Sizing your dust collector appropriately for your application and particulate volumes is one of the most important considerations in air quality system design. A big part of that equation comes down to the air-to-cloth ratio, also known as filter velocity. Here's what you need to know about air-to-cloth ratio when it comes to dust collector sizing and selection.
There are two important elements to consider when it comes to dust collector sizing:
Air-to-cloth ratio (or filter velocity) is simply the amount of air going through each square foot of filter media each minute. It is calculated by dividing the amount of airflow (CFM) by the amount of filter media in the dust collector. For example:
In general, applications producing large volumes of particulates will require more filter media than those producing fewer particulate. Expressed another way, we can say they require a lower air-to-cloth ratio.
The more particulates are in each cubic foot of air coming through the collector, the lower the air-to-cloth ratio will need to be. Source capture systems will usually require a lower air-to-cloth ratio than ambient systems, because particulates are more concentrated.
It's important to get the air-to-cloth ratio right when selecting a dust collector. If you have more filter media than you really need, you may be spending more on your dust collector than you need to. But skimping on filter media can have serious adverse impacts on filter life, equipment life, and the overall efficiency and effectiveness of your system.
When air-to-cloth ratio is too high (e.g., not enough filter media for the airflow and volume of particulates you are producing), dust is driven deeply into the filters faster than it can be pulsed off by the filter pulsing system. As dust accumulates, negative pressure builds up on the clean side of the filter, which makes it even harder for the pulsing system to push dust out of the filter and into the containment bin. This causes rapid filter clogging, significantly reducing filter life. Facilities will find that the costs of frequent filter replacements, in terms of both consumable costs and maintenance time, will rapidly outweigh any savings gained by choosing a dust collector with less filter media.
A RoboVent solutions director can help you determine the optimal air-to-cloth ratio for your application type, the size and volume of dust you produce, and your facility's characteristics. RoboVent's VentMapping Engineering Process uses computer modeling to optimize complex air quality system. Getting air-to-cloth ratio right will ensure that your air quality system delivers the performance you expect while minimizing your equipment and operating costs.
Receiving a consumer&#;s complaints about their newly purchased jackets or pants? Have you wondered if the complaints are attributed to the quality of the fabric, the most important material in your garment?
On average, around 20% of garment defects are associated with fabric defects, and this truly highlights the importance of assessing the quality of fabric pre-production. A fabric inspection can do just this and can ensure the quality of key materials from the beginning.
Fabric inspection helps understand quality in terms of colour, density, weight, printing, measurement and other quality criteria prior to the garment production. We are covering some of the basic things about fabric inspection so you can get practical tips on this, whether you are a merchandiser or a garment supplier.
As mentioned above, a fabric inspection can prevent defects in the final product but there are several other reasons it is a crucial element for any factory.
Whether it is a reduction in productivity or increased overheads, garment brands/suppliers can face production challenges from defective fabric such as:
Inconsistencies in the cuttable width will impact their fabric consumption/wastage.
Different colour shading among rolls or within the same roll impacts product quality and requires special management during the cutting/sewing/packing and other production steps to segregate by colour shades.
High defect rates in the fabric ( such as stains/holes etc.) will impact the consumption per garment and increase the risk of defects found in the garment.
There are several grading systems adopted for fabric inspection such as the 10-point system and the Dallas system. Among all, the 4-point system has become the most commonly adopted system for fabric inspection.
The 4-point system works on a penalty point basis and as its name has probably suggested, points are deducted from 1 to 4, with 4 points being the highest deduction for major defects.
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Unlike product inspection which adopts AQL System (read this piece on AQL if you are interested in learning more), the sampling size is 10% of the total lots in meters per order per colour.
As mentioned above, defects are graded and points are deducted accordingly. Defects for fabric are measured mostly by length. Below is a table showing the calculation of defect deduction on 4-point fabric inspection:
Length of defect Penalty Point 7 cm or less / 3 inches or less 1 8 to 15 cm / 3 to 6 inches 2 16 to 22 cm / 6 to 9 inches 3 Over 22 cm / Over 9 inches 4 Holes and OpeningsWhen assessing, defects that are not visible on the face of the fabric are not counted, and a maximum of 4 points are deducted for any single defect on the same fabric.
The result is calculated by an equation below:
Points per 100 square meters =
(Total points per roll x ) / Length inspected (meter) x cuttable width (cm)
At Eurofins, we take 24 points per 100 square meter as the passing score, which is a moderate level of stringentness. If your fabric is of higher value, you can consider lowering the passing score to below 20.
When examining the quality of the fabric, different criteria are used by the inspectors.
The identification stickers, shipping marks, packing lists and packing quantity are checked against the requirements and specifications.
The weight of the fabric is a key indicator of the conformance of these materials. Measured mostly in GSM (grams per square), the fabric weight is a good reference of fabric density, composition and construction.
To measure the weight of a woven fabric, a sample is cut out by a circle cutter and weighed by one roll of each lot. For knit fabric, a minimum of 10% of rolls from each lot is to be examined for weight.
Inspectors work either with fabric samples provided by clients as the comparison samples or, in the absence of fabric samples from clients, the beginning and end of the roll will be cut for conformity checking against the inspected roll.
Conformity is assessed on
Needless to say, quality is a must to be inspected. Common defects of fabric include holes, stains, fabric bar, poor finishing, coarse yarn and running knit.
Depending on the seriousness of the defects, fabric might be discarded and a replacement will be required. For instance, different colour shading among rolls requires special management during cutting to segregate by colour shades.
In some other cases, defects of fabric can be avoided during the cut & sew phase as defects are marked by defect stickers clearly.
Looking to safeguard the quality of your textile goods from step one? Leverage our fabric inspection to get your production off to a great start!
For more information, please visit Industrial Filter Fabric.