Tectra Automation was recently approached by Hytec Fluid Technology (HFT) to design and build South Africa’s first solution for pressure testing hydraulic accumulators. This was necessary for the recertification processes which are now required by law.
Tectra came up with a system that could test up to three accumulators at a time and measure, record and provide a report of the test results. As HFT stock and supply a large variety of sizes and capacities of accumulators, the test bench had to be adjustable in order to accommodate the smallest one litre through to the largest 150 litre accumulator.
“In essence the testing process involved pressurising the units to a certain test pressure and then checking for leaks. Once the pressure was released the accumulators were checked for permanent deformation using a mechanical go/no go gauge,” says Kevin Lombard, general manager of Tectra Automation. “In our opinion, this presented a problem as it was necessary to rely on the operator to confirm that the gauge was in fact used correctly. It also presented a problem in that it required several different sizes of gauges to be manufactured, as HFT tests many different sizes of accumulators.”
Tectra Automation therefore decided to manufacture the test rig using its Bosch Rexroth aluminium profile range. The design entailed using three vertical beams with adjustable holding plates to accommodate the various lengths of accumulators.
Instead of having the expansion checked manually, Tectra developed an electronic measuring system using two Bosch Rexroth guide rails mounted back to back. The one unit allowed the re-positioning of the fixed measuring face to accommodate different diameters whilst the second unit consisted of the Bosch Rexroth integrated Measuring System (IMS) with a measuring resolution of 1 micron.
“As the whole test is conducted under very high pressures the test system had to have the highest level of operator safety possible. This we achieved by placing the test system behind a safety guard made from Bosch Rexroth Ecosafe fencing with 6 mm polycarbonate sheeting in place of the woven wire mesh. The safety was further enhanced with an interlock on the cell door that prevented the operator from testing the system with the door open. The calibration of the system was performed by a local authority and the person performing the calibration was astounded by the level of accuracy achieved for such an application,” adds Lombard.
Besides the mechanical structure, Tectra Automation was also responsible for the design and integration of the data capturing and certification system. A Bosch Rexroth L20 PLC was used to control the complete test procedure as well as to perform the data capturing from the measuring system and to control the pressure in the Maximator pressure intensifier. The captured data was transferred to a desktop PC which housed the visualisation and reporting software.
All software was developed in-house by Tectra Automation, with the information being stored in an MS Excel database allowing for ease of reporting and storage. The ease of integration between the Bosch Rexroth measuring system and the PLC enabled the company to produce a robust industrial type measuring unit capable of very high accuracy in a fraction of the time it would normally take to develop such equipment.
“HFT was extremely satisfied with the outcome of the test unit as it was not only the first of its kind in South Africa, but it also surpassed the test units used by the overseas manufacturers of the accumulators,” concludes Lombard.
For more information contact Kevin Lombard, Tectra Automation, +27 (0)11 971 9400, [email protected], www.tectra.co.za
| Tel: | +27 11 971 9400 |
| Fax: | +27 11 971 9440 |
| Email: | [email protected] |
| www: | www.boschrexroth.africa |
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