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U.S. Economy Grew 0.7% in the First Quarter of 2017

Friday, 28 April 2017  |  Chris Guy

Real GDP in the U.S. fell short of expectations, increasing at an annual rate of 0.7% in the first quarter of 2017; this according to the advance esti...

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Industry Headlines

Mueller Water Products Reports 2017 Second Quarter Results

1 DAY AGO

For its fiscal second quarter ended March 31, 2017, Mueller Water Products’ net sales were up 1.3% to $199.7 million and net income was $73.3 million, or $0.45 per diluted share. Operating income from continuing operations was $10.9 million. The quarter's results included $68.6 million of income...

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Weir Group Reports First Quarter 2017 Results

1 DAY AGO

The Weir Group's first quarter input was 15% higher than the prior year period with good sequential growth primarily driven by increased activity levels in North American Oil & Gas and strong aftermarket orders in Minerals. Group-wide aftermarket orders were 21% higher than the prior year period w...

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Permian Basin Oil Production Continues to Increase

2 DAYS AGO

Crude oil production in the Permian Basin is expected to increase to an estimated 2.4 million barrels per day in May, based on estimates from the U.S. Energy Information Administration . Between January 2016 and March 2017, oil production in the Permian Basin increased in all but three months, even as...

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East Coast Refiners Eye Texas as Alternative to North Dakota

3 DAYS AGO

“Major U.S. East Coast refiners profited from railing hundreds of thousands of barrels of discounted Bakken crude to their plants daily from 2013 until 2015. But as more and more pipelines were built in North Dakota, the discount began to disappear, and so did the rail cars,” Reuters repor...

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U.S. Economy Grew 0.7% in the First Quarter of 2017

1 DAY AGO

Real GDP in the U.S. fell short of expectations, increasing at an annual rate of 0.7% in the first quarter of 2017; this according to the advance estimate just released by the U.S. Department of Commerce. The 0.7% figure, down from 2.1% in the fourth quarter and 3.5% in the second half of 2016, and is...

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Survey Shows Small Business Confidence Increasing

2 DAYS AGO

The second annual Allstate/ Small Business Barometer finds increasing optimism and innovation among small business owners, despite the rising cost of doing business. Nine in 10 local entrepreneurs say the benefits of owning a business outweigh the challenges. This year’s Barometer found that, ...

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Hydraulic Actuators Gaining in Use

vmsum11_actuatorsHydraulic actuators (in black) for flow control valves in a distribution terminal of a pipeline help control gasoline, diesel and other products.

Although the actuator market is dominated by pneumatic and electromechanic products, a growing number of niches require the performance levels of electrohydraulic actuators.

Pneumatics have been the mainstay of control valve manufacturers for the better part of the last century—just imagine how large the installed base has grown to be. Electromechanical designs, on the other hand, date back almost as far as pneumatics, but have only recently been seriously considered for throttling control applications.

But what about hydraulics? The basic technology also has been around a long time, but the technology was never considered mainstream because of the complexity, maintenance requirements and costs. Still, some people argue that today, hydraulically driven actuators are among the highest performing modulating designs with the widest range of thrusts and torques. And, over the last 20 years, advances in hydraulic actuator technologies have opened doors to applications previously categorized as either pneumatic or electromechanical opportunities.


THE DIFFERENCES

So, what changes have we seen over the last few decades? Here are some thoughts on that issue.

Operation has changed from “continuous” to “discrete”: Conventional hydraulic technology, whether a central hydraulic reservoir power unit or a valve-mounted individual reservoir, is based on a servo system that uses a continuously running unidirectional motor and pump. This technology has superior frequency response (small spool valves for directional changes) and offers extremely tight positioning control with high available stroking speeds. A potential drawback is that these systems use gravity-fed reservoirs that communicate with the atmosphere. This can lead to ingress of condensate and particulates, requiring significant filtration and maintenance.

Discrete operating technology utilizes a bidirectional motor and pump in a truly self-contained, sealed hydraulic system. This eliminates the need for an active reservoir. It also means the oil volume is a small fraction of what would be required for a continuous system. The motor and pump operate discretely, only running when required to make a position change. Power consumption is lower than any other control actuator technology.

While the frequency response available with a discrete system is high, it can’t compare to the continuous system. However, the hydraulic fluid filtering and maintenance are eliminated, and the positioning accuracy and control remains as good as a continuous system.

“Self contained, discrete” technology has gained more acceptance in the control actuator market: What this really describes is a form of electromechanical actuator with a hydraulic transmission instead of a gear train. Electromechanical actuators use reversible motors and operate discretely (just like the discrete type of hydraulic actuator). Most traditional electromechanical actuators are designed for isolating duty and as such lock in position and power down when set point position is satisfied. Unlike the self-contained hydraulics, traditional electromechanical actuators are usually limited to fail-in-last-position on loss of motor power. Some newer designs of electromechanical actuators can replicate the functionality of the hydraulic or pneumatic actuators; however, most traditional electromechanical actuators have limitations on duty cycle and life cycle when compared to hydraulics or pneumatics.


A COMPARISON

So what does the self-contained discrete hydraulic technology have in common with pneumatics? Pneumatics are revered by most control valve manufacturers as the foundation of control valve positioning. They are the puppet controlled by the puppet master, which is the smart positioner. Pneumatics have been proven performers, with about 100 years as the staple of control valve actuation. That’s why it’s hard to stack up this younger, self-contained discrete hydraulic technology against the legend that is pneumatics.

However, both types are capable of continuous movement. They both have a variety of failure modes—through the use of simple springs or stored energy devices such as accumulators and volume tanks. However, pneumatics is more akin to conventional hydraulic technology regarding the power source. Just as a conventional hydraulic uses a continuously running unidirectional motor and pump to maintain pressure, the pneumatic has stored energy (supply pressure) from a central air compressor. Both approaches consume much more power than either the electromechanical or the discrete electrohydraulic technologies.

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