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Where Valves Are Used: Everywhere!

Where Valves Are Used: Everywhere!

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Oxygen Cleaning: A Validated Process is Critical for Safety

Oxygen Cleaning: A Validated Process is Critical for Safety

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Inspiration and Automation: Keys to Best-in-Class Operations

Inspiration and Automation: Keys to Best-in-Class Operations

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Industry Headlines

Emerson Opens Solutions Center in Singapore

Friday, 17 November 2017  |  Chris Guy

As part of its drive to make Singapore a hub for the delivery of Industrial Internet of Things (IoT) technologies and services for customers across As...

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Industry Headlines

Emerson Opens Solutions Center in Singapore

2 DAYS AGO

As part of its drive to make Singapore a hub for the delivery of Industrial Internet of Things (IoT) technologies and services for customers across Asia Pacific, Emerson opened a customer-focused Solutions Center at the regional headquarters of its Automation Solutions business in Singapore. To mark...

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Emerson Proposes to Acquire Rockwell Automation

3 DAYS AGO

Emerson chairman and CEO David N. Farr has sent a letter to Rockwell Automation president and CEO Blake D. Moret proposing to acquire all outstanding shares of Rockwell for $225 per share, consisting of $135 per share in cash and $90 per share in Emerson shares. The total enterprise value of the tra...

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Energy Outlook Shows a World in Transformation

5 DAYS AGO

The resurgence in oil and gas production from the United States, deep declines in the cost of renewables and growing electrification are changing the face of the global energy system and upending traditional ways of meeting energy demand, according to the World Energy Outlook 2017 . A cleaner and more...

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U.S. Shale Output Expected to Rise Again in December

5 DAYS AGO

“U.S. shale production for December is expected to rise for a 12th consecutive month,” according to the Energy Information Administration (EIA), “as oil prices remain near their mid-2015 highs.”

Reuters reports that “projected gas output would increase in each of the major...

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U.S. Industrial Output Up 0.9% in October

2 DAYS AGO

Industrial production rose 0.9% in October, and manufacturing increased 1.3%. The index for utilities rose 2.0%, but mining output fell 1.3%, as Hurricane Nate caused a sharp but short-lived decline in oil and gas drilling and extraction. Even so, industrial activity was boosted in October by a return...

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Empire State Manufacturing Survey Shows Continued Growth

3 DAYS AGO

Business activity continued to grow strongly in New York State, according to firms responding to the November 2017 Empire State Manufacturing Survey. Though the headline general business conditions index fell eleven points from the multiyear high it reached last month, it remained firmly in positive ...

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Today’s Coatings Provide Solid Protection for Valves

vmfall09 beyond valves 1Figure 1. High velocity oxygen fuel coating of a Ball Valve component.Like anything made of metal, valves are subject to corrosion and other natural forces that compromise their performance. However, the right coating can protect those valves not just against corrosion, but erosion and wear.

Many coatings in use today, including both organic (paints, for example) and inorganic (zinc, chromium, nickel, aluminum and others) are applied to the outside surfaces to protect those surfaces. However, protecting the inside of a valve is a bit trickier because of the myriad of factors that come into play. This article concentrates on those challenges, covering coatings for the insides of valves that resist corrosion, prevent wear of the trim and other moving parts, and reduce erosion by abrasive media.

CHOICE OF METHODS AND MATERIALS

vmfall09 beyond valves 2Figure 2. Hardcoating being applied to a valve seat.A wide selection of coatings is available today. Control Valves, part of the ISA Practical Guides for Measurement and Control (1998), lists electroless nickel to protect steel bodies and bonnets from corrosion, aluminizing for protection from high-temperature corrosion, boronizing to prevent internal erosion and a variety of sprayed coatings.

Many methods covered in this area are presented by the companies that make or provide them as alternatives to chrome plating—which is desirable because the newer coatings promise better properties and because chromium is facing ever-stricter environmental restrictions.

The requirements of individual applications determine which type of material is optimum for helping a valve resist corrosion, wear and erosion, says Dore Rosenblum, director of marketing, Sub-One Technology.

“For example, let’s say a valve is operating in a purely corrosive environment—gases flowing or something. Then, the goal is to make sure the coating is thick enough and doesn’t have any holes in it or pinholes that can cause corrosion,” Rosenblum explains.

The coating in this case could be a simpler one than a valve that had a very heavy sand flow, “where you have to worry quite a bit about erosion or abrasion or some other wear occurring in addition to corrosion,” he says.

For that second case, “we would create … a different type of coating that would be able to support the erosive flow through it and protect against damaging the surface of the valve,” he explains.

Hardcoating (Figure 2), which deposits a fairly thin layer of material and is often done with a thermal spraying technique, is distinguishable from hardfacing, which uses a form of welding for a thicker deposit, though considerable overlap in applications exists. The choice of which to use “usually has to do with the geometry of the part followed up by the volume of pieces that needs to be done,” says Ozzie Bell, manager, business development, Deloro Stellite. Manual methods used include MIG or TIG welding or oxyacetylene. If volumes are high and the part geometry is simple, he continues, “then there will be an automated process where we would have something like a plasma transferred arc piece of equipment being used, or an HVOF [high velocity oxygen fuel] system.” (Figure 1)

One of the oldest hardfacing materials used in valves is Stellite 6 (the name Stellite was trademarked in 1911), which is based on cobalt, chrome and tungsten carbide. However, Tribaloy alloys are increasing in popularity; the alloy consists of cobalt, chromium and molybdenum. Bell explains that: “They tend to stand up better under high abrasion and high corrosion applications.” They’re typically “used on the trim, on stem, seats, some bushings and possibly some of the flapper valves,” he says.

Another hardcoating gaining favor is Hardide Coatings’ tungsten carbide-based material, which consists of tungsten carbide nanoparticles dispersed in a tungsten metal matrix. This material is applied using chemical vapor deposition (CVD), which can coat both external and internal parts. The coating has been approved for use on a new line of coated metal ball and seats.

Meanwhile, Sub-One Technology uses a different deposition technique; the company employs a process applied by using “hollow cathode plasma immersion ion processing,” which can deposit carbon-based coatings, metal carbides and oxides—for example silicon, tantalum and chromium carbides—and diamond-like carbon films on the insides of objects (Figure 3). As this description implies, the process does not involve putting a part in a vacuum chamber and spraying or bombarding it with the material. Instead, says Rosenblum, “we … create a chamber within the part where we create a vacuum. We then apply the process so that it deposits the coating onto the internal surface.”

vmfall09 beyond valves 3Figure 3. A completion valve with internally coated surfaces.What that allows the company to do is to support a variety of components formerly very difficult to coat because the line of sight was not good. This is generally done while the valve is being manufactured—parts are sent for processing, which the company does, “and they [the valve manufacturer] would then complete the manufacturing process for the component,” Rosenblum explains.

A LOOK AT THE FUTURE

Technology seldom stands still, and valve coatings are no exception. An interesting development at the Fraunhofer Institute for Manufacturing Engineering and Automation and the University of Duisburg-Essen was reported recently in an article in MIT’s Tech­nology Review. The article explains that researchers are developing a way to electroplate metals containing liquid-filled nanoparticles. The hope is that these particles could be filled with liquid polymers or other materials that would be released if the plating was cracked or scratched, effectively sealing the crack and preventing corrosion.

This development and others like it ensure the valves of the future will have even more protection than those in years past.


Peter Cleaveland is a contributing editor to Valve Magazine. Reach him at This email address is being protected from spambots. You need JavaScript enabled to view it..

 

 


Composite Electroless Nickel Coatings

By Michael D. Feldstein

Electroless Nickel (EN) is generally an alloy of 88% to 99% nickel with the balance being phosphorous, boron or a few other possible elements depending on the specific requirements of an application. It can be applied to numerous metals, alloys and nonconductors with outstanding uniformity of coating thickness to complex geometries. In addition, its super fine particles can be added to form composite EN coatings that can enhance existing characteristics and add entirely new properties. Particles from a few nanometers up to about 50 microns in size can be incorporated into coatings that are a few microns up to many mils in thickness. The particles can comprise from 10% to over 40% of the coating depending on the particle size and application.

The widest use in the valve industry for these coatings is for increased wear resistance. Particles of many hard materials can be used in this process, such as diamond, silicon carbide, aluminum oxide, tungsten carbide, boron carbide and others. Diamond is the most common and has a Taber wear index of 1.159. Where low coefficient of friction, dry lubrication and repellency of water, oil and/or other liquids are crucial, the coating can contain 20% to 25% of sub-micron PTFE particles. Tests show that the lowest coefficient of friction is achievable when both mating parts are coated with composite EN-PTFE. Where high heat is a problem, composites with particles of ceramics such as boron nitride (which can withstand temperatures above 1562º F [850º C]) are used. When loading is high, the coefficient of friction of EN-BN and conventional EN actually decreases as the load increases.

EN coating can also be made to fluoresce under ultraviolet light, which can be useful in telling genuine OEM parts from counterfeit parts as well as in identifying specific manufacturing lots. The fluorescent material can even serve as an indicator layer, warning when the coating has worn off and replacement or recoating is necessary.


MICHAEL D. FELDSTEIN is president of Surface Technology, Inc. Reach him at This email address is being protected from spambots. You need JavaScript enabled to view it..

 

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