Teledyne Hastings Instruments Blog

It’s hard to believe that it is now March, which means that Pittcon 2013 is right around the corner. Teledyne Hastings Instruments will have Applications Engineers and representatives in attendance to answer all of your mass flow and vacuum instrumentation questions.

Pittcon is an annual conference on laboratory science that is organized by The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. Pittcon started as a small technical conference held in 1950. The first 18 conferences were held in Pittsburgh, Pennsylvania, but the conference has since grown. Locations now vary from year to year with this year’s conference being held at the Pennsylvania Convention Center in Philadelphia, Pennsylvania from March 17-21.

There have been many changes over the 60 plus years of the Pittsburgh Conference, and remains a worthwhile event to attend. Teledyne has had a presence at the event for the past 35 years. Included in the weeks events are thousands of exhibitors, numerous technical programs and lectures, and short courses. It provides the opportunity to meet and interact with scientist from across the country and around the world. Papers and articles are presented daily, illustrating the advancements in science in the past year. And finally, it allows for a single location to walk around and see over 17,000 companies and exhibitors with their products and technologies.

Teledyne Technologies Incorporated will have 4 companies in attendance at Pittcon this year. In addition to Teledyne Hastings Instruments, Teledyne Tekmar, Teledyne Leeman Labs, and Teledyne Judson will be exhibiting. Teledyne Tekmar is a leader in the design and manufacturing of analytical instrumentation including products for gas chromatography sample introduction, total organic carbon (TOC) and total nitrogen (TN) analyzers. Teledyne Leeman Labs is a producer of world-class instruments for elemental analysis including ICP spectrometers, atomic absorption spectrometers and mercury analyzers. Teledyne Judson is a leading designer and manufacturer of high performance infrared detectors and accessory products. The Teledyne family of companies will be located in booths 916 and 917, which are located near Entrance D to the Pennsylvania Convention Center. Teledyne employees will be giving presentations on a variety of topics while at Pittcon. If you would like more information on the schedule or the topics to be covered please contact us or stop by our booth and we can provide that information.

Teledyne Hastings Instruments has a great deal of experience with the analytical instrumentation industry. We are always interested in new applications even if they do not exactly fit into the standard product design for mass flow or vacuum instrumentation. We are very willing to examine possible custom designs to meet the requirements of your system. Some examples of previous custom applications include a variety of non-standard packages for both our mass flow and vacuum products, modified electronics, high pressure designs, and even custom designed flow and vacuum sensors.

We welcome your comments and your questions and look forward to seeing you at Pittcon 2013. Please stop by our booth and discuss your projects with either Vikki Jewel or Brandon Hafer. You can also email your questions to Victoria.Jewell@Teledyne.com or Brandon.Hafer@Teledyne.comand we’ll be happy to respond and work with you. 

Brandon Hafer is an Application Engineer with Teledyne Hastings Instruments. He was raised in Pottsville in Eastern Pennsylvania and is a fan of the Philadelphia Phillies and Philadelphia Eagles. He is looking forward to returning to the Philadelphia area for Pittcon 2013. If you would like to contact him, he can be reached at brandon.hafer@teledyne.com.

As I go through the day looking at various mass flow applications, I often notice that it is very easy for users to overlook one of the crucial items required for calculating mass flow. Looking at an application with its established requirements, we often jump right to determining “what flow rate is required?” However, it is important to remember that mass flow applications using volumetric units must reference a standard temperature and pressure. But why is this the case?

When examining liquid flow instruments, we know that liquids are incompressible and thus the amount of a substance present is determined by the volume being used. This leads to a simple calculation using density with the already determined volume to find the mass present in the volume or the volumetric flow.

Gases, however, ARE compressible and so the volume is only one factor in determining the amount of material being measured. If we look at the ideal gas law that you may remember from a chemistry class school (PV = nRT), we understand that temperature (T) and pressure (P) must also be considered in the equation. Otherwise it is impossible for us to know “how much” of the substance (n) there is in the space (V) or flowing through the system.

But given all of this information do we actually end up with the mass flow? The actual quantification of this “how much” calculation is expressed in moles (n), which is an extremely large number of molecules of a gas stated as Avogadro’s number, equal to 6.02x10²³ (Don’t be scared by this value, though. A mole is a number, just like one dozen is 12, so one mole is 6.02x10²³ molecules). Since the number of molecules of a gas and the mass are directly related for each gas type (i.e. molar mass), we are able to calculate the mass of the volume or volumetric flow based on the number of moles present. This is based on the assumption that the measured gas is pure and not contaminated with any other gases.

We’ll look at an example of the difference of STP conditions in a mass flow meter.  Teledyne Hastings Instruments assumes STP of 0°C and 760 Torr, but would prefer the customer to specify their STP conditions for the application. We will use the frequently referenced STP of 20°C and 760 Torr for the second part of this example. Suppose that we are looking to  measure 1 SLM (Standard Liter per Minute) of Nitrogen gas. As I’ve discussed earlier, the 1 SLM must be referenced to an STP value, so we will use our assumed conditions of 0°C and 760 Torr. If we were to change to the second set of conditions, the number of moles present in the flow (Molar Flow Rate) would change, and our mass flow rate would thus change (based on the direct relationship between mass and moles). Our initial mass flow rate of 1 SLM of Nitrogen at 0°C and 760 Torr would now be 1.074 SLM of Nitrogen at 20°C and 760 Torr.

An important item to note is that the STP conditions are not actually present during the calibration of mass flow meters and mass flow controllers. Gas conditions are not brought to 0°C and 760 Torr prior to running calibration of equipment. The substance may not even be in gas phase at 0°C. The STP conditions are simply stated to define the standard volumetric flow rates of a substance IF it were an ideal gas at standard conditions.

This is also the reasoning for the addition of the “S” or “Standard” at the start of the stated volumetric flow rate (e.g. Standard Liters per Minute (SLM) or Standard Cubic Centimeters per Minute (SCCM)). We are stating the volumetric flow that would be present using standard conditions. So, using the information that we learned earlier, by stating the units in Standard Volumetric Flow Rate we are actually stating the Molar Flow Rate. This information changes based on the standards we are referencing and emphasizes the importance of stating the required STP conditions.

We welcome your comments and your questions about mass flow. Please complete the form below:

Brandon Hafer is an Application Engineer with Teledyne Hastings Instruments. He completed his undergraduate degree studying meteorology at the Pennsylvania State University before serving as an officer in the United States Navy. He received his master’s degree in Systems Engineering from George Washington University and has been with Teledyne Hastings Instruments for two years. If you would like to contact him, he can be reached at brandon.hafer@teledyne.com.