V-Belts: Proper Care (1979)

[Music] The V-B belt is one of industry's most popular means of power transmission. Essentially, the V-B belt is easy to install, simple to select, and will provide years of reliable service through the proper installation and maintenance procedures. In general, there are four main areas that will ensure good V-B belt maintenance and operation. They are shiv groove inspection, belt installation, alignment, and belt tensioning. Whenever beginning to inspect any type of electrically driven machinery, always lock out and tag the main disconnect of the equipment being worked on. Remove the belt guard and clean it. This will prevent dirt and other foreign material from dropping off the guard and collecting on the belts or in the shiv grooves. The guard also protects the belts from the surrounding outside environment. Examine the V-B belts. If they are cracked, frayed, or swollen, replace them with a matched set. V-B belts should be kept clean. If dirt has been caked on, a stiff bristle brush may be used to clean the belts. Particles of dirt tend to embed themselves into the belts, making them coarse and rough, causing shiv wear. Soap and water may be used to clean the belts in environments that cause oil and grease to collect on them. Oil or grease will make the belts soften and swell up. Once these physical properties of the belts are changed, it is not long before they fail completely. Under no circumstances is the use of belt dressings recommended. They often have a solvent effect upon rubber compounds which will increase the pulling power at the expense of belt deterioration. Inspect the shiv grooves for any foreign materials. Materials lodged in the shaves will force the belts from their path in the grooves causing them to turn over. This problem is resolved by cleaning the shav. Check the tensioning of the belts. 95% of all problems encountered with V-B belts will be due to inadequate tension. In most cases, the problem can be corrected by tightening the belts. Loosen the motor hold down bolts and tighten the belts by increasing the distance between the two shafts. On most drives, this is done by moving the motor mount back until both spans of the belts are snug. Be sure to rettighten the motor hold down bolts. Alignment should be checked anytime there has been a change made in the distance between the two shafts. Probably the easiest and most common way of determining shiv alignment is with a straight edge. The straight edge is placed between the outside edges of the two shivs. Contact should be made at two distinct points along the outside perimeter of each shiv. Rotate the shivs a half turn and check again. Two distinct points of contact should be made on each shiv. In some cases, a straight edge may not be practical due to the distance between the shivs. A string line may be used to check the alignment. As with a straight edge, there should be two distinct points of contact made on the outside perimeter of each shiv. Repeat the process only this time on the inside face of the shaves. Again, two distinct points of contact should be obtained on each shiv. On horizontal drives, check for angular misalignment by seeing that both shivs are in the same vertical plane and the belts are not twisted. While the machinery is operating, it is important to look at the slack side of a drive to be sure that all the belts are running with a slight bow. If one or more of the belts is running loose, the drive needs to be retensioned or the belts replaced with a matched set. If the belts need to be replaced, begin by loosening the motor mount and remove the old belts. Never attempt to force or pry belts on or off a drive. This will cause the outer fabric of the belts to crack or rupture the inner cords, resulting in a shortened belt life, turnover, or belt breakage. Shiv grooves should be cleaned of all foreign matter. Dirty shaves can be cleaned using a safe solvent and rag. If left unchecked, dirty shaves will greatly reduce the operating efficiency of the belts and increase groove wear. To check for shiv groove wear, use a shiv gauge. Select the proper gauge according to the shiv diameter and insert it into the groove. The gauge rim should rest on top of the outside diameter of the shiv and the inside should lie flush against the side wall of the groove. On multiple belted drives, be sure to check all the shiv grooves for uniformity. A common pattern for groove wear is one where the sidewalls become concave or dished out. If it is to the point where the belts no longer possess their wedging action or more than 132nd of an inch, then the shivs should be replaced. Normally, this will occur on the smaller shiv. If the shivs are in good condition, then proceed to install the new belts. Take the properly marked and matched set of belts. Install them by simply placing them over the shiv grooves. Allow for the motor mount to be loosened sufficiently so that no force is needed to put the belts over the shiv. Arrange the belts so that all the slack is on one side. Loosen the motor hold down bolts. Then tension the belts by increasing the distance between the two shafts until the top and bottom spans of the belts are snug as a standard procedure. And after any adjustment in the distance between the shafts, check the shiv alignment. Before making any more adjustments, run the drive for about 15 to 20 minutes. This will give the belts time to seat themselves in the shiv grooves. Visibly, the drive should run with the tension side tight and the slack side with a slight bow. Some important steps to remember when installing multiple belts are to make sure all belts are replaced as a matching set. New and used belts should never be used together. Used belts have already gone through a stretching period whereas the new ones have not. Since new belts would be tighter around the shaves, they will absorb the brunt of the load. This not only causes the new belts to wear rapidly, but also causes shiv groove wear. It is also recommended that belts by different manufacturers not be used. Different manufacturers belts will have different strength and stretch patterns. Mixing them will cause mismatching resulting in short belt life. Sticking with one manufacturer will make identification and selection of belts much easier and also result in better drive performance. Here are some simple but accurate ways of determining correct belt tension. Using the eyes, observe the running drive. It should operate with the tension side tight and the slack side with a slight bow. When operating at peak load or at startup using the ears, listen for a squeal when the drive is started or at peak load period. If a squeal is heard, the belts are too loose. Tighten the belts until the squeal is no longer heard. Using the hands, feel the shiv grooves. They should not be running hot. If the mechanic can place his hand in the groove for any period of time, then they are running cool enough. Hot shaves are usually caused by belts whose wedging action is lost, resulting in belt slippage. Due to the nature of the materials used in belt construction and their initial stretching characteristics, it may be necessary to retension the new belts after a day or so of operation. Another method of checking V-B belt tension is with a tensometer. Always follow the manufacturer's guides and tables when using this method. Belts that are overtensioned can be a problem. Tight running belts cause the bearings to overheat as a result of too much strain being put on the drive. To correct overloaded bearings, loosen the belts and apply the correct tension. Mounting the shiv close to the bearings will also reduce this strain. Once in a while, drives may be shut down over a long period of time. In such cases, it is recommended that the tension of the belts be relaxed. This is done to avoid having the belts set. When belts set, they stiffen and harden, causing them to lose their strength. Relax the belts by loosening the motor. The belts will hang loosely over the shaves without setting. When returning the drive back into operation, the belts have to be retensioned and the shivs realign. Looking back on what has been discussed about the V-B belt, the single most important factor in obtaining the best operating efficiency is to maintain the proper belt tension. Keep in mind that V-B belts generate power through their wedging action between the shiv sidewalls and the V-belt. Tension is applied to gain this wedging action. On drives with long spans, vibration or pulsating loads can cause individual V-B belts to turn over, break, or jump off the drive. This is referred to as belt whip. Banded belts are used in these circumstances to dampen the vibration, reducing belt whip. Another consideration in V-B belt operation efficiency is belt fit. As a rule of thumb, each belt should ride in the shiv groove so that the top surface of the belt is just above the highest point of the shiv. This may differ slightly with different shivs and belt selection. In accordance with the occupational safety and health act, remember to reinstall the belt guard covering the belts and shaves. Properly installed and maintained V-B belts will deliver years of reliable service. To ensure the quality of the V-bs, proper storage should be practiced. V- belts should be stored in a cool, dry place and out of direct sunlight. If belts have to be stored in boxes or piles, the contents or stacks should be limited to a small number. Belts stored on top of one another will cause the bottom belts to distort. Some definite don'ts in V-B belt storage need only a little common sense to correct. Never store belts on the floor. Floors can get cold and damp, causing belt materials to deteriorate. Never store V-B belts near a heater, radiator, or in the air flow of a heater. Heat will cause the belts to become dry, brittle, and even crack. It is easy to see why V-B belts are one of industry's most popular means of power transmission. Shiv groove inspection, belt installation, alignment, and belt tensioning are four essentials to remember when considering good drive maintenance and operation. [Music]