Thinking Critically in Process Troubleshooting

process troubleshooting

In past blogs, I’ve talked about reactive and proactive process troubleshooting. Reactive troubleshooting requires quick action to look at mechanical issues, upstream and downstream equipment, and operational procedures.  In proactive troubleshooting, we ask probing questions and walk around the plant to uncover potential problems and offer solutions.  

Dirk Willard, Contributing Editor of Chemical Processing, in his recent article “Read and Think Critically” offered more to think about on this subject. 

Dirk used an example of trying to write a debottling report and discovering several missteps:

  • The product manual was poorly written
  • The plant engineer had not identified what was missing from the manual and what he didn’t understand
  • No logic was applied to decide who would know best how to run the equipment — “the engineer who built it or the process expert who operates it”
  • The engineer could have paid more attention to the section that was more detailed on the topic at hand.

Ultimately, what was missing? Critical thinking! He called for “questioning the value of information, its relevance and validity, the agenda of the source and, most importantly, the logic on which the data are based.”  

process troubleshooting
Photo by Bernal Saborio G. (berkuspic) on Foter.com / CC BY-SA

He offered real world examples of critical review, “identifying what’s being done, how it’s done, why it’s done, and who’s doing it” with a paper mill selecting a close-coupled water pump without considering all angles of the decision.

Take a Critical Approach to Process Troubleshooting

I bet you can easily add your own examples. For instance, there always seems to be a question about instrument and compressed air for the process. The process design for valve actuation has one pressure, but the operators know that in normal operation there is high demand. So the instrument air pressure drops and the valve actuates more slowly. Slow actuation results in lower production. Thus, we need to keep in mind the actual conditions versus the design conditions.  

As for compressed air, it used to be “free” at the plant. Not any more. Every plant now considers this a cost of operation. Once again, operators know that during high demand, the air pressure drops. But the process designers may not have considered this. Next time, design in a compressed air tank so that your process can meet the requirements.  

To do your best work, keep thinking, keep reading, and keep asking questions. If you have an area of expertise, let me know; I am always learning and maybe I can use your skills. I’m always interested in learning more about process troubleshooting.

Real World Examples of Particle and Cake Formation Influences

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Process engineers might love it if all of the filtration technology solutions they developed ran flawlessly, at all times, under all conditions. But, this isn’t realistic. Something might go wrong with the filtration mechanism itself. A change in the environment — upstream or downstream — could cause problems with particle or cake formation. Even the smallest shift in the operation process or procedure can prompt the dreaded phone call to the engineer: “the filtration system isn’t working.”

In my work at BHS-Sonthofen Inc., I’ve seen filtration technology impacted by particles and cake formation that weren’t predicted in designing the solid-liquid separation solutions. 

Particle Sizes Changes from Lab to Production

The existing process was a batch crystallizer operating at 0 – 5 degrees C with 13- 20% solids  to a batch vacuum filtration operation. The filter was designed for a five inch cake height. The objective of the process optimization was to move to a continuous process of continuous reaction to continuous filtration, cake washing and drying.

The BHS rotary pressure filter was installed for continuous pressure filtration.  What did the client find out?  Only the particle size has changed from lab to production!  As you can imagine, this was not a small change.

cake formation

Going back to the drawing board and testing processes again, we made the following changes to the filtration system:  new filter media, increased cloth wash pressure with a new solvent and finally a reduced cake thickness.  Yes, this trouble shooting required about 6 months of work, but problem solved!

Troubleshooting Filtration Technology

In another instance with grey water treatment units, a clarification application for the purge water treatment unit (PWTU) was installed and started up for a year of successful running. Then, inexplicably, the performance changed and the filter began plugging quickly during cycles.

cake formation

 

Troubleshooting the system we had to re-examine the filtration system under different conditions:

  • Clarifier overflow with no coagulant / no flocculants 
  • Clarifier overflow with only coagulant / no flocculants
  • Clarifier overflow with both coagulant and flocculants
  • Clarifier overflow with only flocculants / no coagulant

Taking a holistic approach to the system, we were able to determine chemical changes caused the larger particles to settle out. Only the smaller particles were reaching the filtration system, which was blinding the filter media.  By eliminating the flocculants  and reducing coagulant usage (even though this was better for the client, and not necessarily BHS as the chemical supplier, we were able to improve filtration rates and once again offer a consistent PSD.

Ultimately, with the right approach to troubleshooting, and by embracing the idea that we do on a daily basis is an art coupled with science, we can enjoy a strong sense of satisfaction when we get that filtration technology up and running again.

This blog is based on a presentation I made to the  8th World Congress on Particle Technology. View the presentation slides in full!

Become a Filtration Tech Troubleshooting Expert

filtration tech troubleshooting
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Recently I addressed the too-familiar telephone call that the “filtration system is not working.” When the call comes in — and so seldom during regular business hours —  filtration tech experts have to react quickly to solve the problem.

Now, the question is how do you avoid getting these types of calls in the first place?  Well, you can turn off your cell phone, but maybe isn’t the best idea.  Instead, the better approach is proactive troubleshooting. 

Proactive Filtration Tech Troubleshooting Ideas

As you know, I’m a big fan of Sherlock Holmes. The great sleuth talks about checklists and separating the consequential from the inconsequential facts. This systematic approach works perfectly for troubleshooting — take a systematic approach with a comprehensive set of questions and logic charts.  After all, we all know that most problems, maybe 90% or more, that arise with the filtration system have been experienced before.  

A different approach involves “walking around” or random analysis.  Sherlock and Dr. Watson are also very good at this. They see what’s not there to uncover the facts. This observation approach can help with the unique problems. I’ve written before also about the Japanese approach of “Genchi Genbutsu,” which further explains this option.

Becoming an Expert Troubleshooter

Becoming an Expert Troubleshooter, though, requires developing several “soft” skills over and above your technical expertise and great depth of knowledge in many areas. These characteristics include:

  • Critical thinking: Ask probing questions to everyone at the plant from operators, mechanics, to process and R&D engineers to encourage conversations
  • Excellent communication: Listen to the answers and ask the same questions in a different way or use the answers to formulate different questions and keep an open mind.
  • Empathy: Try to understand potential frustrations.
  • Motivational: Praise everyone who provided you with the answers, ideas, etc. to inspire the plant
  • Ability to teach: Look for teaching moments so problem-solving permeates through the organization.

In the future of work, we’re going to be looking more at talents in addition to expertise. Cultivate your troubleshooting chops. Keep walking around and keep learning. In the meantime, let me know your area of expertise; maybe I can use your skills.

Troubleshooting When the Filtration System is Not Working

 

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These are five dreaded words that no engineer wants to hear on a Saturday night or Sunday morning: “The filtration system is not working.” Of course, we never seem to get this call at 10 in the morning on a work day!

No matter the time of day, let’s not panic, take a deep breath and begin the analysis.  

There are normally three main areas that must be examined when you learn the filtration system is not working:

  1. The filter itself for mechanical reasons
  2. The equipment around the filter is not working
  3. The filter operational procedures are not correct.  

To fully understand the problem, it’s necessary to separate the symptoms from the causes. So, let’s examine each of these groups in more detail.

Troubleshooting Filter Problems

The first thing that should be checked is the filter itself. There could be a failure of the equipment mechanics such an internal components, seals, etc. Many of these issues will be described normally in the preventative maintenance section of the filter’s O & M manual. 

Second, keeping in mind, the filtration system is part of the entire process it’s important to examine the upstream and downstream equipment. For example, you might check:

  • Are the reactors performing correctly in terms of agitation, temperature control, etc. in order to produce the specified crystals?  
  • Are the precoat and body feed systems in tune for mixing, feeding, flow rates, solids loading, etc.?  
  • Are the valves and instruments operating correctly and reading the correct variables (calibrations), etc.?  

Next, take a look at the pumps that feed the slurry and washing liquids as well as the compressors the feed the gas streams for drying and cake discharge.  The pumps must produce the required pressure, flow rates, etc.  The compressors must also produce a certain gas flow at a specific pressure for a certain amount of time.  Are their interlocks in the control system or a control communication problem that are not being recognized that are causing the filter problem.  Finally, if flocculants and chemicals are being used, have these changed?  

Process Engineering Problems? 

The last place to look is the process or operational procedures. These could be responsible for the filtration problems.  For example, the particle size distribution may have changed, the amount of solids in the slurry may have changed, the cake compressibility may have changed, etc.  In terms of the operation, has the filtration pressure changed, timers changes, speed changed, etc.?  Finally, determine whether or not a process parameter has changed.  

Trouble shooting is not easy, but solving the problem brings a great sense of satisfaction. 

Let me know some of your troubleshooting horror stories! I’d love to share some in a future blog. Together, we can make it easier to handle the situation next time we hear those five dreaded words.  

filtration system
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