dimension of execution compared to what they had done for us in previously projects.
Developing such a large shock absorber requires heavy technical calculations, with many elements needing approval.
– One of the biggest challenges was finding cylinder dimensions that could handle the necessary forces with the safety factors required by regulations. We had to go back and forth to find the maximum pressure. It was a challenge to get them to fit perfectly with the length of the cylinder, Sæther explains.
How do we absorb large forces that we don't have complete control over? At the same time, it had to be as small as possible for the machining to handle it.
This became a recurring question.
A new manifold solution was needed where two accumulators are attached to a manifold.
The largest shock absorber Servi had previously delivered had 4 accumulators – with a well-established construction where a manifold held them all together. Now, with 10 accumulators, a completely new manifold solution was required.
There are a number of regulations that must be met when creating such a complex unit.
– The unit must satisfy a number of different regulations from the classification society DNV, Sæther explains .
When it's the very first time someone does something like this, there are also many things that need to be redefined. In addition to being the largest unit we had ever made, it was also the first time we delivered a complete hydraulic shock absorber with a control system.
– This required additional approval and made the process more demanding, says Sæther.
– The materials are carefully selected and produced to order. Such dimensions are not available in stock, so mainly forged blanks are used. These are rough-machined first, then fine-machined with all necessary tolerances for dimensions and surfaces, so the parts fit together perfectly, Dahle explains.
The assembly of the shock absorber is carried out with great precision, followed by extensive testing to ensure that all components function optimally. The surface treatment was performed in-house, providing full control over quality.
The use of specialized machines and tools is crucial in this process. The machinery in Rissa has been producing hydraulic shock absorbers for several decades and is particularly noted for its ability to deliver high quality and precision.
It required careful logistical planning to test and quality assure such a large hydraulic shock absorber.
- The unit underwent thorough functional tests of both the control system and the pilot system before it was fully assembled. This included partial testing to ensure that all components functioned optimally. A highly advanced WiFi system was also implemented, which helped prepare the shock absorber to become autonomous and operational in challenging environments, Nils Harald Flaa explains, who has been responsible for the pilot system of the shock absorber.
The control cabinet consists of a hydraulic unit, batteries with associated charger, and an electronic control system. It is crucial to have a control system on the shock absorber to:
– What is challenging about building such a large hydraulic shock absorber is that we have to recreate an actual operation before it is in operation. We have built test systems to simulate what happens inside the large unit before it is fully assembled. We load the control system exactly as it will be loaded when it is put into use, Flaa explain.
Part of the testing involved extending the rod on the shock absorber. To do this, the rod had to be removed from the building.
Approvals of the project were carefully monitored, and all calculations had to be approved by a third party before they could be implemented.
All testing, including the control system, the hydraulic system, and the electrical control system, was thoroughly evaluated and approved by an independent party to ensure top quality.
Throughout the supply chain, quality control was carried out with great precision, and there was close cooperation with subcontractors to maintain high standards.
A hydraulic shock absorber is used to control and dampen movement by absorbing energy from shock and vibration. Cranemaster supplies hydraulic sock absorbers for offshore lifting operations in offshore wind and oil and gas, which will ensure heavy lifting between boat and installation.
Safety and efficiency are essential in such a lifting operation. The hydraulics have a unique ability to perform precise control of movement within very large loads and shocks that can occur during lifting operations at sea.
The materials used to build an offshore hydraulic shock absorber are corrosion-resistant to withstand the ocean's application of salt and moisture. This allows the shock to perform its task with a long service life, even during continuous use.
Can we develop even larger shock absorber? What are our future prospects for the hydraulic shock absorber of the future? In the picture we see production employee Ingar Erøybakk walking next to the damper's spare part.
- The advantage of using such a large hydraulic shock absorber is that one damper can handle the large loads. If you have two shock absorbers, which will handle 2,000 tonnes, you need two 1,00-tonne dampers – and then you need lifting yokes above and below the damper, which uses a lot of the crane height. With a shock absorber, you don't have to use the height of these," Flaa explains..
What's next? Will they produce even larger shock absorbers in 5-10 years?
Aage Dahle believes that at some point it will cause a physical limitation, in relation to the manufacture of parts, etc.:
– It is probably still possible to stretch this a little further, but the probability of building units of the same size or smaller is perhaps the most relevant.