Analytic Expert

Greetings! Pete Anson here. I’m a Senior Product Manager here at Emerson Process Management and responsible for all liquid analytical instrumentation. A customer recently came to me asking how he could use the temperature data from an installed Rosemount 644 temperature transmitter for compensation of conductivity on a boiler feed water application. The customer really trusts the reliability and accuracy of the Rosemount transmitter and wants to integrate the output to support a liquid analytical measurement.  

Nice concept but the only thing that makes it practical is if you have the ability to receive and algorithmically integrate the temperature data for compensation of the conductivity measurement.    

Fortunately, Rosemount Analytical does have a solution for this “out-of-the-box” scenario. Using the Model 1056 installed with a current input signal board, any 4-20mA signal from any device can be received, integrated as compensation data for conductivity, and displayed locally. The user simply selects the programming option to use the 4-20mA data as temperature for conductivity measurement with the installed Model 400 Endurance line contacting conductivity sensor. The input of temperature data from the 644 transmitter is received at 1/second to provide immediate determination of conductivity, which is highly affected by temperature.

Further, the Model 1056 can power the transmitter (up to 36 volts DC) to avoid additional DC loop power leads of the temperature device. The temperature data and the measured conductivity can be output to a PLC or DCS if wired to the 4-20mA output. HART configurations of Model 1056 can report all live variables and diagnostics associated with the conductivity loop to the DCS including the temperature data converted from degrees to 4-20mA readings.

Using the versatile 4-20mA input capability of the Model 1056, many other inputs can be accepted and displayed.  Variables such as atmospheric pressure can be input to compensate dissolved oxygen measurement for partial pressure.  And, almost any type of measurement can be input and displayed for the convenience of field technicians and I&E. This is especially useful in the field if the 4-20mA device does not have a local display, aka “blind transmitter.”  

The Model 1056 offers an innovative solution for this unconventional but reasonable request.  The solution described using the Model 1056 with the current input board will elevate the customer’s confidence in the process measurement, allow real-time local display and reporting of live temperature readings from the adjacent transmitter, and potentially save wiring of leads to power the temperature transmitter.

Please feel free to check out our Model 1056 page for more information, including product data, features and benefits.

Doug Simmers here again. And this week, I’d like to talk about one of the most pervasive analytical applications — the measurement of oxygen in combustion flue gases.  A burner is inherently an inhospitable environment, so measuring the flue gas composition flowing out of this violent process has come to be a good way of establishing the optimum fuel/air ratio for best combustion efficiency. It is also beneficial in minimizing pollutants such as NOx, and CO2. As climate change concerns increase, carbon dioxide’s status is changing from that of a natural result of combustion to one of a new polluting gas.

Some of the earliest measurements of combustion gases were:

• The Orsat – a lab technique that was taken out to the field.  It was not a continuous measurement, and there was no signal to send to the control room.
• Another type of measurement uses electrochemical cells that generate a small electrical signal when O₂ is reacted with a specific chemical in the cell, but service in continuous operation usually results in significant drift of the O₂ reading over time.
• Paramagnetic analyzers use the magnetic properties of Oxygen to get a reading of O₂, but usually require that the flue gases be cleaned of ash and condensing moisture prior to measuring.

Flue gas analysis took a decided step change (read improvement) with the development of the zirconium oxide (ZrO₂) sensing technology.  This was developed as a technology transfer from the Apollo moon program in the early 1970’s.  The ZrO₂ technology had significant advantages over past measuring techniques. 

1. The sensor is heated, so it could be placed onto the end of a probe, and inserted right into the hot flue gas stream. 
2. The sensor works on the partial pressure difference of O₂ on the reference side of the cell and that on the process side. 
3. The cell is non-depleting, and lasts for many years.
4. The sensing cell is like a thermocouple in that it develops it’s own millivolt signal, or electromotive force (emf). 
5. Further, this emf is inverse, and logarithmic.  The raw millivolt signal gets stronger at the typical O₂ levels found in flue gases (2-5% O₂).   This is all represented mathematically in the Nernst equation, EMF = KT log10 (P1/P2) + C.

We have a good description of how it works in this PowerPoint. If you’d rather have a copy e-mailed to you, please just let me know and we’ll send you one.

The ZrO₂ technology spread quickly throughout industry, and into automotive applications.  Every car manufactured since the late 1980’s has one or more of these O₂ sensors in the exhaust, and we will soon be seeing them applied to the small engines used in lawn mowers, chain saws, etc. Little wonder this technology is still the standard for industries that have a smoke stack in the process.

How much money can you save by controlling your fuel/air ratio to the optimum level?

Tune into my next post to find out.

Future Blog Subjects

History of combustion flue gas analysis

Operators are the real customer

Rethinking Hazardous areas

Furnace diagnostics

Deep dives into how analyzers work

G’day, my name is Shane Hale and this is my first effort at writing on our shiny new blog.  When thinking of a subject matter for my post, it seemed logical to talk about the first component of any analytical system, the sample handling system.  As the product marketing manager for natural gas, I deal mostly with gas chromatographs on pipeline and natural gas processing applications; however, the principles that I talk about here are applicable to any analyzer that extracts the sample from the process lines.

When I travel around talking to people about their applications, I always hear two things – “Our gas is always clean and dry,” and “We don’t need heat trace, it never gets that cold here.”  Unfortunately, the cynic in me knows that these two statements are never true 24/7 over the lifetime of the gas chromatograph (GC).  It is on that rare occasion that “bad gas” does enter the system that the sample handling system steps up and does its job, or fails and results in inaccurate measurement and/or equipment failure.

The role of the sample handling system is to extract a representative sample from the line, remove gas and liquid contaminants, reduce the pressure, and deliver the sample to the analyzer in a timely manner.  When the sample is in the liquid phase, the sample handling system takes on the added role of vaporizing the sample as well.  All of this should be done while also maintaining the sample composition.  It doesn’t matter how good the analyzer is if the sample it’s analyzing is different from the composition that is inside the pipe – the results will be wrong.

When designing the sample system, a lot of people make the mistake of designing to the “expected” or “normal” composition and process conditions.  However, it is when the unexpected happens that you need to ensure the best measurement so that you can make operating decisions to rectify the situation. For pipelines, you may be shutting in a supplier for high hydrocarbon dew point or high CO₂.  In processing plants, you need accurate compositions to regain control of the process.  When these events occur, the sample handling system should be designed to handle the unexpected in order to ensure the analyzer receives a representative sample while not causing contamination of the analyzer internals.

When we sell a natural gas GC, we typically sell an integral sample handling system that uses a 2 micron filter, and a moisture membrane filter/shut-off.  However, this is the last line of defense.  By the time a “bad” sample (dirty or wet) has made it to the sample system at the GC, the rest of the sample system has been contaminated.  The best solution is to also incorporate solids and liquids filtration at the sample point, and to ensure the sample is always kept well above the hydrocarbon dew point by using heat trace which will maintain the sample well above the original sample temperature.  Sample probes that incorporate filters at the sample tip, or locally mounted systems, are both excellent steps in ensuring the results you receive truly represent what is in the process.

So, even though your sample may always be “clean and dry,” and your weather is always warm, it’s best to design for that day when it is not.

Hi — my name’s Dave Anderson. This week I’m blogging about pain points in pH and, from an analytical perspective, there are a number of them within a biopharmaceutical plant where effective analytical monitoring can improve operations. First and foremost, the Process Analytical Technology (PAT) Initiative has opened the door to take traditional off-line, laboratory measurements and put those methodologies in the process or at the process. The customers benefit through real time measurements of key parameters. By automating the process, customers can capture the data as well as document the calibration logs electronically.

One particular pain point is with pH control in bioreactors. Customers are asking for tighter pH control, some as tight as +/- .01 pH units. One customer mentioned if they can improve pH tolerances by 10%, they estimate savings of $250,000 per batch.  The problem with maintaining tight pH measurement is how the sensors are used in the process. Prior to a batch, the pH sensors are calibrated with pH buffers to ensure the sensors will accurately respond to real process changes. After the sensors are calibrated, those chemicals must be cleaned from the sensor. The typical cleaning process is to steam sterilize the vessel at a minimum of 121º C for 30 minutes.  Some processes require steam cleaning at 145º C for 60 minutes.  The pH-sensitive glass will become stressed from the exposure to high temperatures and subsequent cooling. This stress can result in significant offsets in the pH readings or critical failures in the form of cracked glass. Because of these concerns, redundant sensors are often utilized.

To optimize plant productivity, there are new pH sensors with Accuglass^® technology that can withstand the thermal stresses from the cleaning process. For example, comparison testing with competitive sensors proved the Model 3800 steam sterilizable pH sensor will withstand more steam-in-place cycles than any sensor on the market.

Additionally, today’s transmitters can deliver real-time diagnostics at the operator’s work station. Monitoring one pH loop locally at a transmitter is simple, but when operators have hundreds to thousands of I/O points with different measuring technologies to manage, it can be overwhelming. Diagnostic information such as “glass impedance” and “zero offset” will update the operators whether a sensor has a critical failure or is beginning to drift. For those operators with less experience, there can be Embedded Help Menus that explain in detail what the conditions mean and appropriate actions to take. This is easy to access in AMS^® Suite by clicking and dragging the question mark over the field in question.

These two technologies allow plants to confidently automate pH measurement, greatly minimizing operator interface. When an operator needs to get involved, these tools allow them to make informed decisions with the assurance of accuracy and stability in the process.

Hello, my name is Doug Simmers, and I’m worldwide product manager for combustion flue gas analyzers at Rosemount Analytical. Although I’ve been involved with process instrumentation and control for 25 years, my initial experience came from marketing distributed control systems. This gave me a rich exposure to many different applications, from power plants to refineries, to pulp and paper mills to water and wastewater plants. To me, an analyzer was just another bubble on the piping and instrument diagram. An engineer would establish a control loop around this bubble, and –“done!” On to the next loop. On startups, however, I noticed that the analytical loops were frequently left in manual and no one could provide a clear answer as to why. Process engineers appeared to consider the measurements critical for the good control of the process. The control logic didn’t appear to be particularly challenging. Final control elements (usually fans and dampers) didn’t appear to be a problem.

Closer investigation uncovered an inherent mistrust of the analyzers themselves. As I moved away from the DCS world and got more deeply involved in analyzers, I came to understand that this mistrust was not always undeserved. Over the years, I’ve made up a list of the most common negative concerns made about process analyzers:

• “Analyzers drift too much”
• “Analyzers require too much maintenance”
• “Speed of response is too slow”
• “We put in redundant analyzers, and they never agree”

Every operator had his or her own horror story about a process upset caused by an analyzer that wasn’t working right. The stakes are high when controlling most processes, and instruments that cause upsets are not endured for long. As a class of instrument, analyzers are found to be abandoned in place more frequently than instruments taking physical measurements, like pressure, temperature, flow and level.

As I learned more about analyzer technology, I came to understand the challenges and principles that cause analytical measurements to be mistrusted:

• Analytical measurements are inherently more difficult than physical measurements, though very important to process optimization.
• Analyzers measure the actual composition of a process gas or liquid — not just its temperature or pressure.
• Analyzers drift because they are frequently in direct contact with the process. While physical measurements are often protected from the process (thermowells for thermocouples and isolation diaphragms for pressure transducers), analyzer sensing cells have to endure the temperature and acidity in process fluids.
• Maintenance is often high because some analyzing technologies such as infrared spectroscopy require sample conditioning systems that are more costly and maintenance intensive than the analyzers themselves. Sample conditioning systems also reduce the speed of response.
• There can be complex interferences — one component of a gas stream can affect the measurement of another component.
• Analyzers are more difficult to understand than most common process instruments

So it’s clear that analytical instruments are often mistrusted, but there are reasons for this mistrust that can be overcome by better understanding of how they work, and what to expect from them. For example, unlike many other measurements, most gas analyzers can be calibrated automatically on-line with the process running, with calibration gases sequenced to the sensors and adjustments made via microprocessors.

This will be an underlying theme of this blog — improving the understanding and the resulting confidence in combustion flue gas measurements.

Despite all of the problems (real or perceived), one thing is clear — a good analytical measurement provides direct indication of the process composition, which reduces process variability, improves efficiency,  maximizes throughput, and provides a great diagnostic of process equipment degradation failure.

Nothing optimizes a process better than a reliable analyzer!

Future Blog Subjects

• History of combustion flue gas analysis
• Operators are the real customer
• Rethinking hazardous areas
• Furnace diagnostics
• Deep dives into how analyzers work

Hello. My name is Dave Joseph and I’m industry manager for the chemical, pulp and paper, and metals and mining industries at Rosemount Analytical. I want to share some news about how you can improve pH sensor maintenance and make your life easier.

If you see someone carrying a plastic tray with small multicolored bottles of liquid at work, there’s a good chance they’re going off to work on pH sensors (unless you happen to be in a bar or a plane…).  The standard calibration for pH sensors is to immerse the sensor in two different buffers to prove that the sensor works and to calibrate the sensor’s response. This works great but may not be too convenient if the sensor is located where it’s really hot or wet or noisy or, well, you get the point. Our new smart sensors have a chip inside that stores all calibration data, which allows the sensor to come pre-calibrated from the factory. Subsequent calibrations (as needed) can be done in a lab or workshop and the sensor is easily moved from place to place since the cable connection is a VP quick disconnect. Pull sensors from the field, calibrate them in the lab, and return them to service on the next visit.

Smart sensors will be available on nearly all our pH models and will replace the preamplifier that is typically required to process the mV signal from the pH sensor. The latest analyzers, including models 1056, 1057 and 6081, are smart-aware, but the beauty of the smart design is backwards compatibility — other analyzers can use the smart sensors to measure pH just like before, but when connected to a newer analyzer, the additional smart features are activated.

Early adopters have liked the smart sensors so much that we offer a benchtop calibrator that incorporates a 1056 analyzer and has everything you need for periodic calibration of sensors.

Next time, I’ll talk about how the smart sensors help you manage sensor diagnostics and schedule periodic maintenance.

Oven Options 

New technologies in airless ovens offer a more flexible, cost-saving choice over traditional air-bath ovens. The airless oven enables the GCs to perform well in environments with changing temperatures. Air-bath ovens rely on plant or compressed air to heat the analytical oven to a constant and optimal temperature – which means a temperature above the dewpoint and optimized for component separation. Airless ovens don’t require expensive air sources, and consequently, consume less power. This means that the GC can be mounted closer to the sample point, reducing sample line run lengths, and ultimately, saving money, reducing the volume of sample required, and in installations requiring heated lines, reducing utility requirements. In fact, an airless oven can reduce overall operating costs by up to 70 percent. In addition, they take up less space than air baths. Reduced space and energy requirements make them well suited for a number of process applications. 

Shelter Options 

Analyzer shelters can be one of the most substantial expenses associated with your analytical solution. There are three choices – analyzer house, a three-sided shelter or sunshield, and a field-mounted gas chromatograph with no shelter. 

• Analyzer House — An analyzer house is ideal for plants in extremely hot or cold climates and where the safety and comfort of the employees is a key consideration. Complete analyzer houses are also the most costly option, however. In addition to an expensive enclosed structure, there are significant hidden costs associated with an analyzer house, including high shipping fees, extensive cabling and tray requirements, increased assembly and installation costs, high maintenance fees, more required spare parts, and high utility and power consumption. Because an analyzer house can potentially entrap hazardous gases, additional capital expenses, including hazardous area compliance, safety systems, and fire and gas detection systems are often required.
• Three-sided shelters or sunshields — Because they are designed with an open structure, three-sided shelters and sunshields have no risk of entrapment of hazardous gases, and as such, offer a lower cost solution by not requiring HVAC equipment, a safety system, or fire and gas detection systems. Also, shipping expenses are significantly less because a three-sided shelter weighs considerably less than an analyzer house. There will still be capital expenses associated with cabling and trays, assembly and installation, and maintenance and spare parts, but it will be lower than the capital expenses associated with an analyzer house.
• Field-mounted solution (no shelter) — Field-mounted gas chromatographs that offer a flameproof and weatherproof enclosure provide the greatest overall savings. There are no shelter-related expenses, in most cases, the only cabling that is required is the cabling that comes with the gas chromatograph, and shipping expenses are very low.

Regardless of what kind of analyzer shelter you select for your process application, one tip for reducing the total cost of ownership is to re-evaluate the upgrade path. Rather than replacing the entire analyzer house when a new chromatograph is necessary, you can instead install a new non-temperature-sensitive field-mountable gas chromatograph into your existing shelters. This substantially reduces costs and implementation expenses. 

The right analyzer is always unique to your application, but it can have a tremendous impact on capital expenses and long-term operating costs. By considering these options, you can greatly impact the bottom line.

Hi, my name is Jim Gray. I am the application manager at Rosemount Analytical in Irvine, California and now blogging about wireless for the Rosemount Analytical Group.

Purpose

The purpose of this blog is to discuss the application of liquid and gas analyzers and systems. It will also serve to introduce new approaches to these applications made possible by new developments in analyzer hardware and software.  It is hoped that we can begin a conversation that will provide you with new insights that will make it possible to apply analyzers more effectively, reliably, and at a lower installed cost.  Because we cover a large range of topics, the blog will not always be written by the same person as we want to include experts to comment on their own subjects. You will get to know all of us over time. We want to hear from you with comments and suggestions on what you would like us to cover.

Words on a Wireless Trend

Rosemount Analytical Vice President, John Wright, has advised me that one of the first places industrial and municipal plants are putting wireless analytical technology to work is for remote effluent monitoring. Being able to put pH and conductivity analyzers into the “no man’s land” beyond the fence without the need for wiring is a huge boon. I agree and in addition, since the analyzers are based on WirelessHART™, they send back a full complement of diagnostics, meaning plant managers can schedule maintenance only when it’s needed while assuring they stay in compliance. It’s a trend worth considering.

Wireless Story about Cost Savings

John Wright also told us about a customer who had an emergency when they accidentally cut a bunch of analytical wires with a backhoe. They discovered they could replace the whole installation with wireless for less than the cost of replacing the wires that had been destroyed. Now that is cost effective.