Without careful consideration, fans and impellers can suffer from reduced lifespan, higher costs from servicing and maintenance, as well as lost operating time and money through unnecessary downtime. The fan may also perform at lower capacity, resulting in higher energy costs. To prevent this, impellers must be accurately designed, specified and manufactured.
Customer requirements to be considered include necessary air volume and pressure, air density and working temperature ranges. Any other operational conditions such as ATEX (hazardous, explosive materials) or smoke ventilation can affect selection, and should therefore be factored in as well.
Elta Fans offers a fan selection programme to facilitate correct specification. Impeller stress calculations are also built into the programme to ensure safe selections.
Once all elements have been determined, ventilation professionals can select the appropriate impeller and design the fan in line with customer needs. Different types of blades should be considered depending on the application. For example, in marine environments, glass reinforced plastic, certain grades of aluminium and anti-static impellers could be suitable. Across all material choices, it’s important that blade design incorporates adjustable pitch and solidity for a wider range of options.
Coating and resistive properties should also be decided to provide an effective solution. In specific applications where impellers need additional protection, they can be painted, flame sprayed or anodised to prevent corrosion or wear and tear.
TESTING
Once an accurate specification has been agreed, it is important that quality and performance is guaranteed in the subsequent manufacturing process. Here, the critical measure is what factory production controls are in place to provide assurance that all fans built are being run-tested to check for vibration, running current, and speed.
Thorough testing is vital to achieve optimum performance and should be carried out in line with applicable regulations. Customers should look to fan suppliers that test in accordance with industry standards such as BS ISO 5801.
Acoustics and airflow are also key factors to consider. The principal standards to adhere to are air performance (ISO 5801 and AMCA 210) and sound (ISO 13347-2, ISO 5136, AMCA 300), for which all impellers should be fully tested to. Third-party testing is also a key sign of quality, and at Elta, testing is performed in the company’s own laboratory, which is accredited by AMCA for performance and sound. Customer witness testing can also provide added peace of mind.
Alongside the testing of the individual components, during the fan construction process impellers need to be dynamically balanced to operate correctly and thus prevent vibration back to the fan, motor, bearings, and surrounding structure. Again, regulatory testing must be conducted to meet the conditions of ISO 14694, along with providable certificates for credibility.
Quality is equally important. In the interests of quality assurance, many of Elta Fans components are manufactured at foundries in the UK. As well as materials, comprehensive ‘start’ and over-speed testing to verify stress limitations is a crucial step to ensure performance and reliability.