Low-Pressure-Blower

The pros and cons of using high pressure air, PD blowers & regenerative blowers

Many people ask us what type of air source is the best for supplying their air packer with the processed air needed to fluidize / pressurize the machine and deliver the best production results possible.  There are, of course, several ways that the required process air (high volume, low pressure) can be produced.  However there are pros and cons to each approach.  To aid with determining which is right for your application, below is our analysis of the options and when each might be right for you.

The pros and cons of using high pressure air, PD blowers & regenerative blowers

Air packers require not only a source of high pressure air for pneumatic control, but they also require a good source of low pressure, high volume air to fluidize and flow the product from the pressurizing chamber into the bag.

Like anything, there is more than one way to generate that air for the machine.  The 3 most prevailing sources of creating this air are:

  • Using high pressure plant air,
  • Using a PD blower package and
  • Using a regenerative blower

I will explain the advantages and disadvantages of each in detail.

High Pressure Air

Pros

  1. The most quiet of all methods of air generation – there are no motors or pumps other than what are already used to generate the high pressure air itself
  2. Less equipment to be purchased – theoretically you can connect high pressure air directly to an air packer and it can /could /might fill a bag without making any special accommodations.  However, for best results we recommend feeding the high pressure air into a reservoir tank via a regulator so that when the air packer calls for air it will have sufficient pressure and volume to fill the bag instantaneously
  3. Reduced maintenance costs – No blower, motor or filter maintenance

Cons

  1. Possible water in the product from condensation – high pressure plant air is notorious for containing a great amount of moisture that is naturally in the air and condenses when it is compressed.  The low pressure air is pumped directly into the product which depending on the product and the amount of water can cause problems.
  2. Possible introduction of contaminants into the product – air generated by an air compressor frequently has oil, rust, and other contaminants that come from the lubricants used in the compressor or rust from the inside of the piping carrying the compressed air from the compressor to the air packer.
  3. Greater risk of slower bags fills resulting in slower fills – especially if no air reservoir is used, the inrush of air to the pressurizing chamber will be limited by the line size of the high pressure line feeding the machine
  4. Reduced ability to force the bag open to its max size and force product into a bag – creating optimal product flow requires both pressure and volume to be balanced correctly.  When using high pressure air, it is more difficult to balance the conversion of pressure to volume while keeping them in the right balance.
  5. Risk of over-pressurizing the air packer – Plant air is typically between 80-120 psi.  Most air packers are rated for a maximum of 30 psi to be applied to the pressurizing chamber (often times much less).  If too much pressure is applied to the pressurizing chamber, a pipe bomb will have been created.

PD Blower                                                                                                 

Pros

  1. Ability to force the bag open to its max size and force product into a bag – as mentioned above, creating optimal product flow requires both pressure and volume to be balanced correctly.  PD blowers are designed to output a constant amount of air pressure and volume simultaneously.  Volume and flow are needed in the correct ratios to fluidize the product and move it into the bag.  The Pressure side of the equation is also needed to fully open the bag to its maximum potential and deliver the product and sufficient velocity to prevent it from mounding up at the discharge of the spout (which will cause weight inaccuracy, longer fill times, under filled bags, product spilling when the bag is removed and other negative side effects.
  2. Capable of delivering the highest level of production output – directly related to the above explanation.  Same explanation applies here.
  3. The blower can be located up to 100 feet away from the bagger keeping the noise away from people and the blower out of the dirt and dust of the working area.
  4. Rebuild able – PD blowers use standard TEFC motors and drive components that can be purchased locally

Cons

  1. PD Blowers are noisier than running on compressed air (typically 85 db and sometimes greater)
  2. Higher install cost – not only does a 2-2.5″ supply line need to run from wherever the blower is installed to wherever the baggers are, electrical must be run from supply to the motor and controls must be mounted at the bagger for ease of access.
  3. PD blowers require maintenance (periodic checking of oil and cleaning air filters).  However, it should be noted that the maintenance PD blowers require is very little.  The oil needs to be checked once every 6 months or so and the filters need to checked / cleaned once a month.  Checking both together will take no more than 3-5 minutes at each interval.
  4. The expense of capital to buy the blower (compared with buying nothing to power by high pressure air)

Regenerative Blowers

Pros

  1. Increased production capability verses high pressure air – regenerative blowers are capable of creating the volume pressure balance that is required for optimal product flow if sized correctly.
  2. Typically quieter than PD blowers – regenerative blowers are typically quieter than are PD blowers.  However, it should be noted that regenerative blowers typically have to be mounted at the location of bagger verses the PD blower being capable of being mounted up to 100 feet away from the bagger outside of the building, up on a roof or in some other location that is not offensive to the ears of operators.
  3. No / low install costs – Ability to mount on board the bagger allowing all electrical and pneumatic connections to be pre-plumbed and wired at the factory. This reduced the costs of installation at the plant site.

Cons

  1. Regenerative blowers need to be mounted on or very close to the bagger putting the noise of the blower near operators and the blower in the dirt and dust of the bagging application which has a greater likelihood of creating more expensive, unplanned maintenance.
  2. Regenerative blowers typically require more horsepower to generate the same air flow as a smaller PD blower resulting in higher energy consumption and no great saving in purchase cost (relative to a PD blower) when comparing apples to apples air volume output.
  3. Regenerative blowers do not build pressure as quickly as PD blowers so the upstart of a bag being filled by a regenerative blower will take somewhat longer than will a bag being filled on the same machine using a PD blower.

While all 3 of these air sources can work and do have application for delivering the low pressure, high volume air needed to power air packers, we at CBE have found over 35 years of working with these machines that PD blowers deliver the most in terms of production output, greatest performance and lowest overall operating costs for this application.  Our leading / primary recommendation for optimal results is to use PD blowers with our air packers.