Hydraulic upgrades: the business benefits
02 August 2012
Hydraulic systems as old as 50 years may still provide good service; but while this is evidently testament to their quality of manufacture and durability, current technology has transformed the performance of modern hydraulic power transmission systems in terms of their efficiency and productivity.
Matthew Livesey discusses the benefits of replacing ageing hydraulic systems, and supports his argument with the positive results of work recently carried out by his company for a major customer in the North West.
Hydraulic controls once traditionally comprised simple solenoid valves to control large flows and these basic systems were frequently subject to high shock loading. Over time these shocks cause fatigue damage to components and pipe work, leading to leakages and eventual failure.
This all adds to operational costs, both in terms of oil replacement and cleaning, as well as production losses if the leakage is of sufficient severity. Costs certainly start to ramp up if product is contaminated as a result of hydraulic fluid leakage. Water ingress too can cause premature failure of rotating equipment like pumps and motors.
Nowadays, the performance of hydraulic systems is vastly improved. For example, valves now offer proportional rather than on-off control to smooth the action of hydraulic actuators and thus eliminate shocks. Through a combination of new product and industry expertise gained over many years, end users now have the benefit of an hydraulic system that can take care of pressure control, flow control and decompression of large volumes of fluid under pressure.
Pumps can also be added to regulate flow and pressure with both power and load control. This not only improves the general efficiency of the hydraulic system, but also its functionality in order to match the process requirements. These additional items can be provided in customised power units, manifolds and subassemblies, designed by trusted and reputable manufacturers.
The Eastman experience
Eastman’s chemicals, fibres and plastics are used as key ingredients in products that people use every day. The global company is headquartered in the USA and in 2010 reported sales of $5.8bn. The company has developed a valuable method of performance analysis to determine maintenance issues by listing the failure modes of all items of plant equipment.
This exercise has enabled it to identify key areas for reinvestment, with the ultimate goal of eliminating unnecessary production losses. Part of this project examined the reliability of hydraulically driven balers typically found at the end of the production lines. Hydraulic oil leaks were quickly identified as the highest cause of baler failure.
Bosch Rexroth began working with Eastman at its US headquarters to address these issues with its baling press hydraulic systems. Following a successful initial project outcome, the Rexroth team turned its attention to Eastman’s UK plant in Workington. At this location, a filter material used in the cigarette industry is manufactured then compressed by the baling presses to reduce the volume of the final product for economical packaging and transport to overseas customers.
The first improvement was an expansion of capacity to meet growing market demand, with Rexroth overseeing the installation of several new presses. These were installed using a new ring main hydraulic system where one power unit supplies many presses, each with individual control provided by close proximity valve stations.
Material from the production lines is continuously fed to press boxes where it is evenly layered; when each box is full, a stripper bin is raised by two hydraulic rams before the main press cylinder produces a compact bale, ready for packaging.
The power unit comprises a large cylindrical reservoir and a bank of ten motor pump sets which provide low pressure, high pressure and recirculation. Each press is provided with a dedicated valve control module located at the press, thus reducing the distance between the valves and press cylinder. This reduces flow paths to improve performance and keep the required piping to a minimum.
Following a successful trial production with the new ring main system in place, the decision was taken to upgrade the remaining baling presses and thus significantly reduce the maintenance problems that the company had hitherto been experiencing.
Three options were considered: simply replace the piping (though this would still be subject to shock loading and all its attendant problems); to replace the piping and the main control valves (solving the shock problem, but retaining ageing pumps and motors), or to replace the whole system and gain all the advantages of a modern upgrade.
To reduce production losses during installation it was decided to replace the systems progressively, two presses at a time, using a dedicated hydraulic power unit for each pair, including redundant motor pump sets. This stage of the project, involving many existing baling presses, got underway in November 2011. The upgrades are now complete and are reported to have improved both productivity and profitability. Eastman maintenance engineer, Pat Enright, comments on the project:
“Upgrading the press hydraulics is a major reliability initiative at Eastman Workington. Following the successful commissioning of the first new system back in November 2011, the benefits of reduced maintenance costs and increased equipment reliability have now been reaped across the site.”
Of course, there are many factories and plants across the UK that are still using hydraulic systems that were installed many years ago, some of them performing poorly and progressively burdening their operators with higher maintenance costs, and presenting them with unwelcome health & safety and environmental issues.
There are numerous benefits to be gained from the installation of a new hydraulic system. The elimination of leaks, water ingress and delays in production speak for themselves. Modern high integrity power packs offer not just higher efficiency but ultimately a more reliable system, often with redundancy built in for peace of mind.
Matthew Livesey is with Bosch Rexroth, based in the North West of England
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