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Pulleys - Technical data
Dimensioning pulleys
According to the position that they occupy in a belt conveyor, the pulleys must withstand
the forces imposed by both belt tension and conveyed load.
To be as efficient as possible both for replacement and for new installation, proper selection
of pulleys requires the following data that allows the determination of the construction
characteristics and dimensions.
The principal data necessary to design a pulley comprises the following:
belt width;
diameter of drum in relation to the belt type and characteristics;
locking arrangement of the shaft to the pulley (locking ring, key, welding);
position of pulley (drive, return, snub, etc.)
wrap angel of belt pulley "alpha";
belt tension T1, T2 or T3;
distance between the supports and flange of the pulley "aga";
type of lagging required..
Shaft importance
Excessive deflection of the pulley shaft constitutes the major reason for failure of the drum
structure.
The correct sizing of the shaft is therefore of the greatest importance and must take into
account an extra high safety factor.
Limitation of deflection and rotation
After having sized the diameter of the shaft for various pulleys, the next selection check
is to very that the deflection of the shaft does not exceed allowable values.
Upon request for pulleys with characteristics and dimensions different from those indicated
on this Web pages it is advisable to supply a dimensioned drawing of the pulley with the required
features.
General construction data
Our suppliers pulleys have been developed using a high degree of security in the dimensioning
of the flanges, in the sizing and penetration of the welding and the assembly between the shell,
flange and hub.
All components have been normalised after machining or welding, to allow internal stresses
to be eliminated to facilitate assembly and to turn disassembly, and also to eliminate reasons
for cracking or deforming under load.
Continuous wire feeds are employed during the welding process, utilising an inert gas atmosphere,
which guarantees the maximum uniformity and resistance of weld.
Both the welding system and the welders themselves are certified.
Pulleys may be cylindrical or machine crowned to aid belt tracking. Shafts are normally manufactured
from high strength steel bar.
Types and designs
On this Web pages numerous designs and types of pulleys are proposed, to meet the great variety
of uses.
To meet duties of the severest working conditions they may be supplies rubber lagged. Lagging
prevents belt slippage (in particular when water is present) and increases the drive traction
of the pulley.
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