A Redesign and Rebuild Was Required
To Bring Wire Drawing Machine On Line
(01-03-2011) A major US rolling mill contractor recently faced a challenge with a newly-built coil compacting system being installed in a wire drawing mill in China. For help they turned to Sorensen Systems of Northborough, MA, a subsidiary of THG Corporation, to identify and solve the problem.
The first phone call was placed to a hydraulic sales engineer, at The Hope Group, requesting help in identifying the problem and offering a solution. One of customer's machines, which compresses large coils of wire and then secures them with either wire binding or steel strapping, was not working correctly. The machine had been built from a non-local design and it developed an inconsistent compacting force and coil positioning. A solution was needed.
Engineering Challenge
The customer brought the challenge to the engineering department of The Hope Group, which operates as Sorensen Systems LLC. With its team of engineers, technicians and skilled fabricators, Sorensen Systems designs, builds and installs hydraulic, pneumatic and electrical control systems for commercial and industrial manufacturers and for water-to-wire hydro-electric applications from its 60,000 sq ft, ISO 9001:2008 certified facility in Northborough, MA.
The customer met with Mike Gardella, Engineering Manager for Sorensen Systems and worked together designing needed changes to the hydraulic control system used on the compactor. According to Gardella, both sides of the compactor would come together to squeeze the coil, but the force of one side would periodically push the other out of position. Additionally, force control was erratic due to inconsistent pressure control. Both issues combined to produce coils with inconsistent compaction and resultant potential damage to the coil.
Inconsistent Positioning
Gardella said, "After analyzing the circuit and the power unit, the first issue of inconsistent positioning was determined to be a result of using large DIN cartridge valves, whose performance is susceptible to dirt and debris in the system. To match the filtration level of the hydraulic power unit, we chose low leakage poppet style pilot operated check valves to replace the DIN valves," he added. "In order to meet the expected flow rate requirements, we installed two poppet PO checks were installed in parallel for each DIN valve," said Gardella.
Inconsistent Pressure Control
The issue of inconsistent pressure control was found to be caused by over pressurization of the system during initial cylinder approach, according to Gardella. "Specifically, the cylinders were run in regeneration mode for the initial approach and dropped out of regeneration mode for final compaction. However, due to system resistance the pressure required for regeneration mode was greater than that required for final compaction," he added.
Gardella described the situation this way: "Because control of pressure was being accomplished by a proportional pressure relief valve – lowering the pressure set point at the time of compaction resulted in periods of instability as the valve attempted to lower the system pressure to the desired level – adversely affecting compaction force."
Solution Achieved
The solution was achieved with the replacement of the existing valves with faster, larger Parker proportional directional and relief valves, along with a wholesale redesign of the manifold, simplification of the hydraulic circuitry, and enlargement of associated piping and hoses, which resulted in lowering regeneration system pressure to levels well below compaction pressure, greatly improving compaction reliability.
According to Gardella, once the redesign was completed, the hydraulic control system was assembled, tested and packed for shipment to Shanghai, China. Gardella packed too and went to Shanghai to oversee the start-up, along with the customer.
According to Gardella, the types of machines built by the customer are both horizontal and vertical compacting systems, using a modular design, which provides for unique configurations with standard components. Both the Morgan horizontal compacting system and the vertical compacting system include step-less variable press-force from 6 to 40 tons, high-carbon and low-carbon modes, multi-stage compacting and are available with either wire binding or steel strapping units. Both the horizontal and vertical systems are designed to be easily integrated with Morgan's conveyor transfer system; however both can also be adapted to fit existing conveyors.
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