Belt Accessories

What are belt accessories?

Belt accessories are the tools and parts used to install, tension, align, and maintain belt drives. They include belt tension testers, tensioners and idlers, belt fasteners, belt dressing, and alignment tools. A belt drive only performs well and lasts its full life when the belt is correctly tensioned and the pulleys are properly aligned, and belt accessories make it quick and easy to get both right.

A typical range of belt accessories covers:

• Tension testers, which measure belt tension so it can be set correctly
• Tensioners and idler pulleys, which apply and maintain the right tension on the belt
• Alignment tools, which check that the pulleys are lined up with each other
• Belt fasteners, which join the ends of open-length belts
• Belt dressing, which helps restore grip and reduce slip on some belts.

Correct tension and alignment are the key to belt life.

• An under-tensioned belt slips, glazes, and wears quickly, and can overheat.
• An over-tensioned belt puts extra load on the shafts and bearings, and wears the belt and pulleys early.
• Misaligned pulleys make belts wear unevenly, run noisily, and come off the pulleys.

Belt accessories are used on industrial and agricultural belt drives of all types, from V-belts and wedge belts to flat and toothed belts.

Why are belt accessories essential?

Most belt failures are caused by incorrect tension or poor alignment, rather than by the belt itself. Guessing the tension by feel often leaves belts too tight or too loose, and checking alignment by eye rarely gets the pulleys truly in line. Belt accessories take the guesswork out of installation and maintenance, so belts run efficiently, last longer, and put less strain on bearings and motors.

They also save time and money. Setting tension and alignment correctly the first time reduces repeat repairs, unplanned downtime, and wasted belts, and helps drives use less energy.

Typical applications include:

• Installing and replacing V-belts and wedge belts
• Routine maintenance of industrial belt drives
• Agricultural machinery belt drives
• Fans, pumps, and compressor drives
• Conveyor and material handling drives
• Machine tool and workshop drives
• Joining and repairing open-length belts

The main types of belt accessories

• Belt tension testers - Tools that measure the force needed to deflect the belt by a set amount at the middle of its span. The reading is compared with the recommended value, so the belt can be tensioned accurately.
• Belt tensioners and idler pulleys - Spring-loaded or adjustable arms with a pulley that presses on the belt to keep it at the right tension. They are used where the motor cannot be moved, or to take up stretch automatically.
• Alignment tools - Straight edges, alignment gauges, and laser alignment tools that check the pulleys are in line and parallel, so the belt runs straight.
• Belt fasteners - Metal or plastic fasteners for joining the ends of open-length belts, such as flat or link belts, so they can be fitted without dismantling the machine.
• Belt dressing - A spray or stick applied to belts to improve grip and reduce slipping and squeal. It is best used on older leather and flat belts, and is not a cure for a worn or incorrectly tensioned belt.

How to choose the right belt accessories?

• Belt type - Choose accessories that suit your belts. Tension testers, for example, are often designed for particular belt types, such as V-belts and wedge belts.
• The job - Use a tension tester and alignment tool when fitting new belts, a tensioner where the drive needs automatic or ongoing tensioning, and fasteners for open-length belts.
• Drive size - Choose tensioners and idlers that suit the belt section, pulley size, and power of the drive.
• Accuracy - For critical or high-power drives, a laser alignment tool gives more accurate results than a straight edge.
• Frequency of use - For regular maintenance, a dedicated tension tester and alignment tool quickly pay for themselves through longer belt and bearing life.

Essential references and specialised ranges

How the numbering works:

Belt accessories do not follow a single numbering system. They are usually referenced by type, brand, and the belts or drives they suit, for example:

Belt tension tester for V and wedge belts = a tester designed to check the tension of V-belts and wedge belts

Belt tensioner for SPA belts = a tensioner sized to suit an SPA section belt

Belt fasteners are usually referenced by size and the belt thickness range they suit.

Check the belt type, section, and size the accessory is designed for before ordering.

Suffixes:

Belt accessories rarely carry standard suffixes. Where they do, they usually show the size, belt section, or version.

Suffix codes vary between manufacturers, so check the supplier’s catalogue for the exact meaning.

FAQ - All you need to know about belt accessories

How do I use a belt tension tester?

Fit the belts snugly around the pulleys, then work out the deflection needed, usually about 16mm per metre of centre distance between the pulleys. Set the tester to this deflection, press it at right angles on the belt at the middle of the span, and read the force needed. Compare it with the recommended value and adjust the tension until it matches.

Why should new belts be tensioned higher at first?

New belts bed into the pulley grooves and stretch slightly when they first run. Many manufacturers recommend tensioning new belts to around 1.3 times the normal value, then rechecking and resetting to the normal value after a short period of running, such as 30 minutes.

How do I check pulley alignment?

Place a straight edge or alignment tool across the faces of both pulleys. It should touch both pulleys evenly at two points on each. Any gap shows the pulleys are offset or angled, and the motor or pulley should be adjusted until they are in line.

Should I use belt dressing on V-belts?

It is generally not recommended. Belt dressing can hide problems such as wrong tension, misalignment, or worn belts and pulleys. If a V-belt is slipping, check and correct the tension and alignment, and replace the belt if it is worn.

When should I use a belt tensioner?

Use a tensioner where the motor cannot be moved to tension the belt, where the drive needs to keep a constant tension automatically, or to increase the wrap of the belt around a small pulley.

How do I identify the accessory I need?

Check the belt type, section, and size on your drive, and the brand of belt if you are choosing a tension tester designed for particular belts. For tensioners, also note the pulley size and the space available.

How can I tell if a belt accessory needs replacing?

Warning signs include:

• Tensioner pulleys that are noisy, rough, or wobbling
• Tensioner springs that are weak, broken, or no longer hold tension
• Tension testers or gauges with worn or unreadable markings
• Belt fasteners that are worn, loose, or damaging the belt
• Alignment tools that are bent or damaged