A specialist in class-leading load-handling equipment has switched to Eaton’s popular Walterscheid tube-fitting and forming technology in a demanding application involving high loads, elevated pressure and significant mechanical stress. The move has contributed to lower fuel consumption thanks to a reduction in tube weight, and eliminated previous tube failures.
The manufacturers truck-mounted loader cranes are renowned the world over. Built for uninterrupted work, these products feature high-tensile steel construction, reliable seals and protective covers that resist weather and impact. The cranes undergo a punishing series of lab and field trials to meet a range of different demands, including air-transportability, climate/terrain conditions or specialised installations.
A common denominator among the variants of truck-mounted loader crane produced by the manufacturer is the need for reliable, yet low-weight hydraulic steel tubing and fittings. With any vehicle, weight has a direct influence on fuel economy.
As the manufacturer is constantly striving to improve and update, when the company began to experience one or two field failures of its standard hydraulic tubing due to incumbent pressure levels and mechanical stresses, it spotted an opportunity to make simultaneous improvements in two areas: weight and strength.
“Peace of mind was critical for our customer,” states Juan Moreno, sales engineer, Eaton Hydraulics Spain. “Given our trusted relationship, they knew we could be relied upon to ensure success for them and their stakeholders as one of the world’s foremost manufacturers of mobile load-handling equipment.”
The weight challenge
The primary objective was to reduce weight across the loader crane; less weight means less load and less fuel consumption for users. It was essential to achieve this project goal in unison with delivering extra reliability to prevent tubes from cracking or bursting. Unfortunately, the side-load function of the loader crane exacerbates the potential for this unwanted outcome by imparting high mechanical stress on the tubing.
In the first instance, higher strength E355 grade tubing with thinner wall thickness replaced standard E235 tubing on the loader cranes. E355 seamless cold-drawn tubing offers higher tensile strength than standard tubing, but at a lower net weight. The elevated strength of E355 allows users to achieve similar operating pressure for thinner tubing. In this case the manufacturer was able to switch from 16mm diameter, 2 mm thick E235 tubing, to 16 mm diameter, 1.5 mm thick E355 tubing. The 0.5 mm difference in wall thickness reduces the weight from 0.69 to 0.54 kg/m (a 22% saving).
With the material identified, thoughts turned to assembly and Eaton’s series of Walterscheid fittings, connectors and tube-forming technologies. Although Eaton and the manufacturer enjoy a close working relationship that extends back a number of years, there was a clear need to avoid underestimating the importance of tube forming and fittings in this application.
“The loader crane is very demanding in terms of operating pressure and dynamic pulsation, while strong axial and radial forces also place additional stress on the tube assembly,” outlines Juan Moreno.
Testing the potential benefits
Eaton’s Walterscheid WALFORMplus-SR system extends the proven advantages of the WALFORM platform to thin-wall tubing such as the 16×1.5 mm product identified for the this application. An additional support ring (SR) located behind the formed tube increases resistance to vibration and bending stress. Using WALFORMplus-SR it was possible to undertake tests that would help draw comparisons against the previous tubing solution.
WALFORMplus-SR is a positive-locking, cold-forming tube-fitting system for increased safety, even under extreme loads. The mechanically reshaped tube-end screws together using an additional support ring, as well as a conventional DIN/lSO stud and a DIN/lSO union nut. Moreover, the only possible leakage path is sealed-off in two ways: first by the WALFORMplus soft seal, and second by means of the metal-to-metal seal between the patented WALFORMplus shoulder and the fitting stud. Thanks to the positive-locking connection and additional support ring, WALFORMplus-SR ensures secure retention and greater resistance to dynamic loads.
Simulated pressure impulse and bending stress tests in the Eaton Walterscheid laboratory categorically demonstrated that the WALFORMplus-SR system could offer a higher resistance against dynamic load compared with other forming systems, resulting in longer operating life. This was borne out when applying the WALFORMplus-SR system in the actual application, thus verifying that the occurrence of failures was entirely preventable. The WALFORMplus-SR geometry of the reshaped tube ensures excellent performance under dynamic loads, such as reversed bending stress and dynamic pressure impulses.
Ultimately, the adoption of WALFORMplus-SR and thin-walled E355 tubing material has helped to optimise both the strength and weight of its mobile loader cranes, with the latter contributing to reduced fuel consumption.
Among further advantages, the manufacturer now enjoys the protection of Walterscheid Guardian Seal plating, which is particularly important in environmentally challenging applications such as mobile loader cranes. Their location on the rear of a truck exposes these lifting devices to the elements, as well as salt spray and other contaminants from the road surface. Guardian Seal is a zinc-based surface treatment applied by electroplating. The 11-15 µm thick zinc guarantees exceptionally high levels of durable protection against corrosion and meets DIN EN ISO 9227 standards.
Another benefit is simplified assembly. Due to short tightening rotation and low torque, the installation process only takes a fraction of the time required for conventional tube-fitting systems.
“Our customer-focus was key to the success of this project, as was a high-capability manufacturing plant that always lives up to its promises and has a 100% on-time delivery track record. Walterscheid manufacturing in Germany, Lohmar, and extensive support structure across Europe helps to develop an efficient Supply Chain close to European manufacturing plants. says Christian Kuenstel, Product Manager Connectors Eaton Hydraulics EMEA. Eaton now stands ready to provide the customer with long-term future support for repairs, spares, servicing or upgrades as required.
“We are always ‘in it together’ with our customers, working towards mutual success,” adds Juan Moreno. “This project really brought that ethos to life.”
Today, WALFORM machines located on the manufacturers production lines across Europe are delivering repeatable steel tube assemblies for the company and its customers. Automating the process is the best way to ensure excellent tube-fitting performance. For this reason, Eaton manufactures its own bespoke assembly machines to optimise the production of Walterscheid systems. The company produces around 80 such machines in-house every year, alongside the associated tooling.
For WALFORM (6-42 mm diameter), Eaton offers the reliable M-WF385Xplus, which suits demanding tube-forming applications in steel and stainless steel. The M-WF385Xplus also enables additional sealing, easy machine assembly and robust performance. In particular, fast cycle times allow efficient and economical production, while simple and quick tool changes reduce set-up times. Tools are colour-coded to avoid mistakes in the forming process.
Ultimately, the WALFORM machines are delivering repeatable assembly, reducing any potential for misalignment of fittings and, in turn, creating less opportunity for hydraulic fluid leakage. With reduced weight and reliable strength, this sector-leading manufacturer of load-handling equipment has received a notable lift in the number of USPs it can now offer to customers.