Tech Articles Industrial

Belt drives are the most cost effective, reliable means of shaft-to-shaft power transmission speed change but they require regular inspection to ensure proper performance. Follow these steps for best practices on belt drive installation and inspection:

1. Check temps: check the ambient temperature of the belt itself with a temperature gun (preferably while still operating). V-belts should not be run above 140°F (60°C) and synchronous belts should not run higher than 185°F (85°C). For every 18°F (10°C) increase in belt temperature – which is a 36°F (20°C) ambient temperature change – belt life is cut in half.
2. Shut down the system: given the nature and size of these machines, typically a complete shutdown is necessary as is a number of other precautions like tagging the machine and locking machine power in the off position so others are aware and testing it to ensure it’s safe for inspection.
3. Inspect the belt: remove the safety guard and mark a line on the belt. Work your way around it, looking for cracks, frayed spots, cuts, missing teeth and unusual wear.
4. Replace belt if needed: if a belt needs replacing, never pry it on or off a drive, always loosen the take-up bolts and move the sheaves to create slack. Only use new belts from the same manufacturer on one drive. Never mix and match belts from different manufacturers.
5. Check drive alignment: using a straight edge, string or laser alignment tool, check positioning. There should be 4 points of contact across the drive if it is properly aligned. The larger the misalignment, the greater chance for belt instability, wear and V-belt turnover. V-belt drives should be aligned to within .5° or 1/10″ per foot of center distance span. Synchronous drives and poly-V drives should be aligned to within .25° or 1/16″ per foot of center distance span.
6. Check bushings/sheaves: ensure proper installation was complete as incorrect bushing installation can result in sheave misalignment as well.
7. Measure tension: using the Force/Deflection method and a tension tester, check the tension of the belt. V-belt drives should be tensioned as per the manufacturer’s recommended tension chart at the force rate specified. The deflection distance is to be 1/64″ per inch of span length. So if the span length is 32″, then the deflection distance should be 1/2″ (32/64″) to reach the specified force.
8. Doublecheck alignment and tension re-iteratively: if you change one then you must check the other until neither needs to be adjusted again. Under-tensioned V-belts will cause slip and excessive heat while under-tensioned synchronous belts will jump teeth and possibly snap in half. Over-tensioned V-belts and synchronous belts both cause reduced belt and bearing life due to excessive loads and tension.

If you have a belt drive system that is under-performing or you’re looking for improved drive life, below are Dayco’s top tips on enhancing performance:

• Increase the sheave or sprocket sizes: larger sheaves increase the HP rating of the drive.
• Increase the belt length: longer belts reduce the bending stress and allow for more cooling.
• Increase the number of V-belts or widen the synchronous drive: a wider drive increases the HP rating of the drive.
• Improve the drive ventilation: maximize the airflow through the drive to improve belt life.
• Take advantage of idler options: if the drive utilizes idlers, use the largest possible diameter and position them on the inside of the lowest tensioned span if possible.
• Always use proper tension and alignment procedures: this will help maximize best possible performance.
  Incorporate a “break-in” period when using new belts. When new belts are installed, tensioned and aligned, it should have a run-in period of ideally 24 hours and then the belts should be re-tensioned. This allows the belts to seat properly in the sheave grooves. Once re-tensioned after this run-in period, the belts should not have to be checked again until the next normal scheduled maintenance.

Many maintenance managers report V-belt drives only last two-three months but the reality is premium heavy-duty industrial V-belts are designed to run at least 22,000 hours, which equates to almost 2.5 years of continuous 24/7 operation. So why aren’t V-belts lasting as long as they should? Here’s five key reasons, according to recent data:

1. Improper maintenance: It’s estimated that over two-fifths of failures are caused by improper drive maintenance. Not going back to check tension on belts, improper sheave alignment and not checking sheaves for physical damages or wear.
2. Poor drive design: Approximately 1 out of every five belts doesn’t last as long as it should due to improper drive design. This includes using the incorrect belt for the application, having an over-designed or under-designed belt drive and using the wrong sheaves.
3. Improper installation: About 20% of failures are due to improper belt installation. This includes incorrect belt tension, rolling or prying of the belts and general mishandling.
4. Environmental factors: About 1 in 6 problems are due to environmental factors, like dust, sand and high temperatures. It’s important to choose a belt construction that can help to reduce and minimize external factors and its influence on belt life.
5. Improper storage:  Belts should be stored in a cool dry environment. Excessive heat, light or humidity can impact their shelf life. In addition, they need to be used in the order received which is not always what happens.

Getting the Most out of V-belts

One way to address these issues is by implementing a proper V-belt preventative maintenance program. It can help your company save thousands of dollars in labor costs and downtime, parts usage and administrative costs. Dayco provides unparalleled technical support, including free training, engineering assistance and top-quality products to help minimize the emergencies in your plant. Our team offers a free preventive maintenance seminar to customers on site for maintenance personnel that can dramatically increase belt life and service intervals.

Your Dayco team can also help ensure you are picking a belt that will save money and reduce down time.

The reality is V-belts are not always put at the top of the priority list or companies are choosing to select price over quality and that’s a big mistake. Replacing V-belts is time consuming so there is a significant disadvantage to having to replace belts more frequently than necessary.

Belts used in HVAC applications are frequently found in exhaust and ventilation fans on rooftops. Often exposed to sunlight, humidity and extreme temperatures, these belts typically run in a very small sheave (usually variable pitch sheave on the motor) with a life that is extremely limited. Many repair technicians report replacement intervals occur 3 to 12 times per year using 4L and 5L V-belts. But these light-duty belts have low temperature resistance – usually up to 145oF – and high stretch.

Our team recommends replacing 4L and 5L belts with Dayco GOLD LABEL AX and BX notched (cogged) belts. There are a number of advantages to doing this:

• Provides protection from -40°F to 300°F (-40°C to 150°C), the highest temperature range on the market.
• Higher tensile strength offers higher service factor and longer life. For every 10% of increase of service factor, the belt life is doubled.
• Notched construction allows optimal performance in small sheave applications.
• Minimum elongation translates into higher life and less labor.

Techs can go from multiple replacements every year to ONE annual belt change, saving both labor costs and the need to buy multiple belts. For more information on Dayco’s industrial belts click here.

Many maintenance managers do not have a proper procedure for storing and handling power transmission belts, yet it makes up one of the top five reasons for early belt failure. Here’s four critical details you need to keep in mind:

1. Location is everything: proper belt storage starts with the environment. Belts should be stored in a cool dry environment under 85oF (29o C) and below 70% relative humidity, with no direct contact with sunlight, UV light and Ozone. Ultraviolet light from sunlight and fluorescent lighting can cause UV degradation, which has a serious detrimental effect on rubber. It accelerates deterioration by producing photochemical reactions that promote the oxidation of the rubber surface, which results in a loss of mechanical strength.

2. Note the shelf life: Dayco belts have a shelf life of 7 years so keeping an adequate FIFO system (First In First Out) is critical. However, we often see a LIFO system instead (Last In First Out) as belts are hung as they come and then taken as needed, always leaving a group of belts that don’t move at all. In most industrial parts warehouses, it is not uncommon to see about 25% of belts past their shelf life, making them unusable and unreturnable.

3. Read the date codes: to make sure your facility’s belts haven’t surpassed their “shelf life”, it is important to learn to read the manufacturing date of the belt on the code printed on the belt:

• WW: Week numbers from 1 – 52 in a calendar year
• YY: The last 2 digits of year
• ZZZ: Sequence numbers to indicate the position of the belt on the mold
• Example: 2221001 –> means the belt was manufactured in week 22 of year 2021

4. Store properly: there’s a number of ways each type of belt should be stored:

• Single V-belts: we recommend single V-belts be hung on the wall, using large diameter pegs made from PVC pipes, as its diameter is large enough to avoid “memory” in a single point of the belt.
• Large V-belts: our team suggests “coiling” the belts to avoid excessive weight in a single point. The way to produce coils is to grab both extremes with the belt, one with the right hand, and the other with the left hand. At the same time, rotate the belt, one hand clockwise, and the other, counter-clockwise. Ensure to not over-coil your belts though. If a belt is coiled too many times, it puts undo stress on the cords inside the belt and can cause them to fray due to over-twisting.
• Banded V-belts: joined V-belt constructions, due to weight, should not be hung. They should be left inside a box lying flat on a shelf.
• Synchronous belts: also called timing belts and HTD belts, like Dayco’s HT Power, HT Power Plus and HT Power Carbon, these should be stored in original package and should avoid any manipulations. One very common practice is to remove these belts from their original package, tie them together really tight with a tie wrap and store them in drawers or bins to save space. When you do this, there is a great chance that you may compromise the internal cords of the belts by breaking them (crimping), leading to premature failure.

Dayco experts suggest switching from a 4L or 5L V-belt for some industrial/HVAC applications to a GOLD LABEL raw edge (notched) belt for increased performance and longevity. Here is how to cross reference these belts using the part numbers:

• 4L = AX section
• 5L = BX section

The remainder of the part number gives you the OUTSIDE circumference divided by 10.

AX and BX section part numbers are given by the INSIDE circumference:

• AX part number + 2 = outside circumference
• BX part number + 3 = outside circumference

Example:

4L440 = AX42 (4L = A; 440 = 44″ OC; 44 – 2 = 42 IC thus AX42 – *X for notched belt*)
5L550 = BX52 (5L = B; 550 = 55″ OC; 55-3=52 IC thus BX52)

Our team does not recommend replacing a 4L belt with an A section wrapped belt due to the difference in the minimum pulley diameters (see chart). Going from 4L to an A section or from 5L to a B section is risky due to minimum pulley diameters. A BX can survive on a 3.5″ pulley and given the much higher capacity and temperature range, compensates for reduced life due to smaller than recommended pulley diameter condition.