Knowledge Base
To assure the efficiency and effectiveness of compressed air systems, the measurement of flow is crucial. Not measuring means not knowing about the efficiency of your system. And since efficient and reliable measuring is a demanding task, every now and then a question comes up.
We're here to assist you and thus, hereby provide answers to most frequently asked questions by our customers. However, in case your topic hasn't been addressed yet, don't hesitate to contact us. We're happy wherever you are and eager to help you out.
Frequently Asked Questions
What is the difference between atmospheric and pressure dew point?
Atmospheric dew point is the dew point at no pressure under normal ambient conditions, such as in expanded compressed air. If the air is compressed the moisture contained therein is forced into a smaller volume. Thus, the moisture per unit of volume increases so does the dew point. The pressure dew point is always measured under pressure.
Why has a dew point be checked at the point of use?
Due to the fact that the natural phenomena of equalization (balancing unstable conditions by flow) humidity from the ambient is able to penetrate compressed air piping even the air is pressurized. As a normal compressed air system has countless connection points through which humidity enters the piping. This results in influencing the dew point negatively. The effect has to be considered for applications where the dew point is critical and therefore point of use is the only reliable way to avoid any risks for the production.
Why is thermal mass flow principle the most suitable technology for flow measurement in CDA?
The thermal mass flow principle measures the heat loss of a heated sensor a moving gas. Depending on the mass and the velocity of the gas passing through, the signal is proportional to the standard flow rate. This principle is very reliable over a wide range. Specifically for the detection of small air flows, as caused for example by leakage. Due to the small size an easy installation under pressure without interrupting the production is possible – another advantage over other principles.
Why has to be up- and down-streams of a flow sensor straight piping?
Almost all modern flow sensors require a so-called fully developed flow profile for accurate measurement. This profile is disturbed by obstacles and the direction changes in the pipeline and must be “straightened” over longer straight runs. That`s why particular inlet and outlet sections are defined and specified in multiples of the pipe diameter.
What is the difference between standard and actual flow?
The actual flow rate is the volume of a gas somewhere in the system, independent of its density, that flows through a certain point. The term actual flow rate is not clear, when it comes to the mass of a gas flowing through a given point, because gas is compressible. If the pressure is doubled, then for an ideal gas, the mass which flows at a constant flow rate through a particular point is also doubled. To take this enlarged mass flow into account, for gases usually the standard volumetric flow is used, because this is based to certain standard conditions and is thus comparable to the mass flow. In compressed air the standard usually is at 1 bar absolute and 20 degrees C.
What is the difference between standard, maximum and high speed range calibration?
SUTO flow sensors are calibrated at almost real-world conditions in the lab. Several calibration points are used to achieve a good accuracy. Depending on the measuring range (Standard, Max, High-speed) the calibration and testing efforts in production are increasing. It is recommended that the range to be chosen can cover the maximum flow rate safely with enough “room” at the upper end.
Why is calibration so important?
Every high precision device which is exposed to tough or fluctuating operational conditions therefore a sensor has to be checked and reset on a regular base. What many people do not know – this is even stipulated in the ISO 9001. We suggest to perform this calibration at least every 12 months.
Why there are particles in compressed air?
Due to the fact that pollutants are in the ambient air which is sucked in by the compressor also the compressed air is loaded with dust, particles, humidity or oil vapors. Particles are harmful for many production processes, e. g. electronics industry, pharmaceutical industry or R & D labs and therefore have to be monitored reliably.
Why does pressure drops occur in a compressed air system?
The compressed air has to pass many obstacles between the generation of the compressor to the point of use. This leads to a pressure drop.
How to monitor differential pressure for a purification system?
The purification system of a compressed air system consists out of staged filtration and drying systems. As the compressed air has to travel through filter elements, heat exchanges or desiccant layers with small diameters and many bends pressure is lost. Corrosion, retained particles or absorbed oil & water clog filters and dryers and cause significant pressure drops which is a loss of energy. Monitoring the pressure drop is easily performed by utilizing a pressure sensor up-streams and another one down-streams and calculating the differential pressure. The gained information helps for efficiently timing filter element exchange and dryer overhauls.