There are several different types of blowers in the market. In many applications, air flow and pressure (or vacuum) level requirements may determine what type of blower should be used. There are many areas however, where there may be over-lapping in performance capabilities. It is those areas, this may require a more in-depth evaluation of blowers that could potentially be used. The performance ranges that are likely to require additional consideration are in the volumetric capacities up to 1000 CFM, pressures up to 8 PSIG, or vacuum levels to around 15” Hg. Some of the common blower choices in these ranges may include:
- Regenerative (side channel) blowers (single stage or 2-stage)
- Rotary lobe positive displacement blowers
- Multiple stage centrifugal blowers
- High speed centrifugal/turbine-type blowers
- Rotary vane blowers
- Liquid ring compressors/vacuum pumps
- Rotary Claw pumps
When applying any of these blower types, some of the considerations may be:
- Mechanical Efficiency. (which blower will do the job for the least energy?)
- Maintenance requirements affecting long term operating cost
- Operating noise levels
- Compatibility of materials of construction with air borne or ingested gases that may exist in the installation environment
- Space limitations
- Initial Capital cost
- Installation requirements and cost
- Is the supplier of the product a reliable source for future parts requirements or replacement of the product
With some of the above considerations, one or more aspects might prevail over other considerations. For example, a user may be willing to pay more in energy costs if the application requires a very small footprint and low noise levels. On the other hand, if space or noise level are not as relevant, the greater mechanical efficiency may be the prime consideration, with future maintenance requirements being a further consideration. In evaluating mechanical efficiency, the operating pressure may be a primary detail which determines the best solution. The following category listings outline some general considerations based on application capacity.
Single Stage Regenerative Blowers
Performance range: Single Stage Regenerative Blowers pressure range is of 1-5 PSIG in the 200 to 700 CFM range. Pressures up to 4 PSIG under 100 CFM.
- Lowest initial capital cost
- Low installation cost
- Most Compact
- Least Maintenance (totally dry pump, bearings are the main wear item)
- Low noise levels
- Reliable under normal operating conditions
- Limited to smaller flows as shown above. In the high end of the pressure range, mechanical efficiencies may be lower than other blower types.
- Not usually available in special materials of construction, so not always suitable for corrosive/harsh environments.
- Not suitable where water or particulate may be ingested.
2-Stage Regenerative Blowers
Performance range: 2-Stage Regenerative Blowers pressure range of 3-6 PSIG UP TO 100 CFM range. Pressure range of 4-8 PSIG from 100 to 700 CFM range.
*Benefits and Disadvantages are same as shown above for single stage units.
Rotary Lobe Blowers
Performance range: Rotary Lobe Blowers pressure range up to 15 PSIG, approximately 20 CFM and up.
- Mid-range initial capital cost
- Mid-range installation cost
- Larger footprint requires more space.
- Available in various materials of construction so may be adapted to applications with corrosive/harsh environments.
- Good mechanical efficiency when driven at conservative speeds.
- Adapts well to variable frequency drives for control or flow.
- Higher noise levels – especially when driven at higher speeds.
- Many versions are belt driven requiring more maintenance. Some models may be direct driven at motor speeds through a flexible coupling. For those models, take into consideration the sound levels at the higher speeds.
- Require more space than some other types.
- Requires changing of gear oil at required intervals
Performance Range: Multi-Stage Centrifugal is best suited for larger volumes (over 700 CFM) and for pressures up to approximately 20 PSIG.
- Higher capacities and pressure/vacuum capabilities
- Mostly direct driven
- Low maintenance
- Higher capital costs
- Less compact at lower end of the performance range
- Not always well suited for variable speed drives due to surging.
Rotary Vane – Dry Vane Type
Performance Range – Rotary Vane – Dry Vane type for lower volumes up to approximately 200 CFM, and for higher pressure or vacuum levels. Best suited for vacuums to approximately 20-25” Hg. or for small volumes to pressures up to 15 PSIG. Most popular for smaller systems requiring under 50 CFM flow.
- Low initial capital cost.
- Most are direct driven, so no vee belt maintenance.
- Compact and well suited for mounting on process equipment.
- Low noise levels.
- Carbon composite vanes require replacement at specified Intervals, in addition to bearings and seals.
- Limited in volumetric performance range.
- Usually require outlet filter to capture carbon residue from vanes.
Liquid Ring Pumps
Performance Range – Liquid Ring Pumps have very broad range and suitable for pressures and vacuum levels to approximately 100 PSIG and 29.5” Hg. They are available in single and 2-stage pumps and enter into the compressor performance pressure range. More suited to vacuum applications, but can be used for specialty pressure applications where corrosive gases may be a factor, and special materials of construction may be needed.
- Special materials of constructions to suit corrosive applications.
- Quiet Operation
- Simple design, relatively low maintenance.
- Usually direct driven, so no vee belt maintenance.
- As compressors, air discharge temperature is maintained at a low level due to the contact with the water ring, so no after-cooling is required.
- As vacuum pumps, some solid particles, condensable vapors and gases can be flushed through the pump without damaging effects.
- Require water or other seal liquid. If a once through water system is used, operating costs will be high. Although water may be partially recovered, the system will require more control features.
- As a compressor, pumps are inefficient operating at higher pressures, and will be more suitable for lower pressure applications (under 20-30 PSIG).
- When water is used as the seal liquid, calcium deposits may build up over time, and could affect downstream components or air quality when used as a compressor.
- Installation costs will be higher due to water supply requirements and control of feed water.
Rotary Claw Pumps
Performance Range: Rotary Claw Pumps are generally used for vacuum service up to approximately 24” Hg. and volumes under 1000 CFM.
- Mechanically high efficiency operation.
- Compact design – reasonably small footprint.
- Direct driven so no vee belts.
- Usually supplied with vacuum limiting regulator to prevent operation at excessive limits, which could result in over-temperature.
- High initial capital cost.
- Gear oil will require changing at specified times.
- As they are air-cooled, they should be protected with temperature and vacuum level monitoring/limiting devices.