Belt life

The closed-belt conveyor is not readily adaptable to the handling of sticky materials, and special designs may be required for materials which are highly susceptible to aeration. Initial cost per foot is relatively high because of belting cost, but power requirements are low and with proper instaUation and maintenance belt life is good. 

The magnitudes of the forces on a belt have significant impact on belt life. When a V-belt bends around a pulley, compressive forces develop in the bottom of the belt and tension forces develop in the top of the belt. The magnitude of each force is a function of the diameter of the pulley and the cross-section of the belt. 

Forces increase with smaller diameters and larger cross-sections. Therefore, minimum recommended diameters were developed for each belt cross-section. These minimum diameters can be found in V-belt selection guides provided by belt manufacturers. Using pulleys that are below the recommended minimum will always result in shorter belt life. 

Extreme heat In the manufacturing process, belts are cured with scientifically controlled heat for given periods of time. If standard belts are operated below 140°F, their materials of constmction are not affected. However, at temperatures above 140°F, over-curing will occur and belt life will be shortened. Therefore, the use of standard V-belts above this temperature should be avoided. Often, adequate shielding between the heat source and belts can be provided. 

Added load damage Added loads shorten effective belt life. Always check to see if any other load has been added to the belt drive since original installation. Figure 58.9 illustrates the possible effects an added load may have on the motor belt life. 

The first rule for long belt life is to maintain correct belt tension. Loose belts slip, causing belt and pulley wear. The snapping action of loose belts adds sudden stress and often breaks the belt. To test for tension, press down firmly... 

A clean discharge is vital to good belt life. On the return run the carrying side of the belt is in contact with the return rollers, and any material adhering to it is ground in or deposited on the roller. Extremely sticlcy material may require a belt-cleaning device in the form of a... 

Test results from experimental studies on belt life suggest the following as the major belt failure modes tooth root cracking, wear, cord failure and fabric separation [14,15,16, 17, 18], and this classification has support from field data [19, 20]. Figure 12.2 shows examples of tooth root cracking, cord delamination and fabric separation failures. 

In attempting to identify parameters which allow the belt life to be predicted within the adhesion related failure modes identified above, the most common approach has been to use measures of belt distortion. Dalgarno [17] examined belt life data from belt failures within the tooth root cracking, fabric delamination and cord separation failure modes. 

Gerbert and Fritzson also developed a procedure for predicting belt life within the cord separation failure mode, based on the shear stress in the cushion region. The overall shear stress arises from four individual components of shear stress ... 

Of these shear stress components i), ii) and hi) all act along the length of the belt, with iv) acting across the belt width. The combined effect of these four shear stresses is shown to have a good correlation with belt life where cord separation is the failure mode, and is used as part of a belt life prediction procedure (based on finite element analysis) which encompasses all the failure modes identified by Gerbert and Fritzson. 

Prediction of Belt Life in Delamination Failure Modes... 

If we take an overview of how the belt delamination failure modes have been analysed by researchers to develop belt life prediction routines it is clear that the different methodologies have a lot in common, and it may be of value to highlight how these belt... 

Be sure to properly align the motor and driven puUeys. V-belt drives should be aligned to within V° or Vw in/ft of center distance. V-ribbed and synchronous belt drives should be installed and aligned to within V° or Mo in/ft of center distance. Misaligned drives can result in V-belt turnover and premature and unusual belt wear leading to shorter belt life. 

The best tension for the belt is the lowest tension at which the V belt will not slip, or synchronous belts will not ratchet (jump grooves).Too much tension shortens belt life and may... 

Routine maintenance will extend the life of the sheaves and belts. Belt-drive maintenance requires little time, but it must be done regularly. Keeping the belts clean and free of oil and grease will help ensure long belt life. See Figure 23-14. 

Belt grinding performance generally improves with an increase in load and a decrease in speed. Speeds of the order of 5 to 10 m/s (1000 to 2000 sfin) and pressures in the vicinity of 0.7 MPa (100 psi) provide optimum productivify and belt life. 

Diy polishing is more appropriate than wet for some applications. For these operations, belts or cloth wheels with silicon carbide abrasive may be used. Soaps and proprietary compoimds may be applied to the belts to improve polishing and to extend belt life. Abrasive belt materials that incorporate solid stearate lubricants offer improved results for dry polishing operations. 

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