August 2007 – Featured Article

The Importance Of Proper Maintenance Inspections On Belt Conveyors & Bucket Elevators

The following article is an extract of the presentation given by Charles Pratt, Kinder & Co Sales Manager, at the Powder & Bulk Materials Handling Seminar held in Perth WA on 26th July 2007.

Irrespective of the material handled, the same type of conveyors are used. They all use the same technology, operating principles, operating parameters and safety measures and each has equally its own challenges in the transportation of the material from point A to point B.

Whether using conveyors or bucket elevators, the same basic technical expectations exist, which in brief are:-

  • To provide a clean and safe work site free of spillage.
  • To achieve rated service life from conveyor belts.
  • To achieve rated service life from conveyor hardware. (Idlers, pulleys, etc.)
  • To limit outages during production caused by conveyor problems.

Likewise, whether using conveyors or bucket elevators, the same Objectives often exist, including:-

  • Improving productivity.
  • Improving reliability.
  • Operate safely without incidents.
  • To be cost effective.
  • To be environmentally responsible.

Conveyors and elevators have been around for many, many years. So what has changed in today’s harsh environments?

  • Safety is the number one priority.
  • Environmental responsibility is now paramount.
  • Many plants operate with unskilled labor and limited access to skilled labor.
  • Ageing skilled workforce not being replaced.
  • Safety Is Now A Measure Of Conveyor Performance.

The measure of success in all production operations should use safety as its primary rule of measure and there are a number of reasons for running a safe operation.

  • It is good business practice.
  • It promotes and maintains high staff morale.
  • It helps to retain the best highly skilled staff. (Especially in a period of skill shortage.)
  • It’s the law and there are some tough penalties for serious breaches.

Identifying the Risk

Conveyor Maintenance not only includes proper care of the belt itself, but also care and maintenance of the frame and conveyor hardware. More importantly, it includes eliminating the risk of injury and death to personnel operating in the vicinity of the “live” conveyor.

Belt Tracking is considered a route cause of many problems. Left unattended, incorrect belt tracking can lead to serious damage, including;

  • Structural Damage.
  • Belt Damage.
  • Spillage.
  • Dust Leakage.
  • Entanglement of operating personnel.
  • Fire

Regular conveyor and elevator inspection is critical in any preventative maintenance regime. Regular inspections can lead to early problem detection, which in the long run save both time and money. Areas to check include;

  • Structural damage.
  • Missing, loose or damaged rollers.
  • Belt/splice damage.
  • Chain damage.
  • Belt mistracking. (Belt/chain tracking is considered a route cause of many problems leading to further serious damage or risk exposure.)
  • Elevator casing (looseness or corrosion)
  • Missing, loose or damaged buckets.
  • Chain stretch/damage.

Always remember that good housekeeping is a critical part of preventative maintenance!!

Belt Tracking

Why is it so important that the belt runs “TRUE” ?

To use an analogy, it’s a bit like a laden truck on a freeway. The situation is worse when the truck is travelling at high speed without proper steering.

The goal in achieving proper and consistent belt tracking is to ensure safe, consistent, trouble-free, economical conveyor system operation — in short, to be able to walk away from the system and not worry about its operation for reasonable periods of time.

Belt tracking is also a route cause of spillage, reduced belt life and the cause of many serious accidents, some resulting in the loss of limbs or worse, the death of workers. So don’t accept that conveyors will not track true under all operating conditions and work towards rectifying the faults.

Use the signs of spillage and belt damage during inspections to find the cause of belt misalignment.

Common Causes of Belt Misalignment.

Their are numerous causes of belt misalignment, but among the most common are;

  • Sunken or not level foundations.
  • Driving and idler pulleys not normal to the conveyor centreline and not parallel with each other.
  • Seized or out of round rollers.
  • Transverse forces applied to the belt by items such as over tight angled belt scrapers.
  • Material build up on the pulleys, belt or rollers.
  • Damaged, twisted and or missing conveyor idler frames.
  • Crosswinds.
  • Uneven placement of load on the belt or the belt being loaded off centre.
  • Uneven skirting pressure.

Common Signs of Belt Misalignment.

  • Poor workmanship with belt splicing/slitting/ends squaring. This includes localised edge repairs with associated tension differences.
  • Transition idlers not installed or unevenly adjusted.
  • Poor quality pulley manufacture with the diameter not symmetrical to the centreline of the belt. (Pulley faces may be worn.)
  • Excessive tensioning of the belt preventing all of the idlers from helping to direct the belt.
  • Under tensioning of the belt, which restricts the pulleys from controlling the belt. This also applies to all pulleys including take-ups.
  • Uneven or misaligned pulley take-up carriage forces.
  • The belt hotter on one side than the other, for example near a furnace.
  • Worn pulley faces, pulley lagging unevenly worn or pulley shaft locking elements worn.
  • Trough and return idlers not installed at right angles to the axial centreline and therefore the belt not making proper contact with the rollers.
  • Trough idlers installed back the front with the lead roller not leading.
  • Offset trough idlers being used on reversing conveyors rather than in-line idlers being used.
  • Out of round or seized rollers giving the belt contact forces asymmetric to the centreline.
  • Poor belt quality with the weave / fabric asymmetric to the centreline.
  • Incorrect belt storage, which has caused the belt to warp or bow.
  • Belting of a different manufacture in the same length.
  • Travelling trippers and shuttle not running true.
  • One side of the belt running wet.
  • Extraneous articles fouling the conveyor belt.
  • The belt too stiff for the idler width or trough angle, therefore not allowing the idlers to direct the belt.
  • Return idler spacing too great to direct the belt.
  • Existing self-aligning idlers worn out, seized, or locked into position.
  • Existing self-aligning idlers installed incorrectly or in wrong location.
  • Mechanical fasteners not installed square. Conveyor rollers of various diameters installed.

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