Metals, Mining, Minerals

Emerson's Fisher division recently announced a new three-way, temperature-control valve and actuator system. The release highlighted its potential use by process manufacturers:

The new GX 3-way has the ability to accurately control the temperature of water, oils, steam, and other industrial fluids. Applications include heat exchangers and lubricating skids.

For those not well versed with three-way valves, you'll find use for them in both flow mixing (converging) and flow splitting (diverging) applications.

I caught up with Brad Smith, the global GX control valve product manager, about some potential applications for this valve. Brad began by sharing the development objectives for this valve. Typically, when a process manufacturer cannot achieve the required control, they must reassess process-piping arrangements, often going to a 2-valve arrangement. This GX 3-Way valve provides the level of control to avoid re-piping and 2-valve arrangements.

Brad shared with me that the biggest application focus for this 3-way valve is in temperature control around heat exchangers. It was designed for high-capacity applications and precise linear characteristics required for accurate temperature control. Brad cited a specific heat exchanger application in beer brewing where the wort temperature is maintained with a glycol coolant.

Another common application for this 3-way valve is pH control on feedwater to a boiler. When the pH of the feedwater rises beyond a predetermined level, a three-way valve adds fresh make up water to reduce the pH back to target levels.

A third application Brad discussed was for test separator manifolds. Test separators are mainly used in oil & gas production facilities to measure the amounts of oil, gas, and water from the well. The manifold contains three-way valves coming from each wellhead that uses the test separator. Some installations use the three-way valves while others prefer globe valves.

A final application Brad shared was in the steel industry. Rod mills require good temperature water box control.

Most process manufacturers have temperature control applications requiring mixing flow streams or splitting flow streams. This three-way valve might have the flow characteristics and properties your application requires.

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My trusty Emerson RSS feed alerted me to a new liquid analysis application guide for the metals extraction and processing industry. This guide, published by Emerson's Rosemount Analytical Liquid business, covers the liquid analysis solutions for the following processes: leaching and ore extraction, concentration and separation, finished product purification and waste disposal.

I confess to knowing little about mining and metals production processes, but after reading this application guide, I have a much better appreciation for the processes and some of the challenges.

In the leaching and ore extraction section, precious metals such as gold and silver are commonly processed using cyanide compounds. As the guide succinctly puts it:

Cyanide dissolves the precious metal by forming a chemical complex with it, thus separating the precious metal from the other constituents of the ore, which do not dissolve.

The challenge is accurate pH measurement for both safety and efficiency. pH values lower than 11 favor the formation of hydrogen cyanide gas, which is colorless, odorless and poisonous in sufficient concentrations. Continuous pH monitoring and control is critical to prevent the formation of this gas. Measuring pH is complicated by the finely ground abrasive ore which can coat and abrade the pH sensor. The guide describes the Rosemount Analytical pH probe, jet spray cleaning attachment, and measurement analyzer best suited for this application.

The guide has easily understandable process flow diagrams for flotation cell pH measurement, titanium dioxide (TiO₂) manufacturing, Alumina/caustic ratio control, steel treating, cyanide oxidation and waste disposal via scrubbers. It provides a good overview description of the process, the measurement and control challenges, and the liquid analytical products that can help address these challenges.

If you're in the metals extraction and processing industry, this guide helps you understand the products Emerson offers for a particular application. For those of us not familiar with the industry, the guide provides a great overview of some of the major production processes and the challenges engineers from this industry face.

Given recent trends in metal prices, if you're a process automation engineer or engineering student, you may want to learn more about this industry. If you do, you'll find this guide to be a useful overview.

Jack Murray, a member of Emerson's Metals, Mining, and Minerals industry team, shared a paper he had co-written with an Alcan Gove bauxite mine and alumina refinery staff member and Emerson fieldbus consultant, Sudhir Jain. Alcan was recently purchased by Rio Tinto.

Their paper, Fieldbus Technology on a Large Scale Mineral Project, describes Alcan's path from the 4-20mA analog world to a digital bus communications world. Alcan's investigation of the benefits of moving from analog to digital began in 1999. They had seen possible ways to reduce their project costs and improve operations by using digital busses.

Their first step, like most when undertaking something new, was a small step. They chose to implement Foundation fieldbus in a non-critical area of an existing facility. Their initial installation consisted of 20 I/O. They chose fieldbus devices from a number of automation suppliers to obtain a greater breadth of experience. They also chose Profibus DP for their motor control centers and variable speed drives.

This experience proved beneficial when the decision was made in 2004 to nearly double refinery capacity to meet growing demand. The project consisted of 5,000 field devices and 15,000 total I/O including motors and drives. They used a DeltaV system and the two digital busses, Foundation fieldbus and Profibus DP, for which they gained experience to connect the majority of this I/O. A key part of their decision was to work with Sudhir during the front end engineering design (FEED) process to assist in the segment design, training of key personnel, and to establish wiring best practices and standards.

Sudhir related to me how they developed new hazard analysis procedures (CHAZOP, short for control HAZOP) to ensure that failure of any bus segment would not leave a critical part of the plant unmonitored or uncontrolled. Segment segregation practices were developed to address the findings from this analysis. They also had a 3D model of the plant site, so that questions of distance and pathways could be quickly addressed to help rapidly advance the engineering effort.

They chose a modular construction approach using pre-assembled modules (PAMs). These modules were assembled and fitted off-site and fully pre-commissioned before they were delivered to the plant site. These PAMs were self-contained units and included process vessels, piping, pumps, instrumentation and valves, all fully wired and tested.

The digital busses fit into this modular approach with test procedures developed and a portable DeltaV system used to test field devices and fieldbus segments within the PAMs. Once delivered to the plant site, it was much faster to hook up fully tested segments than to individually terminate and retest devices as had to be done on their analog-based projects.

The project team followed elements of the Construction Industry Institute (CII) PepC model. The paper describes this model:

In the new model procurement transactions for the most critical elements of the project (indicated by capital P) happen first and to a large extent define the next step, the main body of the engineering effort for the rest of the project (Capital E). This is followed by procurement of the materials for the rest of the project (small p), followed by the actual construction (capital C).

This model helped Alcan take advantage of the expertise of the suppliers involved in the project and aligned with their globally distributed engineering and procurement practices. It also supported their modular approach and the use of PAMs.

As with most every bus-based project, they documented savings in cabinet space, installation and commissioning. The real value was in the accelerated project timeline. In five fiscal quarters, 95% of the engineering, 76% of the PAM fabrication, and 54% of the on-site construction was completed. Alcan was able to meet their aggressive project schedules and get production on-line sooner.

Update: Welcome readers of Carl Henning's PTO PROFIblog. I'm not sure about the "voice of reason" part, but like Carl, I certainly agree that the benefits from the digital bus technologies outweigh the change in status quo from the analog world.

Read the Crossing the Chasm article to which Carl refers and judge for yourself. Feel free to let me know what you think.