Joshua Ramos 11/05/2017
What is the difference between internal and external temperature compensation, and how can it affect you?In ultrasonic level instrumentation , a controller measures the time-of-flight of the sound wave produced by an ultrasonic transducer for the round trip between the transducer and the target (material level). The speed of sound is the distance travelled per unit time by a sound wave. In dry air at 68°F, the speed of sound is 1,129 ft/s....
Factors that contribute to the calculation of sound velocity are temperature and the medium it is traveling through such as air or a gas. To measure distance using time-of-flight, you have to know two things accurately:
- How long did the round trip take?
- How fast was the sound wave traveling?
So why is temperature compensation an important factor with ultrasonic level technology?
First, we must understand what occurs to the sound velocity with temperature. The hotter the air is, the faster the sound velocity becomes. The colder the air is, the slower the sound velocity.
Modern ultrasonic transducers have built in temperature sensors . You might also need an external temperature sensor as well. So, how do you choose whether to go with an internal or external temperature sensor? Let’s make one thing clear: whether it is internal or external sensor, they both compensate the speed of sound as the temperature changes.
Years ago, I had a conversation with someone who was using ultrasonic level transmitters to measure the level of corn, potato flakes and flour in a silo. His issue was that the units were not measuring accurately and the transmitters were reporting a lower level. He stated that he encountered these issues every year during the summer months. After visiting the site, we found that the transducers were on top of metal silos and exposed to the heat of the sun. As the day progressed, the temperature registered by the transducer increased more than the actual temperature in the vessel. This was a result of the transducer being in direct contact with sunlight.
It is a good practice to utilize a sun shield whenever instruments are in direct sunlight, and more so when the external heat source can influence a level measurement. The integral temperature sensor in the transducer is surrounded by the transducer housing and a potting compound. Due to this, it takes more time to heat or cool the integral temperature sensor to meet the actual temperature inside a vessel. In this case, the solution was to bypass the integral temperature sensor and use an auxiliary temperature sensor inside the vessel to detect the air temperature in the process.
This issue could have been resolved with a sun shield and thus, the integral temperature readings would have not been influenced by external factors.
Alternatively, you can use an auxiliary temperature sensor. The auxiliary temperature sensor is not an expensive solution, but it is also not as practical or economical as using a sun shield. An auxiliary temperature sensor requires a cable run from the controller to an available port on the vessel. The latter is not always ready available, which can lead to additional costs if a retrofit is needed.
If you have an application where faster temperature response is required, than an auxiliary temperature sensor is the preferred recommendation. The critical nature of the application may or may not require temperature compensation beyond the ultrasonic transducer capabilities.
Have you encountered inexplicable discrepancies in level monitoring that made you question what you are using to measure?
Rachael McGovern 04/05/2017
For the last 17 years, I’ve worked in level and weighing instrumentation as an Application Engineer. During that time, I have occasionally seen situations where a level sensor or a level transducer has been unreliable due to excessive condensation build-up on its face plate.
How do you know if your level transducer or sensor is not performing correctly?
Operators at most sites perform rotational checks often enough to be able to identify when their instrumentation isn’t performing correctly. When it comes to condensation issues, you’re going to be able to spot the problem pretty early on because your level instrument will either lose its level signal or start acting erratically when overwhelmed by too much condensation. The excess condensation will be apparent on the sensor itself. After your transmitter dries, the level device should start working again without issue. However, depending on the environment your instrumentation is located in, you may have dust or some powdery material that, when moistened or wet, cakes onto the transmitter and potentially causes monitoring issues.
Although it is nearly impossible to remove condensation in some environments, we have found some ways to mitigate or even avoid the adverse effects caused by condensation.
- Radiant barrier works by preventing radiation cooling of the sensor to the point where the temperature is below the dew point on a clear night. Radiant barrier is more effective on a clear night than on a cloudy night but can still help to some extent.
- Tilting the transducer slightly one or two degrees does the job in most cases.
- Applying Rain-X on the tilted transducer face will also assist in clearing/condensate build-up from the transducer face.
These ideas are sensor installation dependent and will often require experimentation to determine what works to reliably avoid or significantly reduce condensation and therefore improve the sensor performance. There is a cost benefit factor in order to implement one or more of these ideas that must be weighed by the end user.
Keep in mind the need to resort to the suggestions above would only be in an extreme case of condensation. By design, the pulsating action on the face of the transducers is sufficient to vaporize most condensation that otherwise will form on the sensor. But, if your application results in excessive condensation, the above suggestions are a good approach to consider tackling such nuisances.
What applications do you have issues with due to condensation?
Jack Roushey 28/04/2017
Flow measurement is more critical in more areas of a plant than ever before. Do you have places in your process where you now wish you had included a process flow measurement? Are there problems in those locations where making a quality measurement is difficult? Things like process lines you can’t shut down, pipes you can’t cut into, specially lined pipe or exotic pipe materials because of the nature of the process, non-ideal pipe runs, high pressure process lines or difficult process mediums?
These issues and more can make the addition of a flow measurement point seem impossible. But is it really?
Did you ever consider or think that you could just clamp a device to a pipe and measure flow and measure it accurately? What are you currently using for flow measurement and meter verification in your plant?
Clamp-on ultrasonic flow can help with many of the adverse conditions listed above and the new Siemens SITRANS FS230 digital platform clamp on ultrasonic flow meter can expand on the traditional versatility of clamp-on technology. Now you can measure flow where...
- You have less than desirable pipe straight run by using either a multiple path ultrasonic and/or by utilizing the Siemens patented pipe configuration software.
- Deal with pulsating flow: the FS230 offers the fastest update rate in the industry.
- Complicated set ups are no longer required. The menu driven wizards of the FS230 makes setting up the transmitter easy, even for the most challenging applications.
- You need an understanding of what’s going on in your process measurement. Siemens offers diagnostics that open the window into your process, providing variables not offered by any other flow meter on the market.
- You have a wide range of pipe sizes where measurement is required. Installation is available on line sizes from 0.5” to 394”; and because it is clamp-on technology, it isn’t affected by pressure in the process line.
- Cutting into the pipe is not an option. Our clamp-on meter is designed to mount easily on the outside of the pipe, and doesn’t require the shut down of your process for installation.
Just when you thought there wasn’t a measurement solution for the areas in your plant that may not have been designed around flow instrumentation, you can now take advantage of the fact that Siemens has engineered solutions to alleviate these problems.
To learn more about the SITRANS FS230, please click here.
Eric Heilveil 30/03/2017As manufacturing procedures can sometimes delay production with, waste materials handling and process change over or recipe adjustment, more plants have begun to automate their procedures than we have seen before....
From level instrumentation and pressure gauges to weighfeeders and belt scales, you can find a a significant amount of instrumentation in manufacturing facilities. One group of instruments recently making their way into the manufacturing world are high accuracy flow meters.
While you may think of flow meters as measuring the flow of liquid and/or gas in oil and gas industries, food and beverage plants, and water and wastewater facilities, flow meters – in particular mass flow meters – are making their way into the production facilities of manufacturing plants.
Lano Carpets, a carpet manufacturing company in Belgium, recognized the need to automate their color batch process after production delays and significant waste impacted their overall performance and profit margin. To avoid time loss and product waste, Lano decided to switch from traditional batch manufacturing to a continuous process based on an inline mixer that injects coloring agents into a collector containing a premix.
Using Siemens Coriolis flow meters , the coloring agents required to manufacture a specific color or shade are injected into the inline mixer in proportions that must stringently adhere to the set points. Now when the machine changes from one product to another the new set-up shows just how effective it is.
To read the entire case story, click here .
Interested to learn more about the SITRANS FC410 Coriolis flow meter? Check out the links below.
Watch our SITRANS FC410 Coriolis webinar today !
Click here to learn more about the SITRANS FC410 Coriolis flow meter.
Rachael McGovern 23/03/2017
Not to worry! Siemens Process Automation has developed a mobile showcase that displays how process instrumentation and analytical products will look in your process setup. With over 50 feet of space, we’re able to show you how instrumentation looks in its natural habitat.
Unsure of how a flow meter or a level transmitter would be positioned in an oil and gas application? We’ve got you covered!
With our Showcase, we’re able to show you exactly how instrumentation, analytical products, communication and automation will appear in a plant. We believe that ‘to measure is to know,’ and we’re trying to help one customer at a time with our unique, interactive experience.
As we’ve recently made some changes to our interior and exterior walls, we’re going to be showcasing our latest improvements next month on our Oil and Gas Summit and Technology Tour.
Interested to learn more?
Register today and experience the Mobile Showcase for yourself! In addition, you will have the opportunity to speak with industry experts on industry trends and where the market is moving next.
Don’t miss out on two great opportunities!
Register Here - Wednesday, April 12, 2017
11:30 a.m. – 8 p.m. CST
Register Here - Wednesday, April 26, 2017
12 p.m. – 8 p.m. CST
Corpus Christi, TX
John Dronette 16/03/2017
After a belt scale has been installed and calibrated in an application, as with any other piece of equipment, you have to consider what type of periodic maintenance should be performed. Routine calibration is one of those considerations. There can be many reasons why recalibration should be performed.
It can be as simple as:
- Temperature or weather changes
- Maintenance to the conveyor
- Material buildup on the weighbridge
- Settling of the conveyor structure
- Anything that has the ability to change the effects of the material on the belt or rollers may affect the scale
To understand the importance of proper belt scale calibration, consider what proper belt scale calibration should do. Proper belt scale calibration should:
- Provide early identification of a scale error
- Allow for an inspection of the scale and conveyor
- Test the scale’s repeatability
- Properly adjust the calibration of the scale as required
Let’s look at each of these items individually.
Early identification of a scale error
Changes in a conveyor belt system can occur slowly over time. These changes can cause a small error in the scale. As the changes in the conveyor accumulate over time, so do the errors in the scale. In many industrial environments, belt scale calibration is required when quality control reports a problem. At that point, the scale has already developed enough error to cause product quality issues. Regular periodic maintenance and calibration of the equipment assures that it operates within acceptable tolerances.
Scale and conveyor inspection
Conveyors are designed for continuous operation over long periods of time. For this reason, conveyors often receive little maintenance unless a problem develops that threatens to prevent the conveyor’s operation. When a belt scale is installed in a conveyor, it becomes an important part of the weighing system and should be inspected periodically for changes that may affect the scale’s accuracy. For example, an idler that is not aligned properly may have very little effect on the operation of the conveyor; however, if the idler is in the area of the scale, it could cause errors in the scale. When a periodic calibration is performed on a conveyor belt scale, an inspection of the scale and conveyor should be done to verify that changes that have occurred on the conveyor, will not affect the performance of the scale.
Test of the scales repeatability
When regular scale calibrations are performed, the scale should be tested for repeatability. The scale’s repeatability can easily be tested when doing a routine calibration by performing two consecutive calibrations in a row without making any changes to the scale or conveyor. If the error repeats, a correction can be made to the scale’s calibration. Consider a scale that has the desired accuracy of ± 0.50%. If a single calibration is performed and the scale is adjusted for that error but the error is not repeatable, the scale could be inaccurate.
For example, let’s say a scale indicates an error of 1.25% after the first calibration. To ensure this error is repeatable, a second calibration is performed without any changes to the conveyor or scale and this calibration shows an error of 0.10% (a difference of 1.15%); there is no adjustment that can be made to the scale to achieve the desired ±0.50%. In this case, a thorough inspection of the scale and conveyor should be done to determine the source of the error. However, if the second test shows an error of 0.95% (a difference of 0.30%), the scale’s calibration can be adjusted by 1.10%. This would leave the scale with an error of ±0.15%, well within the desired accuracy of ±0. 50%.
Adjust the scales calibration
Repeatability tests and an inspection of the scale and conveyor should indicate any issues that may be developing that will impact the scale’s accuracy. After preforming these checks, it may be found that the scale’s calibration is still within the acceptable limits. In these cases, no adjustment to the scale’s calibration is required. It is important to keep in mind that sometimes changes in the conveyor, e.g. conveyor maintenance or weather changes can cause errors in the belt scale. After it is determined that the scale is performing correctly, the calibration of the scale can be adjusted to keep the scale reading accurately.
Importance of calibration
To understand the importance of calibration, let’s think about the costs associated with an error in a belt scale since it can vary depending on the application.
Direct loss of finished product
If errors develop in a belt scale used for billing, it could result in the direct loss of material. For example, consider a scale that is loading a railcar with 95 tons of material; if the loading scale has a 1% error, the railcar could have as much as 95.95 tons. That may not seem significant, but on a 50 car train that could be as much as 47 tons. Now consider 50 cars per week over a year. That would be 47 tons over X 52 weeks = 2444 tons per year from an error of only 1%.
Excessive equipment wear and increased energy costs
A scale out of calibration can produce excessive wear on equipment in a couple of ways. If the scale is used to control the feed rate into a processing machine, the machines are usually designed to be fed at a specific rate. If material is fed into the machine below the designated rate, the machine will need to run longer to process the same amount of material. On the other hand, if the material is fed into the machine too fast, the material may not be properly processed so the material has to be transferred through the machine a second time. In either case, the machine will need to run longer to produce the same amount of product; thus, increasing wear on the machine, labor and energy costs.
Excessive use of raw material additives
In applications where the scale is used to measure multiple components in a blending application, the material is blended in the correct proportions based on the output of the scale. In these applications, if an error develops, it can result in an increased use of raw materials. Additives typically cost more than the base product. If the scales are not reading correctly, more additive may be added than is needed, which in turn increases the production cost. In cases where the error has grown large enough, it may produce material that is out of specification, increasing the amount of scrap product.
Properly calibrated and maintained belt scales are capable of reducing production costs in a variety of ways. However, if the scales are not properly calibrated and maintained, the investment in the scale is only achieving a portion of the savings it was intended.
What periodic maintenance program do you have for your belt scales?
Jonas Norinder 09/03/2017
When it comes to working with hazardous materials, the possibility of a storage tank overspill is a daily battle for the chemical industry. Although overspills do not happen regularly, the threat still exists, the risks are high and the effects can be severely damaging to your plant in more ways than one.
Not only will an overspill result in a loss of material and system downtime perspective, but it can also impact the safety of your personnel and the environment. That is why it is important to look at your plant’s system regularly to see how you can efficiently and effectively run your plant.
Can you automate your manual instrumentation or implement instrumentation to increase safety measures for your workers? Do you have existing processes that have been in place for years that could be updated to work more efficiently?
Just remember, tank overspills happen for a number of reasons, most of which can be prevented, or at least drastically reduced. It is important to focus in on the questions that can potentially prevent a disastrous situation from occurring.
To learn more, download my recorded webinar here. We are going to be delving into this topic and will be discussing real-life, on-the-job issues that you face daily.
Download my webinar today!
Mike Gavan 02/03/2017
For much of my 30 years of non-contacting level measurement experience, I believed that there was an element of magic associated with it. When applications were successful it was good magic, and when they weren’t, it was black magic.
As time went on, and my experience and knowledge levels rose, I realized that there was not quite as much “magic” as I initially thought but “REASONS” why things acted the way they did. Well, most of the time…but, not all of the time.
My most baffling experience happened in an application involving solids materials. This application shouldn’t have presented any problems and was a routine fix. On this particular application, a site was experiencing erratic behavior from the level sensors - and they had the trends to prove it. Every time we would send a technician, and sometimes that technician would be me, we couldn’t figure it out. There was absolutely zero reason for this behavior to happen. The echo profiles looked fine and the erratic behavior captured on the trends were of such a frequency and randomness that the technician would have to actually sit by the unit (for who knows how long) waiting to capture the right moment. Miss a chance and poof! The clock starts all over again.
Thanks to a colleague, and the constant bizarre behavior, we were able to resolve the issue with a little patience and resolution. It turns out that silo discharge geometry can play a major role in how the material flows during discharge. My colleague explained the difference between mass flow and funnel flow, but until I actually saw the difference I was not convinced. Then it happened: I saw the difference.
This particular site had six silos that had a wedge-shaped lower discharge section, and the very bottom was slanted in a vertical orientation that allowed the material to dump into the lowest part of this section where there was the takeaway screw.
They also had two newer silos that had the more traditional cone discharge section. Before I scaled the silos, I asked the operators if they noticed a difference in behavior between the six older silos and the two newer silos. They said they have never had an issue with the newer silos so, now I knew what to look for: the differences between the six older silos and the two newer silos.
The difference was the bottom discharge section. The proof was literally staring me in the face when I looked inside the first old style silo. There was a very large section of the material surface that had fallen away, leaving sides that looked like an ice berg looks when a large piece falls off into the ocean. The hole must have been a good 10-15ft. in diameter and about 6-8ft. deep. Our level transmitter was mounted right above the lower portion of the screw and, obviously, right above this newly created hole.
It is easy to imagine that the material would compact as it tried to discharge through this relatively small discharge area, and depending on the make-up of the material this “bridging” could stand up for some period of time before collapsing. Until this collapse occurred, the top level of the material would be a nice smooth surface. The kind we always want to see in these solids applications.
So, what did I learn? Well, in conclusion, not all of the erratic behaviors and apparent unsuccessful applications are a result of the level instruments’ capabilities. A little more investigative research/observation and a little less magical thought is now in my approach to troubleshooting problem applications.
So if you find yourself frustrated and starting to question the capabilities of your instrumentation, do yourself a favor and make sure you have looked at every potential influence that might be keeping your technology from being successful in the application.
Add an inspection of the silo from top to bottom to your troubleshooting checklist. And, if you can correct your discharge issues, or even avoid installing a silo that won’t lend itself to steady flow conditions, you would be doing yourself a big favor. This would even allow you to start trusting the level readings your instrumentation generates.
John Dronette 24/02/2017
Each year thousands of experts from around the world gather at the GEAPS Exchange to learn about the latest topics affecting the grain industry, exchange ideas and explore innovative products and services. With 250,000 square feet of exhibits and over 40 hours of educational programs, this year’s Exchange is sure to impress.
The nearly 3,000 attendees come from all aspects of the grain industry including suppliers and those in the grain handling and processing industry. Operations professionals include those directly engaged in grain handling, feed milling and processing operations. The suppliers represent businesses or organizations that supply equipment to these industries. GEAPS also draws safety professionals and government officials from across the global to discuss challenges from a governing standpoint.
Some of key topics to be discussed at this year’s Exchange are:
- Maximizing operational efficiency
- Choosing storage options
- Selection criteria for bulk material handling equipment
Siemens has solutions for these concerns, be sure to stop by the Siemens booth, booth #601 and let us show you how we can help! My colleagues and I will be available throughout the conference and we would be happy to discuss ways to improve your efficiency, reduce your operating cost, and improve safety in your facility.
In the booth, we will be demonstrating the SITRANS LR560 level radar. The SITRANS LR560 is the world’s first W band level radar; it’s great for measuring in tall (up to 328 feet) dusty bins and silos. The SITRANS LR560 has also proven very effective in helping the grain handling industry leaders manage their inventory levels.
In the booth, Siemens will also be displaying the award-winning MSI conveyor belt scale, which has won the Weighing Review Readers’ Choice Awards for “Best Industrial Scale” for the second year in a row. The MSI’s use of the patented triple-beam parallelogram load cell has proven itself successful around the world. In the grain handling industry the Siemens MSI is often used to accurately measure inventory and reduce shipping costs.
What do you hope to see at GEAPS Exchange 2017?
Eric Heilveil 14/02/2017
As Siemens’ SITRANS FC430 Coriolis flow sensor has been selected by Control Engineering's readership as one of the best "Process Control - Flow Meter, Process Sensors,” what’s not to love? The Siemens SITRANS FC Coriolis flow sensor delivers mass flow, volume flow, density, fraction and temperature measurement of both liquids and gases with exceptionally high accuracy and low pressure drop. It is user-friendly and easy to set up for day-to-day use.
The SITRANS FC430, series of high-performing Coriolis flow meters, has a footprint small enough to meet your process requirements! The FC430 can stand up to the most demanding process industry conditions and continues to operate in the noisiest of environments – from hazardous chemicals to fiscal metering, custody transfer to compressed natural gas fuel dispensing. Its compact design makes installation easy even in the tightest spaces.
Watch the SITRANS FC430 in action!
To learn more about the SITRANS FC430, please visit www.usa.siemens.com/coriolis.