For maximum performance of the ship’s engine a durable, high-tech hydraulic system is needed that is capable of withstanding high working pressures in the saline environment
More than 600 offshore drilling platforms for oil and gas are on duty in the North Sea. Yet the wells are gradually running dry. The task is now to dismantle the installations by 2040 in a way that is both environmentally friendly and affordable.
State-of-the-art twin hull vessels are deployed for this purpose. For maximum performance of the ship’s engine a durable, high-tech hydraulic system is needed that is capable of withstanding high working pressures in the saline environment. Any defects result directly in costly maintenance and repair.
The main power transmission elements are the piston rods in the hydraulic cylinders. To meet the demand for a compact package, they must also transmit more power while keeping the same design size. The solution is chrome-plated special steel bar from Ugitech. Its features include a high resistance to wear, optimised corrosion resistance and a good price-performance ratio – attributes that are the result of high competence in steel production.
The largest and most state-of-the-art twin hull ship currently sailing the seas is the Pioneering Spirit owned by Swiss offshore service provider Allseas. The vessel, like other so-called pipelayers, is equipped with a diesel-electric propulsion system and transports platforms weighing up to 50,000 tons. The work boats are used to install and remove large structural elements of offshore oil rigs.
The hydraulic system is the heart of the in-line and V-engines used in ship propulsion. On the high seas, demands for operational and occupational safety are extremely high. In the worst case scenario, machine failure results in pollution on a grand scale and in an inability to maneuver the vessel. In addition to imminent distress at sea, risks also include high operating cycle costs originating from costly maintenance work, etc.
Consequently, it is all the more important that the corrosion-resistant steel used is able to ensure reliable continuous output of the hydraulic system. Moreover, the system manufacturers and the shipyards also keep an eye on material prices. At their plant in St. Etienne, France, Ugitech, a subsidiary of the SCHMOLZ + BICKENBACH Group, has run a competence center for chromium-plating of steel bar for more than 40 years: the product UGICHROM is a special steel with high-performance chromium plating and optimally meets the requirements for the piston rods essential for power transmission in ship hydraulics.
“The decommissioning and dismantling of oil rigs has developed into an industry in its own right,” reports Mikaël Marret, Product Manager Chromium Plated Products at Ugitech. “With our chromium-plated steel bar, we make an active contribution to the ongoing technical developments in this area of application.”
Hydraulics on the high seas
The piston rod surface quality is decisive for process safety and functionality during use. This is because the material is subjected to a high working pressure. UGICHROM special steel with its low coefficient of friction is ideal because it prevents signs of wear like leakage.
“Zero error” – that is the claim of the shipbuilders. Special steel with chromium plating has the advantage that the corrosion-resistant stainless steel is also protected from corrosive media such as salty sea water. The lifecycle costs of the part drop. The thickness of chromium as well as surface quality of the bar and the homogenous distribution of chromium are essential for the quality of corrosion protection. “Thanks to our special electroplating technology, we are one of the few suppliers to offer excellent quality for a wide range of stainless steel grades,” Mikaël Marret emphasises.
The UGICHROM chromium layer has a uniform thickness of 25 µm and has up to 2,000 micro cracks/cm2 – a result Ugitech developed together with their chromium supplier. This is because the number of micro fissures is an indication of the homogeneity and fineness of the crack structure which in turn is decisive for the degree of corrosion protection. After electroplating, Ugitech polishes the special steel to ensure good surface roughness and thus the required wear resistance. Once the material has been tested, the bars are individually wrapped in plastic film or packaged in cardboard tubes to protect the material from damage during transport.
Lightweight construction meets performance
Another challenge steel bar faces when used in the hydraulic systems of state-of-the-art work ships is to improve performance without increasing part diameter and thus part weight. The lighter the part is, the less fuel is needed. Ideally, a steel grade would be used with extremely high mechanical properties. The companies of SCHMOLZ + BICKENBACH Group support their customers in selecting the best steel grade. They also develop and produce special steel grades in their own plants for specific requirements.
“Duplex steel is the optimum feedstock for the applications required at sea. Compared to austenitic stainless steel grades, it is also much more affordable,” explains Mikaël Marret. “This is the reason why we have already adjusted our production volume of chromium-plated steel bars to the new market and customer needs.” UGICHROM steel bars also have excellent machining qualities: It has been optimised for machining and, unlike conventional chromium-plated steel bar, it improves the productivity of component manufacturing by up to 20% despite hard chromium plating. Users profit from reduced costs in the piston rod manufacturing as well as a much longer lifetime of the parts when used at sea.
