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Machine builder gets the best of both worlds

04 December 2013

High pressure is Poppe + Potthoff's business. From high pressure lines, pipe components and precision parts, to machines and services for testing, the group develops and produces advanced test stands for a variety of industries. Burkhard Balz describes one development that took advantage of a single supplier of both hydraulic and electrical components.

At its Nordhausen site, Poppe + Potthoff designs and manufactures test systems for burst tests, autofrettage, pulse tests and rotating bending fatigue. The latest machines from this manufacturer include a burst pressure test stand that is suitable for testing tube fittings and hydraulic hose lines.

The test sequences that this machine performs can be pre-programmed by the user to allow pressure ramp cycles, static high pressure and burst pressure testing. Protected by a stainless steel safety cage, test objects can be burst tested in a controlled manner at pressures of up to 4,000bar, for which the data are recorded accurately in real-time at the rate of 100,000 measured values per second. 

Normally, Poppe + Potthoff would have outsourced the supply of the hydraulic power unit; however, the machine builder decided to pursue a different approach with its new burst pressure test stand. So, in partnership with Eaton, an in-house hydraulic power unit was developed, with the necessary controls also supplied by Eaton.

In order to create the high pressure necessary for burst testing, the hydraulic power unit uses two pressure amplifiers with different piston diameters. This enables a fast pre-fill, thanks to the larger pressure amplifier, and high-resolution pressure regulation using the small pressure amplifier. Proportional valves ensure the precise control of the pressure amplifiers and thus the pressures in the test chamber.

The proportional valves are among a number of other hydraulic components supplied by Eaton for this project. These include axial piston pumps and vane pumps, as well as valves from Eaton's Vickers product range, Aeroquip hoses, tube fittings from Walterscheid, screw- in cartridge valves from Integrated Hydraulics, as well as Internormen pressure filters and ventilation filters for the tank system.

For the machine builders in Nordhausen, the service offering of Eaton's distribution arm in Düsseldorf also played an important role. Hyflexar Schlauch- und Armaturen GmbH - Eaton’s designated service partner for Poppe + Potthoff - not only kept all tubes, pumps and fittings in stock, but also configured and installed on site and maintained a 24/7 spare parts service.

The control system
Poppe + Potthoff chose Eaton's modular XC200 for the PLC, as Poppe + Potthoff software development engineer, René Karwoth explains:

“For us, the XC200 offers two major benefits for this test stand. Firstly, the integrated Ethernet interface allows us to connect the PLC directly to National Instruments’ LabVIEW and the network without having to use MPI or PPI converters as was necessary before. Secondly, the CoDeSys-based software [SW-XSoft-CoDeSys-2] and the extensive range of functions of the closed-loop control toolbox enable us to complete programming and commissioning faster and more conveniently than before.”

Eaton's closed-loop control toolbox contains around 120 ready-to-use function blocks that make life easier for the developer by providing ready-implemented closed-loop control know-how, so that custom applications can be developed simply and quickly by combining and cascading the standard function blocks.

A commissioning screen created with the XSoft-CoDeSys Target visualization shows all important parameters at a glance and, as such, not only noticeably simplifies commissioning, but also supports the end user when undertaking future optimisation and upgrades.

For the burst pressure stand, Poppe + Potthoff also obtained key components from Eaton in terms of switchgear and panel equipment, including contactors, motor-protection circuit-breakers, soft starters, power supply units, miniature circuit-breakers and residual current circuit-breakers. The system is also provided with a two-hand control arrangement, an emergency-stop circuit and interlocking doors that are switched using Eaton safety relays. Frank Baudler, head of engineering/R&D at Poppe + Potthoff, summarises:

“Thanks to this project and the close cooperation with Eaton, we are now able to offer our customers Eaton hydraulic power units in future for different test stands. The fact that we can source both the hydraulics and the electrical engineering from Eaton as a single supplier opens up new possibilities for us. By taking on our suppliers as partners, we can also increasingly give them greater responsibility.”

The company now plans to use Eaton hydraulic power units in different performance classes – something that should be easy to accomplish, thanks to Eaton’s broad-ranging product offering and the ease with which systems can be seamlessly integrated and scaled.

Burkhard Balz is with Eaton Industries Manufacturing GmbH

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