Tag Archives: QuadraTherm

Flare Gas Metering Solutions

sierra flare gas solutionsWaste gases must be flared in numerous industries ranging from oil refineries and well drilling operations (like shale gas fracking) to wastewater treatment plants and landfills. Due to government regulations, flares are subject to stringent regulations requiring accurate measurement. Requirements to monitor the flow rate and consumption of flare gas involves measurement at points within a complex series of feeder and header pipes, as well as the actual flare stack.

Thermal Mass Flow Meters provide an accurate and repeatable, low-pressure drop, direct mass flow measurement with the wide turndown required to cover the broad range of flows in a typical flare system. For large flare stacks, multi-point thermal mass flow meters greatly improve the accuracy of the measurement. Next generation QuadraTherm four-sensor thermal mass flow meters now drastically improve the measurement accuracy of flare gas to 0.5% of reading rather than the typical 1% to 5% of full-scale accuracy.

Fast response to excursions in flare gas flow rate is no issue for the 200 millisecond response time of the BoilerTrak 620S-BT, now available to ship same or next day from stock.


Part 2: Accurately Measuring Flare Gas — Innovations Promise More Economical Choices

Flare Gas Flow Meter MeasurementIn my last post on flare gas flow measurement, I shared how the rise in hydraulic fracturing has led to more stringent state and national mandates to regulate the measurement of waste and excess gases that are produced as a result of this process. If you’re affiliated with an oil or gas company, you know that the cost of compliance can be steep. You need a flow meter solution that not only provides accurate measurement, but one that is cost-effective as well.

Enter the four-sensor thermal mass flow meter, which takes advantage of recent innovations in thermal mass flow sensor technology to provide users with flexibility in the field while still maintaining accuracy. But more on the many benefits of QuadraTherm air flow meters in my next post. For this installment, I want to focus on why current flow measurement technologies may not provide you with the best solution for your company’s flare gas measurement needs.

Flow Meter Accuracy Concerns

Over the last five years, multiFlow Technology Comparison-path transit-time ultrasonic meters (typically four-path) have been used for flare gas measurement. Given the flare gas measurement challenges they face, multi-path ultrasonic flow meters perform very well. But in some applications, dirt, wax, tar, and paraffin in the flow causes internal erosion or build-up of material on the inner wall of the pipe. This degrades the flow measurement accuracy without obvious indicators.

Since multi-path ultrasonic meters are built into in-line pipe sections, called spool pieces, the entire meter must be removed to clean and re-condition them. Susceptibility to the effects of flow profile, especially swirl, will also cause degraded accuracy. In addition, the cost for a four-path ultrasonic flow meter is several times more (as much as 10x) than the traditional flow meters.

Other technologies such as averaging pitot tubes and insertion turbine meters have poor performance for measuring flare gas. These devices measure volumetric flow, not mass flow which is the desired measurement. They require a clean flare gas with constant gas composition. Additionally, even though we first invented the multivariable mass vortex back in 1997, these meters successfully measure low pressures of flare gas, but they need to know the gas composition for accurate measurement.

For more comparisons of technologies used for flare gas measurement, download my white paper, Flare Gas Mass Flow Metering: Innovations Promise More Economical Choices. Let’s keep innovating! And check back for my next installment on the benefits of four-sensor thermal mass flow meters, a true breed of their own in measuring flare gas more accurately.



Overcoming Natural Gas Sampling Challenges in Oil & Gas Applications

It is a fact that in order to comply with various government rules and regulations, oil and gas companies have to continually take natural gas samples to prove the gas composition and amount of gas flowing in their oil fields.

The challenge comes in trying to actually take an adequate gas sample representative of the gas flow.

  • First, engineers must carefully consider where the “representative” gas sample will be taken from in the source stream all the while maintaining chain of custody to avoid contact with contaminants.
  • Then engineers must also reduce and control the pressure to the analytical tool, stabilize and control the flow, all the while protecting the analytical instrument from particulates, moisture, and pressure/flow excursions.
  • Add to that, engineers must take the gas sample in as real time as possible, so that it correlates with the actual process flow.

hydrocarbon-engineering-cover-1116_highThe goal for oil and gas engineers is to take the most accurate gas flow sample, as quickly as possible, with the lowest incurred cost. This may seem impossible, but advances in flow meter technology are tackling the challenges of natural gas sampling – head on.

In our technical article in Hydrocarbon Engineering, learn how flow meter technology advancements solve all the inherent challenges in gas sampling applications like:

  • Accuracy at low flow rates
  • Metering accuracy in changing gas compositions
  • Managing changes in varying pressure
  • And more…

The article is an informative look into natural gas sampling and how to overcome those challenges. Read the article today.

Cold Weather and Your Mass Flow Sensor

Baby It’s Cold Outside

Sierra is a global company, so we sell our mass air flow sensors into some pretty extreme cold weather environments.   Indeed, we are seeing more and more applications in the far North, where immersible thermal flow meters like Sierra’s Steel-Mass® Model 640S and our new QuadraTherm™ Model 640i are used in the oil fields and tar sands to monitor gas flows for flares, natural gas, and compressors.  One common question we get from our customers in these and other cold weather applications is “how do your flow meters handle cold weather”?

The answer is “pretty well”, but there are some caveats to be aware of.  Over the next few weeks, we will look at these in detail.

Part 1: Cold Weather and Mass Air Flow Sensor Electronics

Mass air flow sensors, like Sierra’s Steel-Mass® Model 640S and our new QuadraTherm™  Model 640i, typically have an ambient temperature rating of -40°F to 120°F (-40°C to 50°C).  So what happens at -40°?  This rating is primarily based upon the temperature where the LCD DISPLAY becomes difficult to read.  You may have seen this same effect on your cell phone display; the display will fade in very cold weather but will “come back” without any permanent damage once warmed up.   The same is true of the displays used on Sierra’s mass air flow sensors.  Other than that, there are no lasting physical effects on the flow meter.  In fact the heat dissipated by the operation of the electronics typically keeps everything a snug 40°F (22°C) warmer inside the meter’s red housing.  Recall too that Sierra’s red housing is rated IP 67 and keeps moisture out, so ice and snow won’t be a problem.

Cold weather does affect the accuracy of the meter, though… sometimes by a lot.
We will look at how in Part Two of this series.

Part Two: Cold Weather and Mass Air Flow Meter Accuracy-Effects of Stem Conduction

Learn More About The QuadraTherm 640i



Talking Biogas Production In Europe

Europe is quickly becoming a hotspot for the biogas industry, and Sierra and our local French distributor Alto Instruments took advantage of that fact by exhibiting at BiogazEurope in France. Attendees learned about the entire biomass process, from the bio side of things (mass) to the energy side (electricity).

Some trending applications featured at the show included:

  • Biomass digesting
  • Optimizing/upgrading biomass
  • Precise flow measurementSierra-Alto Booth at BiogazEurope 2014

Overall,  trend was the need for high-accuracy flow meter measurement throughout the whole biogas process to optimize production and bring efficiency while creating electricity (energy) from fossil fuels.

To really monetize biogas and create the most efficient fuel sources, you must accurately measure how much biogas is produced in each stage of the process. Although biogas flow measurement is a challenging—mainly due to changing gas composition, low pressure, and dirty, wet gas—it’s not impossible. Which is why we featured our QuadraTherm 640i at the BiogazEurope show.

The 640i meets the criteria for successful biogas measurement by managing changes in:

  • Gas composition
  • Gas mass flow rate
  • Gas temperature
  • Gas pressure
  • Outside temperature
  • Pipe conditions (size and roughness)
  • Flow profile

These common fluctuating conditions inherent in biogas production can all be managed with accurate readings (the 640i maintains accuracy at +/- 0.75% of reading above 50% of full scale), without sending the flow meter back to the factory for recalibration. Who doesn’t want to reduce downtime and save money?

For more information on precise biogas flow measurement, download our white paper.

Sierra’s Top Flow Blogs of 2017

best of 2017

Another year has come and gone, and it certainly was a big one for Sierra and our customers! Let’s look back at the news and top content that we shared with you in 2017.

Most Popular Blog Posts from 2017

We love sharing our news and providing useful flow meter information with you through our Let’s Talk Flow Blog. Here are the posts that resonated best with our readers last year, complete with links so you can catch up if you missed any.



Measure All Flow Energy in Your Facility-ONE Solution-Three Metering Technologies 

The pressure is on your shoulders to make the smartest decisions in 2018 to measure all the gas, liquid, and steam flow energy in your facility. In this video, learn how ONE complete flow energy management solution can simplify the flow energy management in your factory.


minute.flow.tip.John.S.1.3.17[Minute Flow Tip Video] Mass Flow Versus Volumetric Flow Technology

What’s the Mass Flow Advantage? Chief Engineer, John Smitherman explains the vast differences between gas mass flow rate and volumetric flow rate.  Learn why mass flow technology greatly improves measurement accuracy in this Minute Flow Tip Video.


scott.video.207i.installation.1.3.17Making Ultrasonic Liquid Flow Meter Installation Easier
Clamp-on Ultrasonic flow meters are the perfect flow meter for liquid flow measurement. But finding the perfect signal can sometimes be difficult. Sierra’s Product Line Director, Scott Rouse, demonstrates how on board Software Apps on an InnovaSonic 207i ultrasonic liquid flow meter make set up simply with an easy “12-step” program.


compod.blog.2017.Best.of.1.3.17How to Supercharge the SmartTrak Mass Flow Controller with Compod
Learn how to streamline, simplify, and save time and money with the Compod upgrade for the SmartTrak 100 mass flow meter and controller.  Set up simple process control systems driven by SmartTrak with Compod without the need for PLCs or computers.




4-20.image.2017.best.of.1.3.18 Understanding  4-20 mA Current Loop Communications
Many times, customers ask  “how do I get accurate 4-20mA output readings?” for 4-20mA output devices. Kam Bansal, Director of Engineering, explains 4-20mA communications protocol, step-by-step to dispel the complications and confusion around the protocol to get you set up and running.



Oldies, but Goodies

The more things change, the more they stay the same. Or so it seems based on the continued popularity of these older posts that continue to draw readers.

Tuning Your Boiler for EPA Boiler MACT Compliance
Our most popular new post in 2016 remained hot through 2017 as the three-year grace period on the EPA’s Boiler MACT expired in January 2017. In the article, we discussed the regulations, three ways to tune a boiler for compliance, and how flow meters can help your company comply.

Flow Meter Do’s and Don’ts with Ammonia
Five years after it was published, this post is still one of our most popular. We knew we had to write this post when a number of engineers and researchers stopped by our booth at Pitcon in 2012 to ask about ammonia flow measurement. Years later, the precautions stand true and are critical if you are using a flow meter for an ammonia application.

Methods & Pitfalls of In-Situ Calibration Validation of Thermal Flowmeters
“In-situ” means in place, meaning that you don’t have to return your instrument to the facility to have it recalibrated and recertified. You can certainly see the allure of that, but there are pitfalls. Read this post to learn how to get reliable results and avoid false positives.

We hope you enjoyed this look back at 2017 and that you continue to follow us through 2018. We look forward to bringing you more of the best flow information online in the coming year.

Part 2: Cold Weather and Mass Air Flow Meter Accuracy (Stem Conduction)

In Part One, we looked at the effects of cold weather on mass air flow meters like Sierra’s Steel-Mass® Model 640S and our new QuadraTherm™ Model 640i. As discussed, cold weather typically doesn’t cause any physical damage to the flow meter, but it can affect the meter accuracy. Let’s look at how.

Flowmeters That Are Reliable and Accurate

In many applications, the gas in the pipe is hotter than the surroundings; in the Far North in the winter it can be dramatically so. We all know that heat flows from hot to cold, so, with a flow meter inserted into a pipe, it is only natural for heat to flow from the hot gas, up the probe stem of the flowmeter, then to the surrounding cold air. Since a thermal mass air flowmeter works by measuring the heat removed from the sensing element (mostly by the flowing gas), this heat conducted up the stem looks like flow. The bigger the temperature difference between the gas in the pipe and the outside air, the bigger this error. It can be up to 20%! Most companies do not manufacture an air flow meter that can account for this temperature difference.

Flowmeter With a Four-Sensor Advantage

Sierra’s new QuadraTherm 640i was designed with this problem in mind. The QuadraTherm uses four sensors instead of the traditional two, with two extra temperature sensors installed to measure the heat lost via stem conduction. By measuring and subtracting this heat loss out of the energy balance using its iTherm brain, The QuadraTherm 640i becomes independent of ambient temperature and achieves accuracies never before possible (up to 0.5% of reading).

Chemical Engineering Magazine Article By Sierra’s Founder

Chemical Engineering Flow Meters

Sierra’s Founder, Dr. John G. Olin, looks at the Principles of Operation, Installation, Calibration and Best Applications for Thermal Mass Flow Meters…

Read the full article in Chemical Engineering Magazine.

Understanding the iSeries Totalizer for Gas Mass Flow Rate

flow totalizer.blog.1.19.18

Do you have questions about the iSeries flow meter Totalizer App that comes standard with every QuadraTherm 640i/780i Thermal Mass Flow Meter or want to learn more about gas mass flow rate? We get many support questions regarding the app, generally covering the same few points, so let’s spend a few minutes and discuss how to use and understand the power of the iSeries flow meter Totalizer.

What is a Flow Meter Totalizer

Simply put, a totalizer is a running total of how much fluid (gas, liquid, steam) has passed by the sensor within a given time. For example, “in the last 60 seconds, there have been 30 gallons of water flowing by the sensor.”

Along with the totalizing of the flow, there are additional features available for the iSeries Totalizer:

  1. Activate a relay pulse whenever a known quantity of flow has passed over the sensor. An example of this would be, “pulse the relay for 50ms whenever we flow 2 gallons.”
  2. Activate a relay if the totalizer value is less than (Low Alarm), more than (High Alarm), or outside a low and high value (Window Alarm). An example of this would be “Activate the alarm if we exceed 30 gallons of totalization.” This would be considered a “high alarm.”
  3. Do not totalize if the flow exceeds fullscale, utilizing the Totalizer Clipping option.

Understanding Units Per Pulse

Let’s say that our fullscale is 600 gallons per minute. When we’re speaking about fullscale, this means the maximum flow we expect, not the current flow. Say we want to pulse the relay for every 20 gallons that have passed by the sensor. There is a setting in the totalizer screen called the “Units Per Pulse” (UPP).

flow totalizer app

So, back to our example. We have a fullscale of 600 gal/m (gallons per minute), and we want to totalize and pulse the relay every 20 gallons. Setting a value of “20” in the UPP field tells the meter that we want to totalize and pulse every UPP amount, or in this case, every 20 gallons.

That’s it!

well, kind of.

It’s the “kind of” part that causes us headaches!

What Causes Totalizer Headaches and How to Solve Them

In the current release of the iSeries Raptor 2 platform (version 1.x), we have a historical rule that states that we cannot pulse the relay more than 1Hz, meaning that we cannot pulse the relay more than once per second. This is a carryover from the older products and was honored with the v1.x of the Raptor platform to be backward compatible.

We need to ensure that we do not pulse more than once per second. Said another way, the UPP value cannot be such that it would “break” the 1Hz rule. So how do we account for this? Simply put, all we need to do is determine what would be the lowest possible UPP value that would not break the 1Hz rule. To do that, we just have to make sure that the value we use is equal or larger than that value.

For our fullscale of 600 gal/m, we would first determine what the UPP value would be for a valid 1Hz pulse. This is done by simply figuring out what our fullscale flow would be per second. Since our fullscale is 600 gal/per minute, we just take that value of 600 and divide by 60 to make into seconds. So 600/60 = 10. So that means at fullscale flow, we will be flowing 10 gal/second. So, for our UPP value, we must use a value equal to or greater than 10.

If we were flowing 600 gal/per hour, then we would divide 600 by 3600 (60 seconds * 60 minutes) = 0.1666. We must ensure that the UPP value is equal to or larger than that.

Rule: A valid UPP *must* be greater than or equal to the fullscale value converted to seconds

So, what would happen if you entered a UPP value that breaks the 1Hz rule? For example, what if instead of entering a 10 for the UPP (10 = 1Hz), you entered a 5 for the UPP (5 = 2Hz, 2 times per second)?

Well, the totalizer updating would not be affected. It would still correctly totalize the flow. The issue would manifest itself in the physical pulsing of the relay. It’s the relay pulsing that honors the 1Hz rule. To do that, it will continue to pulse at 1Hz, but will buffer/remember that it still needs to keep pulsing. For our working example of UPP=10, we would pulse the relay 60 times per minute (if flowing at fullscale). Using the wrong value of UPP=5, we would need to pulse the relay 120 times per minute, but since we are honoring the 1Hz rule, it will actually take 120 seconds. What that means is if we were to go to zero flow after 1 minute, we have only pulsed 60 pulses of the 120 we need to do; we would continue to pulse the totalizer relay, even if we have no flow!

If you ever “see” the totalizer pulsing after the flow has gone, you have entered the wrong UPP value, or you are flowing beyond the fullscale value. If you are flowing beyond the fullscale, you could activate the “Force Totalizer Clipping” functionality to stop it.

Fullscale Clipping (QuadraTherm)

What happens if you don’t want to totalize if the flow exceeds the fullscale value? Easy, we have a checkbox in the totalizer screen that tells the meter not to totalize the flow if it exceeds the fullscale.

flow totalizer fullscale clipping

Once the flow returns to fullscale or lower, the totalizer continues to work “as normal.”

Understanding Pulse Width

The Pulse Width is the time duration that the relay is active for. Entering a value of “50ms” (milliseconds) means that we will pulse the relay for 50ms. The user can select the duration of the pulse. You cannot exceed 1000ms (1 second) per pulse.

More examples

Let’s look at a few more examples to illustrate how we determined the UPP value.

Example 1:

Fullscale is 5 MMSCFD

We want the totalizer to pulse every 1000 SCF

Let’s calculate the minimum UPP we can use, just to make sure we don’t violate the 1Hz rule. Since our fullscale is 5 MMSCF D (per day), we divide it out until we get seconds. UPP = 5 / 86400 (60 sec * 60 min * 24 hours = 86400 seconds) = 0.00005787 MMSCF S (per second). We now know that whatever value we use for the UPP, it must be equal or greater than this value to honor the 1Hz rule.

Now we want to pulse the totalizer every 1000 SCF. Since we are in MM units for the fullscale, we must convert the 1000 to MM to make both numbers equal regarding units. 1000 SCF = 0.001 MMSCF. So, setting the UPP=0.001 tells the meter to pulse the totalizer every 0.001 MMSCF units, or every 1000 SCF. Since the 0.001 value is greater than the minimum UPP of 0.00005787, we have not violated the 1Hz rule.

Answer –

Fullscale is 5 MMSCFD

We want the Totalizer to pulse every 1000 SCF

Set the UPP=0.001

It should be noted that the UPP value must be in the same units as the fullscale. Since we are in MM units, the value in the UPP must also be in MM units; hence why the 1000 = 0.001 (MM).

Example 2

Fullscale is 22,000 gal/h

We want the Totalizer to pulse every 5 gal

Let’s calculate the minimum UPP. 22,000 gal/h = 22,000/3600 (60 sec * 60 min) = 6.1111. So our minimum UPP cannot be lower than 6.1111 gal for the 1Hz rule.

We want to pulse the totalizer relay every 5 gal. Setting the UPP = 5 would not work as the minimum UPP is 6.1111! Tricked you! This is a bad example.

So as you can see, we cannot do a relay pulse every 5 gallons as it violates the 1Hz rule.

Example 3:

Fullscale is 22,000 gal/h

We want the totalizer to pulse every 15 gal

Since the 22,000 and the 15 are in the same units (meaning they’re not MM nor M), we can leave the numbers alone. We set the UPP=15 to indicate we want a pulse every 15 gallons that have flowed by.

Answer –

Fullscale is 22,000 gal/h

We want the totalizer to pulse every 15 gal

Set the UPP=15

Be a Flow Totalizer Expert

That’s it. Keep the formula in mind, and you should be a full-fledged, flow totalizer expert.


If you have any questions, please contact us in engineering and support. We always enjoy solving problems for our customers by making sure that your flow tools are the right fit for your process.


Part 3: Cold Weather and Mass Air Flow Meter Gas Temperature (Gas Properties)

In Parts One and Two of this series, we looked at the effects of ambient temperature on mass air flow meters such as Sierra’s FastFlo™ 620S and our new QuadraTherm™ Model 640i. As discussed, cold weather has few physical effects on an air flow meter, but can degrade accuracy due to stem conduction, unless accounted for, as does the new QuadraTherm 640i.

While we have talked about the temperature of the surroundings, we need to also look at the temperature of the gas in the pipe, since this too can be affected by the surrounding temperature.

Influence of Temperature on Mass Flow Controllers

Thermal mass air flow sensors are famous for being “independent of temperature and pressure.” Since these are mass flow meters and not volumetric meters, this is mostly true, but there is some influence by temperature. As mentioned previously, thermal mass flow controllers work by measuring the heat conducted away by the flowing gas. The amount of heat lost is a function of gas heat transfer properties such as heat capacity, density, viscosity and thermal conductivity. All of these properties have some dependence on temperature and pressure.

Most thermal flow meter manufacturers do not take this into account and assume a constant process temperature and pressure. Using its unique QuadraTherm sensor and iTherm brain, Sierra’s new QuadraTherm Model 640i continuously calculates the values of these heat transfer properties at process temperature, ensuring the most accurate reading no matter what is going on inside or outside of the pipe!