04192018Thu
Last updateThu, 19 Apr 2018 4pm

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Air Valves in Piping Systems

Air Valves in Piping Systems

Liquid piping systems are prone to colle...

Are Valves from Low-Cost Countries Getting Better?

Are Valves from Low-Cost Countries Getting Better?

The last 25 years have seen standards cr...

Managing the Generation Gap: Much Ado About Nothing?

Managing the Generation Gap: Much Ado About Nothing?

The baby boomer generation was the most ...

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Industry Headlines

Emerson and BlueFin Form Strategic Partnership

Thursday, 19 April 2018  |  Chris Guy

Emerson and BlueFin have signed a working partnership agreement to deliver the Roxar gauge technology to the U.S. Gulf of Mexico (GoM) region. The part...

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Industry Headlines

Emerson and BlueFin Form Strategic Partnership

-1 DAYS AGO

Emerson and BlueFin have signed a working partnership agreement to deliver the Roxar gauge technology to the U.S. Gulf of Mexico (GoM) region. The partnership will deliver a combined offering of Emerson's technology coupled with BlueFin's installation services and chemical injection systems.

BlueFin, a...

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Flowserve Expands Partnership with Unisys

22 HOURS AGO

Flowserve, a client of Unisys Corporation, will expand its use of the Unisys Stealth microsegmentation solution through a new agreement to implement the solution more broadly across the enterprise. Under the new agreement , Flowserve will increase the number of servers and endpoints protected by Steal...

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OECD Natural Gas Production Up 2.4% in 2017

-1 DAYS AGO

An assessment of monthly data shows that in 2017 Organization for Economic Co-operation and Development (OECD) natural gas production grew by 2.4% compared to 2016. This growth was driven by increases in production across all OECD regions, particularly in Asia Oceania (+17.7%), whilst the Americas and...

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Major Trends Changing the Chemical Industry

1 DAY AGO

“The accelerated globalization of the chemicals market is one of four major trends that we at SAP see shaping the chemical industry through the remainder of 2018 and beyond,” writes Stefan Guertzgen, global senior director for industry solution marketing, chemicals at SAP.

“Amid such ...

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Beige Book: Solid Outlook Despite Tariff Concerns

1 HOUR AGO

Economic activity continued to expand at a modest to moderate pace across the 12 Federal Reserve Districts in March and early April. Outlooks remained positive, but contacts in various sectors including manufacturing, agriculture and transportation expressed concern about the newly imposed and/or prop...

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IMF Predicting Global Economic Upswing

1 DAY AGO

World growth strengthened in 2017 to 3.8%, with a notable rebound in global trade. It was driven by an investment recovery in advanced economies, continued strong growth in emerging Asia, a notable upswing in emerging Europe, and signs of recovery in several commodity exporters. Global growth is exp...

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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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