Cleanliness is sometimes an overlooked part of the material handling industry. The truth is, a lot of aggregate producers only settle for satisfactory when it comes to cleaning their aggregate; and while “satisfactory” works, the most common hydraulic methods used for washing are hardly perfect. Despite potentially sub-par methods of washing, there is generally an “allowable percent of deleterious matter” that’s acceptable in materials.
The goal of washing construction aggregate is to make it meet specifications—whether that’s a standard of quality for that particular aggregate, or to make it useful in other applications. Beyond washing, aggregate manufacturers can use washing equipment to handle:
- Classifying or separating
- Removal of clay and silt
- Removal of soft stone, shale, coal, roots, twigs and other debris
- And more
There’s definitely more to wash equipment than washing, but many in the industry aren’t effectively utilizing the versatility of their equipment. The other issue making it difficult for some is the potential time sink or prohibitive costs of the equipment and water required to make the aggregate conform to specifications. As it turns out, this isn’t always the most economically practical thing to do.
The problem with washing equipment has more to do with the source deposits
The real issue with trying to use washing equipment to sort and classify has to do with nature: You’ll seldom find the ideal gradation in naturally occurring deposits. If part of quality control involves getting the aggregate to an ideal gradation, then you’re forced to rely more on additional processes such as screening, crushing, and blending. Even after using any of these to achieve your target gradation, you’ll still need to wash the material to meet a cleanliness specification. Those additional processes have costs and they add up considerably.
The easiest way to determine the economic suitability of the aggregate is to test the source, which is usually done by the project materials engineer. This should be done before production starts so that you have a grasp on what equipment you’ll need and how much time you’ll have to devote to getting the material to conform to specifications. It really pays to put thought into which pieces of equipment you buy based on the aggregate source itself. A specific material might require more work to conform than the same aggregate from another area, but only testing beforehand will tell you whether that’s the case.
Specifications are becoming more stringent
As specifications become more stringent, aggregate manufacturers have to find smarter ways to effectively wash and classify their material. Operations based in pits or quarries especially need more effective methods of washing and classifying. The further these operations go into their reserves, they see a decline in easily extracted material, which translates to more silt and clay that needs to be removed from the aggregate. While washing may be enough to rinse some material, others may need to be scrubbed in order to remove clay and the like.
Sand and gravel in particular benefit from having the right equipment in place as both domestic gravel and sand are typically processed prior to being used. Because there are so many market applications for sand and gravel, no two operations will have the same arrangement of equipment or processes to achieve the target specifications.
Common equipment combinations might include portable/stationary washing and screening plants; sand classification tanks and systems; dewatering screens; coarse and fine material washers; blade mill washers; and more.
Common pitfalls of washing equipment use
Washing equipment tends to be fairly reliable for everyday use; however, there are some ways washing can lose its effectiveness over time. If operators neglect regular maintenance or aren’t aware of how changes to certain parts or products can affect the washing side of things, washing equipment can lose its efficacy.
Daily walkthroughs of plants are recommended to ensure both the equipment and the entire system is functioning properly. When you only look at each individual piece of equipment, it can be difficult to troubleshoot issues that come up. This is because you may think one piece of equipment is the problem, but it could be some other part of the system that’s giving you problems elsewhere. If you can’t do it daily, then at least a weekly walkthrough of the plant should suffice in keeping you abreast of the system’s condition and efficiency.
If you’re in the market for washing equipment or need help finding the right solution to your washing needs, Kemper carries a large selection of washing equipment and wash wear parts, including sand screws, wet dust suppression systems, log washers, plus urethane and hard alloy wear parts.