Customised energy-efficient pumps offer many user benefits

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Michael Gundlach, Product Manager at Parker Hannifin, explains how the integration of energy-saving, customisable hydraulic systems can reduce footprint, noise and energy consumption of hydraulics while retaining or even increasing equipment longevity.

Customised energy-efficient pumps offer many user benefitsThere is a complex trade-off at the heart of modern industrial machinery which challenges the minds of engineers on a daily basis. On the one hand, hydraulic systems are expected to be quieter and more efficient, with less of an impact on the environment. Yet, there is also an expectation that these advancements will have no impact on a host of other performance factors such as power density, reliability and control. This represents quite a balancing act.

The challenge is magnified by the fact that hydraulic systems comprise a broad range of discreet components that need to fit together in the best possible way. No two systems are identical, and effective integrations require a deep understanding of hydraulic systems, hydraulic pump and electric motor technologies, and control algorithms – and how these interact with each other.

Fortunately, there is a solution to this conundrum, which comes in the form of Drive Controlled Pumps, an innovation which allows for the integration of energy-saving hydraulic systems with a level of customisation that hasn’t been available before. This technology is achieving rapid adoption in several key industrial sectors, such as marine, automotive, machine tools and die casting, where there is an unstoppable demand to reduce the footprint, noise and energy of hydraulics while retaining or increasing equipment longevity.

A more intelligent approach

Before we look in greater depth at the sorts of technological benefits that Drive Controlled Pumps can deliver, though, it is worth looking at some of the drawbacks to conventional hydraulic power units. Historically, these systems have required oversized pumps and motors to ensure performance during a system’s highest duty-cycle demands. In years gone by, when energy costs were low and predictable and environmental regulations were less of a consideration, the wasted energy and high CO2 emissions were not viewed as being problematic. However, that is no longer the case.

With environmental considerations top of the agenda, there is a strong desire to move towards systems which can precisely modulate power to the requirements of specific tasks within highly complex hydraulic systems. That is where Drive Controlled Pump technology comes in - as it provides a synergistic approach in which electronic drives, electric motors and hydraulic pumps are seamlessly integrated to meet each local load demand within a hydraulic system. Specifically, variable frequency / speed drives manage the electric motor’s operating torque and speed, producing the precise, variable pressure and flow required at any given point in the machine or duty cycle. Drive control is directed through the use of field-tested control algorithms designed to provide standardised and customisable hydraulic functions.

This versatility provides the answer to a multitude of system requirements. During fixed displacement hydraulic pump applications, hydraulic power unit efficiency approaches zero per cent during pressure-holding conditions. By lowering the pump speed using flow control function, Drive Controlled Pump systems can reduce inefficiency by as much as 90 per cent. In these applications, the Drive Controlled Pump system performs well with variable axial piston pumps.

When used with variable displacement pumps, which are typically controlled using a variety of hydraulically operated pilot controls, lowering the pump speed can reduce inefficiency by as much as 50 per cent in low-flow or deadhead conditions. Drive Controlled Pump technology uses the control function to extend system capabilities, regulating the operation of fixed and variable displacement pumps/motors through the closed-loop pressure control by using the pressure feedback signal. In addition to these most commonly used functions, Drive Controlled Pump technology enables hydraulic system design engineers to deploy a wide range of application-specific customised and standardised control functions.

Meeting needs across industry

This new approach is proving increasingly popular in sectors where environmental concerns have risen up the agenda. In marine, for example, as emissions regulations have become more stringent, on-board energy wastage and high CO2 emissions have become increasingly problematic, particularly in near-shore situations. This has required a transition to more efficient systems where power is precisely modulated to the requirements of specific tasks. Drive Controlled Pump technology can be optimised for battery operation, providing an energy-efficient option with low noise levels.

In industrial sectors, such as machine tools, the technology can reduce the energy required during the main movement, while enabling energy delivery for quick clamping actions and auxiliary movements, therefore optimising pump sizing. In die casting applications, meanwhile, it can be used to adjust flow and pressure to meet the highly varying requirements of closing and injection slides, enabling a variety of pump combinations while reducing motor size requirements. Also, in metal forming processes, it can reduce the energy, noise and component size required by taking advantage of the extended speed range of the electric motor.

Calculating the return on investment

It is clear that Drive Controlled Pump technology represents an innovative new approach to hydraulic system design, in which precisely controlled, variable-speed-pump modes are custom-configured to meet the functional requirements of each process within a complex hydraulic system. In terms of the business case, it provides the most rapid return on investment with conservatively designed hydraulic systems using oversized components engineered to meet the maximum flow and pressure requirements.

Simply put, if cooling is required for a hydraulic system, it is operating at less-than-optimum efficiency. A preliminary assessment of probable energy savings will take into consideration the voltage of the power source and electric motor horsepower. It will also consider the number and types of pumps used, the length and frequency of deadhead conditions, whether or not a pump unloads during idle, pressure control requirements, both oil and ambient system pressures, HPU cooling requirements and the desired level of noise control.

Due to the rapidity of return on investment, the use of variable speed drives to manage hydraulic power allocation is expected to more than double by 2019. Easy adoption of the Drive Controlled Pump technology is best achieved through a customised process in which a multi-disciplinary team of drive and motion system, fluid power and control technologies engineers perform a number of tasks. These include conducting energy audits with predictive analysis of energy savings and evaluating and replacing individual components, as appropriate, with more compact, less energy-wasting alternatives. It also includes the integration of variable speed drives that modulate speed and torque to meet specific flow and pressure requirements through the use of customised modes, and the ability to initialise the system and monitor performance to validate ROI.

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