Article written by: Jason Danaher Ph.D.
Regenerative blowers are commonly used to supplement oxygen concentration in a variety of aquatic systems. A regenerative blower uses an electric motor to rotate the multi-vane impellers inside its chamber. Atmospheric air enters through the blower inlet and the force of the impellers’ rotation compresses the air. The process continues as the electric motor constantly rotates the multi-vane impellers compressing the air entering the housing before directing the air to the blower outlet. Most regenerative blowers used for aquatic system life support and oxygen supplementation are classified as single-stage blowers where the air rotates around the inside of the housing once before being exhausted through the blower outlet in a low-pressure, but high-volume state. The discharged air volume is often measured in cubic feet per minute (cfm) or cubic meters per hour (m3/h).
Figure 1. Regenerative blower assembly typically used for aquatic system life support.
The combination of low pressure with high-volume flow makes regenerative blowers an ideal choice for small and medium-sized aquatic systems because the technology is relatively inexpensive, comes in a variety of sizes (i.e. horsepower specifications) to meet flow and pressure requirements, can remain portable, or can be easily mounted vertically or horizontally in a fixed location. In addition, a regenerative blower creates a clean, oil free volume of compressed air.
A correctly sized regenerative blower will provide the aquatic system with the desired amount of air flow even with restrictions caused by the plumbing, diffusers, and water depth. Correctly sizing the regenerative blower for the aquatic system will maximize the operating time of the unit, which means it could last over a decade with minimal maintenance. However, incorrectly sizing the regenerative blower and restricting the volume of air discharged can cause the blower motor to overheat and damage the unit.
Below are some general factors to consider when selecting and sizing a regenerative blower:
1) Location
a. Ambient conditions such as temperature, moisture, or dust can have an adverse effect on the operation and lifetime of a regenerative blower.
i. It’s important to make sure the regenerative blower is in a cool, well-ventilated area to maintain low operating and exhaust temperatures.
ii. The area should be moisture free. Excessive moisture is bad for a regenerative blower because it can result in damage, corrosion, and destructive effects on the blower's operation and lifetime.
iii. The blower should be located above the water level of the aquatic system it is supplying air to. In addition, a check valve should be installed to maintain one-way flow of air and prevent water from back siphoning and entering the blower if there is a power outage or during system maintenance/downtime.
iv. Cleaning the inlet filter frequently is a vital maintenance procedure required for a regenerative blower, especially for units located outside of a closed building.
v. Regenerative blowers located outdoors should be installed above any potential flood level and housed in an enclosure to reduce exposure to rain and direct sun. The enclosure should not restrict the volume of air entering the blower inlet or prevent heat from dissipating away from the unit.
vi. Regenerative blower noise pollution is approximately 75 decibels. This is similar to a noisy restaurant..
vii. High elevation or altitude above sea level will affect oxygen concentration, airflow capacity, and pressure of blower output; therefore, one size does not fit all for similar aquatic facilities in different locations of the country.
2) Back Pressure
a. Water Depth
i. The maximum output of the blower is based on zero restrictions on its outlet. A zero backpressure scenario does not exist in aquatic system life support. The blower’s airflow capacity decreases with back pressure from increasing water depth.
b. Plumbing & Manifolds
i. Friction loss occurs between the plumbing distribution system and flow of air. The pipe size and types of fittings for the distribution system need to be calculated and is dependent on the volume of air discharged from the blower outlet and the distance the compressed air must travel to the point of discharge. Up-sizing the pipe size on the blower outlet may be beneficial; however, it is strongly recommended not to decrease the pipe size compared to the blower outlet because backpressure and heat damage will certainly occur.
c. Diffuser Type
i. The diffuser style results in back pressure and pressure loss and needs to be known for sizing a regenerative blower correctly.
3) Pressure Relief System
a. It is better to choose a slightly larger regenerative blower, rather than a smaller one. The excess flow of a slightly oversized unit can be diverted downstream of the blower outlet using a bleed valve. Restricting the volume of air discharged can cause the blower’s motor to overheat and damage the unit.
4) Heat Dissipating System
a. The compressed air created by the regenerative blower gives off heat. In addition, friction loss in the distribution system produces heat. It is recommended to install a metal heat dissipation pipe on the blower outlet before connecting to polyvinyl chloride (PVC) pipe. The length of the pipe can vary, but standard lengths of five-feet (1.5 meters) is common. It is not recommended to plumb the blower outlet directly to Schedule 40 or Schedule 80 PVC pipe because either can quickly denature due to heat exposure resulting in failure and reduced air volume reaching its intended point of discharge.
5) Electrical Requirements
a. Regenerative blower motor size increases with airflow capacity requirements. The correct electrical connections will need to be made available depending on the size of the regenerative blower. Common regenerative blower electrical requirements can range from 1-phase, 115V/230V to 3-phase, 230V/460V at either 50Hz or 60 Hz. Keep in mind airflow capacity (i.e. cfm or m3/h) and pressure is decreased at 50 Hz operation.
Proper selection and sizing of a regenerative blower requires careful evaluation of system design, environmental conditions, and operating constraints. A correctly sized blower will provide consistent airflow, extend equipment lifespan, and reduce maintenance needs.
Conversely, undersized or improperly installed units can result in overheating, reduced efficiency, and premature failure. Aquatic Equipment & Design, Inc. can assist you with sizing a regenerative blower whether you’re looking for a replacement unit, re-designing your aquatic system, or constructing a new facility.
Aquatic Equipment & Design, Inc. offers a variety of industry standard regenerative blowers (Sweetwater® & Republic Manufacturing) giving you a broad range of flow rates and pressures to ensure safe, reliable, and consistent quality customized to meet your aquatic system’s specific requirements.
Contact Aquatic Equipment & Design, Inc. at 407-995-6490 or email info@aquaticed.com to learn more about regenerative blower technology for your needs.