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Improving Valve Sealing Performance and Reliability

Improving Valve Sealing Performance and Reliability

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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

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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

4 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

5 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

6 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

4 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

5 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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Water Hammer—Check It Out

Have you ever been in an area of the plant that had just shut down a pump, only to hear an explosive sound a few seconds later? The noise you heard was the pump check valve, accompanied by the water hammer, or reverse flow, that slammed it shut.

Multiple pump systems often use a check valve located between the pump and the discharge header. The purpose of this valve is to prevent backflow from the header to the pump when it is not running. Without the check valve the pump could actually spin backwards.

Depending on the system pressure, these valves can close with such force that they damage the check valve, the pump, and over time even the pump base. Most check valves require reverse flow to close the valve and once this flow momentum has started, it does not stop as quickly as the check valve closes. The result is water hammer, a very destructive force. According to Webster's: Water hammer: a concussion, or sound of concussion, of moving water against the sides of a containing pipe or vessel.

We have seen many plants overcome these laws of physics with the use of an "auto check," also known as a "butterfly check." This concept utilizes a pneumatic-operated butterfly valve, and relatively simple control logic in order to close the valve automatically, prior to shutting down the pump. This action avoids reverse flow, so that the back flow and water hammer never have the chance to develop.

The valves for these applications are typically high-performance butterfly valves with a pneumatic actuator. Accessories include a limit switch and four-way pilot solenoid with two adjustable speed controls. The speed controls restrict the airflow out of the cylinder in both directions, thus regulating the opening and closing speed of the valve.

Control logic for the auto check is simple. When the pump is not pumping, the butterfly valve is closed. When the motor start command is received, either locally or from the PLC, the pump motor is energized. Pressure builds up on the pump side of the auto check valve. A differential pressure switch senses pressure differential between the newly started pump and the header past the auto check. At some predetermined point-such as 1 psi, .5 psi. or .25 psi-the delta p switch makes contact on pressure increase. The switch is sealed in by a relay and energizes the solenoid valve, which opens the butterfly valve smoothly, aided in part by the speed control valves. When the butterfly valve is totally open, a limit switch is tripped and sends a valve-open status to the PLC.

When the motor stop command is received, the pilot solenoid is de-energized and the valve closes at a controlled rate, again aided by the speed controls. When the valve is completely closed the limit switch is tripped, which in turn shuts off the pump motor. This action eliminates water hammer by preventing any back flow from occurring.

BRUCE FENWICK is in technical sales for McJunkin Corporation, Harvey IL. Reach him via 708.225.3120 or at This email address is being protected from spambots. You need JavaScript enabled to view it..

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