November 13, 2017

What Causes Damage to pH Sensor Glass Electrodes?

by Marc Mason, business development manager, liquid analysis, Emerson Automation Solutions

Hi and welcome. pH sensors are a small thing that can have a huge impact on the smooth operation of your plant. When they’re operating correctly, you barely notice them. If they aren’t working well, they can shut you down. Various factors can cause damage to pH sensor glass electrodes – the process, temperature, sodium error, caustic, and hydrofluoric acid (HF).

  • The Process: A glass pH electrode consists of an inert glass tube with a pH sensitive glass tip – either hemispherical (bulb) or flat in shape. The tip contains a fill solution with a known pH, and it is the influence of this solution on the inside of the glass tip versus the influence of the process solution on the outside that gives rise to its millivolt potential. Ideally, the pH electrode will have a slope (response) of -59.16 mV/pH, at 25C, but in practice, a new electrode may only have a slope of -57 to -58 mV/pH. As the electrode ages, its slope decreases.
  • Temperature: In addition to changing millivolt output of the pH electrode, elevated temperatures accelerate the aging of the electrode. Extremely high or low temperatures can alternatively boil the fill solution or freeze it, causing the electrode tip to break or crack. Elevated temperatures can also affect the interior and exterior of the pH electrode differently, giving rise to asymmetry potential, which shifts the zero point of the pH electrode and changes its temperature behavior, thus leading to temperature compensation errors.
  • Sodium Error: More correctly called alkali ion error, sodium ion error occurs at high pH, where hydrogen ion concentration is very low in comparison to sodium ion concentration. The sodium ion concentration can be so high relative to hydrogen ion concentration that the electrode begins to respond to the sodium ion. This results in a reading that is lower than the actual pH. Depending on the pH glass formulation, this can occur as low as 10 pH. Where accurate high pH readings are required, the upper pH limit of the pH electrode should be checked and a specially formulated, high pH electrode used if necessary. Compared to sodium, lithium ions will produce a larger error, while the effect of potassium ions is negligible.
  • Caustic Components Attacking pH Electrodes: As noted earlier, high concentrations of hydroxyl ions shorten the life of pH electrodes. Solutions that approach 14 pH (equivalent to 4% caustic soda) can destroy a pH electrode in a matter of hours. There is nothing that can be done to prevent this, short of simply avoiding pH measurements in these solutions and using conductivity instead.
  • Hydrofluoric Acid (HF): HF also dissolves pH glass, but there are pH glass formulations designed to resist destruction by HF which, when used within their limits, can give satisfactory electrode life. It is important to note that, while only HF attacks glass and not the fluoride ion (F-), hydrofluoric acid is a weak acid. Therefore, a solution can contain a relatively high concentration of fluoride ion at a high pH and do no damage to the electrode. But if the pH of the solution decreases, the fluoride ion will combine with hydrogen ion to form HF, which will damage the electrode. So, it is important to look at both pH and HF concentration to determine the impact on pH glass.​​​​​​​​​​​​​​​​​​

What kinds of problems have you encountered with your pH sensor glass electrodes?

October 26, 2017

Detecting Hazardous Gas Leaks Is a Complicated Problem — Learn How to Solve It

By Edward Naranjo, director of product management,  Rosemount flame & gas detection, Emerson Automation Solutions

Every industrial plant has extreme safety requirements, particularly if combustible gases are present. But selecting gas detection technology isn’t a straightforward issue. There are many different types of gas detectors, each with their own advantages and disadvantages that make them ideal for certain types of gas, but inappropriate for others that exist in the same plant. Anyone concerned with gas safety needs to know the basics of how to select and combine gas detectors for their specific installation. I recently had an opportunity to write an article for Chemical Processing that does just that – walks you through the selection process for gas detection systems. Here is a segment that introduces the challenge:

As shown in the selection decision tree (shown to the right), catalytic and infrared (IR) technologies can detect combustible gases. Of the two techniques, only the optical method lends itself well for point and area monitoring. Choose IR devices for detecting a single type of hydrocarbon or simple mixtures. Because they are unaffected by oxygen levels, such detectors are ideal for anaerobic processes, operations with high concentrations of corrosive agents, and areas with constant background of combustible gases. On the other hand, catalytic gas detectors are a better choice for monitoring hydrogen or hydrocarbon mixtures. Because catalytic detectors require oxygen gas concentrations in excess of 10% by volume to operate, they only suit situations where oxygen always is present. Moreover, catalytic gas detectors perform best in applications where the target gas normally is absent.

For monitoring toxic gas leaks in congested spaces, electrochemical and solid-state gas detectors are the instruments of choice. Use electrochemical detectors in applications where the target gas is not normally present and in environments with relative humidity (RH) above 15%. By contrast, solid-state detectors should be used for extreme high temperatures or low humidity applications or where ambient conditions are stable. Oxygen deficiency is best monitored using electrochemical gas detectors sited near the breathing zone. As for open or uncongested spaces, open-path near infrared or ultraviolet detectors offer the widest coverage per device.

Hazardous material releases can take many forms. For pressurized gas releases, choose ultrasonic gas leak detectors to provide the fastest response to a leak. They excel at detection in open, well-ventilated areas where other detection methods may not be wholly effective. For pressurized liquid releases, select air particle monitors.

Integration of appropriate technologies is essential to meeting each plant’s unique requirements. Which gas detection types should you use in your plant?

For a more in-depth analysis of the pros and cons of gas detection technologies, click HERE.

October 17, 2017

The Right Gas Chromatograph for the Job

By Bonnie Crossland, Product Marketing Manager – Gas Chromatographs, Emerson Automation Solutions

Balancing the right level of gas chromatograph (GC) performance and cost for individual applications and locations within a plant or installation is key for many operators. Increased pressure to optimize processes is driving an increased demand for accurate and timely composition analysis for use in process control and product quality assurance. To continue to meet these demands, Emerson’s Rosemount 1500XA process gas chromatograph adds new enhancements to provide faster compositional feedback and complete, high-resolution analysis, helping operators optimize product specifications and maximize throughput.

Rosemount™ 1500XA Process Gas Chromatograph

The Rosemount™ 1500XA process gas chromatograph is designed for refining, petrochemical, power, and environmental applications where selected components in gaseous or liquid streams must be precisely monitored on a continuous basis. The recent enhancements to the 1500XA enable parallel chromatography, offering oven capacity for up to eight chromatograph valves and four detectors, two of which can be flame detectors. Depending on the application, the 1500XA can include flame ionization or flame photometric detectors for measurement of compounds in the parts-per-billion ranges, or thermal conductivity detectors (TCD) capable of handling applications with parts-per-million measurement requirements.

The 1500XA, like the entire Emerson GC family, is characterized by ease-of-use, ruggedness, and reliability. Emerson is currently the only online GC supplier to offer a lifetime warranty on chromatograph valves. The valves are rated for more than five million operations before repair, which involves simply replacing the diaphragms and can be done easily on-site.

With its numerous valves and detectors, the 1500XA can take a complex analysis application and break it down into smaller, simpler analysis blocks. These blocks are then run in parallel, reducing analysis time and providing faster, easier maintenance and troubleshooting, as well as straightforward data analysis. A complex analysis that may have previously taken 20 minutes may now only take 10 minutes, allowing quicker response to process changes. The 1500XA’s concurrent analysis can be used to reduce the time between analyses by running them at offset times. This can increase the number of analyses within a set time period.

Emerson’s MON2020 software allows the 1500XA to operate completely unattended while making analyzer configuration, maintenance, and data collection easy, either locally or remotely. With intuitive dropdown menus and fill-in-the-blank tables, even new users can quickly navigate through the software.

Since many users are looking for cost-effective and reliable GC solutions, the 1500XA with parallel chromatography and concurrent analysis capabilities more than fulfills that need. When combined with the 370XA and 700XA gas chromatographs, the 1500XA rounds out the widest single selection of gas chromatographs on the market. This makes the Emerson GC family flexible, and reduces costs for integrators and users alike. Used in a wide range of industries, the Emerson GC line allows users to get precisely the performance they require in each location and application while maintaining the same easy-to-use interfaces, the unique software capabilities, and common maintenance requirements.

If you have any questions, comment HERE. Or, to learn more about the right GC for the job, visit

September 19, 2017

3 Steps to Monitoring Critical Electrical Assets – Free White Paper

By Jonathan Murray, Director of Products – IntelliSAW, Emerson Automation Solutions

I’d like to talk about a significant issue in the power industry. Electric utilities strive to improve reliability in the face of challenges such as fewer operators, aging assets and increased cycling. An electrical power critical asset (switchgear, transformers, bus ducts, etc.) failure can result in a forced power outage leading to lost production, environmental issues, personnel safety concerns, potential litigation, and repairing and/or replacing the damaged asset. All of this can result in critical risks and millions of dollars of associated costs.

The following table shows a simple view of the associated average potential revenue lost if a 500MW generator was down due to a forced outage.



To address these issues, asset maintenance is transitioning from traditional reactive and time-based activities to implementing a proactive strategy through continuous condition-based monitoring. Modern sensing technology makes it possible to continuously monitor the health of electrical power critical assets and inform plant personnel when, or even before, problems arise.

I’d like to offer you a white paper that describes the three steps for deploying condition-based monitoring on critical electrical power assets which will lead to a proactive – and eventually, predictive – maintenance strategy:

  1. Prioritize which assets should be monitored.
    Independent of the type of power plant, a typical electrical power delivery system includes assets such as generators, generator circuit breakers (GCBs), line disconnect switches, step-up and step-down transformers, segregated and non-segregated bus ducts, potential transformer cabinets, medium voltage switchgear, motors, and other equipment needed to support the transmission and distribution of power. Prioritizing which assets to monitor is key to success.
  1. Apply continuous condition-based monitoring.
    The 3 most common electrical asset failure modes include thermal breakdown, insulation breakdown, and air dielectric breakdown. Although manual inspections can be used to monitor less critical assets, continuous condition-based monitoring is the preferred alternative for assets which must be kept online at all times. Continuous condition-based monitoring systems are available with temperature, partial discharge (PD) and humidity-sensing capabilities.
  1. Analyze data and evaluate asset health.
    Once data is acquired and brought into a digital space where it can be analyzed, limits and alarms can be placed on data trends. This allows the delivery of actionable information to the maintenance and engineering team responsible for the assets.

The white paper will help you select the best monitoring and analysis approaches for your requirements. Please click HERE for your copy. And if you have any questions, please contact me at

September 12, 2017

New Surface Sensor Innovation Achieves Accurate Process Temperature Measurement Overcoming Challenges of Traditional Methods

by Ryan Leino, Emerson Automation Solutions, Rosemount Temperature Product Manager

As you know, temperature is the most commonly measured variable in the process industry. It’s often a critical factor in determining process efficiency and product quality. There are several ways to measure temperature in the process industry and each one has challenges. I’d like to tell you about a new type of surface sensor technology that can overcome some of these issues for you.

A thermowell and temperature sensor assembly is the most frequently used method of measuring a temperature internal to a process. A thermowell is a component of a temperature measurement point that acts as a protective barrier between the temperature sensor and process. It enables insertion of the temperature sensor into the process where it might not otherwise survive the harsh conditions present. The direct sensor immersion of thermowells into the process helps provide an accurate measurement, but introduces a possible leak point, which is a significant problem.

An alternative sensing method, surface temperature measurement, alleviates many of the pains associated with a thermowell installation as it does not require direct contact with the process. Since the measurement point is external to the process being measured, there is no threat of internal conditions physically damaging it or creating potential leak points. The need for wake frequency calculations and other complex design considerations are eliminated.

Although a traditional surface temperature measurement installation addresses many of these pains and challenges, in many cases it cannot match the measurement performance of a thermowell installation. If an internal process temperature measurement is required, a surface temperature measurement is often not capable of providing an accurate or repeatable representation of an internal measurement.

There are many factors that can impact a traditional surface temperature measurement reading. This makes it difficult to use as a simple point of inference when determining the temperature of the associated internal process. However, by implementing an algorithm with an understanding of the thermal conductive properties of the temperature measurement assembly and corresponding piping or vessel, a surface temperature sensor solution can be utilized to accurately calculate internal process temperature. This unique technology works by measuring the pipe surface temperature and ambient temperature, and combining this information with an understanding of the thermal conductivity properties of the installation and process piping.

In order to understand the unique design of this surface temperature measurement capability which Emerson calls Rosemount X-well™ technology, please access this interesting white paper.

Rosemount X-well Technology offers accurate process temperature measurement without requiring any intrusions or penetrations into the process, eliminating possible leak points, and allowing quicker and easier installation, along with simplified long-term maintenance. Users do not have to design, size, or maintain thermowells. Wake frequency calculations are eliminated, as well as time spent determining material compatibility, the right insertion length, and the necessary profile.

With this innovation, users can also add temperature measurement points without having to shut down a process. It can be installed with a standard pipe clamp procedure and ordinary hand tools, and does not require a skilled contractor.

The surface measurement innovation works best in steady state applications, including the majority of pipe processes –

  • Pipeline monitoring
  • Small line size applications
  • Retrofit projects that need new points
  • Pipeline requiring frequent cleaning
  • High velocities
  • Slurries and heavy particulate fluids
  • Clean-In-Place (CIP) processes
  • High viscosity fluids
  • Harsh processes requiring exotic materials

In the following industries –

  • Oil and gas
  • Chemical
  • Refining
  • Life sciences
  • Metals and mining
  • Pulp and paper

If you have any questions, or if you’ve encountered applications where surface temperature measurement could be effective, please contact me at

And don’t forget to access your free white paper.