Not Every Sampling System Is BiasedBy Alejandro Ehrenberg | Mon, 10/19/2020 - 14:05
To run flawless processing plants, carrying out unbiased metallurgical accounting is of the essence. However, most sampling equipment in the market is biased by design. This is not due to fraudulent intentions. Rather, the problem is that manufacturers are hardly ever trained in the Theory of Sampling. Only a handful of manufacturers in the market, including Santiago de Chile-based TecProMin, are fully conversant in this discipline.
This sampling knowledge is today available in Mexico hand-in-hand of Promimex, TecProMin's distributor in the country.
Sampling systems are a set of equipment and elements that work together to obtain representative metallurgical samples. To guarantee the absence of bias, the design of a sampling system has to comply with the Theory of Sampling and international standards. Furthermore, the manufacturer must include a series of additional considerations, mainly in terms of maintainability, reliability, automation and constructability. Moreover, the safety of operations and maintenance personnel needs to be integrated into the station’s design.
The components of the systems can be divided into two main groups. The first group encompasses equipment that deals with increments of a sample or lot in each of the stages of the metallurgical system. Generally speaking, renowned manufacturers deploy correct engineering practices with respect to this first group of equipment. They take into account variables like materials, mechanical design and appropriate thicknesses for the required applications. Equipment is thus able to handle the flows and impacts to which it is subjected with each increase. In the same way, there is an abundance of associated literature and standards from which references and design recommendations can be obtained.
The second group includes auxiliary or complementary equipment or components that are not directly associated with taking increments for sampling purposes. As a whole, this second group includes essential pieces of technology that the system needs to work correctly: compartments, chutes and ducts for storing and transporting material.
A key aspect to consider is that equipment must not only be well-designed according to the considerations indicated above but they must also be arranged and located correctly within the system. Distances and inclinations directly influence the material’s transfer speeds. Not getting this aspect completely right may result in partial losses of some of the elements that are part of the sample. It can also lead to segregation by sizes and densities that lead the system to have a varying bias that is impossible to quantify. This applies to new and existing projects.
When designing a sampling system, TecProMin considers a series key of variables:
- Safe access for maintenance and cleaning of equipment.
- Evaluate a solution as a comprehensive development of the entire process and not as a piece of individual equipment.
- Field survey for brownfield projects where it is required to install a system.
- Perform hydraulic analysis for pulps and analysis of discrete elements for granulated materials to evaluate the behavior of transfers in each of the stages.
- Provide a comprehensive solution to the client, taking into account the available spaces, and evaluating the interferences and modifications that must be made to guarantee the correct operation of the system.
- Evaluate the impacts that the modifications will have on the installation of a sampling system.
TecProMin’s designs are a tailored solution. This design criterion, together with all the points mentioned above, allows the company’s sampling systems to have a very low bias that, in all cases, is within the parameters allowed by accepted standards.