06192018Tue
Last updateTue, 19 Jun 2018 1pm

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Gaskets Are Not Created Equal

Gaskets Are Not Created Equal

Gaskets are near the bottom of the food ...

Your Valves May Be Weaponized

Your Valves May Be Weaponized

The advent of the Internet of Things (Io...

Fracturing Technology in the New Age

Fracturing Technology in the New Age

According to a 2014 U.S. Energy Informat...

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Industry Headlines

Consumer Sentiment Climbs to Three-Month High

Tuesday, 19 June 2018  |  Chris Guy

Consumer sentiment rose slightly in early June due to consumers' more favorable assessments of their current financial situation and more favorable vi...

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Industry Headlines

A-T Controls Names Andy Cheney Southwest Regional Manager

3 DAYS AGO

A-T Controls recently announced the addition of Andy Cheney as the company’s new southwest regional manager, effective immediately.

Cheney’s new role will cover California, South Nevada, Arizona and New Mexico. He has over twenty years in the valve and automation business and is very famil...

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Forum Energy Technologies Contracted for Submarine Vehicles

4 DAYS AGO

Forum Energy Technologies has received an order from Submarine Manufacturing and Products, Ltd. (SMP) to supply a submarine rescue vehicle (SRV), a work-class remotely operated vehicle (ROV) and associated launch and recovery systems. The ROV and SRV will be delivered in 2019 and 2020, respectively, a...

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Phillips 66 Plans $1.5 Billion Expansion in Texas

-1 DAYS AGO

Phillips 66 is proceeding with an expansion of the company’s Sweeny Hub. This project includes the construction of two 150,000 barrel-per-day (BPD) natural gas liquids (NGL) fractionators in Old Ocean, TX, additional NGL storage capacity, and associated pipeline infrastructure. The project is ex...

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Permian Oil Production to More than Double, Exceed Expectations

4 DAYS AGO

Oil production in the Permian Basin, already a major force in global supply growth, will rise nearly 3 million barrels a day (mbd) by 2023—a level of growth exceeding most recent estimates, says IHS Markit . What the report describes as a “stunning” level of growth will comprise more...

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Consumer Sentiment Climbs to Three-Month High

-1 DAYS AGO

Consumer sentiment rose slightly in early June due to consumers' more favorable assessments of their current financial situation and more favorable views of current buying conditions for household durables. The Expectations Index declined to its lowest level since the start of the year due to less f...

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U.S. Manufacturing Output Fell in May

19 HOURS AGO

Industrial production edged down 0.1% in May after rising 0.9% in April. Excluding motor vehicles and parts, factory output moved down 0.2%. The index for mining rose 1.8%, its fourth consecutive month of growth; the output of utilities moved up 1.1%. At 107.3% of its 2012 average, total industrial ...

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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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