Newmont and Derrick Collaborate on Advancements of Screen Surface Technology

Gold operators are continuously being pushed to increase the capacity of their facilities and as a result, existing equipment is often pushed past its designed limitations. When this occurs, equipment manufacturers are asked for economical solutions to meet the redefined needs. Newmont USA was faced with such a need in two (2) Carbon-in-Leach (CIL) trains in Nevada. In a collaborative effort between Newmont USA and Derrick Corporation, a test was concieved to assess viability of a new vibrating machine and three (3) dimensional screen panel.

In the early 1980’s Derrick developed and patented a unique process for high open area urethane surfaces. Urethane was found to be extremely durable and maintained a high throughput capacity but as a flat surface there was a limit to the overall surface area. Given the need for increased production in the same footprint, Derrick worked on developing a three dimensional pyramid to increase flux. Initially a wire mesh version of the screen was made and successfully used in the oil industry but the wire mesh panels lacked the durability required for a mining slurry. To obtain greater durability, Derrick looked into using a synthetic material.

The CIL circuit was chosen as an ideal test location for the new panel since it’s a hard scalping application in the gold industry. Slurry characteristics are the same as other applications but the CIL contained far more oversized material in the form of carbon than say trash or safety applciations. The goal was to provide a drop in replacement, learn whether the machine would work in this application, and to experiment with different materials for panel construction.

The first test occured at Mill 2/5 in Nevada and the new style machine ran from July 2013 to Nov 2014. It outperformed the older style Derrick machine in terms of slurry throughput (approx. 2000 gpm v 900 gpm) and carbon conveyance and the different material panels tested showed promise for long life spans. This intial Alpha testing gave a proof of concept but didn’t allow us to fully explore the machine’s capacity due to existing plumbing constraints. Also results of each particular test are not shared due to the protection of  proprietary secrets with regards to panel materials and number of iterations. In the image below, the machine with white motors is the new one, and blue is the older style machine. As you can see, given the same flow rate, the old machine is mostly buried and the new one clearly has capacity.

Prior to 2014, the Twin Creeks property was also examining continuous improvement opportunities around the CIL circuit and identified the need for additional screening capacity. After the intial testing at Mill 2/5, Twin was interested in beta testing a drop in replacement to add additional capacity. Using the intial results, the best materials of construction for the panel were identified and minor modifications were made to the panel construction to increase durability.

The Twin Creeks test was concieved and evaulated using a single new Hyperpool machine in the top tank of the CIL circuit. The top tank had five (5) older style Derrick screen. Older style screens were originally designed to accommodate 850 to 950 gpm and the increased feed rate (to 5000 gpm) removed all safety factors. The screens are submerged into the tank and there is no plumbing, valves, flow meters, or other controls to direct, change or measure flow. The test would measure the flow rate to the tank and the flow rate for the new machine would be determined by turning off one or more of the older style machines while maintaining the fluid level in the tank. If the tank level started to rise, one of the older machines would be started back up. Full circuit conditions can be found in the paper we presented at the 2015 SME.

The pic below shows the old style interstage screen running at approximately 850 gpm.

The new style unit is running at approximately 2000 gpm.

The testing concluded that the new style unit can accommodate between 2 and 2.5 times the flow rate of the older style machine depending on feed conditions in a CIL application. The Hyperpool was designed to fit existing Derrick screen installations with only minor structure modifications required which saves substantial capital costs compared to the installation of a larger machine.

This case study was presented at the 2015 SME Meeting and a copy of the paper can be downloaded here.