Bag Leak Detection Blog

Directly Measure Particle Velocity

Just like in dilute phase conveying systems, dust collection systems require the bulk materials stay entrained in the air stream.  This is accomplished when the air speed in the systems remains at or above the minimum conveying velocity for the product. If it dips below the minimum conveying velocity (also called transport velocity) the dust particles will begin to settle out of the air stream. Dust collector systems are engineered for certain parameters based on things like fan size, duct configuration, and filter media.  Once in operation, it is more common that the engineered conditions do not always match the reality of the process conditions.Directly measuring the particle velocity inside the dust laden duct can provide operations the means to understand and even optimize the performance of their dust collector system.

Problems Caused By Low Air Velocity In Dust Collection Systems

Do you monitor your dust collectors?

Baghouses and dust collectors have the reputation for being neglected or a source of constant maintenance problems. Some facilities have to monitor their dust collectors based on their local, state or federal reguations. Thrugh the years it has been common to simply monitor the differential pressure, or just visually inspect the outlet stacks. Triboelectric broken bag detectors and bag leak detection systems have been around for decades now. Let’s take a look at how a triboelectric dust collector monitoring system can bring benefits to your facility.

Many may feel that modifying or renewing an air permit can be a time consuming task, a new permit provides an opportunity to incorporate new monitoring technology that has other benefits. For instance, some may ask whether they should continue using opacity monitoring for their CAM requirements or if can they eliminate much of their manual monitoring by taking the opportunity to review their current practices.

First Emissions Monitoring Methods

Many options exist for monitoring various types of dust emissions including nuisance emissions, ambient/fugitive dust levels or emissions from a pollution control device such as an air scrubber or fabric filter dust collector. 

With ever more stringent regulations and the need for high performance from industrial processes in order to compete in a global marketplace, many facilities can no longer afford to install, operate and/or maintain outdated systems. The need for the best cannot be overlooked when considering operational and compliance issues for your facility. 

3 Reasons Why Accuracy Matters

Accuracy matters because accurate dust collection monitoring provides operators with the needed insight to operate, optimize and maintain these systems. Trying to operate a dust collector without accurate dust emissions data is like flying an airplane without an altimeter or driving a race car without a tachometer. Lack of data means poorer decision making and degraded performance.  

The "Alphabet Soup" of Industrial Dust Detection

Continuous Opacity Monitoring Systems (COMS) for dust detection form an integral part of many facilities’ environmental control systems. While we don't sell COMS dust detection systems, we field a lot of questions from engineering and maintenance teams about how they compare to other solutions. This article will answer a few of the common questions.

In many facilities, COMS systems were required by early permits to monitor particulate matter emitted from the facility. They were the "go to" CPMS (Continuous Parameter Monitoring System) for several years until USEPA first amended the MACT standards to incorporate triboelectric instruments.

Most COMS dust detection systems are placed after the emissions control system(s) such as a fabric filter dust collector to monitor its operation and efficiency at all times. They were an early technology, however, and in recent years, the limitations and inherent drawbacks of COMS for dust emissions detection have led some to investigate new technologies. One such technology mentioned is PEMS or Predictive Emissions Monitoring System. 

Stop guessing & start controlling

Controlling bulk material feed rates is essential for a wide range of industrial processes. Traditionally though process engineers have had to calculate, or frankly, guess. Industry has lacked an effective instrumentation for monitoring actual particle velocity often using gas/air velocity as a very approximate proxy.. Auburn Systems has solved this with an adaption of their patented triboelectric technology for use in bulk flow monitoring.

Positive Physical Control vs. Indirect Control

The two primary means of conveying bulk products are by pneumatic and mechanical conveying with the most common type of mechanical conveyor being the screw conveyor. Both methods have benefits in certain applications over others. In general, finer, more consistently sized materials as well as some granular and pelletized materials work well with pneumatic conveyors whereas larger, irregularly sized materials, as well as moist, doughy, and packable materials work better with screw conveyors. However, in the middle reside the majority of materials for which both systems could be appropriate. 

In cases where either system could be used, sometimes previous hassles or perceptions of pneumatic conveying problems may lead engineers to use a screw type system. Let’s review three of these and consider why engineers should not be hasty to rule out pneumatic conveying - in fact how to overcome these problems to make pneumatic conveying more reliable. 

3 Pneumatic Conveying Challenges:

1. Justifying Investment in “Complex” Pneumatic Systems

Planning for recirculating from a dust collector

NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids provides general guidelines for combustible dust control in industry. The NFPA also has two standards that cover specific guidelines for explosion protection systems (NFPA 68) and explosion prevention systems (NFPA 69). There are also three other standards for specific industries that require slightly different (usually stricter) regulation. These include NFPA 61 that concerns agricultural facilities, NFPA 484 covering combustible metals and NFPA 664 covering woodworking facilities. 

As we considered in our article Different Methods for Measuring PM Emissions and Filter Performance, plants face a difficult task comparing data derived from various methods of measuring PM emissions. Often  fabric filter manufacturers, dust collection system OEMs and other product manufacturers use units that are different than those used by regulatory authorities for emissions standards and for specific requirements of air permits.  

In the last article we considered methodologies used by control equipment manufacturers and their purpose such as grains per standard dry cubic foot, or parts per million. Now we will consider those used by regulatory agencies, their reasons for doing so, and how we can convert back and forth between them when needed. 

Variability in writing and enforcing air permits

Contrary to what you might think, there is little uniformity in air emissions permits from plant to plant. While many look to the Federal Government’s standards for PM emissions (i.e. MACT and other regulations), even these are not always applied uniformly across all applications. The job of actually enforcing most regulations often falls to the State authorities, who then may even distribute the responsibility further to other smaller air control boards that serve specific regions (such as in California). State regulations must be at least as strict as the Federal regulations when there is overlap - but the states have broad discretion on their own enforcement requirements. Even then the exact requirements for each plant can be further modified depending on factors such as the exact location of the plant, the surrounding area’s pollution levels, number of employees, and process conditions among others. 

That means there is a wide variety of language and terminology used on permit documentation.

For this reason, dust collector OEMs and filter manufacturers may not always provide emissions testing data that directly corresponds to the language used on your plant’s air permit. Environmental/compliance engineers often have to interpolate available test data from OEMs to determine if the use of this particular product will enable the plant to achieve compliance. 

That leaves us asking....Why can’t there just be one standard method of calculating emissions data?

This is the first of two articles which will tackle that question and explain how to reconcile the two.