Redesign of Composter Infeed Shield Wear Plates
The Composter Infeed Shield Wear plates at the Neerabup Facility, cost $60,000/year to replace. The use of Arcoplate wear plates in place of the existing BISPLATE® 400 material is expected to save the facility $60,000/year due to the excellent wear properties of the Arcoplate, thus extending the effective service life.
Problem
The Neerabup facility in Perth has two composters that are 65m long and 4.5m diameter. The composters rotate slowly at 1 rpm. They are each loaded with 500 tonnes of mixed solid waste. While the body (or shell) of the composters rotate, the infeed end (called the “Infeed Shield”) is stationary, and hence the rotating product scours the inside face of the infeed shield, causing considerable wear. Because of this wear the internal face of the infeed shield was equipped with 10mm thick wear plates made of BISPLATE® 400, which historically have been replaced on a yearly basis.
Below (Figure 1) is a diagram showing the internal face of the infeed shield with the flat (green) wear plates and the perimeter (pink) wear plates, equipped with a return (or shelf) as shown in the detail in Figure 2. The return is to minimise product spillage between the rotating shell and the stationary infeed shield.
Figure 1. Internal view of the infeed shield showing wear plates.
Figure 2. Perimeter Wear Plate Detail
The wear plates erode so quickly that they have to be replaced on a yearly basis, necessitating a shutdown of one week at a cost of AU$35,000 per day. The total cost of the replacement was AU$60,000.
Solution
The innovation is to use wear plates that are made of a mild steel substrate with a coating of Arcoplate 1600 (see figure 3) in place of the BISPLATE® 400 material. Arcoplate is a high wear resistant alloy steel, with uniform hardness (58 – 62 Rc) and wear rates 4 times lower than BISPLATE® 400, and with high impact resistance.
Figure 3. Arcoplate welded to mild steel substrate
Result
The wear rate of the original 10mm thick BISPLATE® 400 was determined by measuring the thickness of the components of the old wear plates by Ultrasonic Testing at a known operating period.
The wear rate of the BISPLATE® 400 was as follows:
- 10mm Flat wear plates maximum = 10.0 mm/year The expected results of the Arcoplate are as follows:
- 15mm Flat wear plates maximum = 1.5 mm/year
The thickness of the Arcoplate used was determined to provide 5 year minimum wear life for the wear plates.
The total cost of this replacement meant a saving of AU$60,500 per year.
In addition to this saving the additional benefit of removing one installation is the removal of the risk of injury of personnel carrying out the installation. This risk, due to considerable man handling of wear plates is not insignificant.
Test of Keech plates (similar to Arcoplates) installed on one of the infeed shields in 2014/15 prove the excellent wear properties of the alloy coating material. Figure 4 below shows the results of Keech plates with 4mm thickness coating after one full year of operation.
Figure 4. Infeed shield with Keech plates (dark grey) installed in high wear areas