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Quick fixes – part 1

World Cement,


It is easy not to notice a common problem when looking at a belt conveyor system every single day. However, a quick visual inspection can mean the difference between a productive day and a costly day for a cement operation. It is also helpful to know what to look for when walking the line, as sometimes small irregularities can end up causing big problems.

The top ten conveyor challenges that can be identified with a simple visual inspection, what problems they can cause, and how to fix them in a short period of time, are listed below:

Damage to belt cleaners, premature wear of fasteners, carryback, mistracking of belt

Causes

Unskived splices; fasteners interfering with the cleaners.

Solution

Skive the belt before applying splices, when possible, and use low profile fasteners with a coined edge. Skiving the belt reduces the fastener profile on the belt, resulting in improved fastener-cleaner compatibility and increased fastener service life. When the skiving layer is removed, the fasteners are installed so they are even or slightly below the belt surface. This outcome reduces the chances of the fasteners getting caught on belt components and even the structure itself. Any contact with cleaners, rollers and skirting can damage both the belt and the components, resulting in reduced component life, downtime and maintenance issues.


Sometimes the need for quick fixes can be prevented. A properly squared belt can extend the life of the belt and help avoid mistracking.

The process of skiving also creates stronger splices. The splice on a properly skived belt will last much longer as a lower profile is being achieved, while preventing excess wear and tear on the fasteners. Furthermore, when a belt is skived, it removes the top rubber layer from the belt, placing the top and bottom plates of each fastener closer to the carcass, resulting in improved strength of the belt splice.

Premature belt splice failure, uneven lagging wear, early cover wear at trough line

Causes

Poor transition distance.

Solution

Check the transition distances and verify that the distances are in line with CEMA standards. Typically for fabric belts, CEMA recommends a transition distance of four times the belt width. 

Belt ripping right behind the splice, premature belt failure

Causes

Fasteners that are too large for the smallest pulley.

Solution

Check the minimum pulley (where the belt wraps 90° or more) diameters against both the belt manufacturer’s recommendations, as well as the fastener manufacturer’s recommendations. Using a pulley diameter that is smaller than the belt and/or fastener’s recommended size can produce excessive bending stresses with the possibility of belt splice failure.


If fasteners are wearing prematurely, skiving the belt may be the key to longer splice life.

Belt slippage

Causes

Small pulleys; incorrect lagging; worn lagging.

Solution

The proper pulley diameter is crucial to belt performance. When it comes to slippage, the surface area where the belt goes from full tension (top) to partial tension (bottom) and shrinks puts an extensive amount of pressure on the lagging to move with it and prevent slip. While CEMA does not specifically recommend a pulley diameter by application, the engineers of conveyor systems make recommendations for pulley diameters based on the design of the conveyor. Often, the small pulley will be substituted to save costs without consideration for this belt shrink – if they minimise the pulley size, they also minimise the area in which the lagging can help the belt shrink as it wraps around the pulley. Reducing the size of the pulley this much may cause slippage. Additionally, it should be verified that the correct lagging is being used and is in good condition. New rubber lagging that is slipping may indicate that ceramic lagging, with a higher coefficient of friction, should be used instead. If there are any tiles missing or flat spots on older lagging, then it is time to replace it.


Read part 2 here.

Written by Ryan Grevenstuk, Flexco, USA. This is an abridged version of the full article, which appeared in the December 2014 issue of World Cement. Subscribers can view the full article by logging in.

Read the article online at: https://www.worldcement.com/the-americas/10122014/flexco-on-quick-fixes-part-1-991/


 

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