V BELTS - NOMENCLATURE , FAILURE PATTERN STUDY

1.Belt Nomenclature 

All A,B,C,D,E,AX,BX belts list the inside circumference measurement after the letter of the v belt part number. Example: A88 has a 88" inner circumference, then you add 2 inches for the A Section (Listed below) to obtain the outer circumference. If you measure the outer circumference, then you would subtract the number of inches based on the section you have (Listed below) to obtain the v belt number. This is also the same for the banded belts. Measure each individual band for banded belts to obtain the correct width.

Examples of how belt numbers are coded per section:

A Section= Add 2" to belt number (Example A88 = 90" Outside Circumference)

B Section= Add 3" to belt number (Example B88 = 91" Outside Circumference)

C Section= Add 4" to belt number (Example C88 = 92" Outside Circumference)

D Section= Add 5" to belt number (Example D105 = 110" Outside Circumference)

E Section= Add 6" to belt number (Example E144 = 150" Outside Circumference)

AX Section= Add 2" to belt number (Example AX60 = 62" Outside Circumference)

BX Section= Add 3" to belt number (Example BX50 = 53" Outside Circumference)

How fractional & wedge belt numbers are coded

All sections 3L,3V,5V,8V,3VX,5VX belts have the outside circumference after the number and letter(s). Example: Belt # 3V600 has a 60" outside circumference. Inside circumference are not measured for these sections. This is also for the banded belts. Measure each individual band for banded belts to obtain the correct width.

Examples of how belt numbers are coded per section:

3L Section= (Example 3L450 = 45" Outside Circumference)

3V Section= (Example 3V800 = 80" Outside Circumference)

5V Section= (Example 5V1180 = 118" Outside Circumference)

8V Section= (Example 8V2120 = 212" Outside Circumference)

3VX Section= (Example 3VX520 = 52" Outside Circumference)

5VX Section= (Example 5VX810 = 81" Outside Circumference)

Measuring K,L,M Micro Rib Belts:

Width's

K Section= 0.140" X's the number of ribs

L Section= 0.185" X's the number of ribs

M Section= 0.370" X's the number of ribs

All sections K,L,M belts will have the outside circumference in front of the letter. The rib count will be the number after the letter.

Outside Circumference & Rib Count per section:

K Section= (Example 845K8 = 84.5" Outside Circumference and 8 Ribs)

L Section= (Example 540L10 = 54" Outside Circumference and 10 Ribs)

M Section= (Example 940M6 = 94" Outside Circumference and 6 Ribs

Belts are neither measured by diameter nor folding the belt in half. The most accurate way to measure the circumference of a belt is with a v belt measuring tool or using a cloth tape measure (Not a steel tape measure or ruler). An additional option is to wrap a small diameter string/rope around the belt, then measure the length of the string. 
Keep in mind belts do stretch and unfortunately there is no specific given value for how much a belt stretches. 

2.V-Belt Defects

When inspecting a V-belt, look at these areas for signs of uncommon wear:

• Top surface
• Top corners
• Belt sidewalls
• Bottom corners
• Bottom surface
• Undercord cracking
• Sidewall burning or hardening
• Belt surface hard or stiff
• Belt surface flaking, sticky or swollen
   

Top surface wear might be the result of the belt rubbing against the guard, or by a fail of the idler. Control these areas, and fix or change the guard and/or idler to correct the anomaly.

Wear on the top corners of the belt could be the sing that the belt is smaller for the groove in the sheaves. Changing the belt for the right sheave will fix the problem.

 Severe wear along the belt sidewalls  may be due to several factors. The belt may be slipping due to a bad tension. In that case, increase tension until the slipping stops. Another possible problem is sheave misalignment, which needs to realigning the drive. In this case, change the sheaves. Or the belt could simply be the inappropriate size and needs to be change with the right size.

Wear on the bottom corners of the belt may be causes by worn sheaves or an improper fit between belt and sheave. Control the sheaves for wear and change them if needed, or find the right belt/sheave match.

Bottom surface belt wear  may be due to fragments in the sheaves, sheave wear, or the belt bottoming out against the sheave grooves. Bottoming out is due to an improper match between belt and sheave, and can be fixed by choosing the proper match. If the sheaves are worn, change them, and if fragments has gotten into the sheaves, clean them.

Undercord cracking  could be cause by a plenty of factors. Environmental conditions (severe heat or cold) or a bad storage could be responsible. Solutions involve checking the belt drive environment and following the right storage and handling protocol.

Another cause could be belt slip, fixed by re-tensioning the belt to the manufacturer’s suggestions. A sheave that is smaller for the belt section, causing the belt to wrap too tightly around the sheave, could crack the undercord. Changing the small sheave with a larger one may fix the problem. Likewise, a backside idler with a small diameter may be the problem, corrected by increasing the size of the backside idler.

 Sidewall burning or hardening  may be due to worn sheaves or shaft movement or under-designed drive. A slipping belt must be re-tensioned to the manufacturer’s protocol.

A worn sheave must be changed. If the drive is under-designed, ask the manufacturer’s recommendations to redesign it. Shaft movement may be due to a changes in the center distance between the sheaves, and must be controlled and adapted.

If the belt surface is hard or stiff, it may be cause by a severe hot environment or to belt slip. Fix the problem by given more ventilation to the drive or adapting belt tension.

A belt surface that is swollen ,flaking or sticky  could have been contaminated by oil or chemicals. Eliminate the contamination and its source, and never apply belt dressing.

Banded (joined) V-belt problems

Banded V-belts (multiple belts with a common cover that serves as a tie-band) could show signs that point to a drive complication. The following symptoms call for investigation:

• Tie-band separation
• Top of tie-band frayed, worn or damaged
• Banded belt comes off sheaves repeatedly
• One or more belt ribs run outside the sheave

 Tie-band separation  may be the cause of a bad groove spacing. Control the sheaves to be sure that they have been manufactured to industry requirement. Another cause may be worn or wrong sheaves, which needs changing the sheaves. Also control to see if the sheaves are misaligned, which may force a separation of the tie-bands. Realign the drive to fix the problem.

If the top of the tie-band is damaged, worn or frayed, , decide if the belt is interfering with the guard and adapt the guard as desired. Another possible cause is worn or wrong sheaves. Change the sheaves to resolve the problem. Debris in the sheaves could also damage the tie-band, so clean the sheaves if required.

When a banded belt jumps off the sheaves, two cases are possible. Either items has penetrated into the sheaves, or they are misaligned. Align the drive to fix any misalignment problems. If item is a problem cause by the type of use, clean out the sheaves and use single belts rather than a banded belt.

A belt that has ribs running outside the sheaves could be under-tensioned. Control the manufacturer’s protocol and re-tension the belt. Another possible cause is sheave misalignment. Realign the drive to fix it.

Problems Common to Single and Multiple V-Belts

Two problems current to both single V-belts and Poly V-belts include belts coming off the sheave or turning over, and belts stretching beyond the available take-up.

There are a plenty of probable causes and remedial actions for single or Poly V-belts turning over or coming off the sheave

A simplifies trouble shooting for single v belts can be explained as under: