RadiCal & FlowGrid - used in Microbiological Safety Cabinets

By Helen McHugh - Head of New Product Research - 18th October 2017

Introduction

Microbiological safety cabinets are a crucial piece of equipment used by high-tech industries such as pharmaceutical, clinical, life science and research laboratories. They provide a ventilated enclosure which offers environmental protection for both the product and the operator.

Demands to protect personnel, product, and the environment from exposure to biohazards and cross contamination has never been more critical. As a result, the need to improve Microbiological safety cabinets have increased.

RadiCal Centrifugal fan & FlowGrid

To deliver the required level of protection a precisely controlled airflow is essential, therefore fans are a critical component of any safety cabinet, and must not only meet the airflow and pressure requirements but also offer the highest energy efficiency and lowest noise levels demanded for laboratory environments.

The RadiCal centrifugal fan & FlowGrid inlet grille from ebm-papst deliver the performance, energy efficiency & noise levels necessary for the controlled environment of microbiological safety cabinets.

Safety cabinets rely on both fans and high-performance filters to provide the required level of protection, they have historically used AC forward curved blowers for both the downflow and exhaust applications, however EC motors are now more commonly used as they provide the controllability and energy efficiency needed, more recently the trend has been to replace the forward curved blowers with backward curved centrifugal fans to provide the most energy efficient and compact solution.

As leading manufacturers of high efficiency EC fans, ebm-papst’s engineering and design teams work closely with manufacturers of safety cabinets to optimise not only the fan solution but also the system design, providing the highest performance and most energy efficient solution. The optimum solution in many cases is to use EC backward curved RadiCal fans fitted with FlowGrid inlet grille. Combining the use of RadiCal & FlowGrid with low loss filters can result in energy savings of up to 75%, and noise reductions of more than 50%.

The RadiCal backward curved fan not only takes advantage of the highest efficiency ebm-papst EC motors, but also the construction of the impeller from lightweight fibreglass-reinforced plastic gives a noise dampening effect, and its unique blade geometry has been aerodynamically optimised to minimise losses and flow separation as air moves through the impeller, this gives rise to a noise reduction of up to 50%.

To further reduce noise levels the FlowGrid inlet grille is also used, this smooths the air entering the fan by breaking up the vortices which can cause noise as air passes through the impeller, the result is a reduction in the blade passing frequency as well as the overall broadband noise.

Recent Project

An example of a recent project for a leading safety cabinet manufacturer highlights the benefits of using the RadiCal and FlowGrid solution, the result was a more compact unit with a reduction in power consumption of approximately 75%, and a reduction in noise level in excess of 6db.

This project also demonstrates how the engineering and manufacturing service that ebm-papst provide has helped the customer to optimise their design.

Project: Update a Class II safety cabinet to deliver higher energy efficiency.

Aims: The main aim of the project was to increase the energy efficiency of the class II safety cabinet; however it was also essential to meet the required noise levels and if possible reduce the overall noise and vibration.

- Reduce power consumption.

- Reduce noise and vibration.

- Compact design.

Class II safety cabinet design:

A typical class II safety cabinet has both downflow fans and an exhaust fan.

Downflow fans: Multiple fans draw air from the room or use filtered recirculated air to blow air into the cabinet through high performance HEPA filters.

Recirculation fans: Single fan draws air from the cabinet and recirculates or exhausts through HEPA filters.

System Design

The customer was looking to update their class II safety cabinet to provide a more energy efficient model, however due to the environment this equipment is operated in it was also important to make sure that any design changes did not have a negative impact on the noise and vibration levels in the cabinet.

As fans are the main consumers of power in a safety cabinet, switching to the most energy efficient fans is essential to achieve energy savings, therefore the customer asked ebm-papst to provide the optimum solution.

The solution was to replace the original AC blowers with ebm-papst RadiCal BC Centrifugal fans, as the unique design of the RadiCal impeller delivers a high performance whilst significantly reducing both power consumption and noise. In addition to the RadiCal impeller, the noise level was further reduced by the introduction of the innovative ebm-papst FlowGrid inlet grille.

In the original cabinet, the downflow unit used forward curved single inlet AC blowers (typically G2E180), dependent on the size of the cabinet multiple downflow fans can be used, the recirculation unit already used an EC fan, but a single inlet forward curved blower (G3G180).

Using the customer airflow and pressure requirements calculations were made on the potential energy savings and noise levels that could be achieved by switching to EC backward curved fans for both the downflow and recirculation units, initial estimates suggested energy savings in excess of 40% were possible, and at the same time giving noise reductions of at least 3dBa and allowing the size of the fan unit to be reduced. These estimated savings gave justification for the design changes.

The first step was to replace the fans in the downflow unit with 250mm EC RadiCal, this resulted in a significant improvement in performance as well as a more compact solution, however the recirculation unit presented more problems due to the reduced dimensions which meant there was a restricted space available for the recirculation fan. To fit the restricted space, a smaller backward curved fan was selected (175mm EC RadiCal), and to achieve the required performance ebm-papst re-designed the recirculation unit to optimise the fan positioning.

Downflow and Recirculation units:

Results:

Power saving: Energy saving of approx. 75% at a matched duty.

Saving resulting from both the higher efficiency fan, and low loss filters which allows the fan speeds to be reduced & still maintain the airflow.

Noise: Average noise reduction 6dBa.

RadiCal Centrifugal fan is the lowest noise BC impeller and noise is further reduced when it is combined with the FlowGrid inlet grille.

Airflow redesigning the recirculation unit to optimise the fan position resulted in a 12% increase in airflow, allowing a smaller fan to be fitted and still achieve the required performance.

Benefits of using EC fan

- Energy efficiency

- Reduced noise

- Improved speed control

- Increased motor life

- Motors run cooler, minimising the rise in air temperature and improving user comfort.

- Improved Monitoring & feedback, for alarms and status.