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Improving Valve Sealing Performance and Reliability

Improving Valve Sealing Performance and Reliability

From time to time, we are re-posting wel...

A Primer on Fugitive Emissions

A Primer on Fugitive Emissions

Fourscore and seven years ago, no one ha...

The State of Industrial Distribution in 2017

The State of Industrial Distribution in 2017

Key trends for the industrial distributi...

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Industry Headlines

ITT Reports 2016 Fourth-Quarter, Full-Year Results

Thursday, 16 February 2017  |  Chris Guy

On a GAAP basis, ITT Corporation delivered revenue of $588 million in the fourth quarter of 2016, reflecting a 12% decline that included a 2% negative...

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Industry Headlines

ITT Reports 2016 Fourth-Quarter, Full-Year Results

3 DAYS AGO

On a GAAP basis, ITT Corporation delivered revenue of $588 million in the fourth quarter of 2016, reflecting a 12% decline that included a 2% negative impact from foreign exchange. GAAP segment operating income decreased 12% .

In the Industrial Process segment, total revenue decreased 29% to $212 milli...

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Delta Centrifugal Rejoins VMA

3 DAYS AGO

This week VMA welcomed back associate member Delta Centrifugal Corporation of Temple, TX after a one year absence from the association.

Delta produces custom-made castings. Delta’s operations include Texas Stainless, Inc. Texas Stainless is a metals distributor and sells castings produced by Delt...

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How New U.S. Policies Will Affect the Chemical Industry

4 DAYS AGO

“In 2017, barring a recession in the U.S. and Europe or a slowdown in China, Moody’s Investor Service expects EBITDA in the chemicals industry to slip by 1 or 2% year-over-year.”

A new report from PwC predicts that the Trump administration “is likely to embrace policies that are...

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$2.2 Billion Investment Approved for Mad Dog Phase 2 Project

5 DAYS AGO

BHP Billiton has approved expenditure of $2.2 billion for its share of the development of the Mad Dog Phase 2 project in the Gulf of Mexico. During the fourth quarter of 2016, BP, which holds a 60.5% participating interest, sanctioned the Mad Dog Phase 2 project.

Mad Dog Phase 2, located in the Green...

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Philly Fed Manufacturing Conditions Continued to Improve in February

3 DAYS AGO

The index for current manufacturing activity in eastern Pennsylvania, southern New Jersey and Delaware increased from a reading of 23.6 in January to 43.3 this month and has remained positive for seven consecutive months. The share of firms reporting growth continues to increase: More than 48% of the ...

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Industrial Production Down 0.3% in January

4 DAYS AGO

Industrial production decreased 0.3% in January following a 0.6% increase in December. In January, manufacturing output moved up 0.2%, and mining output jumped 2.8%. The index for utilities fell 5.7%, largely because unseasonably warm weather reduced the demand for heating. At 104.6% of its 2012 avera...

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Don't Overlook Linear Actuators on Gate Valves

At a recent sales meeting in California, I was surprised to discover the lack of awareness regarding linear valve actuators. In fact, one veteran of the valve industry remarked, "I didn't know you could operate a gate valve using compressed air and a linear actuator." Most folks in the valve industry are familiar with operating globe valves in this manner, but typically, multi-turn electric actuators have been used when automating gate valves. However, if the control application calls for faster stroke speed, mechanical failure position, precise positioning, or higher thrust, linear pneumatic or hydraulic actuators may be preferred.

The basic principle behind linear actuators is simple: a piston in a cylinder. This type of actuator is very simple and reliable; after all, it only has one moving part. Such a mechanical device has been around for more than 200 years. Pistons in cylinders first saw use in steam engines. Scotland's James Watt crafted the first good ones during the 1770s.

Attaching a linear actuator to a gate valve is fairly straightforward. First, the handwheel and drive nut comes off, exposing the threaded stem. Then, a coupling is used to connect the stem to the piston rod. This allows the linear actuator to move the stem up and down directly. The before-and-after pictures on the left and right, respectively, show the change from a manual valve to an automatic valve with the linear actuator.

Of course, the actuator is now producing "thrust" not "torque," and this is a critical specification for linear actuator design. As it turns out, the size of the cylinder is a function of the required valve thrust and the available supply (pressure x area = force). The cylinder is larger for a higher required thrust and a lower supply pressure. And since the actuator price increases as the cylinder size increases, engineers must verify that the supply pressure given is the highest available at the project site.

Moreover, if the calculated thrust is based on the maximum differential pressure rating across the valve (as defined by ANSI) and not actual operating design conditions, the specified thrust might be much higher than actual, which would require a larger cylinder and thus a higher price. Therefore, it is best to specify thrust based on actual design conditions to get the best price.

Linear actuators can be an effective automation solution for gate valves. As automation increases, so should our choices. That the linear actuator has proven reliable in many applications outside of the valve industry is testament to the enduring design of the pneumatic and hydraulic cylinder.

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