09282016Wed
Last updateWed, 28 Sep 2016 7pm

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Caution: Horizontal Stem Installation Ahead

Caution: Horizontal Stem Installation Ahead

When it comes to linear valve installati...

The Critical Stem Nut: Who is Responsible for Maintenance?

The Critical Stem Nut: Who is Responsible for Maintenance?

One of the most important components of ...

An Alternative Basics Education: Valve Ed Comes to You!

An Alternative Basics Education: Valve Ed Comes to You!

For the first time in the seven-year his...

Give Your Flow Meter a Happy Home

Give Your Flow Meter a Happy Home

Increased emphasis on the need to improv...

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Wolseley Reports 2016 Full Year Results

20 HOURS 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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ValvTechnologies Joins MSS of the Valve and Fittings Industry Committee

1 DAY AGO

ValvTechnologies, Inc. has been unanimously approved for membership in the Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry Committee. Representing ValvTechnologies is Tony Majka, director of engineering.

The MSS is a non-profit technical association organized for develo...

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Construction Chemicals Market to Reach $40,154M by 2022

-1 DAYS AGO

According to a new report published by Allied Market Research, the construction chemicals market is poised to reach $40,154 million by 2022, from $27,162 million in 2015, growing with a CAGR of 5.6% from 2016 to 2022. The concrete admixtures segment leads the construction chemicals market with more th...

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Goldman Sachs: U.S. Shale Firms to Pump More Oil by 2017

-1 DAYS AGO

“Though the collapse in prices caused a wave of bankruptcies, total U.S. oil production has only fallen by about 535,000 barrels a day so far this year compared with 2015, when it averaged 9.4 million barrels, according to the latest federal data,” The Wall Street Journal reports .

“As...

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Durable Goods Orders Unchanged in August

-1 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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U.S. Consumer Confidence Surges to Nine-Year High

1 DAY AGO

The Conference Board Consumer Confidence Index, which had increased in August, improved further in September. The Index now stands at 104.1, up from 101.8 in August. The 104.1 figure is the highest since August 2007.

“Consumer confidence increased in September for a second consecutive month and i...

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Multi-colored Stain on Valves

materials_q_and_a_graphicQ: I am handling high purity-water and keep getting a multi-colored stain on my valves and other equipment. What is this, and how can I prevent it?

A: You are describing a phenomenon called "rouging," a term that pertains to the multi-colored stain you are seeing. Rouging is a problem that is seen primarily in high-purity water applications or steam. Though more commonly associated with the pharmaceutical and electronics industries, it can occur most anywhere. At the lower temperatures rouge is red or yellowish in appearance, but in high-temperature steam it will be dark gray or black. The FDA has not made any formal opinion about rouging, but pharmaceutical companies are concerned about contamination of their products so they go to great lengths to prevent it and to clean their systems when it occurs-incurring undesired downtime and expense.

The mechanism of rouging is still not fully understood and as a result there are some myths and misconceptions about what it is and how to prevent it. Essentially, rouge is a form of rust, i.e., iron oxide, but different than the heavy rust seen when stainless steel is not cleaned properly after heat treatment or welding. While normal rust is a result of improper cleaning during manufacture, rouge is a much thinner layer that occurs when perfectly cleaned stainless steel reacts with high-purity water environments. Rouge seems to be more prevalent at temperatures in excess or 60° C.

We know that stainless steels achieve their corrosion resistance by developing a very thin microscopic chromium oxide layer. The general consensus about rouging is that certain services, such as high purity water with very low oxygen content, dissolve this protective layer and allow the stainless steel to resume corroding. This corrosion is then responsible for the staining we call rouging. These stains have been analyzed as being various types of iron oxide as well as containing traces of chromium and nickel.

While mainly an aesthetics problem, most people still want to prevent rouge in their systems. One commonly held belief is that the ferrite phase in cast stainless steels or welds causes rouging, and purchasers of valves and other equipment frequently impose strict limits on the ferrite content of cast stainless steels. Since wrought stainless steels with no ferrite also experience rouging, it doesn't appear that ferrite is the culprit.

A study conducted by AvestaPolarit1, found that the water's gas content and a metal's surface finish were influential for rouging. Basically, water with high oxygen and low carbon dioxide content was less likely to cause rouging as were electro-polished surfaces of the metal components. This study also found no significant correlation for the different alloy grades, including duplex stainless steels with their high ferrite content.

Since most people find rouge objectionable in their systems, much attention has been given to its removal. Various acids and chelates are used to clean systems of rouge, but these can leave behind their own contaminates or films. In addition, if acid exposure is not controlled closely, the acid can etch the metal surfaces thus destroying the expensive electro-polished surfaces. Therefore, the most effective way to prevent rouge is by somehow introducing sufficient oxygen to the system, which helps maintain the protective chromium oxide layer.

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