Combining hydraulic pumps with variable speed drives increases efficiency while reducing noise and environmental impacts.

With any fluid power system, efficiency is always top of the mind, so components and advanced technology that can improve energy consumption are increasingly necessary. To that end, the NFPA last year commissioned a survey to examine the current and potential use of variable speed drives (VSDs) with hydraulic pumps.

Overall, a total of 1,788 high-quality usable responses were used to generate results, broken down as 43.1% end users, 10.4% distributors, 14% system integrators, 15.2% manufacturers, and 17.3% other. Almost half (46%) of the respondents had an engineering background. The next largest category was “operations management.” Respondents who chose “Other” were given the option to specify their role; the most common role in this category was “repair and maintenance staff.”

Not surprisingly, the overall results showed that respondents believe that the use of VSDs in hydraulic applications will increase over the next three years. They cited VSDs’ high-energy efficiency, improved reliability and low operating cost as key determining factors in the increase of their use. On the opposite end of the spectrum, when asked what discourages the use of VSDs, respondents pointed toward high acquisition or upfront costs, lack of maintenance and after-sales support for VSD technology, and lack of design expertise in their use.

The four main manufacturers of variable speed drives in the U.S. include Eaton, Parker Hannifin, Siemens and Bosch Rexroth. Here, we spoke with representatives from three of those companies—Lyle Meyer, global product manager, Industrial Drives, Eaton Hydraulics; Lou Lambruschi, marketing services and e-business manager, Parker’s Electromechanical and Drives Div.; and Craig Nelson, marketing manager, Drives, Siemens Industry U.S.—to learn how VSDs can change the way hydraulics function in an industrial setting.

Q. What is the biggest advantage to variable speed pump drives than other technologies?

Meyer: There are three advantages variable speed drives offer the market— low noise, longer life and higher efficiency. Depending on what a particular customer’s needs are, low-impact noise could be a primary reason to incorporate a VSD into a machine. Eaton’s pumps are capable of running down to zero rotations per minute, so reduced noise in the overall system—and better overall sound quality—are significant features.

Efficiency is a key driver that brought about Eaton’s variable speed drives solution, and there are several market influencers that have led to innovative hydraulic pump and system level technologies—government regulations and energy costs. Energy costs continue to increase over time, and government regulations are continuing to require fewer emissions, both of which have led machine builders to consider more efficient electric motor solutions. If hydraulic pumps cannot operate in the speed ranges needed to complement the wider speed ranges of VSD motors, they can be replaced by electro-mechanical options.

Nelson: I always want to jump to the energy savings because that sort of relates to the biggest cost right off, and that’s the payback. Average time for payback is about three to four years on a retrofit. On a new machine, it’s a lot quicker, anywhere between two and five years.

There’s another part about it, too, which is environmental … as well as being “green” on the cost is the environmental impact of being less likely to have hydraulic leaks around your plant. That’s something that everybody really has to keep a big check on because of its environmental impact.

Lambruschi: The biggest advantage tends to be energy savings. Other types of pumps will see increased controllability, quieter operation and potentially longer life. Drives equipped with fieldbus communications allow for local or remote monitoring of the pumping process, allowing access to parameters like pump loading, running time and energy consumption.

Q. The NFPA study said that more people are thinking they would adopt this technology in the next three years versus now. What is holding people back?

Nelson: It’s one of those things where you say, here’s a technology that’s better than what existed and what we’ve had in the past. You just expect it to take off just because it was better. It’s just been a little bit slower for people to adopt it.

There is such an installed base of hydraulics out there. I think most of the new machine users are not even giving it a second thought of going with the new technology. What’s been slower is driving people to retrofit out their existing working system for something that’s better, more efficient, takes up less room, less oil, less noise, and all the other advantages that it provides.

Meyer: Generally, there are three things that are holding people back from adopting VSD technology—perception, cost and system design. Perception is now the main issue preventing customers from adopting VSD technology, whereas the number one issue in the past was overall cost. Machine builders initially thought a VSD solution for a hydraulic system was extremely expensive. Today, it is equally cost-effective to make a system hydraulic variable speed as it is to make it electric. Hydraulic components don’t change, and electrical components have experienced much lower costs in the past five years. Fixed-speed starters used to be the lower cost, but now variable speed drives are generally the same or lower cost as fixed speed.

Another perception issue is in the certainty of what a VSD system can handle. Machine owners and operators who have not used VSD solutions may not understand that performance will not change, but machines will last longer and cost less. The industry is facing an uphill battle for OEMs to convince customers to adopt VSD technologies into their systems, with a common view of, “what I’ve used in the past will continue to work.” When regulations for electric motor efficiency come into effect in the U.S., VSD solutions will likely be adopted in more applications.

Q. How do you balance the cost concerns with the efficiency benefits?

Lambruschi: In many retrofit applications with known operating cycles, an estimated payback period can be calculated. In actual applications, this has been shown to be less than 12 months. Cost concerns can also be offset by the fact that many power utilities offer rebates or incentives for the purchase of variable speed drives for pumping applications. Also notable is the fact that cost savings are not just achieved by efficiency, but by less obvious factors such as reduced maintenance costs and enhanced pump life.

Meyer: Duty cycle is key to balancing cost with efficiency. Pumps are capable of multiple speeds, including zero speeds that allow operators to incorporate VFDs—the building block for smart machine architecture. Before you can start designing machine control, you need components that can handle that level of control. If there are cost increases with a VSD, then they must be paid back on the duty cycle.

At Eaton, customers frequently ask how the VSD system compares to a fixed-speed system from a cost perspective, and the answer is the same. It is led by duty cycle. There are some applications with duty cycles that may not reap the benefits of a VSD system, so we work with customers to review their required duty cycles and help determine which solution is the best for their overall operation.

Nelson: When you look at U.S. manufacturers, they are trying to compete on the global market. We’ve always had the quality and now it’s really keeping the cost in check. Moving to automation and making the machines more cost-effective or more efficient is key for the U.S. manufacturing industry. People need to really look at that and say, okay, I need to look at longer-term sustainability than three to five years.

And you need to realize, it’s still about efficiency and going green. If you look at it, even the larger companies, the larger plants, they’re still looking at ways to reduce their energy consumption. This fits well when you have those initiatives. It can offer huge savings. Even though the cost doesn’t start from day one, you start seeing that energy savings from day one.

Q. What markets and regions do you see are driving your growth?

Lambruschi: Within pumping applications, we see particularly good growth in the use of drives on hydraulic power units, replacing proportional valves and similar technologies with a more efficient approach. Growth is seen in multiple regions globally, with concentrations in areas where new production facilities are being built or older ones modernized.

Nelson: I’d say the industries that have the quicker payback are injection molding and presses, in general. Throughout a number of different types of industries, it’s typically where you’re going to see the lower payback periods that are the first ones that are going to adopt.

Meyer: VSD is growing in popularity in both the American and European markets. Europe has efficiency regulations in place that are driving machine builders to adopt VSD technology, and these regulations are now starting to be adopted in the U.S. At the moment, European machine designers are required to design to a higher standard, so U.S. designers are looking at this too. As mentioned earlier, energy cost is another big driver. The more energy consumed, the more energy costs—and the greater the emissions—so it’s cost efficient to reduce emissions, particularly on large machinery.

Q. Finally, how is your variable speed pump drive different from others on the market?

Nelson: For us, it’s all about ease of use. We offer this solution with our standard sizes and software. We use the same components that we use for most of our typical servo systems, not just our servopumps, like our Sinamics S120 drives, 1FK7 motors and 1PH8 motors.

The ease of use starts from the beginning when you actually have to size up the system just by using those standard products and having a standard sizing software. Then we go into the commissioning phase of it. With our standard products, the S120 and the Simotics line, what we have is a combined package that really makes the servo aspect of it plug-and-play.

Lambruschi: Pre-programmed pump application macros and pump-specific parameters, as well as environmental features like conformal coated PC boards, make Parker drives more user-friendly and suited to the tough environments that pumping applications are often a part of. Larger drives used on higher power pumps are constructed with field replaceable power modules, allowing for quick and easy maintenance and minimal downtime in the event of failure. Parker is also uniquely positioned to be a complete system provider, being a manufacturer of pumps, hydraulics, and fluid handling components in addition to variable speed drives.

Meyer: Eaton’s biggest differentiator is low speed—our pump products have been tested down to zero speed. Eaton’s pump products are capable of operating at speeds that are as low as or lower than competitive offerings.

In the past, Eaton pumps or competitive offerings could simply be turned off; however, that function added some complexity to the circuitry. A pump capable of running at zero rpm takes a lot of complexity out of the circuit, in terms of holding pressure. Eaton’s zero-speed capability decreases system complexity and further enables the machine designer to flexibly design the system.

Eaton Corp., Hydraulics Div.
eaton.com/vsd

Parker Hannifin, Electromechanical and Drives Div.
parker.com/ssdusa

Siemens Industry
usa.siemens.com/drives

 

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Filed Under: Fluid Power World Magazine Articles, Pumps & Motors
Tagged With: eaton, parker, siemens
 

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