July-August 2021

42 HYDRAULICS & PNEUMATICS July/August 2021 www.hpmag.co.uk APPLICATIONS When it comes to specifying a hydraulic piping connection system for marine applications there are a number of critical factors to keep in mind. Firstly, the system must carry approval in accordance with the relevant agency specification. Only then can a design engineer begin to scrutinise capabilities such as reliable, leak-free performance. There is also the issue of the corrosive marine environment, which demands a tubing connection system – and fittings – manufactured from stainless steel. Vendor selection is clearly pivotal to system success. Type approvals form the backbone of the marine industry. Originally a requirement of ship insurance companies, many different agencies (with different type approvals) operate in this sector, including DNV GL, Bureau Veritas and ABS, to name only a few. Although the relevant approval usually relates to geographic area, all agencies fall under the umbrella of IACS (International Association of Classification Societies). By fulfilling the type approvals, components used for marine projects are confirming a minimum performance level in terms of mechanical resistance and fatigue life. This performance is required to ensure the functionality of safety- critical systems, as well as behaviour in the event of fire or mechanical exposure. Of course, products that meet the marine sector’s rigorous type approvals can also serve other industries. These approvals provide third-party confirmation that the products meet a wide range of test requirements according to their defined operating pressure. Assuming the system carries the required approval, the design engineer can begin his or her assessment of other selection factors, such as pressure resistance, vibration resistance and safety. For defence applications, designers must also think about the potential for a hydraulic tube-fitting system to retain its functionality after a torpedo strike, for example. Ease-of-installation, soft sealing and resistance to pull-out forces are further considerations. Forming, not cutting Systems based on cold-forming technologies are proving particularly popular in comparison with tube-cutting Selecting a hydraulic tube-fitting system for marine applications systems. There are many reasons for this trend. For instance, the cold forming of materials increases stress resistance at the most crucial points of the tube. Combined with no sharp ends, this effect creates outstanding vibration resistance. In addition, as a dry, non-cutting forming process, cold forming produces no waste or mess. Design engineers should focus on a reliable, easy-to-install forming system that uses minimal components. The system should also provide ultra-high- pressure resistance and the option of a soft seal. Another key factor is process stability, which comes from the machine that forms the tube connection. Any cold tube-forming machine should produce assemblies with the same quality time- after-time, independent of the tolerance influences imparted by the tube or fitting. With such a robust machine, the worker can do nothing wrong, thus providing a significant benefit over cutting-ring systems, which rely on operator skill. Having this process assurance also brings a level of safety with regard to creating a correct, leak-free connection. Rapid set-up and cycle times Some machines provide advantages such as fast cycle times and quick set-ups thanks to easy changeovers with colour- coded tools. In addition, certain machines provide forming pressure control to minimise energy consumption, as well as quiet operation to reduce noise levels in the shop. Due to the tube shape produced, some pipe connection systems ensure extremely high resistance against pull-out forces, significantly more than a cutting-ring assembly. In fact, pull-out torque tests show that, depending on the system selected, a cold-formed assembly has circa 57% more resistance to pull-out forces than a cutting-ring assembly of the same diameter and wall thickness. This impressive result is largely because certain systems produce a locked-in retaining tube that removes any risk of disconnection, thus enabling its use in safety-critical applications. It is also worth noting that a large investment in a forming machine is not necessarily required. Some suppliers offer a rental service that enables an OEM or subcontractor to hire a machine for the duration of the project. Avoid failures Ultimately, not selecting the optimum tube-fitting system can lead to a number of issues, including failure. In most marine applications, failures are traceable to a lack of worker assembly skills. Of course, this issue presents a challenge for manufacturers of tube-fitting systems, who must ensure their systems allow the creation of easy and reliable tube connections, without compromising the necessary resistance to pressure peaks and vibration. By Michael Weidenbrück, manager business development EMEA – Eaton Walterscheid, Eaton Germany GmbH. Almost all vessel types take advantage of hydraulic tube- forming connection systems.