NCF
13
EN
2.5
Operating speed risks
CAUTION!
Risk of equipment damage.
•
Do not exceed the maximum rotation speed indicated by Nederman.
•
Do not use ON-OFF operating cycles unless expressly approved by Nederman.
•
Do not subject the fan to thermal gradients greater than 3°C/minute.
•
A condition of overspeed, even for a limited time, may cause irreversible damage and
create situations of extreme risk hazards. The maximum speeds indicated by Nederman
must never be exceeded.
•
The manufacturer must always be contacted in the case of use of a supply frequency
other than the original design frequency. Do not proceed until authorized.
•
In the case of fan operation with a variable speed cycle of less than 30 minutes, this cycle
must be submitted to approval by the Nederman Technical Office, which will give its
approval and notify the consequent reduction of maintenance intervals and the fan life
span.
•
Inverting the fan rotation direction or starting it with the impeller turning in the opposite
direction may cause breakage of the blades and/or the impeller hub, with the risk of
ejection of metal parts.
•
Resonance phenomena at low frequencies may cause damage to the structure.
Operating speeds greater than those envisaged by the fan design can create conditions of
risk due to the reduction of the operative life span of moving parts.
In case of faults or malfunctions, overspeed conditions may be created due to:
•
Errors in the control logic system
•
Short circuits on monitoring components
•
Driver or inverter malfunctions
•
Mechanical breakage of components, and in particular on encoder
During normal operation, conditions of overspeed attributable to the drive system or motor
may occur, in particular if the fan is supplied “with shaft only” or with motor “without drive
system”.
The use of a supply frequency different from the original design frequency affects all fan
characteristics. The modification of conditions of use requires a complete revision of the
technical information sheet of the fan.
In the case of use at varying fan speeds or with frequent starting and stopping during
operation, rotating organs are subject to mechanical stresses that may affect their
operative life span.
If the rotation direction of a fan must be inverted, or if it must be restarted, this must be
done only when the impeller is in the rest position (total standstill).
Operation at a speed significantly lower than up to 40% of nominal speed (unless otherwise
specified by Nederman) may affect the cooling of the motor and bearings, with possible
malfunctions due to higher temperatures. For electrical components, the user and installer
are advised to provide adequate protection for the drive system or motor, with the use of
heat detection capsules if possible, and also using a servo-ventilated motor if necessary.
Resonance phenomena in the structure must be avoided. These may emerge at specific
rotation speeds, and may cause damage to the structure.