06202018Wed
Last updateWed, 20 Jun 2018 6pm

i

From Cannon Balls to Pressure Seals: Graphite for Sealing

From Cannon Balls to Pressure Seals: Graphite for Sealing

From time to time, we re-publish well-re...

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...

SubscribeSPR18

FREE SUBSCRIPTION*

• Print magazine
Digital magazine
• VALVE eNews
Read the latest issue

*to qualified valve professionals in the U.S./Canada

The Weekly Report

New Products

  • ja-news-2
  • ja-news-3

Industry Headlines

Global LNG Trade Growing, Led by Australia and the U.S.

Wednesday, 20 June 2018  |  Chris Guy

Global trade in liquefied natural gas (LNG) reached 38.2 billion cubic feet per day (Bcf/d) in 2017, a 10% (3.5 Bcf/d) increase from 2016 and the larg...

Readmore

Loading...
Advertisement
i

Industry Headlines

Metso Receives Major Valve Orders in China

1 DAY AGO

Metso has received two valve orders totaling 8,200 valves from major pulp and paper customers in China. The orders are booked in Metso's first quarter 2018 orders received. The total value of the orders and the company names are not being disclosed. Broadly covering China's mid and high-end customers ...

Readmore

A-T Controls Names Andy Cheney Southwest Regional Manager

5 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...

Readmore

Global LNG Trade Growing, Led by Australia and the U.S.

1 HOUR AGO

Global trade in liquefied natural gas (LNG) reached 38.2 billion cubic feet per day (Bcf/d) in 2017, a 10% (3.5 Bcf/d) increase from 2016 and the largest annual volume increase since 2010, according to the Annual Report on LNG trade by the International Association of Liquefied Natural Gas Importers...

Readmore

U.S. Natural Gas Production Could Grow 60% Over Next 20 Years

1 HOUR AGO

A decade since the start of a shale gas revolution that unlocked new supplies and resulted in a “wholesale turnaround” in U.S. production, the overall size of recoverable gas reserves continues to increase and the pace of production growth is only accelerating, a new report by IHS Markit s...

Readmore

Texas Economy Continues to Expand at “Solid Pace”

5 HOURS AGO

The Texas economy is expanding at a solid pace. Employment has grown at a 3.6% annualized rate through May, driven by job gains in the goods-producing sector. Unemployment remains near its historical low, and labor markets are tight. The Dallas Fed’s Texas Business Outlook Surveys (TBOS) suggest...

Readmore

Consumer Sentiment Climbs to Three-Month High

1 DAY 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...

Readmore

Advertisement

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.

  • Latest Post

  • Popular

  • Links

  • Events

BUYERS GUIDE 300x220

Looking for a career in the Valve Industry?

ValveCareers Horiz

To learn more, watch the videos below or visit ValveCareers.com a special initiative of the Valve Manufacturers Association