RadiPac: Preci­sion measure­ment

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).

Fig. 1b: Measure­ment quan­ti­ties and accu­racy levels attained by aeroa­coustic test stand.

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.

Fig. 2

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.