AMB: Why would you recommend Non-Nuclear Density Measurement of mining slurries amongst other techniques?
Arjan Vriend: Conventionally, mines use so-called radiometric or nuclear density meters. These meters have the advantage that they can be placed outside the pipe and therefore there are no challenges with pressure, temperature or wear. However, this technology has a downside, which is of course the use of the nuclear material. The radioactive source is the cause of a lot of practical drawbacks with regard to licenses, training, shipment and operators who have their reservations about using such technology. Furthermore, it has an impact on the business management of companies who have to respond to society’s pressure to reduce nuclear waste, and to operate in a sustainable manner. In the main, reasons for companies to shift over to non-nuclear technology are:
- A more sustainable business management and company reputation
- Demonstrating social responsibility, and responding to society’s pressure to reduce nuclear waste
- Employees who are not afraid to perform checks and repairs
- No need for special RSO trainings or specifically trained personnel
- No concerns about more stringent regulations in the future
- No more challenges when transporting nuclear sources
AMB: In which applications (conditions) in slurry measurement is Non-Nuclear Density Measurement ideal?
Arjan Vriend: Basically in all applications which are covered today by radiometric devices non-nuclear alternatives can be used. However, there are a number of (new) technologies on the market, most of them with downsides. For instance, there are technologies that have problems with gases and others with vibrations. That’s why in our specific case, as Alia Instruments, as we supply inline meters, we always consider the amount of wear of the material. Some very abrasive processes do not suit our technology, as the material would wear the rubber liner within months or even weeks.
AMB: What would you advise mining companies to consider when making a switch from ‘conventional’ techniques to non-nuclear measurement? What particular features of tools should they consider? What is the scope of turnkey solutions that you would recommend?
Arjan Vriend: Often mining companies are willing to consider alternative technologies. I am yet to meet a person who has me that he/she prefers nuclear meters. Generally, when looking for the right products, they should consider what demands they have based on their process, and what technology fits best. In the case of Alia Instruments, I think we have a meter which actually measures all materials, and has no problems with larger parts, sediments or gasses. However, as mentioned earlier, one always has to be careful with sharpest materials.
Most of the potential customers claim we have contacted have told us that they would switch if they can find a viable alternative to nuclear products. In terms of viability, they often mean from a technical and cost-effectiveness perspective. However, in technical terms, I have encountered situations where customers have misconceptions about nuclear. A common mistake in the market is the belief that nuclear density meters are very accurate, and therefore can be used as a reference for other types of meters. But what people do not understand is that more often meters measuring errors are experienced with these meters, especially when they are not recalibrated. The half-life of the source makes that a requirement with those meters, and this task is typically done by the supplier. Furthermore, often, people might not be aware that the signal of a nuclear meter is significantly delayed, and when they only they notice a change in the signal, the material would have already passed, for instance, after 20 seconds ago.
On the financial side, it would be fair to make a good comparison between the total cost of ownership of the nuclear meter with the alternative. Definitely, purchasing costs should not be the only aspect to be considered. Users should also consider the costs of RSO certification, the high disposal costs, and last but not least, the lost hours of all the hassle of importing and transporting the meter, permits and the maintenance by the supplier end-users have to undertake.
Alia Instrument’s meters
In 2017, Alia Instruments supplied its meters to the dredging market, which have now been installed. Alia Instruments is a new player in the mining market, having just started to offer its meters to mining companies only recently. This year, the company is looking forward to making its first sales in the mining market, hoping to convince mines about the efficacy of its new technology.
Alia Instruments’ meters are very relevant to industry demands. With a simple design, it is an in-line density meter that is robust and exceptionally easy to install and use. The design makes use of Newton’s second law of gravity to determine the mass of the slurry, while the volume is a known factor in the meter. This means that the output data is immediate and accurate regardless of pipe diameter or slurry composition. In order to yield accurate results, all non-gravitational forces working on the device are mitigated. In particular, to overcome arduous process conditions for example, a dredger rolling on ocean waves, or pipes vibrating under high pressure pumps, an accelerometer is utilised, which can calculate and neutralise any interfering forces simultaneously.
This is how the meter works:
- A small force is applied by means of an actuator, which is built in into the chimney of the meter
- The force causes the measuring tube to vibrate
- These vibrations are measured by means of three accelerometers
- The vibrations are a measure for the mass of the measuring tube
- The same accelerometers are used to compensate for external movements of the meter and / or external vibrations