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Hydro

Below the video, we provide the questions and answers from the webinar.

  • What is the ideal space for reading this sensor?
    From the point of view that the comment concerns the sensing distance of the transducer (displacement sensor - proximeter). The selection of which distance the sensor to use will vary according to the characteristics of the machine (e.g. maximum bearing clearance). Commonly, for radial measurement, a sensing distance of 0-4mm is more than enough.
  • Does the shaft rotation frequency impact this inductive proximeter reading?
    Yes! Generally, due to the unbalance of the machine, there will always be a component related to the machine's rotation frequency. Generally the problems will also be related to harmonics of this frequency.
  • Does the anisotropy of the shaft material interfere with the proximeter measurement?
    In fact, the anisotropy of the shaft material interferes with the measurement of the inductive proximiter, as well as the effect of residual magnetism, and this causes the runout effect (the measurement will show a "vibration" that is not from the machine, but from the imperfection) . Treatment to correct this "defect" is complicated. The standard suggests, for example, "Shaft plating" for correction. But this is generally unfeasible. When this occurs, it is recommended to choose another axle track. If this is not possible, a test can be carried out to check the influence of this runout on the measurement. With data acquisition from the installed proximiter and a phase reference, the machine is started to run at the lowest possible speed. This way, the result measured by the proximeter will have minimal influence from external forces (unbalance and any other problems that may appear) and will display the "quality" of the track. Knowing this runout, in future analyzes you will be able to take into account the results of these tests.
  • Because a lot of people get confused... for pressure in suction tubes and spiral boxes, I've seen people using static pressure sensors, but is it worth it? It makes sense?"
    Generally, for vibration analysis, you want to use “dynamic pressure” sensors. This means that the sensor must respond to pressure variations that occur over a short period of time (e.g. frequencies of 500-1000Hz). Also, due to the better frequency response, it is common to measure vibration at points such as the suction tube (in addition to pressure) – in this case, dynamics that are not detected by the pressure sensor are measured. “Static pressure” (average) can be useful for measurements in steady state, where you do not want to record transients. It is still useful, for example, to try to identify pressure losses (in the grid, conduit, etc.) during machine operation.
  • Is it always interesting to have more than one type of data capture from the same point?
    Generally yes, as they will be “observing” different behaviors. For example, in a sliding bearing, it is recommended to install proximeters (measurement of relative vibration of the shaft in relation to the bearing), and acceleration sensors (absolute vibration of the bearing) – Even standards (ISO 20816-5, for example) recommend these points, a topic that will be covered in Webinar 2 of our series.
  • We are planning to install proximity sensors in our PCH's. The problem is that we don't have an ideal track on any of the axes and sending the axles to be machined is unfeasible. Do you have any solution?
    In fact, the uneven surface on the shaft will influence the measurement, causing what we call runout (it can have electrical or mechanical characteristics). Machining is the most recommended... It is common in the field for maintenance personnel to sand the shaft, which in terms of safety is dangerous, and this will generally only remove rust or paint. Perhaps, as a recommendation, it is worth carrying out a test to verify the influence of this runout on the measurement. With the data acquisition from the installed proximiter + a phase reference, the machine is started to run at the lowest possible speed. This way, the result measured by the proximeter will have minimal influence from external forces (unbalance and any other problems that may appear) and will display the "quality" of the track. Knowing this runout, in future analyzes you will be able to take this result of these tests into account.
  • Are vibration measurement routines in these cases constant (measuring all the time) or intermittent (e.g. once a day)?
    You can work with different types of processes and systems. For example, monitoring can be done through routines with portable equipment or through a permanent 24/7 monitoring system. In both cases there are associated costs. Generally, when talking about hydrogenerators in the turbine-generator set, permanent monitoring is economically viable.
  • Where can we acquire this buffer? I have already made a quote and we are looking to purchase a standard for calibrating the accelerometers, but at the time the cost-benefit ratio was not viable, if you have any recommendations, I would be grateful."
    I understand that “buffer” means you are referring to the “shaker” that generates a known vibration pattern. In this case, in fact, they are expensive instruments. The one we have is from Modal Shop (a PCB/IMI company). There are simpler models, which, for example, only generate a fixed vibration reference (frequency and amplitude).
  • I would like you to comment a little about the sensor manufacturers, difference in quality, national vs. imported and cost-benefit ratio."
    In AQTech's experience, in general, we came across few national sensing manufacturers. Some of the ones we have already tested fail in terms of their quality of finishing and documentation. For example, there are imported sensors that come with a calibration letter at 3 different frequency points, some national ones only inform the nominal value in the data sheet. National alternatives are not always cheaper either. It is common for our customers (generally dealerships) to have preferences for a certain manufacturer, and within monitoring system projects we try to take this into account, mainly evaluating the nominal technical characteristics and laboratory tests to prove these characteristics.
  • Is it possible to access the application remotely, for example via TCP to access event histories through some software and embed applications?"
    Yes, it is possible to access vibration monitoring applications remotely. Speaking a little about AQTech solutions, as they are based on PC platforms, they adapt to the most diverse IT architectures. Today, for example, with some clients we have remote access for system maintenance. This same remote access allows our customers to even carry out tests on the machine remotely, in addition to allowing remote consultation. If we are to evaluate technological evolution in a more general way, we will soon have this data stored in the cloud and viewed through a Web Browser. In the area of generation we still have to break the paradigm of “removing” data from the plant, which is generally made difficult by the area of network and IT security (in addition to the fact that in many plants we do not have a communication link with sufficiently cheap bandwidth). .
  • Regarding vibration of speed reducers. Radial Proxymeter (2x) or accelerometer on the housing (sides coupled), which would be the best solution, since it is gear equipment."
    Generally for evaluating gearboxes, given the harmonic characteristics involved, accelerometers are more suitable.
  • About the surface finish of the axes for the installation of proximeters. We can't machine it.
    In fact, the uneven surface on the shaft will influence the measurement, causing what we call runout (it can have electrical or mechanical characteristics). In fact, machining is the most recommended... However, I have seen maintenance personnel in the field sanding the shaft, which in terms of safety is dangerous, and this will generally only remove rust or paint... Perhaps, as a recommendation, it is worth carrying out a test to check the influence of this runout on the measurement. With the data acquisition from the installed proximiter + a phase reference, the machine is started to run at the lowest possible speed. This way, the result measured by the proximeter will have minimal influence from external forces (unbalance and any other problems that may appear) and will display the "quality" of the track. Knowing this runout, in future analyzes you will be able to take this result of these tests into account.
  • Do sensors with and without electronics have problems with cable lengths? Because the rotating equipment supplier is using a certain sensor and says we can't shorten the lengths."
    In sensors without built-in electronics, the cabling characteristics (including length) do influence the measurement. (Just to be clear, cabling between the sensor/probe and the signal conditioner. The cable from the signal conditioner to a measuring device generally has a much smaller influence, sometimes even negligible - this needs to be assessed on a case-by-case basis). In the case of the proximiter, only the caps remain on the probe. The cable characteristic (RLC), therefore, will influence the measured result. Generally, when you buy a proximeter without built-in electronics, you already define the size of the probe cable and/or extenders, and the conditioner is calibrated for this condition. In fact, it is usually a specific cable, already connected, and it would not be easy to reduce the length. In the case of sensors with integrated electronics, the effect of cabling continues, but it can be considered negligible in most cases (the characteristics of the sensor and the data acquisition equipment must be evaluated). Specific to the proximity sensor, those with integrated electronics generally have a 0-10V or 4-20mA output. If we consider the output at 0-10V, it is unlikely that the cabling impedance is significant in relation to the input impedance of the acquisition equipment, but you have to evaluate its characteristics to be sure.
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