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The Challenges of Slurry Valve Packing

The Challenges of Slurry Valve Packing

Because of the difficulties of dealing w...

The Many Layers of Valve Qualification

The Many Layers of Valve Qualification

While there has been much rhetoric from ...

Valves Help Achieve Net-Zero Water Use

Valves Help Achieve Net-Zero Water Use

With drought and climate change affecting ...

Valve Selection in Pulp and Paper Operations

Valve Selection in Pulp and Paper Operations

Over the centuries, the pulp and paper i...

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Industry Headlines

Wolseley Announces Name Change, CEO Succession

Wednesday, 29 March 2017  |  Chris Guy

Wolseley plc is officially changing its name to Ferguson plc, subject to shareholder approval. Ferguson is the most significant brand in the Wolseley ...

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Industry Headlines

Wolseley Announces Name Change, CEO Succession

10 HOURS AGO

Wolseley plc is officially changing its name to Ferguson plc, subject to shareholder approval. Ferguson is the most significant brand in the Wolseley Group of companies and accounts for 84% of the Wolseley Group’s profitability.

The company also announced that CEO Frank Roach will retire on July ...

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Spirax Sarco Employees Build Prosthetic Hands for Children

16 HOURS AGO

Spirax Sarco hosted their annual charity event at the Westin Hotel in Savannah, GA on Saturday, March 11, 2017 where participants built prosthetic hands for children in third-world countries who are missing limbs.

There are 300,000 landmine rated amputees globally and 20% of those are children. Emplo...

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In Blow to Nuclear Industry, Westinghouse Files for Bankruptcy

16 HOURS AGO

“The Westinghouse unit of Japanese technology giant Toshiba plunged into Chapter 11 bankruptcy Wednesday as the Cranberry Township, Pa.-based division faces cost overruns and delays with its U.S. nuclear plant projects,” reports USA Today .

“The company said the bankruptcy does not aff...

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Colorado Seeing Surge in Oil & Gas Investments

1 DAY AGO

“Drilling applications and investments by oil and gas companies are surging in Colorado after crude prices partially rebounded from their collapse in recent years, pushing the industry deeper into residential communities largely unaccustomed to drilling,” the Associated Press is reporting .

&...

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Four Out of Ten Jobs Could be Lost to Automation by 2021

1 DAY AGO

Automation is the new norm across sectors and will affect the bottom of pyramid so much so that four out of every 10 jobs globally would be lost due to this by 2021, experts say. As automation adoption increases, all high transaction and labor intensive jobs will take a hit. According to PeopleStrong...

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U.S. Durable Goods Orders Rose 1.7% in February

2 DAYS AGO

New orders for manufactured durable goods in February increased $3.9 billion or 1.7% to $235.4 billion, the U.S. Department of Commerce announced . This increase, up two consecutive months, followed a 2.3% January increase. Excluding transportation, new orders increased 0.4%. Excluding defense, new or...

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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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