Hydraulic cylinders are indispensable in offshore and underwater applications. Whether for pipe installation, in gripping and vibrating tools or in underwater vehicles – wherever electrical or pneumatic systems reach their limits, hydraulic cylinders reliably deliver enormous forces.
In marine applications, hydraulic cylinders must withstand extreme environmental conditions. Unlike in conventional industrial applications, these cylinders are exposed not only to high mechanical loads but also to specific stresses caused by the water environment:
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Corrosion in Saltwater
Seawater is highly corrosive, which requires targeted material selection and surface treatment.
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Leak Tightness
Under water, absolute leak tightness must be ensured to prevent both the ingress of water and the leakage of hydraulic fluid.
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Pressure Conditions
With increasing water depth, the ambient pressure rises, which can place significant demands on the sealing systems and the cylinder design.
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Operational Safety
Underwater cylinders must operate reliably even after long standstill periods and must not exhibit failures due to seizure or seal failure.
Case study: hydraulic cylinder for offshore gripper operation
A customer approached ACONA with a special challenge: for the construction of wind turbine foundations and offshore platforms, massive foundation piles have to be anchored in the seabed. A core drill loosens the material, while an underwater gripper removes it from the borehole. Two hydraulic cylinders perform the crucial task of reliably opening and closing the gripper jaws under water – a function where precision and fatigue strength are decisive for the project’s success.
While ropes can still be used to open and close the gripper jaws at depths of up to around 60 metres, their elongation over greater distances leads to significant loss of force. At greater depths, hydraulic cylinders therefore act directly at the point of application and transmit the load without detours – exactly where it is needed. However, this solution comes with extreme requirements: at a depth of, for example, 200 metres, more than 20 bar of hydrostatic pressure prevails, and any leakage or material weakness would have immediate consequences. In addition, the corrosive effects of seawater place the highest demands on material selection, sealing technology and surface protection.
ACONA´s engineering solution
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Protective Coating
Corrosion-prone steel areas were protected with seawater-resistant coating, further enhancing the overall protection of the cylinder. Critical areas were additionally sealed.
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Wiper
We used hydrolysis-resistant wipers that reliably function even under increased ambient pressure and securely prevent water ingress.
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Piston Rod Coating
The piston rod was provided with a proven nickel-chrome coating, which ensures consistently high resistance even under highly corrosive operating conditions.
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Joint Sealing
Since the piston rod thread could not be nickel- or chrome-plated, all joints were additionally sealed with a marine-grade silicone to eliminate any potential ingress points for corrosion.
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Rod End
To prevent corrosion, the rod end was additionally fully nickel-plated and zinc-coated.
Result
The cylinder developed by ACONA was successfully commissioned for underwater use. The gripper now operates reliably at 150 m water depth and withstands the high stresses of seawater and ambient pressure.
This project underscores ACONA's engineering expertise.
Whether underwater or underground – ACONA's hydraulic cylinders excel where precision and durability are required.
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