Do you know why Mass Flow reference conditions matter
ou would think that measurements of mass flow would be expressed in units of mass, such as grams/hour, milligrams/second etc. Most users, however, think and work in units of volume. That’s OK, at least when we are talking about the same reference conditons. Let me start with an example:
Mass versus Volume
Imagine you have a cylinder of 1 liter, which is closed by means of a moveable piston of negligible weight. This cylinder contains 1 liter of air at ambient pressure, approximately 1 bar. The weight of this volume of air at 0°C is 1.293 g, this is the mass.
When we move the piston half way to the bottom of the cylinder, then the contained volume of air is only ½ liter, the pressure is approximately 2 bar, but the mass hasn’t been changed, 1.293 g; nothing has been added, or left out.
STRAIN GAUGES 101
A strain gauge is a sensor that varies its resistance as it’s stretched or compressed. When stress or compression is applied, the strain gauge converts force, pressure, tension, and weight into a change that can then be measured in the electrical resistance.
At the heart and soul of every load cell is a strain gauge. This is the pinnacle technology that allows engineers to collect and analyze force data. In the industry, it is known as force measurement.
Strain gauges are made through a photo-etch process using a flexible backing and a very thin foil. The way a strain gauge works is when the backing and foil stretches or compresses, resistance goes up and down respectively. We know this as force. Think of stretching like a three-lane highway switching to two lanes, and vice versa for compression with two lanes going into three. As the load cell’s internal strain gauge experiences force, it sends a signal with a precise measurement of the amount of force it’s experiencing.
Wet Gas Flow measurement from FCI
Moist or wet gases present a measurement challenge for all gas flow meter technologies. In many applications it is condensation droplets which impact the flow meter’s accuracy and repeatability, rather than entrained moisture. While best engineering practice would recommend removing the moisture from the gas using gas dryers, knock-out pots, or heat wrapping the pipe, those are not always feasible or only partially effective. Moisture, and condensation droplets, can be in the flow steam moving with the gas flow or can also be experienced in the form of rain coming down in an open, vertical stack, in which case the rain is traveling in the opposite direction of the gas flow. Common moist gas applications, and often condensation droplets are found in biogas recovery (WWTP digesters, landfill gas, biogas production systems) and reactors, while rain droplets found in open vertical stacks and flues are common in power plants, oil and gas operations, chemical plants and refineries.
For many years, FCI’s constant power technology has been the proven and preferred thermal mass flow meter solution for gas flow measurement in moist gases. Now, FCI’s new, innovative “wet gas” sensor delivers accurate, repeatable gas flow measurement in the presence of even more moisture and condensation droplets. Available with the Model ST80, this new “WG” sensor can be applied for use in entrained moisture and rain-shielding applications.
To learn more and see recommended installation techniques, specifications, and how to specify, please download our informative new “Best Practices in Moist and Wet Gas Flow” white paper today.
About Positive Displacement Flow Meters
Positive displacement flow meters measure the volumetric flow rate of a moving fluid or gas by way of precision-fitted gears or rotors containing cavities through which precisely known volumes of fluid pass. A basic analogy would be holding a bucket below a tap, filling it to a set level, then quickly replacing it with another bucket and timing the rate at which the buckets are filled (or the total number of buckets for the “totalised” flow).
Positive displacement flow meters are very accurate and have high turndown. They work best with clean, non-corrosive, and non-erosive liquids and gases, although some models will tolerate some impurities. They require no straight runs of pipe for fluid flow stream conditioning though pressure drop can be an issue. They are widely used in custody transfer and are applied on residential home natural gas and water metering.
Constant Power/Constant Temperature Technology
With thermal mass gas flow meters, there have always been two measuring techniques, constant power (CP) and constant temperature (CT). Both of the techniques are viable, popular, and have both advantages and disadvantages. Historically the trade-offs were about range, response times, sensor life, and susceptibility to moisture in the gas and power consumption. Over time, all the reputable manufacturers continuously tried to improve their products to overcome some aspect of their preferred technique’s short-comings.
But what if you just combined both techniques in the same flow meter, and made it field changeable. Should than the actual installation conditions not be as expected? Wouldn’t that be the ultimate solution? Today, this “both” techniques is a reality in Fluid Components International’s new ST80 thermal flow meters. The ST80s incorporate both FCI’s patent-pending AST™ technology (Adaptive Sensing Technology), which is a hybrid drive that combines both CT and CP together, and CP mode. AST utilises fast responding CT technique at lower flow ranges and seamlessly, and automatically, shifts into CP mode at higher flow rates. This AST hybrid technique then provides a faster response, wider flow range and low power consumption in the same flow meter. And, if the application contains any moisture or where the AST response time is too fast, the ST80 can be set to run in the better application matched CP mode only.
So, if you are specifying, designing or using thermal flow meters, you no longer need to make product selection. Trade-offs based on the measuring technique with ST80 are no longer an issue. Further, if your actual application and installation could be different than expected, with the ST80 you can change the measuring technique between AST and CP modes in the field, to adapt to your discovered, actual installed conditions.
KING-GAGE Advanced Non-Contact Tank Level Measurement
KING-GAGE® LevelWAV radar level transmitter provides continuous measurement suitable over a broad range of temperatures, pressures and density variations in liquid storage or processing tanks. This radar transmitter can be used in process conditions exhibiting visible vapors, foam and/or surface agitation. Non-contact measurement is possible for highly corrosive materials (caustics, acids, solvents) and slurries.
KING-GAGE LevelWAV utilizes advanced microwave circuitry that automatically adjusts transmit energy and receiver gain to detect only the reflection from the media surface. 2-wire technology is easy to install and simplifies wiring requirements at the tank. Accurate and reliable operation with no moving parts or product contact eliminates maintenance requirements of other level technologies.
Compact size and mounting footprint makes tank top installation of the LevelWAV radar transmitter suitable for even tight spaces. Radar level measurement is a practical solution in retrofit applications to replace failing or erratic level transmitters.
Output from the LevelWAV radar transmitter can be monitored on KING-GAGE indicators and multiple tank displays enabling tank level to be represented as total volume, weight or depth of contents. Each of these display options also provides excitation power (24Vdc) to the transmitter through the signal loop cable.
Bronkhorst mass flow meters and controllers in the food industry
In the food industry there are many applications in which gases or liquids need to be measured or controlled with mass flow meters and/or controllers. For example, these applications include the aeration process or the dosage of additives, like flavours and colourants. Indirectly, surface treatment applications like the sterilization of packaging is of high importance as well. Bronkhorst has published many stories regarding the omnifarious and demanding food industry and I would like to share some of these stories with you.
Additive dosing for confectionery industry
There is a huge variation in candy available on the market, each brand with its own taste, texture and appearance. Erwin Broekman had the opportunity to visit Haas-Mondomix, a machine builder that is specialized in equipment for the food industry. With ultrasonic volume flow meters, Haas-Mondomix measures the amount of additives – flavourings, colourings and acids – that are added to the main stream of the production process. Please read the blog to learn more about this application.
In the chocolate confectionery industry, there’s an ever increasing number of variations in flavours as well. Due to this enormous growth, mass flow meters and controllers find their way into the confectionery industry. Coriolis flow meters in combination with a pump are an ideal solution for dosing flavours and functional ingredients. Read more about dosing flavour into chocolate.
Aeration within the production process of delicacies like ice cream and cake
Ice cream is made by freezing and simultaneously blending air into a brewage of fat, sugar and milk solids. Air makes up anywhere from 30% to 50% of the total volume of ice cream, so aeration is crucial during production. A side effect of adding air to ice cream is that it tends to melt more quickly. Thus, for attaining an optimal structure of the ice cream, it’s important to have a stable inlet air flow in the production process with a constant cream/air ratio. This can be achieved by using a mass flow controller. Read the blog about the production of ice cream, and get to know your favourite summer treat.
Intrinsically Safe Impedance Dew Point Transmitters to ensure safety of Hydrogen Coolant
Within the power generation industry, it is common practice to use hydrogen as a direct coolant for the generator stator windings. Hydrogen is used because it has an extremely high heat transfer capacity – it is much more efficient at transferring heat than any other medium.
The re-circulating hydrogen removes heat from the generator, transferring it, via a heat exchanger, into a secondary cooling circuit which uses de- mineralized water. Often this de-mineralized water is then cooled either by sea water or river water, dependent upon the location of the power station.
As it is not possible to hermetically seal the generator set casings there is the potential for moisture to ingress from the surrounding air. Similarly, as the heat exchanger gradually becomes more porous with age, it too will allow moisture to get into the hydrogen. So it is important that the circulation loop for hydrogen gas on such an installation should include a desiccant dryer, to continuously remove absorbed moisture. The greatest fear, should moisture be allowed to build up in the hydrogen, is that condensation will occur on exposed live metal parts – leading to the risk of flashover. On generator sets which typically produce 22 kV at 19,000A, this could be disastrous. It is therefore recognised practice within the industry that the dew point of the hydrogen gas leaving the generator set should be maintained at a safe margin below the minimum casing temperature, typically an upper limit of 0 °C dew point at system pressure is observed. Should the hydrogen dew point rise above this upper limit, it is important for immediate action to be taken – either to decommission the generator to effect a repair or more likely to take immediate remedial action by pumping fresh, dry hydrogen into the system.
Calibration for Crane Scale and Dynamometer Applications
Interface is well-known for excelling at calibration services for load cells. Did you know this service excellence extends to dynamometers and crane scales?
Interface can calibrate dynamometers and crane scales with capacities of 100,000 pounds of force or more. This family of devices is often found in industrial, commercial, energy, military, and aerospace industry applications.
Crane scales are used as overhead weighing solutions ranging from light to heavy capacities and are normally placed in the load string of a crane. The devices provide crane overload protection, as well as information about the handling of bulk material. Some models are equipped with wireless communications to allow monitoring from safe distances at multiple locations.
Selecting Instrumentation For Functional Safety (SIL) Applications
Over the past couple of decades, the process industries have seen many changes when it comes to the design and implementation of emergency shutdown/safety systems. The introduction of several international and regional standards requires a more rigorous approach to the overall safety lifecycle of a system compared to the use of best engineering design practices of the past. As a result, a broader and significant increase in the implementation of these standards has been noted within the industry.
The standards most commonly being referenced by customers are:
• IEC 61511: Functional Safety – Safety Instrumented Systems for the Process Industry Sector
• ANSI/ISA-84.00.01 (IEC 61511 Mod) – Functional Safety: Safety Instrumented Systems for the Process Industry Sector
• IEC 61508: Functional Safety of Electrical, Electronic, Programmable Electronic Safety Related Systems