March 2019 – Expert Process Control

March 30, 2019June 5, 2022

“Why” Is The Most Interesting Question

Every day we ask and answer a multitude of questions. They all have one of the W’s at their core (Who, What, Why, Where, and When). My kids know which one of these is the most interesting and valuable. WHY. Why this? Why that? Why? Why? Why? As annoying as it is to answer a 10x string of “Why Daddy?” I understand the need to know.

You can’t plan and organize your life if you don’t understand why things happen. Why people react the way they do. Why systems work and why they might fail. In order to thrive and understand their world, kids need to know why things are the way they are. We can translate this to ourselves personally and to the process industry. Below are some of the important “Why” questions that I ask myself and the associated answers (as of today. Always pending change.) Maybe you will have different answers or better questions. If you do, please add them to the comments.

Why seek outside council?

I fancy myself a Jack of All Trades – Master of Some. We are all good at some things and not others. There is no way to become proficient at absolutely every skill and well versed in every discipline. If you can learn to accept that your time is better spent on the things you are truly good at or truly enjoy, you will come to the conclusion that delegating that expertise to others is a good thing. That way everyone can be as productive as possible and things run smoothly. When designing a plant or process, seek the help of those who work on the component systems regularly and ask them for advice. For that matter, ask your operators and maintenance people how they would like to interact and maintain the systems before implementing changes. An operator that has been running a portion of the plant for 20 years is an expert on running the plant. Even if changes are necessary, their input is valuable and will help avoid pitfalls later.

Why work to optimize a process?

Sometimes good enough is good enough. Sometimes it is not. It takes time to examine a system and determine how efficient it is. Once you know where you are currently, you can evaluate whether or not you could improve. If you can improve, how much time and money will it take to get where you want? If your time and money investment will pay for itself and more, then go for it! Improve that process!

Why is this not working?

This is one of my favorites. Whether debugging code, fixing the car, or figuring out why my process can no longer maintain it’s temperature setpoint identifying a problem and taking the steps to troubleshoot is so much fun. Being able to logically step through a process and get the answer is very gratifying. Getting the answer to this “Why” is the best.

Why did this fail?

This one is similar to the above, but I see this as a root cause analysis rather than a system fix. You may fix the problem over and over, but it keeps breaking. That is a waste of time and resources. Why not determine the root cause of the failure and fix that and prevent the failures from reoccurring? The answers to these “Whys” can have massive paybacks.

Why ask why?

I can’t help myself.

Why call me?

Call us because we can help. We love process control. We are experts in instrumentation, valves, analytical, and heat trace. You’re good at running your plant and we’re good at specifying and designing instrument and control systems. Leave a comment below if you made it this far.

March 12, 2019March 17, 2022

How To: Controlling Steam

Almost every process facility requires steam. It is used for heating, drying, power, etc. Steam is an excellent way to convey energy from one process to another. The heat and energy of the steam needs to be measured and controlled into the next stage of the process.

Steam flow and pressure is controlled with an orifice. You can use a fixed orifice, a line sensed pressure regulator, or a full control valve. There is no adjustment with an orifice. A regulator is given a fixed output setpoint, but is not adjustable by the control system. A control valve can vary the orifice size according to the output of the control system which has measured the flow, pressure, and/or temperature from process instrumentation and sensors.

When controlling system, it is always done with an orifice which creates a pressure drop. The higher the flow rate and pressure drop, the noisier the valve will be. There are two problems with noise. First is the loud environment and potential damage to your hearing. The second is that noise is vibration and that vibration can damage the physical components of the valve. 85dB or lower is the ideal noise level. You can avoid high noise by taking the pressure down in small increments rather than one big drop. This can be accomplished within a control valve or through a fixed drop low decibel cassette inline with the control valve.

There is a way to make almost every steam control application low noise and highly reliable. You must select the proper method of controlling and regulating the steam with the proper number of pressure drops. For help with your next steam application, please contact us.

March 8, 2019March 17, 2022

Methods of Measuring Solids Flow

If you are like me, you started your adventure into process measurement with measuring liquid and gas flows, temperatures, and pressures. I got very good at designing systems using the proper instrumentation to measure and control these. However, I didn’t pay much attention to solids measurement. This has since changed. I work with solids control in a large percentage of my projects now. I have come to realize that the expertise gained in liquid control does not always directly translate to solids measurement.

There are 5 main ways to measure solids flow. They are as follows:

Belt speed measurement
Conveyor motor amp draw
Belt Scale Conveyor
Impact Mass Flow
Radiometric Absorption Conveyor

Belt speed measurement is the simplest method, but it is also the most inaccurate. This method just measures the linear speed of your conveyor or screw and estimates the mass of the dry product it conveys per minute. Sometimes this is ok, but it assumes a steady feed rate and steady product density. This method shouldn’t be used for control or inventory tracking.

Conveyor motor amp draw measurement assumes that increased amps is an increase in mass being conveyed. This is a better idea than purely monitoring the conveyor’s speed, but it too has massive drawbacks. It assumes that the conveyor itself is steady state mechanically. Does your conveyor have a consistent friction at all speeds and temperatures? Probably not. Do mechanical systems wear over time causing “calibration” drift? Probably. Does the amp increase vary linearly with mass increase? Probably not. I personally don’t like these systems as they don’t work very well and give a false sense of having measured something well, when in fact you have not.

Belt scale conveyors are the gold standard in mass flow accuracy. They consist of load cells on independently supported rollers under a conveyor belt. There can be from one to 4 of these roller/load cells in series. As solid product rolls over these load cells, it is weighed. This weight and an output from a speed sensor combine to give you an extremely accurate mass flow. These systems, depending on the number of load cells, can give a mass flow reading of up to +/-0.25%. These systems aren’t very expensive in the scheme of things, but they do require a lot of straight space in your belt to install and work properly. They also rely on moving parts and are exposed to the dust from the solids which will require maintenance and periodic recalibration with provided reference weights. Overall, these are the most accurate systems you can get.

Impact mass flowmeters are the next most accurate solids flow measurement device. These require that product be lifted above this “box” and dropped through it down to a bin or secondary conveyor. This “box” consists of a top entry chute and a bottom outlet chute. In the middle of this box is a angled plate attached to a load cell. As solids fall into the box, they strike the load cell plate and then fall off and out of the box. The load cell sensor assembly is sensitive enough to track the rate and mass of the solids going through it and gives you a reliable +/-0.75 to 1.00 percent accuracy spec. These require less maintenance than the belt scales, but still need cleaned periodically as the sensor is exposed to dust and the plate is open to wear from the impact of potentially abrasive solids. These are a great option if you have the vertical space to fit it into your process.

Lastly is relatively unknown method of radiometric absorption. This method uses a radio isotope to emit gamma rays at a known and regular rate. The conveyor and the material being conveyed absorb these gamma rays. The conveyor never changes density, so it absorbs the same amount of gamma all the time. The change in absorption over time is therefore directly related to the change in product mass flow. The levels of gamma rays emitted are so low as to make these safe for install in the field. In fact, (only with Ronan) no special certificate or government regulation applies to most of their installs. These systems do not make contact with the product and are installed outside of the conveyor. This means they require no maintenance as dust and abrasion are not a factor. They have a pretty good accuracy rating of +/-1-2% in most applications.

Now that you know the main ways to measure solids mass flow, it’s time to include this in your plant’s mass balance calculations and inventory controls if you haven’t already. If you have questions about how to implement this in your process or how to correct an install this isn’t living up to your expectations please contact us.