Introduction
Sampling is used for many reasons, including to:
- Verify the value or composition of a material
- Verify the value or composition of a material purchased
- Ensure that product specifications are met
- Set or confirm the value of as-shipped or as-received material
- Verify that the product meets contractual requirements
The goal of any sampling program is to produce representative samples. These relatively small portions of material must accurately reflect the large amount of material and do so with repeatability.
Manual sampling of stopped belts, stockpiles and transfer points is common but not necessarily the most efficient, cost-effective, accurate or safe method of collecting sample increments.
Automated sampling with machines installed over belts, stockpiles or transfer points offers a mechanical means of collecting samples for quality analysis with minimum human interaction.
Types of automated Sampling Systems
There are several different types of automated sampling systems. automated Sampling Systems such as Cross Belt Samplers, Falling Stream Samplers and Auger Samplers are mechanical replacements for manual sampling methods.
Cross Belt Samplers
Cross Belt Samplers collect a sample increment by rotating a counterweighted sample cutter perpendicularly through the moving material flow on a conveyor belt. They are a cost-effective and easily implemented means of sample collection comparable to manual stopped belt sample collection but without the labor and without interrupting plant operations. Cross Belt Samplers can be applied nearly anywhere dry bulk materials are transported via belt conveyor.
Falling Stream Samplers
Falling Stream Samplers cover a wide range of sampler designs. They key characteristic all these designs have in common is that sample material is collected from a main process flow that is either in a free-falling condition or traveling through some trajectory, such as at the discharge of a conveyor.
These types of samplers tend to be simpler in design and function and usually offer highly reliable operation and relatively low maintenance requirements. They are well suited to high-flow rate applications where minimal downtime is a requirement, such as loadout systems.
Depending on the style of Falling Stream Sampler being considered, this sampler type usually requires a larger vertical clearance for installation and is usually more invasive and expensive to install.
Auger Sampling Systems
Auger Sampling Systems collect samples from transport containers and bin-type containers using a rotating auger. This type of Sampling System is ideal in as-shipped and as-received situations when there is no other option for sampling other than to collect samples from the transport container.
Sampling/Pilot Plant Crushers
Sampling/Pilot Plant Crushers are small-scale versions of crushing equipment used for the size reduction of sample increments for further processing and analysis. Typical Sampling Crushers include:
- Rockertooth Crushers
- Sampling Hammermills
- Sampling Jaw Crushers
- Sampling Roll Crushers/Sizers
Automated sampling advantages
Automated sampling has many advantages over manual sampling, including:
- Safety
- Improved accuracy and repeatability
- More efficiency
- Lower long-term sampling costs – particularly indirect or hidden costs
Safety
Safety is one of the biggest advantages of automated sampling over manual sampling methods. With automated sampling, the equipment does all the work. Personnel doesn’t have to be on or near potentially unstable stockpiles, falling material streams or moving equipment.
Automated sampling systems limit personnel exposure to operating equipment and minimize manual material handling requirements.
Improved accuracy and repeatability
Automated sampling systems eliminate human discretion in sample collection and reduce potential human error in the sampling process. They allow the composition of a material to be correctly determined and as-shipped or as-received material to be correctly valued.
More efficiency
With automated sampling systems, producers don’t have to stop production to take a sample, making their sample collection process more efficient. Automated sampling systems collect material from moving conveyors or material flow, so there is no interruption to production.
Lower long-term sampling costs
Long-term sampling costs can come in several forms. There’s the labor associated with having personnel physically collect the samples, and there’s the potential downtime associated with having to stop production for sample collection. Automated sampling systems lower these long-term costs by minimizing the labor costs and eliminating the interruptions to production.
There are also hidden or indirect costs that sampling systems can help to alleviate. Sampling can help to identify when components of production equipment need to be replaced, and automated sampling systems make that process much simpler and easier to carry out. Automated sampling systems offer producers a way to be proactive rather than reactive when it comes to quality or process control.
Automated sampling ROI examples
Sampling equipment is not typically regarded as production equipment – equipment that is directly tied to producing a finished product – and thereby not regarded as equipment that will generate a profit.
While that may be technically true, the costs of not sampling, or sampling correctly, can have a significant impact on the bottom line of a production facility. These costs may not be immediately visible or easily quantified, but they do exist in the savings that can be realized by increased safety for sampling personnel, tighter quality control of the end products, improved ability to assign an accurate value to product sold and increased efficiency in the plant.
In these ways, automated sampling systems are invaluable, and they can actually pay for themselves relatively quickly. Here are a few of the ways automated sampling systems provide a return on investment.
1. Eliminate production interruptions
Assume a sand and gravel producer selling crushed stone at $7.50 per ton is making 4,000 tons of product over a typical 16-hour day, or 250 tons per hour. They take a sample collection every 1,000 tons (or every four hours), and it takes 10 minutes to collect the sample increment.
Taking four samples a day means 40 minutes of downtime per day, which equates to 167 tons of production lost per day. In a dollar value, that 167 tons is worth $1,253, which over the course of a standard 10-month operating year, adds up to $250,600 in lost production.
Adding an automated sampling system would eliminate the need to stop production to collect samples, adding that $250,600 back into the producer’s wallet.
2. Process control for efficiency
Assume a producer needs to crush material to 1” minus, and they do not have a recirculation circuit to deal with oversize. Their customer will not accept material with an excess of 1” material.
An automated sampling system can help the producer to monitor crusher wear through particle size analysis. Once the particle top size reaches a predetermined value, the producer will know to adjust or maintain the crusher. Maximizing crusher wear and minimizing maintenance can be realized in this scenario with sampling. The idea of cost savings by minimizing invisible costs that are difficult to quantify is a common concept in sampling applications.
3. Improve sample accuracy
Assume an application where the value of material meeting Spec A is $10 a ton and the value of material meeting Spec B is $7 a ton. The producer intends to deliver 10,000 tons of material that meets Spec A to a customer, but due to results obtained from incorrect sampling practices, the material appears to only meet Spec B. The receiver accepts the shipment but only at the value of Spec B, which means the producer is out $30,000.
Automated sampling systems help producers improve sampling efficiency by removing human bias or error.
4. Knowing what you shipped
Assume a shipment of 15,000 tons of product valued at $40 a ton is contracted to meet a certain characteristic or else a 25% shipment value penalty will be applied. The material is sampled at the receiving party but not at the shipping party. The receiving party claims the material does not meet the agreed specs, and the shipping party has no way of refuting that claim, so the loss on the shipment is $150,000.
Sampling the material ahead of time would have allowed the shipping party to verify the material met spec before it was shipped, and they could refute any contract violation claims.
Automated vs manual sampling
Automated sampling is significantly more efficient than manual sampling and offers better results in most cases. Sampling equipment may not contribute to the production of any particular commodity, but it is crucial to correctly valuing that commodity. Correct sampling and quality sampling equipment allow for an organization to better understand and streamline their operation.
