At ebm-papst, use is made of an aeroacoustic fan test stand for the simultaneous recording of air performance data and noise values. For this purpose the fans are installed in the test chamber with free inlet and free outlet in accordance with installation type A (Fig.1a). The chamber or combination test rig consists of two low-reflection half chambers with high-impedance floor conforming to accuracy class 1 for acoustic measurements. On the combination test rig it is possible to conduct air performance measurements at an air flow of up to 100,000 m³/h with a static pressure increase of up to 3,000 Pa (Fig. 1b). The characteristic curve of the fan is determined on the combination test rig by operating the test specimen at a constant speed and gradually throttling the air flow. The noise, air flow, static pressure increase, speed and reaction torque required to determine the power consumption are recorded in the various operating statuses. A fan characteristic curve is made up of at least 10 operating points. This measurement is then repeated at different speeds. The characteristic curves determined in this way yield the so-called fan map (Fig. 2).
Accurate measurement results
To ensure consistently precise, reproducible measurements, the test facilities and test equipment are subjected to regular checking. The routine monitoring of test equipment by Quality Assurance with measurement quantities traceable to national and international standards (German Calibration Service DKD, Germany’s national metrology institute PTB) is standard practice at ebm-papst. Determination of the air flow and regular leak testing are based on ISO 5801. Since the middle of 2014, calibration of the air flow measuring instruments and traceability to the national standard of the PTB have been part of the quality assurance process. The applicable range is from 100 m³/h to 40,000 m³/h with a reference measuring instrument accuracy of ± 0.5 % of the measured value. Internal validation provides both assurance for the company and information for customers. The documentation is available for viewing at all times.
The inspection authorities (TÜV Süd) have confirmed that the test stand satisfies all the requirements of DIN EN ISO 5801 in an air flow range of 500 m³/h to 39,000 m³/h with a pressure increase of up to 1,000 Pa (Fig. 2). Acceptance testing for the acoustic properties of the combination test stand was performed by the Fraunhofer Institute, Stuttgart. The institute confirmed the Class 1 rating for the ebm-papst noise measurement chamber.
To sum up
At ebm-papst the product documentation for all fans is based on measurements taken on certified precision chamber test rigs. Constant internal monitoring of the test facilities used and the values obtained guarantees the consistently high levels of product quality and fan dependability you can always rely on.
What the inspection authorities demand of a test stand
As a certified manufacturer, ebm-papst fully conforms to the following criteria as specified for test stands by the guidelines of the AHU manufacturers’ association: “An expert report/test report for fans will be accepted if testing was performed in accordance with the latest standard DIN EN ISO 5801:12-2010 (ISO 5801:2007 incl. corr. 1:2008) by a named test body on a suction-side chamber test rig and the component is manufactured without any modifications.”