Vibration diagnostics of fans and dynamic balancing of impellers on-site are very important tasks. With the new vibrometer-balancer BALTECH VP-3470 these tasks can be easily and quickly solved.
Different constructions of fans can have different vibration parameters according to construction, installation and operation of fans.
There are two main types of fans: centrifugal and axial fans. A centrifugal fan (also called as a radial fan) consists of impellers rotating in a spiral-like housing. Usually the air enters the housing in an axial direction of rotating blades and then is forced to the rim of the impellers. The airflow is parallel to axes of the impellers. As a rule fans have airfoil blades, which have a close clearance with the fan housing.
Airfoil fan blades are called so, because they are shaped in the cross section as airplane wings.
Due to their aerodynamic form airfoil blades have efficiency about 90 %; this is the most effective kind of blades of a centrifugal fan.
Due to their high efficiency fans with backward-curved (or airfoil) blades are used on big ventilation facilities such as coal mines and tunnels.
Airfoil fan blades are usually hollow-bored (otherwise they might be too heavy and too expensive in production). In blade airfoils there can be several edges, which add to toughness and allow keeping the form of blades.
The term “pitch” denotes the angle of the blade with the imaginary plane perpendicular to a shaft axis.
E.g. fan blades with zero pitch are parallel to the plane, which is perpendicular to a shaft axis. Fan blades with a pitch of 10 grades are located to each other with an angle of 80 grades to the shaft axis and with an angle of 10 grades to the plane, which is perpendicular to a shaft axis.
Unbalance and misalignment are the most popular defects of fans.
As centrifugal fans have impellers of a relatively large diameter, balancing is often a huge problem. Unbalance is shown in a spectrum as vibration peaks (harmonics) at fan rotation speed and as a rule radially. If fans were balanced before and unbalance appeared just recently, the reason is often connected to deposits or damages on impellers. For that reason we recommend to check visually fan impellers before balancing. Simple cleaning of impellers can again normalize vibration level.
Misalignment, defects of rolling element bearings, looseness, resonance and bent shafts belong to other fan defects. All kinds of defects can be easily detected with the devices for fan vibration diagnostics BALTECH (e.g. analyzers CSI 2140 or BALTECH VP-3470).
Раздел: Оборудование, инструмент → Промышленное оборудование → ВАLTECH GmbH - Vibration diagnostics of fans with the vibrometer-balancer BALTECH VP-3470
Добавлено: 11 апреля 2014; 244 просмотров
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