Maintenance Tip of the Month: Measuring Filter Bags & Cages for the Perfect Fit

Measuring Filter Bags

Top Load, Snap Band Filter Bag – Felt

1. Flat width: Flatten bag and measure width across.
2. Length: Measure along the seam running the length of the bag. Start at the center of the snap band and end at the first stitch at the bottom of the bag.
3. Cage-to-Bag (Bag-to-Cage) fit:  Should have ¼” to 3/8” pinch; the bottom of the bag should have about a thumbs width between the bottom of the cage and the disc bottom of the bag.

Top Load, Snap Band Filter Bag – Woven Fiberglass

1. Flat width: Flatten bag and measure width across.
2. Length: Measure along the seam running the length of the bag. Start at the center of the snap band and end at the first stitch at the bottom of the bag.
3. Cage-to-Bag (Bag-to-Cage) fit:  Should have 1/8” or less pinch, but shouldn’t be stretched tight around the cage.

Top Load, Snap Band Filter Bag – Felt with membrane

1. Flat width: Flatten bag and measure width across.
2. Length: Measure along the seam running the length of the bag. Start at the center of the snap band and end at the first stitch at the bottom of the bag.
3. Cage-to-Bag (Bag-to-Cage) fit:  Should have 1/8” or less pinch, but shouldn’t be stretched tight around cage.

Shaker style Filter Bag

1. Flat width: Flatten bag and measure width across.
2. Length: Measure along the seam running the length of the bag. Start at the end of the snap band to the end of the bag, not including the tail.
3. Length of the tail: Measure along the seam from the end of the bag to the end of the tail
4. Flat width of the tail: Flatten tail and measure width.
5. Determine if the tail is 3 ply or 4 ply by pinching the material and feeling for layers.
6. If there is a wear cuff at the snap band end of the bag, measure length and width.

Measuring Cages

Measuring Cages, Step-by-Step

1. Full length of the cage:  Measure from top to bottom.
2. Diameter: Measure diameter in the middle of the cage at the widest point between wires. Ideally, using a Pi Tape to determine circumference will yield a preferred measurement.
3. Bottom construction: Determine if the bottom cup is crimped or if the wires are welded to the cup.
4. Number of rings: count the number of rings.
5. Space between rings:  Measure the space between the rings. Note: the space between the last ring and the bottom of the cup may be different
6. Number of vertical wires: Count the number of vertical wires running the length of the cage.
7. Material: Plain steel, galvanized, coated, 304 stainless steel, or some other material?
8. Determine the top construction of the cage.
   • If the top has a split top, measure the space between the groove in the split top and the end of the top
   • If the top has a venturi, measure the length of the venturi.

The Micronics Engineered Filtration Group is here to help

Proper fit for your baghouse’s dust collector bags and cages is an integral part of ensuring excellent baghouse performance. The Micronics team and trusted brands – NFM, Filterfab, SFM, CPE, and UPC – love clean air and assisting you in optimizing your baghouse’s performance.

If you would like assistance with measuring filter bags and cages or installing filter bags in your baghouse, you can benefit from Micronics’ dust collector training seminars which we will conduct on-site in your facility.

If you don’t want to deal with the manpower requirements & hassle associated with filter bag installation, Micronics has some of the best full-time, certified baghouse maintenance & service crews in the industry.

Contact Us and let us know how we can help with all your baghouse filter bag, parts, and service needs.