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Choosing the right bag machine for your operations

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article image Efficient ducting design, slide gates and quality, anti-static flexible hose, all contribute to delivering the optimum solution

Paul McGregor from Airtight Solutions gives a few pointers on selecting the right bag machine for maximum performance.

Many portable systems claim high CFM or air volumes but this performance depends on minimal resistance in the duct layout. The type of waste that goes through the duct also has an impact on performance. For instance, fine dust will very quickly block filter material and may even pass through it, but light or large fluffy dust may cling or stick to the filter fabric instead of dropping into the bins. Many installations end up with far more connections than they were originally designed for, diluting the performance throughout all the machines.

Dust extraction is not rocket science; however certain rules do apply and ignoring or pushing those limits generally results in poor performance. Many portable DC units work well in the beginning but lose efficiency over the following months. 

Rule number 1: 

You can never have too much filter area, however you can definitely have too little.

The more filter area a system has, the less back-pressure (restriction) will be created, resulting in greater suction (air volume) at the business end. A dust collector with 24 filter socks measuring 220Ø and 1.35m long will have more than twice the filter area and less resistance, compared to a similarly sized unit with 4 filter bags of 500 dia. and 1.5m long. Both units use a 3000rpm 10hp (7.5kW) fan. The one with the least resistance will perform much better and work over a longer distance, and the filter fabric will last longer. These units can also easily be modified for outdoor use or as pre-filters.

Rule number 2: 

Good extraction is a balance of horsepower, resistance, DC design and filter area. 

Applying more horsepower into the same filter area won’t help; it just forces the dust faster through the filter material. Eventually dust either blocks the holes in the fabric creating restriction, or bleeds through the fabric. Horsepower is wasted when there is resistance. Reducing resistance increases airflow, and is done by using efficiently designed fans, correctly sized short duct runs with the least amount of bends possible, short lengths of flexible hose, slide gates to concentrate performance, and a dust collector with as much filter area as possible. The fabric must be cleaned regularly.

There are many portable bag machines available on the market with similar appearance and function. Where they differ is in the design and quality of the fan and the amount of filter area. 

One proven alternative is a multiple filter sock unit that will enhance performance with increased filter area, heavy duty fan construction and high efficiency impeller. 

The dust collector is only part of the equation. Efficient ducting design, slide gates and quality, anti-static flexible hose, all contribute to delivering the optimum solution. Inefficiencies in small portable units can reduce performance considerably. It is optimistic to expect cheap massed produced systems made from lightweight metal and basic fabric to cope efficiently with some of the modern requirements and volumes some machines need these days. 

It’s like using a fabric gazebo instead of a garage to protect a prized car. They will both protect it from the elements and environment; one simply does it better than the other. 

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