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Q1 - What is the current position that EPA is taking with respect to Tribo and Opacity… or other technologies?
A1 - EPA's Position on Triboelectric Bag Leak Detector vs. Opacity Meters The USEPA United States Environmental Protection Agency) believes that baghouse leak detection represents state-of-the-art compliance assurance for baghouses, and has implemented it in all new source MACT (Maximum Achievement Control Technology) standards since 1995. MACT standards are an important component of the National Emissions Standards for Hazardous Air Pollutants (NESHAP). Electrostatic Bag Leak Detection Systems (BLDS) are designed to monitor events and to locate leaks before catastrophic dust breakthrough occurs. This differs from opacity monitors which only monitor continuous emissions. New rules, such as these developed under the part 63 NESHAP program, emphasize direct measures of compliance. Bag leak detection systems provide this higher level of compliance assurance.
Q2 - Can you discuss operator interface a little?
A2 - Looking at the operator interface on a triboelectric BLDS can vary from manufacturer to manufacturer. In Auburn’s experience, we have tried to improve the interfaces as the product line has evolved. The early units did not have much interface to speak of as you had to rely on how many turns of a potentiometer screw to know where you might be at. Over the years, the user interface became much more intuitive to how the units worked. And our latest product line the TRIBO.dsp series is extremely informative and efficient from a user’s point of view. We carried that philosophy over into our software as well, allowing for user customization so that they can easily see and navigate to find the data they need.
Q3 - The focus has been around filter bags, in your experience, are pleated cartridges less apt to fail?
A3 - During the webinar, we did seem to focus on the filter bag. Often when we say baghouse, we use it as a generic term for dust collector, but in truth our detectors and monitors have been used on all types of fabric filters, whether they are in a typical baghouse or cartridge filter collector. Because monitoring applications all have their own unique set of physical conditions, it is hard for us to say if one type of filter is better than another. So much can depend on how the collector is run and maintained. Although I know that pleated filter bags have their advantages, I can say that we are often used to monitor this style of filters as well.
Q4 - How do you deal with particle buildup?
A4 - Depending on the application, the probe that is installed in the duct or pipe can experience no build-up or excessive build-up. It is important when deciding to install a detector what the conditions in your application will be. This is why we always take the time to find out information about your particular application. When we know the process conditions we can anticipate the need for a special probe for these circumstances. For instance, if your process handles a conductive material that tends to coat everything, we will use a jacketed probe to protect against false signals like material bridging or battery effect. IF you know that you only sometimes have moisture present which can cause some material to build-up but is corrosive we will use an alternative probe material to handle the possible corrosion. Also – all of our Tribo.dsp series of products have an automatic “probe error check”. This feature alerts the user for when there is a false signal due to excess material or moisture and is an indication that the probe may need to be cleaned. This is a good question – and the most important point is to discuss your application details with us – so we can help provide the best probe configuration and eliminate extra work and frustration for your operators and maintenance personnel.
Q5 - Has the device EPA certification?
A5 - The EPA recognizes triboelectric style instruments as qualified for use to satisfy the Bag Leak Detection System requirements. Our equipment has been installed for many years to help our customer meet their EPA, state or local environmental requirements. Our technology exceeds the minimum BLDS requirements stated by the USEPA for MACT Standards.
Q6 - How does moisture affect a differential pressure gauge?
A6 - We can look at that question in one of two ways – moisture affecting the material being collected by the filter and moisture actually affecting the instrument. If there is moisture in the air stream into the collector and it is condensing, there is a concern of blinding the filter media which will cause the DP reading to increase – which means your fan is working harder to try and pull the air through the collector – Higher DP means higher costs. As for how will moisture affect the actual device, from our experience, any time we have supplied a DP monitor to a customer it is very important that they are installed so that moisture does not get into the switch nor into the pitot tubes – that will affect the measurement and performance of the device. Consult with the manufacturer of your device for more specific guidance.
Q7 - Does your device need to be calibrated with an isokinetic test?
A7 - This is an interesting question as it can speak to how to set up a unit or how to use it for certain applications. As far as set up of Auburn detectors and monitors, all of our equipment is shipped from the factory ready for use and does not need any field calibration. All TRIBO.dsp series products use all digital no-drift circuitry so that periodic zero adjustments or tests are not needed. This means even less maintenance for your operators. Some customers however, do want to correlate our pico amp signal to the concentrations that are being emitted from the process. For this an isokinetic test can be performed. More commonly customers will perform an EPA Method 5 test to measure the output from the process. This data is then matched to our recorded signal during the same time period and a correlation factor is determined. As long as the process conditions are relatively constant, the user can monitor using milligrams per cubic meter, or grans per dry standard cubic foot. Some of our monitors can be set up to read in these engineering units. In applications where velocity is variable, we can also measure the velocity to keep a good correlation for the process.
Q8 - Can you correlate reading to actual emissions number in mg/m3 or gr/ft3?
A8 - This question is answered above.
Q9 - How large a duct can the standard probe handle?
A9 - Our standard probe sizes range from ½” for process flow application to 36” for duct sizes up to 72” in diameter. We try to make sure that an inserted probe extends to at least halfway across the diameter or longest dimension in rectangular ducts. When the duct sizes exceed these dimensions, we will either use two probes daisy-chained together or use a wire rope sensor to span longer distances.
Q10 - What happens in case of moisture in stack coming from wet scrubber?
A10 - Auburn equipment is currently being used to monitor wet scrubbers. Typically we will use a jacketed probe due to the constant presence of moisture. This prevents the high signals that would be generated using a standard stainless steel probe. The probe will detect the rise in particulate or the failure of mist eliminators to help personnel properly operate and maintain their wet scrubber.
Q11 - My permit states I am only required to monitor the differential pressure of my baghouses – won’t they tell me when my baghouse is starting to have a problem?
A11 - Differential Pressure gauges or meters are a valuable instrument for running your baghouse. It gives you the information you need to know for when to clean, perhaps control your timer board. But as an early warning detector that can detect the onset of tiny leaks – a DP sensor can’t do that. By the time that the differential pressure would let you know that you have hoes in your bags – it will be at the visible emission point – it’s just not what they were designed to do. Another point is, I have talked to many customers who installed a bag leak detector and then did not have to monitor and record the DP anymore. Since they were reading the gauges manually – it translated into instant labor and time savings.
Q12 - I know there are different companies that sell the triboelectric style monitors – are they all the same?
A12 - That’s a good question – and no, they are not all the same. Basically you will run into three types – the older generation triboelectric like we talked about. Some detectors on the market are inexpensive, but they still are using older electronics, based on the “DC” triboelectric effect – like our early models were. These types are prone to the same problems of false signals and limited ranges. Another type you will see are those that only monitor a portion of the triboelectric effect – the “AC” portion or the induced signal caused by passing particles. These have their place for certain applications, but they basically ignore the most linear part of the signal, the “DC”. Lastly, You will find Auburn’s 3000 series, our latest improvement, formally introduced back in 2013. This monitor is all digital, using a unified monitoring platform. This means it sees the entire triboelectric effect, giving the end use the best of both worlds by monitoring the “DC” and the “AC” signals simultaneously. This gives you the most reliable repeatable signal in a bag leak detector. It also opens up may process applications – but that is a topic for another day. So to answer the question, don’t approach the decision about a detector thinking they are all the same – do your homework, or check our website and give us a call and we can go into further detail for you.