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Wastewater Treatment

Wastewater Treatment

Society’s desire for a clean envir...

Controlling Our Water Systems, Part II

Controlling Our Water Systems, Part II

To better understand the actuators and c...

Controlling Our Water Systems

Controlling Our Water Systems

Actuators and controls are a critical pr...

Hardfacing Alloys and Processes for Advanced Ultra-Supercritical

Hardfacing Alloys and Processes for Advanced Ultra-Supercritical

Cobalt-based Stellite 6 has been the wor...

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Basics of Elastomeric Seal Design

Basics of Elastomeric Seal Design

Wednesday, 20 July 2016  |  Kate Kunkel

Engineers need critical design information when choosing a seal for a particular valve application. This includes:

  • Operating temperature and pressure r...

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Industry Headlines

Pentair Valves & Controls Rolls Out Customer Education Program

2 DAYS AGO

Pentair Valves & Controls has introduced the Pentair University customer education program for past, present and prospective clients and industry leaders in various locations throughout the world. Pentair University’s invitation-only seminars are free to attend. In some regions of the worl...

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Watson Valve Names Bob White New President

2 DAYS AGO
Watson Valve Names Bob White New President

Watson Valve Services Inc. has named Robert “Bob” White as its new president. The current president, John M. Watson, will remain as the company’s CEO.

Bob has served as executive vice president, and ownership, of Watson Valve Services since its inception in 2002. He has continued to p...

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Canadian Oil & Gas Earnings Signal Industry Recovery

1 DAY AGO

The Canadian oil and gas earnings season began yesterday with “signs of an industry recovery as Encana Corp and Precision Drilling Corp outlined plans to boost activity,” Reuters reports .

Analysts say “the uptick in optimism might be mirrored by some U.S. shale companies like Pioneer ...

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U.S. Lower 48 Sustains $150B in Cuts by Upstream Developers

2 DAYS AGO

Out of the more than $370 billion in global capital expenditure cut by upstream developers across 2016 and 2017, $150 billion was slashed in the U.S. Lower 48 alone — more than three times any other single country. Largely due to responsiveness and flexibility in the unconventional space, spen...

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STEM Jobs in the U.S. Growing Faster Than Other Fields

2 DAYS AGO

The U.S. Department of Commerce estimates that jobs in STEM will grow 17% by 2018—that’s 55% faster than non-STEM jobs over the next decade. Several reports have linked STEM education to the continued scientific leadership and economic growth of the U.S. However, economic projections also ...

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IMF Cuts Global Growth Forecast After Brexit Vote

3 DAYS AGO

The International Monetary Fund (IMF) cut its forecasts for global economic growth this year and next as the unexpected U.K. vote to leave the European Union creates a wave of uncertainty amid already-fragile business and consumer confidence.

The global economy is projected to expand 3.1% this year a...

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Actuation in Nuclear Power Plants

vmfall11_nuclear_h

The thousands of actuators used in a nuclear plant face some pretty tough conditions as well as rigorous testing.

Currently, 104 nuclear power-plant reactors are working in the United States, and all of them have operating environments that are extremely challenging. Of those 104 plants, 35 are classified as boiling and 69 as pressurized water reactors.

While the design details vary from plant to plant, each nuclear facility has thousands of valve actuators used in various processes and applications. The newest-generation nuclear plant has more than 13,000 valves.

It’s clear, then, that valve actuators play vital roles in maintaining process safety, efficiency and productivity in a wide range of situations.

This article contains a brief description of some of the special circumstances encountered in challenging nuclear environments and the different styles of actuators used to meet demanding operational and safety requirements.

STRICT GUIDELINES AND REQUIREMENTS

vmfall11_nuclear_electric_actuatorWith O-ring sealed covers in place on this electric actuator, the motor, limit and torque switches, as well as other electrical components, are housed within a pressure-tight enclosure. This keeps out dirt and moisture and prevents breathing from expansion and contraction of the internal air caused by temperature changes.All equipment used in nuclear plants built in the United States is certified under stringent guidelines mandated by the Nuclear Regulatory Commission (NRC). Verification of reactors or equipment to standards from other countries is not acceptable for the 104 working reactors in the U.S.

To understand basic requirements the nuclear power industry faces in this nation, a review of the similarities and differences between nuclear power and fossil power is helpful.

In a fossil power plant, coal might be crushed and mixed with air to boil water, which produces steam to drive a turbine. With nuclear reactions, the process is different, but the operational objective is essentially the same—to heat water to produce steam to drive a turbine. With a coal steam generator, the activity of burning the pulverized coal and producing steam is contained within what is termed the “boiler island.” Because of the strong similarity to what happens in the coal plant, many engineers and technicians in a nuclear plant refer to the area where steam generation occurs as the “nuclear island.”

vmfall11_nuclear_cutawayThis cutaway illustration shows the internal components of a typical electric actuator.Within the nuclear reactor, equipment must meet rigorous standards. Since radiation is very high, the standards require all equipment materials used in this phase of the process to withstand high levels of radiation for the life of the plant. Therefore, materials such as iron or steel are required rather than aluminum. Also, temperatures in this portion of the plant are elevated, which will affect seal materials. The combination of severe environmental conditions determines the various coatings and paints allowed for use in this area, which is known as “inside containment.”

To be suitable for service in a nuclear reactor, an actuator must go through specific testing by outside testing agencies. The test reports produced must then be reviewed not only by the actuator suppliers, but by consulting engineers and the utilities themselves. Many documents also are reviewed by the NRC.

The tests for actuators used “inside containment” apply to all styles. The plants use electric motor operators as well as pneumatic cylinder actuators and hydraulic cylinder actuators. All of these actuators must be tested to ensure they can withstand the environment for their expected lives. Also, in addition to environmental concerns, the actuators must be able to operate during extreme accident conditions such as an earthquake.

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