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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...

Ball Valve Repair 101

Ball Valve Repair 101

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

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Industry Headlines

U.S. Jobless Claims Fall to Near Five-Month Low

Thursday, 20 July 2017  |  Chris Guy

In the week ending July 15, the advance figure for seasonally adjusted initial claims was 233,000, a decrease of 15,000 from the previous week's revis...

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How to Choose the Best Rapid Prototyping Method

How to Choose the Best Rapid Prototyping Method

Tuesday, 18 July 2017  |  Kate Kunkel

As new products are designed, including valve bodies and the parts that comprise the finished valve, prototypes must be created. How that is achieved ...

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Industry Headlines

Badger Alloys Joins VMA as Associate Member

1 DAY 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

1 DAY 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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EPA Selects Projects for Water Infrastructure Loans

-1 DAYS AGO

The EPA is inviting 12 projects in nine states to apply for Water Infrastructure Finance and Innovation Act (WIFIA) loans. These potential applicants were selected from a group of projects that represent large and small communities from across the U.S. that submitted letters of interest to EPA in Ap...

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U.S. Shale Oil Production Growth to Slow in 2018

21 HOURS AGO

In its newly released North America Watch , ESAI Energy projects that by the end of 2017, U.S. shale oil production will hit 5.6 million b/d, over 1 million b/d higher than at the end of 2016. But the pace of growth will slow in 2018 as current oil prices below $50 per barrel are likely to put a check...

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U.S. Jobless Claims Fall to Near Five-Month Low

-1 DAYS AGO

In the week ending July 15, the advance figure for seasonally adjusted initial claims was 233,000, a decrease of 15,000 from the previous week's revised level. The previous week's level was revised up by 1,000 from 247,000 to 248,000. The 4-week moving average was 243,750, a decrease of 2,250 from t...

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Empire State Manufacturing Survey Dropped in June

1 DAY AGO

Business activity grew modestly in New York State, according to firms responding to the July 2017 Empire State Manufacturing Survey. Manufacturing firms in New York State reported that business activity continued to expand in July. After reaching its highest level in more than two years last month, ...

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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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