Operating notes

NITROLL
EFFECTIVE CLEANING AND TRACKING BELT CONVEYOR SYSTEMS

It frequently happens that designers, manufacturers and end users of belt conveyors forget about additional components that considerably improve the reliability and operability of the transport route and primarily draw attention to the conveyor’s performance parameters and basic equipment.

The absence of that equipment or the use of unreliable and ineffective sub-assemblies adversely affect the movement and increase costs of operating conveyors.

All the operators responsible for the movement of conveyors know best how big and important is the problem of insufficiently cleaned belts or the necessity to continuously adjust the location of idlers.

However, the use of some additional equipment components considerably reduce the nuisance and the frequency of service and repair processes that affect costs of using the conveyor. The improvements enhance the system sustainability, reduce the noise and dust levels and prevent any production stoppages.

Our objective is to improve the standard of performance and use of belt conveyors, which results in measurable economic benefits for their users.

We primarily focus on two most common issues:

  1. Removing remains of load from belts in an effective way
  2. Guiding the belt moving towards the lateral direction of the conveyor.

The layout of equipment supporting  the operation of belt conveyor.

1 – impact cradle bed, dumping sealing

2 – regulator RBTGJ, RBTGR-C, self-adjusting top ZGS unit or movable top ZGP unit

3 – multi blade pre-cleaner (front scraper) ZC-1, ZC-U, ZC-2 MAX

4 –  lower unit scraper ZPR-1, ZPR-U, ZPR-2 MAX, ZPL-1, ZPL-U, ZPL-2 MAX

5 – centralising idler TLS, regulator RBTDJ, RBTDR-2K

6 – plough scraper PCD, PCD-U, PCJ

I. Removing load remains from belts:

The belt that is badly cleaned of load remains causes:

  • Material losses and decreased performance of conveyor.

– uncleaned belt and 1/10 mm thin layer
– belt width B=1000 mm
– charge width = 0.8 B = 800 mm
– belt speed = 2.50 m/s
– working time = 16 h/d, 250 d/year
– quantity of load that falls from the vibrating belt itself = 30%

Total quantity of load gathered in an uncontrolled manner under the conveyor tracking equals to:

0.0001 m x 0.8 m x 2.50 m/s x 3600 s x 16 h/d x 250 d/year x 0.3 = 864 m3/year !!!

  • Difficulties in starting up the conveyor (decreased friction coefficient).
  • Increased wear of bearings and coats of idlers and pulleys.
  • The belt does not run axially (destruction of belt edges, damage to conveyor structure).
  • Decreased resistance to corrosion of the conveyor structure.
  • Necessity to hire new employees to clean the tracking and the conveyor structure.
  • Operation stoppages due to the system failure.

When analysing the cost-effectiveness of using the scraper, it is necessary to compare its purchasing cost and its operating costs (costs of scraper spare parts, time necessary to clean the conveyor in a traditional way, material losses, wear of sub-assemblies and production stoppages).

According to the comparative research conducted in 40 companies by the Swedish Royal Institute of Technology, the quantity of material not removed from the discharge pulley (caused by the poor quality scrapers) equals to 0.2% of the transported material and the total cost of the loss amounts to 1.10 $ per each tonne of the transported material.

To avoid this problem, it is necessary to apply scrapers relevant to a kind of load and conveyor characteristics. Those scrapers should be highly effective in cleaning the belt without abrading its running cover.

  1. Centralising the belt in the conveyor axis:

The moving belt should be centralised, i.e. it should be along the conveyor axis within tolerances of the lateral decentralisation. The admissible misalignment may be max. 5-8% of the belt width. The belt decentralisation that exceeds the admissible misalignment leads to losses resulting from:

  • Abrading  and destroying the belt edge and the conveyor structure.
  • Scattering the transported material.
  • Increasing the movement resistance (up to 16% of the total resistance of the conveyor movement).
  • Stopping the operation due to the system failure.

To avoid such effects, it is necessary to apply devices centralising the belt. Their centralising power that results from the appropriate chamfering of the idler or a set of idlers appears only when the belt is off-centre (contrary to sets with the so-called overtake). It is necessary to apply those devices centralising the belt that are self-operating only when the belt is off the conveyor axis (beyond the admissible and safe level).

It should be emphasised that the conveyor belt should be particularly protected, considering the fact that it has the least durable and its purchasing cost is 30-50% of the cost of the entire conveyor.