Firstly, the system must carry approval in accordance with the relevant agency specification. Only then can a design engineer begin to scrutinise system 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.
For these reasons, the Eaton Walterscheid WALFORMplus® tube connector system is proving increasingly popular across the industry as it answers many of the questions posed by design engineers seeking an optimised solution to their hydraulic piping requirements.
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
A cold-forming technology system such as WALFORMplus® is proving particularly popular in comparison with tube-cutting 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.
WALFORMplus® represents a reliable, easy-to-install forming system that uses minimal components. The system also provides 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, such as the Eaton Walterscheid M-WF385Xplus for WALFORMplus®, provide advantages such as fast cycle times and quick set-ups thanks to easy changeovers with colour-coded tools.
The M-WF385Xplus, which accommodates tube from 6-42 mm diameter, also offers forming pressure control to minimise energy consumption, as well as quiet operation to reduce noise levels in the shop. Of particular note, there is no requirement to set-up any machine parameters, thus minimising the risk of failure.
Due to the tube shape produced, WALFORMplus® assemblies 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 WALFORMplus® 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 the locked-in retaining tube 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 for those looking to adopt the WALFORMplus® system. Some suppliers offer a rental service that enables an OEM or subcontractor to hire a machine for the duration of the project.
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. These objectives are exactly what the Eaton team has achieved with WALFORMplus®.
Advantages for any kind of vessel
The failure of a hydraulic piping system can prove costly in both downtime and repairs, and possibly present a safety hazard. Above-deck hydraulic systems for vessels include those supporting cranes, lifting gear and winches, so the danger is clear, while below deck, hydraulics serve equally critical systems such as propulsion and steering. For military or defence vessels, hydraulics are also present on the turret machinery that manoeuvres the guns, for example.
Today, almost all vessel types take advantage of WALFORMplus®, everything from military aircraft carriers, frigates, corvettes and exploration ships, to cruise liners, ferries and superyachts. Among the many factors at work here is Eaton’s ability to provide both the piping connection system and the fittings.
Moreover, the company can offer the system and fittings in stainless steel for above-deck applications, which are subject to saltwater spray. Carbon steel is suitable for below-deck applications.
As a further point of note, WALFORMplus® is also proving popular in the marine sector for water-mist fire extinguisher solutions, particularly for large cruise liners where a lot of piping is required. Water-mist systems operate at high pressure, typically 140-160 bar, which makes WALFORMplus® ideal for this application, even though the media is water rather than hydraulic oil.
Often, the preference is to use the system in conjunction with a welded stainless steel tube, which is more cost-effective than the seamless tubes used for hydraulics.
Testing the water
Fundamentally, test results identify the leading contenders when it comes to selecting a hydraulic piping connection system. Alongside tests in accordance with DIN EN ISO 19879 and IACS, special tests under extreme loads will confirm the safety and leak-proof capabilities of a tube-fitting system. For WALFORMplus®, results are available (according to appropriate test institutes) for tests that include combined pressure-impulse and reverse bending tests, as well as tensile and fire resistance tests, to list but a few.
WALFORMplus® has also proven it is resistant to shock loads equivalent to 700 g-force in tests that simulate the effects of a torpedo strike. This outstanding result highlights the system’s impressive resilience.
Of course, achieving these approvals and test results demands enormous effort and input from Eaton’s engineering department. However, the outcome is an extremely attractive offer for sectors such as marine, namely a reliable, easy-to-use, fully certified hydraulic tube-fitting system that adds genuine value.