Specifying A Filter Bag
There are 5 primary steps well will walk you through when ordering your filters.
Step. 1 MATERIAL SELECTION
(choose the right filter media for your application)
You should choose the media from which your filters will be constructed based on the type of application they will be used for. Take the following things into consideration prior to selecting your media:
- Temperature – do your bags need to withstand extreme temperatures
- Product – what are you filtering
- Chemistry – can your bags withstand the chemical make up of the dust particles
- Resistance- is the filter media able to resist the wear and tear of the dust particles
- Partical size-The micron distribution of the particulate being filtered
Choosing the correct filter media is an important and sometimes difficult process. To assist you in the identification of the right media for your bags, keep the following in mind:
Filter bag performance is directly related to how well it can tolerate the environment in which it is being used, how efficiently it can remove the dust particles and it’s ability to clean and renew.
We can help youi dentify the type of filter media currently used in your application. Below you will find a list of typical construction methods:
- Woven felts
- Non-woven felts
- Natural fibers
- Polypropylene (PPRO)
- Polyphenylene sulfide (PPS)
- Polyester (PE)
For additional information on media types please examine our sample chart
A simple test to determine if a material is a thermoplastic is to take a small swatch and put a flame to it. A thermoplastic material will begin to melt when exposed to direct heat.
The selection criterion eliminates materials based on temperature and chemical characteristics. The first cut is usually made based on temperature. Then the chemical characteristics of the gas stream are considered to further refine the search. Chemical Resistance. Next, the efficiency of the material further dictates the construction of the material i.e. – the weight – oz/sq. ft., fiber and surface treatments/membranes. Last but not least, if there are still two or more candidates it comes down to a price versus performance trade off.
Step. 2 MEASUREMENTS
(get accurate measurements for optimal performance)
Most dust collectors have been upgraded over the years rather than replaced due to the need for new permits and the hassles with that process. That creates issues where OEM configurations will have changed. Because of this you likely will need to obtain accurate measurements for your filters before ordering replacement filters.
If you currently have filters installed that are functioning properly, you can pull out one of those filter to get the proper measurements for your replacement order. (spare filters not yet used can also be measured if available) If you are removing a used bag to measure, please be sure to use all necessary precautionary measures set in place prior to removal (i.e. – gloves, protective garments, & respiratory equipment if needed). To see a simple video demonstration on how to measurea couple of types of filter bags, go to our Downloads page to choose which video you wish to see.
Step. 3 and 4 TOP & BOTTOM CONSTRUCTION
The top and bottom construction of a filter bag involves a variety of possible configurations. The type of cleaning process used by the dust collector determines which configurations will be used in the design of the filter bag.
Pulsejet (Reverse jet) Baghouses
– found in almost every industrial environment. They are by far the most popular design and are seen in nearly all industry segments.
GROUNDWIRE – Use to comply with Factory Mutual requirements for static dissipation. Groundwire can be found in stainless steel and copper and actually only works in a localized area of the filter. For optimal static dissipation look at conductive scrim or fiber filters made with Stainless Steel.
WEAR CUFFS – Used to combat abrasion at the bottom of the bag either from “sandblasting” of the bags or bag-to-bag abrasion due to turbulence in the bag house. Usually 2 to 4 inches in length and made of a material similar to that of the body of the filter bag.
SPECIAL FINISHES – There are many finish options that can be added to the filter media at the time it is manufactured. Please refer to the materials selection area for further details. Specialty Materials.
Loop top – Sizing up the loop is simply a matter of the width and the height of the loop. The height measurement should always be taken as an inside dimension, especially for felt loops.
Grommet Top – Look for a number stamped on the grommet. It denotes the size in eighths of an inch (e.g. #3 grommet has a 3/8” diameter hole. Most grommets are brass but not if other construction.
Strap/Tail Top -Measure the width of the tail. The length is from the end to the point where it is sewn onto the bag body. Also note the number of layers of material that make up the tail. Most woven filters have two or three layers.
Metal Hanger – This is a variation on the loop with a metal hanger sewn into the loop. Be sure to measure the length to the center of the hanger. TIP: once you have the length, cut out the hanger and photocopy or make a digital photograph to then include with your RFQ.
Cap – Cap sizing with a measuring tap or calipers is very difficult. It is best to supply the cap if you intend to reuse them on the new bags, else request the bags and caps be supplied as a fitted pairing.
Snap ring -The size of the snap ring (Snap Band) is really determined by the diameter and thickness of the hole it is placed into. Those measurements must be either taken from the bag house drawings or actually measured on the bag house Tube Sheet while it is offline. If this is not possible, send us a snap ring. We can size the snap ring to one of our hundreds of test jigs we have especially for this.
Plain hem w/ clamp – The material is simply folded back and sewn. The length of the cuff may be critical, as this inlet to the bag tends to see the greatest velocity and dust loading and consequently the greatest wear.
Cap Top with Hook – Cap sizing with a measuring tap or calipers is very difficult. It is best to supply the cap if you intend to reuse them on the new bags, otherwise request the bags and caps to be supplied as a fitted pairing.
Compression Band – A Compression Band is similar to a Snap ring but rather than the gasket sealing to a Tube Sheet the compression band seals to a Metal Cap or a raised collar.
Corded cuff w/ clamp – Same as the plain hem but with the addition of a cord or rope inserted at the bottom. This reduces the likelihood of the bag pulling past the clamp and detaching from the tube sheet.
Raw edge/ Soft cuff – Raw edge bags have no measurement Do not if there is a “V” notch cut into the bag. Soft cuffs make for easier fold in of the bag. Measure the amount of the cuff outside and inside the main bag body.
Double beaded Snap ring – The size of the snap ring is really determined by the diameter and thickness of the hole it is placed into. Those measurements must be either taken from the bag house drawings or actually measured on the bag house while it is offline. If this is not possible we can size the snap ring to one of our hundreds of test jigs by having it sent in.