RELIABLE ventilation in underground mines is literally as important as breathing, which is why a Low profile, fixed shape, low friction ventilation duct, developed by Polyline, WA, is transforming how air flows for underground miners.
Ventilation is vital for maintaining workable temperatures, oxygen flowing for both humans and machines and to remove diesel particulates from machinery being used in the tunnel.
Polyline, for the past 21 years has specialised in underground ventilation.
Polyline is excited to introduce a new low friction ventilation duct called “Split PolyDuct”, designed specifically to minimise transportation, handling, running costs and mine downtime.
To enhance its usability, Split PolyDuct comes with reusable storage and transport cradles.
Polyline managing director Justin Reed emphasised the importance of this innovation both or the future of VOD (Vent On Demand) and traditional vent infrastructure.
Constructed from polyethylene, PolyDuct is currently slashing ventilation costs in mines across Australia.
Split PolyDuct improves this even further. The durable nature of the PolyDuct provides mind-boggling statistics around cost savings for mines.
With a traditional vent bag, gashes and rips are a common occurrence which are all but eliminated with Split PolyDuct.
High energy costs are required to inflate Vent bag, which burns fuel needlessly.
Poly Split Duct is semi ridged and thus holds its own shape with zero energy expenditure.
Fragility in PVC vent bag causes blow outs at High turbulence points such as T’s or Bends resulting in regular failure.
Split PolyDuct, being semi-rigid HDPE, is not affected by turbulence.
Ongoing maintenance of vent bags can incur incredibly high costs which are eliminated with installation of the Polyline’s Semi Rigid Split PolyDuct.
Mr Reed put together some figures from two mines that the company has installed duct in for some insight on the savings available with a PolyDuct system.
The first, Sunrise Dam, extracts ore with average gold concentrate, and the other, Fosterville, produces some of the highest gold concentration in the world.
Both mines are in Australia.
“Damage can occur at any time, constantly throughout the day,” Mr Reed said.
“Vent bag could be ripped an hour after it is replaced – it only takes a high load sticking out of the truck and rubbing against the vent bag to cause more damage and further drive shut-downs.”
Unlike Split PolyDuct with its low profile, high impact resistance which will flex and absorb impacts without damage.
The figures shown do not include wasted resources on the general overheads of the mine and wages which continue to be incurred.
It also does not take into account the pre-production phase when ventilation is still required, even though ore is not being extracted, as every hold-up has a direct impact on any mine’s productivity.
Based on down time the average cost of a one-hour repair to a PVC vent bag is $23,700 for Sunrise Dam, and a massive $171,000 for Fosterville.
This problem is eliminated with the installation of the Polyline’s PolyDuct Products.
Construction
As polymers are long chain molecules, they give plastics a memory resulting in high impact resistance.
HDPE is UV stable with a lifespan of 20+ years when stored on the surface in its supplied storage cradles.
Polyethylene is inert making it excellent in damp and salty environments as it does not rust or corrode – making it a superior option to steel.
Fibreglass, like vent bag and PE doesn’t rust, but it is very brittle, and will crack and break when not handled carefully or impacted, the mining environment is not conducive to fragility, few things are handled carefully underground.
The Polyline products are locally made in Jandakot, in Perth, which helps Australian mines with achieving their locally sourced quotas.
The oblique (oval shape) system of the Split PolyDuct allows for the equivalent of 1600 Diameter tube with only 1200 height reducing the drive height requirement.
The space is saved by allowing a greater amount of air to pass through a smaller vent, thanks to the design of the shape, low friction coefficient and the fact that the Split PolyDuct does not require air pressure to keep it in shape.
The properties of polyethylene lends itself perfectly to the underground mine or tunnel environment.
It is flexible and provides inbuilt noise absorption.
Unlike other substances, polyethylene duct is impact-resistance with a very low friction coefficient, making it incredibly robust, maintaining integrity under the toughest conditions.
Huge energy savings and life of mine increases
At a running cost of around $600k per year, twin stage 110KW fans are the air moving work horses for most secondary ventilation systems underground.
The fact that Polyline’s product keeps its own shape along with a low friction coefficient, has allowed mine operators to shut down 1 of the 2 fan stages halving the energy consumption immediately.
That’s $300,000 per year that did not need to be spent running the additional fan stage at that mine.
For example, in the case of Sunrise Dam, the cut off point for production is 2.71g/t and it is getting 2.73g/t – so any savings makes a massive difference.
Split PolyDuct is light weight and very easy to install particularly in the close confines of an underground mine drive.
Designed for efficiency
Polyline Split Duct is very easy to transport and install.
Up to 80 metres of 1600 eqv Duct will fit into a 40ft shipping container or standard truck trailer.
The robust moulded Split Duct is 99% air tight and is easily assembled with a unique clip system.
Split Duct is specifically designed for ease of transport to reduce shipping costs and maximise efficiency.
As described by Mr Reed, the standard product is rated for 3.5kpa or 350Kg per M2, the base materials can be altered to increase this to5Kpa positive or negative pressure.
The polyethylene ducting is fully recyclable and can be collected by any recycling company that deals with recyclable plastics.
The Polyline Split PolyDuct has standard and custom fittings allowing it to be designed around each mines drive and backs profile.
As usual Bends, T’s and all fittings are readily available from Polyline.
