A gradual rise in power demands in mobile equipment and industrial automation systems is creating a market for a new breed of low-power hydraulic valves, say engineers from Parker Hannifin Corp. (www.parker.com).
The industrial giant says it has seen a spike in demand for directional valves that run on as little as 8W of power, which is about one-third as much power as that used by traditional directional valves. "The market seems to be settling into a range of 8 to 10W as the place it wants to be," says Michael Guhde, directional valve product sales manager for Parker Hannifin.
Less Watts: Parker Hannifin's low-power
directional hydraulic valves run on just 8W of power. Guhde above says
they're a good choice for engineers.
The company's engineers point to two factors as driving the rise in demand for low-power hydraulic valves. Mobile construction vehicles are employing more on board implements, they say, and industrial automation systems are more often adopting CAN bus configurations.
"The mobile equipment market represents a huge growth opportunity for this technology," Guhde says. "Because their implements run off a battery, there's a finite amount of power available to them. So they want their valves to consume the least amount of power possible."
At the same time, manufacturing plants are increasingly moving toward bus-based networks for their automation systems.
"Most of the CAN-type technologies are limited to about 12W of output power," Guhde says. "So if you're a design engineer moving to the CAN bus, it makes sense to use a technology like this one."
Also, many industrial users are increasing the number of output points on industrial programmable logic controllers (PLCs), from 8 to as many as 16 or 32, Guhde says. For those applications, system integrators must use bigger power supplies to compensate for the additional outputs, thus creating a need for more costly control systems. To combat that situation, more system integrators are now moving away from traditional 22 to 36W directional valves.
Force Important, Too
Parker Hannifin engineers say that the need for such valves has been evident for over a decade. Valve makers, however, have had trouble developing products that could run on low power and still meet desired force profiles.
Guhde says, however, that Parker Hannifin engineers met those needs by integrating coils with armature tubes and improving coil technologies and manufacturing techniques.
"Over the past three or four years, coil and tube technology has improved, and the amount of force a solenoid can produce has come up," Guhde says. "Because of that, flow and pressure capabilities of low-power valves have increased, and sensitivity to contamination has decreased."
As a result, Guhde says, lower power valves are now able to generate enough force to overcome contamination or flow forces that might otherwise prevent a valve from shifting at the correct time.
During the past year, Guhde says, machine tool builders have also expressed interest in the valves. Most are drawn to the valves because they drive down control system costs.
The main drawback of the new valve technology, Guhde says, is that it doesn't meet tight packaging constraints as effectively as cartridge-type valves.
"But as long as there's enough room for the valve, it's a good choice for design engineers," Guhde concludes. "It allows users to reduce their power consumption by 30 to 50% and at the same time increase their flows by 200 to 300%."