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Last updateFri, 30 Sep 2016 3pm

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Industry Headlines

U.S. Second Quarter GDP Growth Revised Up

Friday, 30 September 2016  |  Chris Guy

Real GDP in the U.S. increased at an annual rate of 1.4% in the second quarter of 2016, up from 1.1% in the last estimate, according to the Department...

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Industry Headlines

Siemens Industry Partners for Self-Funded Efficiency Project

1 DAY AGO

Montgomery County, TN has partnered with Siemens Industry Inc. to begin a nearly $5 million, self-funded efficiency project. The project will begin in late October and will be completed by fall of 2017.

Siemens has guaranteed the savings – including 2,473,263 kWh of electricity per year; 34,154 c...

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Wolseley Reports 2016 Full Year Results

3 DAYS AGO

Wolseley plc delivered an improvement in overall results for the fiscal year ending July 31, 2016, up 8.5% from last year. Revenue of $18.7 billion was 4.2% ahead at constant exchange rates and 2.4% ahead on a like-for-like basis. Price deflation, particularly in the U.S., reduced revenue by 1.5%. Imp...

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Propane Drove 2016 U.S. Petroleum Product Export Growth

1 DAY AGO

In the first half of 2016, the U.S. exported 4.7 million barrels per day (b/d) of petroleum products—almost 10 times the crude oil export volume—an increase of 500,000 b/d over the first half of 2015. While U.S. exports of distillate and gasoline increased by 50,000 b/d and nearly 140,00...

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$900 Million Natural Gas Power Plant Planned for Ohio

1 DAY AGO

EmberClear Corp. of Houston has announced plans for a new $900 million natural gas-fired electric power generation plant. The 1,000-MW Harrison Power Project will be built over 60-acres in Harrison County, OH. EmberClear said it will take 18 to 36 months to win approval of various state and federal ag...

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U.S. Second Quarter GDP Growth Revised Up

5 HOURS AGO

Real GDP in the U.S. increased at an annual rate of 1.4% in the second quarter of 2016, up from 1.1% in the last estimate, according to the Department of Commerce. In the first quarter, real GDP increased 0.8%.

The most notable change from the last estimate to this one is that nonresidential fixed inve...

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Durable Goods Orders Unchanged in August

2 DAYS AGO

New orders for manufactured durable goods in August were little changed at $226.9 billion, the U.S. Department of Commerce announced, following a 3.6% July increase. Economists were predicting a 1.5% decrease in August. Excluding transportation, new orders decreased 0.4%. Excluding defense, new orders...

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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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