FILTERS, CARTRIDGES, BAGS, PANEL FILTERS, DUST COLLECTOR, DUST COLLECTION SYSTEM, COMPACT DUST COLLECTORS, DUST COLLECTOR MANUFACTURER, EFFICIENT DUST COLLECTORS

Here are some of the problems often faced with filters, and suggested solutions

The baghouse gives insufficient draft at pickup points?

There are many potential reasons for not having enough draft at your pickup points. The height and length of your hoods may be incorrect. Your fan may not be sized correctly. You may have dampers that are in the wrong position. You may have air leaks in your duckwork. But often times, the baghouse is partly responsible. If the unit is undersized (air-to-cloth ratio is too high), there could be a large pressure loss across the baghouse that robs the system of draft. Or, if the cleaning is not optimized (frequency, duration, sequence) the filters may have a higher pressure loss. The main point is that you need to analyze the entire system and not simply point at the baghouse only.

What's the optimal duration of the electrical "on-time" for a cleaning pulse for a pulse-jet baghouse

In most cases, 100 milliseconds is suitable. Anything longer than this is usually a waste of compressed air.

How often should the filter bags be cleaned

You should clean filter bags as little as possible in order to maintain the desired differential pressure. Most filter bags require a dust cake to effectively filter dust from the air stream. The dust cake, not the filter media, is what collects all sizes of dust particulate, including sub micron particulate. Over cleaning of filter bags removes the dust cake and allows small particulate to either become embedded in the fabric (causing fabric blinding) or penetrate the fabric altogether and escape out the stack. Over cleaning also causes flex fatigue, leading to premature bag failure. You should always clean bags based on differential pressure, not a fixed time interval.

How to calculate the efficiency of a dust collector?

You need the know the inlet dust loading (IDL) and outlet dust loading (ODL) of the collector.

The formula is:
[(IDL - ODL) / IDL )] x 100 = Efficiency %

(Where IDL = Inlet Dust level, and ODL= Outlet dust level)

At what efficiency should the filters operate?

Efficiency is a mathematical expression that compares the amount of particulate collected to the amount entering the collector. All filters are designed to collect 99% + of the material introduced into a typical system. More advanced products, such as cartridge elements of SANTONI, can significantly increase efficiencies. All the efficiencies, however, are dependent upon the operating design criteria, such as air-to-cloth ratio, particulate size, etc. A 99%+ efficiency assumes that standard engineering principles are being used in the design and operation of a collector. It should never be assumed for permitting purposes that this will always be the case. Keep in mind that efficiency can be a misleading statistic. It may be very high if the inlet particulate loading is very high and much lower if the inlet loading is low.

What is the best way to find leaks in a baghouse?

Structural leaks and holes in filters are not easy to spot. Even a small hole in a filter bag or leak at a door seal can create major headaches. The best way to find leaks is to use a specially designed fluorescent colored powder (called Visolite® Leak Detection Powder). You simply inject this powder into your air stream ahead of the baghouse and the powder accumulates around holes, bad seals, and other types of leaks. After shutting down the unit, you can find the leaks by shining a monochromatic light (called a Visolite light) around the inside of the collector. The Visolite powder glows under the light, clearly indicating any leakage points. After making repairs and/or installing new filters, you should run another Visolite test with a different color to make sure all leaks have been eliminated. Visolite has been used in numerous applications for over 20 years and is still the most cost effective way of finding leaks.

At what pressure drop should my collector operate?

This is dependent upon many variables, of which the most significant are: air-to-cloth ratio, particle size, filter media, particle count and population, temperature, and gas stream chemistry. However, in most systems, a pressure drop in the range of 3"-6"w.c. is desirable. The most important thing to note, with regard to the proper operating pressure drop, is how well maintained a pressure drop is before and after cleaning over a period of time. The ideal situation is to maintain stable pressure drop, which indicates that material is being collected and released properly from a filter bag. For instance, if a systems pressure drop continues even after cleaning, this could indicate a potential blinding situation, in which the material has either become embedded in the filter bag or is not releasing for some reason. Conversely, a pressure drop that decreases continuously even after cleaning would indicate that there is a breach in the system, in which the dust is either going through the filters or around them somehow.

How to know when to replace filter bags?

If you can't maintain a desired differential pressure (even with proper cleaning) and/or when you detect emissions at the outlet, it may be time for new filters. Of course, this requires you to have properly working gauges and particulate monitoring devices. Don't base your decision on time alone - look at the operating conditions of your baghouse. Another suggestion is to use a leak detection powder such as Visolite® to help you spot holes in the bags. Even if just one or a few bags have failed, the dust entering the clean air plenum could cause many other bags to fail prematurely. The key is early detection to avoid a complete change out.

If just a few filter bags a dust collector have failed , can these be spot changed instead of replacing the entire set of filters?

SANTONI recommends that you spot change only up to 20% of the filters in a collector. When you put new filters among existing filters, the dirty air will tend to quickly flow to the new filters, often causing an unequal dust loading on those filters. This can cause premature blinding of the new filters and may lead to changing out the entire collector anyway. Anytime you have failed filters, you should determine the cause of failure. Sometimes it may be the physical properties of the filter itself. But most often, the cause of failure comes from the operating conditions of the baghouse. Make sure that you are using the proper style of filters and that your cleaning system is performing correctly. If you don't address the root cause of the bag failure, you'll probably be replacing more filters in the near future. When you do spot change, it is a good idea to protect the new bags by injecting a conditioning agent such as Neutralite to pre-coat them prior to putting the collector back on-line.

What type of filter are recommended for extremely sticky particulate, such as sugar?

We have helped customers with sticky particulate applications achieve excellent results by using ePTFE membrane filters. These filters have been used successfully in sugar mills, screening, grinding, storage, and pneumatic conveying. The reason for this is that the non-stick surface of the ePTFE membrane provides excellent dust cake release upon cleaning. When sugar mixes with humidity or moisture from the process, this causes a "glazing" on conventional filter media, seriously reducing filter permeability and useful life. ePTFE membrane filters repel moisture and collect particulate on the surface (not allowing it to penetrate the fabric) which enables effective cleaning. Plus, since the membrane filters do not glaze over or become blinded with embedded particulate, this allows for maximum airflow and low differential pressure through your system.