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Uniwersal Ltd.; tel./fax + 48/ 32/ 757-28-51; fax 32/201 87 04; office@uniwersal.com.pl

Tests and measurements

Dynamic balancing of rotors

The quality of balancing of our fans is provided by an electronic balancer of the CIMAT Company. Rotors are balanced in the 2.5Gmm/kg residual balancing class and frequently even in the 1Gmm/kg class. This assures the non-vibration operation of a finished fan, the more so that the final rotating system is ultimately balanced "in the assembled motor own bearings". The weights balancing the dynamical system are permanently riveted with rotor disks and are made of rust-proof materials. Each rotor has its own residual balancing quality identification and the balancing ends with a record which is the base for the rotor's further application in production. The product so identified allows for the complete control and elimination of those rotors whose final vibrations might result in failures of the fan. Upon assembling the rotating system in the finished fan, each piece undergoes the final operating test prior to being delivered to the investor or stored in the finished products store.

Aerodynamic tests

A number of components of the fans manufactured in our company are tested in a washing air stream. This is the case with prototypical fan rotors, elements of the carrying disk and the covering one, some casing elements, etc. There are a number of devices in case of which the construction design input is obligatorily checked and their performance curves are taken in an aerodynamic tunnel as in case of Zefir, Bora and WLO roof ventilators. The conditions in the aerodynamic tunnel allow for testing the device performance in a stream of simulated wind blowing with the speed of 0 to 10 m/s. In our company, a frequent method for quick verification of ventilating devices designs is application of a smoke chamber where smoke is produced by a smoke generator. The chamber is located under the tested devices and connected with them by means of suction holes. A properly designed ventilator creates negative pressure in streams of the washing wind. The negative pressure allows to aspire the smoky air from the smoke chamber and to eject it outside. Such tests are carried out for different air speeds as well as for different directions of the wind inflow on the tested devices.

Flow measurment

The measurements of flow parameters and the fan efficiency as well as the measurements of the power taken by the motor have been made on a standard test stand, as in the case of fans working as exhausters with a free air outlet. The fan is mounted with the suction branch attached to the measuring duct. The efficiency was measured by means of a classical Venturi tube and the pressure was measured through impulse holes on a simulation duct. The pressure drop on the tube and in the impulse holes were measured with a battery micromanometer. The channel inlet was throttled with different diameter flanges to obtain a number of characteristic points. The power was measured by means of a set of electric meters: wattmeters, ammeters, voltmeters connected in the Aron system.

Acoustics

To eliminate the impact of the fan outlet noise at the measurement on the suction side or at the noise measurement with a silencer, sound absorbing acoustic baffles were applied that separate the outlet side from the suction one. The measurements were made in a free sound field at a low level of acoustic background. The meter was placed in the distance of 1 m from the inlet (outlet) surface cross-section at the point which is the least exposed to the flowing-round air stream.

Acoustics tests were made in fan inlet, at 1 metre distance, at maximal work capacity at given rotation. As a measuring instrument of acoustic level, SVANTEK device with actual verification was used. Acoustic level at fan inlet measured in dBA at 1m distance from fan is equal to value at fan outlet, given in the table. Doubling the measuring distance causes 5 dBA decrement of acoustic pressure.

 

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