Friday, 8 January 2016

Highlights in Conveyor Belt Scale Installation and Maintenance

Conveyor belts are a ubiquitous feature in most industrial facilities and for many good reasons. Since the invention by Richard Sutcliffe in the early 1900s, these systems have continued improving efficiency in factories by enabling automation of material movement. They also help in space maximization while also reducing your labor and energy costs. 

One of the features that helps optimize these systems is a conveyor belt scale. These help to measure the material load as it travels over the belt. This is possible because as material moves down a conveyor belt it exerts a force proportional to the material load. 

However, the fact that the scale is out of sight leads to neglect which in turn affects its accuracy of capabilities.  Like any other system involved in handling materials the need for maintenance cannot be gainsaid. When bulky materials are involved the problem is exacerbated thus calling for regular checkups and proper maintenance to avoid inaccurate measurement.
An ideal scale will provide weight results that tally with those provided by National Institute of Standards and Technology (NIST)’s Handbook. While most products in the market offer accuracy guarantee it is important to note that simple maintenance ensures the capability of the scale is not compromised. 

As a facility owner, you need to understand the main installation and maintenance guidelines in order to care for the belt scale as per required standards. 

Main Installation Tips

According to industry experts most scales are affected by poor installation. Lest you fall into this pitfall consider some of these tips to get the most out of your scales:

Correct Positioning

This is one of the greatest factors which determine the functionality of the scale. You must ensure the scale is positioned where there is minimal tension and consistence. The best position according to National Type Evaluation Program (NTEP) is close to the tail section and you should ensure the scale is positioned on rigid mountings. 

The position should also be away from machines that might cause vibrations as this will affect the scale readings. Extensive even horizontal stretches are the best but with the right positioning of idlers even a slope can do. For convex belts the best location should be 12 m to the retreat side and 6 m on the approach side. For convex belts minimum distance from the tangent points of the curve is 12 meters. It is also important to avoid placing the scale too close to the feeder because the material will not have loaded. 

Minimize Variable Belt Tension

Over time, belts tend to sag due to temperature variation and the load.  Such variations in tension will affect the scale and hence a gravity take-up is recommended. This helps to reduce the impact of tension of the slack on the belt. The take-up, however should move freely and consistently place tension on the belt. At the same time you should not overload the belt because not only will this affect the scale but also the belt.

Idlers Alignment

Idlers determine how well your scale will function and they should be precisely positioned. Two idlers should be aligned on both sides of the scale. For higher accuracy levels you can use more than two idlers. To align precisely use a wire over the roller edges and tighten until you are sure there is no slacking. Work on the rollers until you are sure they are even. It is important to only use idlers of the same size, shape, make and style for easy alignment. The idlers also need to be scaled at equal distances.

Leverage Speed sensors

Speed is another important determinant of the accuracy your conveyor belt scale gives. Sensors should be attached to the tail pulley or alternatively the bend pulley shaft where the connection cannot slip. Mounting of a speed sensor should also be on a solid face pulley. If you use wheel driven speed sensors that are used with the return strand of the belt place them close to a return idler. This guarantees a stable drive surface to guarantee accuracy.

Optimize Your Wiring

Speed sensors are susceptible to radio frequency interference and when wiring the unit ensure you follow instructions to avoid inaccurate scale readings.  Use shielded cable, grounded metal conduit and terminal blocks throughout the circuit to avoid such interference.

Invaluable Maintenance Tips 

The way you care for your belt scale determines its efficiency and life.  The question that comes to mind is where do you start? Well, here are some highlights:

General maintenance: Your scale needs to be cleaned regularly and lubricated. You also need to keep a lookout for any slack in tension and also alignment. The belt should be trained to stay on course while extreme loading must be avoided. Belt scrapping also helps you to get ideal readings.

Belt calibration: Determinants in this crucial maintenance procedure of conveyor belt include its condition, seasonal temperature changes, prior maintenance, and expected accuracy. It is advisable to start with a small calibration interval after installation as you learn how badly the scale is deviating. You can later increase the calibration intervals if you find a large deviation from the accuracy you desire. Speed tests, zero tests, span tests must be carried out during calibration. 

Weather factors: Temperature shifts are the worst nightmare when dealing with scale maintenance. You can avoid gravity tensioning device to mitigate effects of temperature changes.  

Your belt scale is an invaluable part of your business. To enhance your scale’s efficiency follow these tips and always remember they are there, lest you forget to maintain them religiously.