Bubbler level measurement. Bubbler level measurement. Do we need a flowrater in bubbler method? I am in a debate with my friends. My point is that in bubbler level measurement, we only need a pressure regulator, a needle valve and a pressure gauge. Through pressure regulator we set the value a little above the head pressure of measuring liquid in an open tank. Needle valve, which is installed just after pressure regulator, is used to set the optimum rate of bubbles. Once the desired bubble rate is achieved through calibration, there is no need to change the opening of needle valve. My friend says that we have to have a rotameter which should maintain the flow rate of bubbles through some sort of built- in control valve. Can anyone decide through equations who is right? You need a differential regulator which can produce a constant gas flow rate under varying head pressures. If the tubing between bubble tube and transmitter is reasonably short, it's convenient to inject the bubble supply right at the transmitter that is purging any moisture or corrosive gas. Electrocardiographically, atrial fibrillation is characterized by the presence of rapid, irregular, fibrillatory waves that vary in size, shape, and timing. This set of findings is usually associated with an irregular. 1900s; Name Class Areas of Note; Winona Keith Algie: 1900: Headmistress, Charles River School . Bloomer: 1900: Yale All-American tackle . Collins: 1900: Publisher & editor, McClure’s. University College Cork, College Road, Cork T12 YN60 +353 (0). I am in a debate with my friends. My point is that in bubbler level measurement, we only need a pressure regulator, a needle valve and a pressure gauge. Through pressure regulator we set the value a little above the head. We normally use a 0- 1 l/m rotameter supplied at line pressure (typically 8. N2) once the flow is set the rate hardly changes for empty or full tank. 2004 Research Publications. 2004 Research Publications are listed alphabetically by section name below. Please note that copies of these publications are not held centrally and all external enquiries about specific.The change in bacpressure is insignificant compared to the drop across the needle valve. Regards. Roy. No, you don't need a rotameter, in fact you don't even need a regulator or needle valve. You just need some method of establishing a small flow. I have used the gauge snubber fittings that have a sintered metal flow restrictor. Merium make a nice device, it has a needle valve and a glass bowl. You fill the glass bowl with light oil or glycol and set the needle valve to give you a bubble every second or so, the flow seems to stay constant for months on end. If your transmitter is far away from the bubble tube it's usual to introduce the bubble gas near or at the bubbler to avoid pressure drop due to changes in flow. I saw an installation once where they had a gauge and selector valve in the control room connected to bubblers in several tanks about 1. To measure the level the operator selected the tank and then puffed up the line with a squeeze pump similar to the old fashion blood pressure monitor. They are also still quite common for flotation level in mining. Your friend is referring to a constant flow regulator, some people spec them but not really necessary. Regards,Roy. The company I work for uses Siemans constant flow regulators (rotameters) to ensure a constant amount of air through both tubes of our DP bubblers. I can't think of any needle valve combination that would be able to ensure accurate readings between both diptubes (we use Rosemount DP transmitters). If you want, check us out at www. Righton Instrument Bubblers. All your asumptions are WRONG. First of all you need to know the relationship between pressure, density, friction loss, line length, air pressure, tube size etc. The case the operator puffs air- - here the the density may not be changing and so is the level. Next accuracy may be +/- 1. I do not know what you are measuring in the name of level. One needs to have a good understanding of bubbler type level measurements and the fundamentals. You need constant air flow depending upon the head of a fluid that has to be overcome. If the level is constant most of the time and accuracy is of no consequence, a simple restriction will do- -- but this is a particular situation and is not a panacea! I am not considering level measurement with variable density her. The bubbler air flow controller (not a rotameter- - since its valve has a fixed restriction) is used to send in constant air flow/bubbles to overcome the head/level in the tank. For a certain period of time the rotameter would appear to work but to be more precise, you need a flow controller to adjust the flow for varying pressure at the downstream side of the rotameter or shall I say bubbler. You need to consider the tubing length, tubing size,friction losses,location of the transmitter before declaring the system is okay. Simple restrictions and bubblers appear to be okay but in the real sense when density does not change and the accuracy of is of no consequence, to the untrained eye these systems seem to perform okay! A good source of information is - - from Foxboro Instruments . The contents are still valid and are good. There is lot more to be covered, I am stopping at this! Hi there roger,I'm glad to have found someone who knows this topic well. I have a few questions which i hope you can help me out. Quoting your previous post,> .. The bubbler air flow controller (not a rotameter- - since its valve has a fixed restriction) is used to send in constant air flow/bubbles to overcome the head/level in the tank. For a certain period of time the rotameter would appear to work but to be more precise, you need a flow controller to adjust the flow for varying pressure at the downstream side of the rotameter or shall I say bubbler. I'm taking the case where density is constant and level is varying. I also wish to ask of the calibration requirements of a bubbler system during operation. There are systems which i saw that claimed self- calibration by timed- controlled purges to ? I'm taking the case where density is constant and level is varying. The basic principal is that the air pressure required to push the tank fluid out of the bubbler tube corresponds to the liquid head above the end of the bubbler tube. You don't actually need to generate any bubbles, but bubbles indicate that you have more than enough air in the bubbler tube to measure the tank head. If you know the liquid density, you can calculate the liquid level from the air pressure required to generate bubbles. The rotameter in the air line is only there to show that air is flowing enough to generate bubbles, since it is generally not convenient or even safe to observe the tank to see if any bubbles are rising. However, looking at the rotameter is a manual operation convenient during startup, but not at any other time. Air flow through the bubbler may have been adjusted when the tank is not full. As the level in the tank rises it creates greater force at the bubbler tip that eventually will cause the air flow to stop and tank fluid to displace air in the bubbler tube. The automation systems you mention are designed to keep the air flowing at all time so you do not need to go back to the needle valve at the rotameter to adjust airflow. Another solution is to always set the air flow when the tank is full. There is no inaccuracy due to excess air flow, but know that you are typically using dried instrument air to do the bubbling, and that is not exactly a . Maybe the automatic airflow compensation would pay for itself, but somehow, I don't think so. Dick Caro===========================================Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,2 Beth Circle, Acton, MA 0. USAE- mail: RCaro . Please note that AIR FLOW has NOTHING to do with the actual pressure measurement: The level indicated by the system's sensing device, such as a pressure sensing load cell with say a 4- 2. A output is merely the back pressure of the air which is effectively leaking out of the bottom of the 'bubbler' pipe. The higher the level in the (open to atmosphere) tank, the higher the back- pressure of the air. If there is nothing in the tank, there would be no back pressure at all because all of the air would be freely flowing out of the end of the pipe - nothing opposing it or nothing causing any back- pressure. The other extreme of course is when the pipe is blocked (say if you placed your thumb over the bottom of the pipe), no air can leak out anywhere therefore you would read full output (full back- pressure) which would be whatever the air supply pressure is set at. If it becomes blocked you can see that the air flow would be zero or very low. Controlling air flow is not necessary, although some people like to put a rotameter in the line simply to keep a constant check on the condition of the bubble pipe (not as a way to accurately control air flow), as the bubble tube system is measuring BACK- PRESSURE, proportional to level and that's all. Having (I hope) better explained . On many of the stock chest bubble- tubes I installed and maintained in a large pulp & paper making site, (many years ago they use mainly ultrasonic in the same vessels now), we also provided a 'water purge' which was also fitted with a rotameter in effort to keep the bubble- tube clear of pulp build- up inside the buubler- tubes, which often very quickly, fully blocked the bubble- tubes.. Note however, that it is important to ensure that the air supply pressure is greater than the maximum level you are measuring. KPa when full) your supply pressure would need to be at least 6. KPa, but typically would be set at say 1. KPa. Always must be a lot more than the max back- pressure (maximum level). Remember it is BACK- PRESSURE (not supply pressure) you are measuring, so the supply pressure can be as high as you like, but not too LOW! We use a bubbler system to measure differential pressure across a traveling screen, the medium we are measuring is river water. If I adjusted the flow to . SCFH, the indication would match my measured results. In raw water, you have to be concerned about algae and other types of build up at the bubbler tip end. Ideally, you should have at least 3/4. In some cases stilling wells are also used. In some cases stilling wells are also used. I am assuming its purpose is as a flow regulator for the air/gas to the bubbler. HELP! John. The word sounds like an internet dictionary translation of air (pneuma) regulator (stat). Bubblers use a constant differential relay (regulator) to create a constant flow rate of bubbles. There's a cutaway drawing of a constant differential relay on the last page of this pdf document (URL below), but its operation is not described. Adding a constant flow regulator is overkill.
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