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Last updateMon, 24 Jul 2017 3pm

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How to Choose the Best Rapid Prototyping Method

How to Choose the Best Rapid Prototyping Method

As new products are designed, including ...

Monitoring Valve Health via the Internet

Monitoring Valve Health via the Internet

Most valve end users are already using s...

Valves in Oxygen Service

Valves in Oxygen Service

In his presentation at VMA’s 2017 ...

Thermal Spray Coating

Thermal Spray Coating

Q: What are the pros and cons of us...

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Industry Headlines

U.S. Fuel Ethanol Production Continues to Grow in 2017

Monday, 24 July 2017  |  Chris Guy

Through the first six months of 2017, U.S. weekly ethanol production averaged 1.02 million barrels per day (b/d), an increase of 5% over the same peri...

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How to Choose the Right Size and Type of Actuator

How to Choose the Right Size and Type of Actuator

Monday, 24 July 2017  |  Carlos Gamero

A common misconception in our industry is that actuating a valve is as simple as putting the most cost-efficient actuator on top of your valve of choi...

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Industry Headlines

Badger Alloys Joins VMA as Associate Member

6 DAYS AGO

This week the Valve Manufacturers Association (VMA) welcomes Badger Alloys as an official associate supplier member. This is VMA’s fourth new member in 2017.

Located in the heart of Milwaukee and founded in 1966, Badger Alloys offers single source capabilities for custom castings. The company pou...

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Thermodyn Joins VMA as Associate Member

6 DAYS AGO

This week the Valve Manufacturers Association (VMA) welcomes Thermodyn Corporation as an official associate supplier member. This is VMA's third new member in 2017.

In 1979, Thermodyn began business with the dual purpose of selling A.W. Chesterton products and manufacturing high-temperature elastomers ...

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U.S. Fuel Ethanol Production Continues to Grow in 2017

12 HOURS AGO

Through the first six months of 2017, U.S. weekly ethanol production averaged 1.02 million barrels per day (b/d), an increase of 5% over the same period in 2016. On a weekly basis, U.S. ethanol production set a record of 1.06 million b/d in the week of January 27, 2017, and it has averaged near or a...

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LyondellBasell to Build the World's Largest PO/TBA Plant

3 DAYS AGO

LyondellBasell has made the final investment decision to build the world's largest propylene oxide (PO) and tertiary butyl alcohol (TBA) plant in the Houston area. The project is estimated to cost approximately $2.4 billion, representing the single-largest capital investment in the company's history...

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IMF Lowers 2017 Growth Forecast for U.S.

12 HOURS AGO

The growth forecast in the United States has been revised down from 2.3% to 2.1% in 2017 and from 2.5% to 2.1% in 2018, according to the IMF’s World Economic Outlook. While the markdown in the 2017 forecast reflects in part the weak growth outturn in the first quarter of the year, the major fa...

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Leading Economic Indicators Increased in June

3 DAYS AGO

The Conference Board Leading Economic Index (LEI) for the U.S. increased 0.6% in June to 127.8 (2010 = 100), following a 0.2% increase in May, and a 0.2% increase in April.

“The U.S. LEI rose sharply in June, pointing to continued growth in the U.S. economy and perhaps even a moderate improvement...

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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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