Automation distributor Tectra Automation has developed South Africa’s first solution for the pressure testing of hydraulic accumulators for recertification processes required by law.

Tectra Automation, which is a member of drives and controls company Hytec Group, was recently approached by fellow group member hydraulic equipment distributor Hytec Fluid Technology (HFT) to design and build the accumu- lator testing system, states Tectra Automation GM Kevin Lombard.

“Tectra Automation provided a system that can test up to three accumulators at a time and that will measure, record and provide a report of the test results,” he says, adding that, as HFT stocks and supplies a large variety of sizes and capacities of accumulators, the test bench had to be adjustable to accommodate the smallest 1 ℓ accumulators to the largest 150 ℓ accumulators.

“In essence, the testing process involves pressurising the units to a certain test pressure and then checking for leaks. Once the pressure is released, the accumulators are checked for permanent deformation using a mechanical go or no-go gauge,” explains Lombard.

“However, in our opinion, this presented a problem, as com- panies have to rely on the operator to confirm that the gauge is, in fact, used correctly,” he says, adding that the use of gauges was also problematic, as it required several different sizes of gauges to be manufactured, as HFTs test many different sizes of accumulators.

To solve the problems, Tectra Automation manufactured the test rig by using drives and controls company Bosch Rexroth’s aluminium profile range, he says, explaining that the design of the test rig entailed the use of three vertical beams with adjustable holding plates to accommodate the various lengths of accumulators.

In addition, the company developed an electronic measuring system by using two Bosch Rexroth guide rails mounted back to back, instead of having the expansion checked manu- ally.

The one unit allowed the repositioning of the fixed measuring face to accommodate different diameters, while the second unit consisted of the Bosch Rexroth Integrated Measuring System with a measuring resolution of 1 μm, Lombard explains.

Further, he comments that the test system has to accommodate for the highest levels of operator safety, as the whole test is conducted under high pressures. The company achieved these safety levels by placing the test system behind a safety guard, he notes.

The safety guard is made of Bosch Rexroth Ecosafe fencing, with a 6 mm polycarbonate sheeting which is used instead of the woven wire mesh, he says, adding that safety is further enhanced by an interlock on the cell door that prevents the operator from testing the system while the door is open.

Calibration of this system was performed by a local authority that was astounded by the level of accuracy achieved for such an application,” he adds.

Meanwhile, in addition to developing the mechanical structure, Tectra Automation was responsible for the design and integration of the data capturing and certification system.

“A Bosch Rexroth L20 programmable logic controller (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,” he explains, noting that the captured data is transferred to a desktop personal computer which houses the visualisation and reporting software.

Tectra Automation developed the software and the infor- mation was stored in a Microsoft Excel database, which allowed 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, which is capable of very high accuracy, in a fraction of the time it would normally take to develop such equipment, Lombard notes.

“HFT was extremely satisfied with the outcome of the test unit, as it is not only the first of its kind in South Africa, but it, in fact, surpasses the test units used by overseas manufacturers of the accumulators,” he concludes.