Dear Winlong

I assume you know that these wing pulleys are normally meant for light to medium strength fabric belts, not steel cord construction. They usually have crowned drum diameters for belt tracking.

There are many designs of wing pulleys. How many wings are required? How are the wing plates fastened? How are the wing plate OD's treated?

All wing pulleys are meant to aid in discarding carryback refuse and/or beating the belt to dislodge adhesive like materials. Some are better than others in how they treat the belt.

Better wing pulleys have dual metal strips or bars, wrapped from the OD edges in symmetric spirals, toward the belt center line, around the radial wings to manitain a circular or concentric rotating shape. They are machined round to minimize belt beating by the wings. They have been used in steel cord belt.

From this preamble I answer your question:

"Is there anything wrong with wing snub pulley and wing bend pulleys?"

Without the spiral wraps the radial wing sections tend to violently, depending on speed, > 1.5 m/s, beat the belt and cause longitidinal strain displacement (shock waves) that results in vibration and speed pertubations. Wing pulleys void of these spirals, should not be used in areas like a drive, drive snub, takeup and takeup bends that will negatively effect pullleys and belt splices, takeup dynamics, from the beating action. Around drives, the variation in belt speed will cause motor power oscillations, structural vibration and maybe excessive loads on adjoining pulleys.

With the spiral wrap and machined with a true OD, the only problem is to properly calculate the pulley metal stresses. With light fabric strength belts, the general rules-of-thumb are probably OK. Pulley stresses have not been properly determined for wing pulley designs of any type, to my knowledge. The stress mechanics are far more complex than turbine end disk type pulleys. The construction requires good welding techniques.

They have their place, where sludge like materials need to be removed, or ice buildup needs added protection at tail stations, or....

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

I simply want to add to Laurence Nordell's comments. wing pulleys can cause shorter bearing life on the system since the beating effect will transmitt to the bearings.

Ron J.Babin ■

The information given by Mr. Nordell is quite interesting. I would like to add only following information :

1) One should use wing pulleys only when the material is being handled is really sticky to belt (muddy lumps, clods, etc) and turning into paste when squeezed between belt & pulley. Wing pulley permit easy escape of such paste.

2) Condition of serial number 1 will only be applicable for pulleys where carrying face of belt is coming in contact with pulley

3) Wing pulleys should be avoided for high tension belt because they would be difficult to properly design for such loads, and are certainly inferior for full support to belt. For long conveyor; it is better to clean the belt face by water jet.

4) Wing pulleys are extensively used in belt bucked elevator boot (bottom) to prevent trapping of material lumps between belt & pulley. In elevator application; there is no substitute to wing pulley and wing pulleys are recognized regular item for belt bucket elevators.

Regards,

Ishwar G Mulani

Author Book : Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in ■

You must also remember that conveyor belt fasteners require an increase of 25% in the minimum pulley diameter with wing pulleys. For example, the 190 fastener requires a minimum pulley diameter of 18" when using standard round pulleys. When using a wing pulley its diameter must be at least 22.5". ■