What value would you assign to a properly designed aggregate processing plant?

What value would you assign to a properly designed aggregate processing plant?

Proper engineering design and equipment reliability are essential to a profitable aggregate processing operation; without which significant downtime and other financial losses are inevitable.

Proper engineering design and equipment reliability are essential to a profitable aggregate processing operation. Just a small interruption in production can affect a company’s bottom line. If your plant is not operational then you are not making money. A primary purpose of your equipment provider and servicer is to get you up and running no matter what brand(s) you are using – a team who are not only experts on their components but also on their competitors’ components. A team who can resolve your problems, alleviate pains, and reduce your company’s operating and maintenance expenses – increasing your R.O.I. Here is an excellent example of how our conscientious solutions team did just that.

Within one month of operation, the company observed the rotary counterflow drum mixer drifting and lunging uphill and downhill. The great force of a unit that is 11 ft. in diameter x 50 ft. long rotating with 250 HP did not just run hard against the thrust rollers (which holds the unit in either the uphill or downhill position), but impacted them hard enough to tear them loose from their hard mounts and even breaking the idlers themselves at times. Within their first 30 days of operation, this failed design caused four of the thrust rollers to rip loose – causing their entire plant to shut down.

In 2005 a major U.S. aggregate processor wanted to consolidate some of their production facilities in the Midwest and decided to go with a large 600 TPH plant. They contracted for a ‘super plant’ with a major manufacturer, who assured the customer that they could supply the plant without any major problems. Yet, appearing to only upsize one of the OEM’s existing models – without executing a thorough engineering study and comprehensive structural design analysis, a string of costly major problems began unfurling.

crew loading a silo onto a barge

Operational damage to thrust rollers, tires and trunnions can often be avoided through proper plant design and precise alignment.

Since the thrust rollers sat at an elevation of 11 ft. in the air, it was very difficult, cumbersome, and concerning safety-wise to get access to them to perform damage repair and component replacement. Plant breakdowns became so predictable that the company was forced to purchase an $80,000 man-lift to provide them with sufficient access to safely change out the broken thrust rollers. Without a better solution on hand, the designated change-out crew had to work hard to reduce the change-out time down from a few days to between four to seven hours that were required to do the removals and replacements.

crew loading a silo onto a barge

An $80,000 manlift had to be purchased to minimize downtime every time the thrust rollers had to be replaced. Although nice to have onsite for maintenance, that was a painful and avoidable expense.

The repetitive scenario for their multiple emergency breakdowns required calling the mobile changeout team, positioning the tools and equipment, and waiting for plant components to cool down to a safe temperature. Meanwhile, as the plant remained idle and the silos stood empty, a queue of hauling trucks would line up for blocks – waiting for their orders to be filled. Imagine the disappointment, frustration, stress and dread this repeated scenario caused the plant operators and owners!

crew loading a silo onto a barge

Unscheduled plant downtime from breakdowns is expensive for plant owners and negatively impact their customers, including material haulers lined up, waiting, and delayed from performing their jobs.

Within the first two years of operation, the company called on the OEM to provide support and some warranty consideration to help lessen their financial losses. The OEM did not honor the request and indicated they would consider looking into the equipment problems as a paid service. Upon looking into the problems, they were unable to fix the root cause of the issues. The operating company was simply told they needed to learn how to operate the plant in a better manner per the written guidelines and ensure that the tires and trunnions were aligned properly. The OEM themselves could not do what they were asking the customer to do.

Throughout the next 10 years, the company experienced nothing but trouble from the OEM’s 11’ x 50’ dryer. During that time, 28 thrust rollers were sheared off, multiple tire-rigging bolts broke, numerous discharge sweep end-rings wore or broke off, and they never truly had operational control of the drum.

Hoping to remedy the situation, the company purchased new heavier duty trunnions, bearing assemblies and trunnion bases from another source, but that didn’t solve their problems. In fact, the problem became more severe. Their next step was to bring in an independent company to diagnose and resolved the issues. But that company failed to get the drum under control. Meanwhile damaged thrust rollers continued to pile up in the scrap yard behind the plant.

crew loading a silo onto a barge

Unbelievable damage to thrust rollers, trunnions and tires can result from improper design. In the poorly designed system revealed in this article, 28 thrust rollers had been torn off from the uphill and downhill thrust of its dryer.

After several attempts to remedy the situation, enduring breakdowns for nine years, the company engaged us at Louisville Dryer Company (LDC) to assess and resolve their drum control problems. Following our initial onsite inspection and measurements of the relevant components, we dispatched a field team of engineers and technicians to observe the problematic dryer in operation. Following several days of inspecting, measuring, and testing, our team came to some dramatic conclusions.

Our solutions team observed that when the rotary dryer heated up and expanded, the supporting base and unitary frame heated up at a different rate. Sean Kyser, LDC Project Engineer, reports that “there was a significant difference between static non-loaded conditions vs. dynamic loaded conditions. This system had a built-in problem of deflection because it allowed movement of the trunnion and base. Thus, the dryer did not have a solid operational base of carrier roll trunnions, framework and thrust rollers.”

It was revealed that the OEM had not had this 600TPH design aggregate dryer system back when they had originally agreed to supply it. They basically had only upscaled the motor horsepower and trunnion size – without upgrading the frame, base support and thrust rollers. Such a quick manufacturing approach ignored fundamental engineering practices. Our team further determined that the OEM’s drum frame had no gusset support or enough trunnion cross-beaming to support the weight of the drum – especially when loaded.

We engineered optimal solutions and submitted our recommendations to the customer. The suggested remedy was to stabilize the dryer by constructing a monolithic concrete pier under both trunnion base assemblies. By building a foundation directly under the load-bearing of the trunnions, this method would eliminate all deflection and vibration in both the trunnion base supports and the dryer main axle beam. The customer agreed with the solution and the project was set into motion.

crew loading a silo onto a barge

To stabilize the dryer, the Louisville Dryer field service team constructed monolithic concrete piers beneath the trunnions.

The customer also engaged us to build a completely new replacement rotary dryer and separate bases to be isolated on concrete foundations. The foundations were installed and adjusted to the thousandths for stability and parallel alignment with the tires.

crew loading a silo onto a barge

Louisville Dryer Company provided the new replacement rotary dryer.

Ed Stump, Sr. Installer with Louisville Dryer, oversaw the change-out and commissioning of the new replacement shell while Steve Smith, LDC Sr. Field Technician, was on-site to optically align and record the elevations and slope. They oversaw the concrete pouring and inspected the grout for new piers on which to mount the trunnion bases. By transferring all the load from the drum directly into the pier, the defection and vibration was eliminated. Further accelerated trunnion and tire wear was avoided, and the recurring thrust roller/idler damage and expensive replacement problems were solved.

After everything was aligned and the trunnions set, start-up was a success. Ever since the repair/replacement solution was provided in early 2017, the drum has produced mix flawlessly and under control. The trunnion drive motor amps dropped, and stack temps are the best they have ever been. Major pains were alleviated, the owner/operator’s investment was recovered.

The Louisville Dryer replacement drum has processed over 3 million tons – with virtually no maintenance needed (other than replacing worn flight clips, which cost less than $3,000 for parts and labor). And, they’ve never had to adjust the trunnions once since our solution was implemented over five years ago. The plant superintendent reported that, “No one touches the adjustment of that dryer except Ed from Louisville Dryer.”

crew loading a silo onto a barge

The aggregate processor is very pleased with the complete solution provided by Louisville Dryer Co.

To say that this customer is pleased is an understatement. Of course, the plant personnel are happy that the sound they hear now is the repetitive reliable rotation of our custom-engineering rotary drum vs. the dreaded impacts from breakdowns including the honking of truck horns, the ringing of cellphones, and the complaints from bosses.

Now the customer has two related decisions:
1. What do they do with the 28 thrust rollers which were ripped loose?
2. Should they sell the man-lift? (Operators like having it for other maintenances.)

While their return on investment cannot be calculated accurately, imagine breaking off a thrust roller with five empty silos, trucks and paving crews standing by on a 6,000-ton day – 28 times!

That situation should never have happened. We at Louisville Dryer Company will do whatever it takes to get you up and running for the long term – at the Lowest Cost Per Revolution.

Furthermore, our pleased customer reports incredibly positive results from their chain supplied by Hotmix Parts & Service. To date, the plant has processed over 4.5 million tons using that same chain!

Louisville Dryer Delivers The Lowest Cost per Revolution

Louisville Dryer Delivers The Lowest Cost per Revolution

5 Proven Ways + 3 Examples

As defined by our customers (global manufacturing companies, process and reliability engineers and maintenance teams), successful outcomes of our custom engineering process are system installations that are:

      • On-Time
      • On-Budget
      • For Decades of Reliable and Precise Performance with Minimal Maintenance.

Over 5,000 rotary drying system installations and hundreds of repeat customers have used Louisville Dryer equipment as a core to their business operations. With that proven experience, following are:

Examples of Outstanding Dryer Longevity

1. Your Process Dictates our Technology:

Whether your application requires New Rotary Dryers, Replacement Drums/Shells, or other Rotary Products, our engineering teams expertly design, build and install entire solutions – including dryers surpassing 140 feet in length, 20 feet in diameter, and 200 tons in weight.
crew loading a silo onto a barge

2. Your Service Requirements Drive our Mechanical Design:

We routinely bring operational needs from concepts to design to production – considering your production requirements and process parameters, material characteristics, site and environmental conditions, and so much more.

steam tube dryer standard steam chest

3. Your Products are Thoroughly Tested in our Testing Lab:

When our customers request our advice on the most effective processing solutions for their specific application, we implement pilot scale testing in our own in-house lab to assess their material performances and outcomes with live test data and analysis.

man performing a quality check on a piece of fabrication

4. Your Equipment is Custom Manufactured in our own ASME-accredited Facilities:

Louisville Dryers are fabricated by our expert craftsmen who build dryers every day. Each dryer has a highly specific written inspection and test plan and quality control assessments. What makes a very large piece of rotating equipment reliable is not only the structural integrity of its design, but the precision with which it is fabricated and assembled.

louisville dryer company crew standing in front of an industrial dryer

5. We provide Professional Field Installation and Commissioning Support:

Our professional rotary equipment installation technicians ensure that each Louisville Dryer is properly delivered, assembled, aligned, and secured on its foundations. The service and maintenance life of any piece of rotary equipment is not based solely on the design and quality of the equipment – but also on the precision in which each component is installed, aligned and performance-tested, and on the thoroughness of the operational and preventative maintenance training provided to your team.

industrial dryer installation in progress
engineers inspecting an industrial dryer

Examples of Outstanding Dryer Longevity

As you can see, it is no surprise that the individuals and companies operating these units are extremely pleased with the results from our dryer systems which operate campaigns, often for months and even years with minimal maintenance or issues.

Success Stories about the dryer longevity our clients have enjoyed:

1. One owner-operator processed highly abrasive materials. We reengineered their system’s components to extend the life from a few months up to years. As one measure, we installed abrasion-resistant cast flighting and chrome carbide liners inside their unit to achieve exceptional performance and longevity.

flighting inside an industrial dryer component

2. As another demonstration of success, a large chemical processing company requested that we perform an extensive FEA (finite element analysis) of a rotary unit which they needed to operate under full load for a five-year period without shut down for maintenance.

tubes running into an industrial steam tube dryer

3. As another example, in recent years a company asked Louisville Dryer to evaluate the potential replacement of rotary dryer units in their processing plant. Their units had been operating dependably for decades and decades. Yet this was a complex project as their building had been constructed around the units, plus there was a river on one side of the building.

replacement dryer being installed by louisville dryer company crew

Louisville Dryer was pleased to assist the customer change-out their units with new shells, drives and bases. And it was not surprising that they selected new Louisville Dryer units since their original/legacy units had also been manufactured and installed by Louisville Dryer – in 1943 – providing over 70 years of reliable operation!

Longevity in Motion

Louisville Dryer custom engineered systems routinely deliver what our customers need and expect:

On-Time, On-Budget, for Decades of Reliable Precision Performance with minimal maintenance.

We provide The Lowest Cost per Revolution for Your Team. Contact us today to learn how.

Alloy-based Rotary Dryers

Alloy-based Rotary Dryers

When prospective customers engage us to provide them with a customized material processing solution, they inquire, “With what materials are your rotary dryer shells manufactured?”

Our Sr. Application Engineers indicate to them that we have built thousands of rotary dryer shells using select metals from the full spectrum of carbon steels, stainless steels and alloys. Yet our recommended dryer shell design for your specific application will be primarily informed by your material’s specifications, your processing criteria, and your production goals. Each Louisville Dryer is custom-engineered and fabricated for your specific purpose.

For industries that process materials with exacting requirements (including distilleries, corn wet milling, wood processing, activated carbon and petrochemical), many common elements of our dryer design recommendations relate to temperature tolerance, pressure resistance, oxidation and corrosion resistance. For these extreme environments of high pressures, temperature and/or corrosivity, rotary dryers fabricated using alloy materials are well-suited for such tough service.

Rotary dryers fabricated with the wrong materials for your specific application can result in excessive wear, damaging corrosion and premature failure – all resulting in very expensive operational downtime.

Watch the following three video segments to learn more from our Application Engineering Team about our alloy-based rotary dryers:

What are your rotary dryers made of?
Which industries need rotary dryers built with alloys?

Learn which alloys Louisville Dryer Co. uses in their custom-built dryers and components, and which industries use them– including distilleries, corn wet milling, wood processing, activated carbon, petrochemical, pharmaceutical, food and others. See some examples of steam tube dryers that we have fabricated using various alloys.

Why would a customer need an alloy-built rotary dryer?
Which materials and processes would benefit from them?

In this segment, Louisville Dryer Co. identifies various applications requiring alloy-based rotary dryers – including considerations of chemical reactiveness (corrosion and wear from acidic or basic environments), potential contamination of the processing material by the dryer, and high-temperature tolerance.

What are some of the challenges when manufacturing rotary dryers with alloys?
And what production protocols and quality control measures do you employ to ensure the integrity of these alloys?


Hear from Louisville Dryer Co. about some of the challenges and QC protocols implemented when building rotary dryers with alloy materials – including our positive material identification tests, specific welding procedures to maintain alloy integrity, and diligent segregation of the alloy from carbon steel.

As you can see, Louisville Dryer Co. application engineers and dryer craftsmen have the industry knowledge, technical expertise, and proven experience to fashion a custom solution with The Lowest Cost per Revolution for your team.

Call or email us today to get one step closer to solving your processing challenges and achieving your production and business goals.
Hemp Activation/Decarboxylation in Steam Tube Dryers

Hemp Activation/Decarboxylation in Steam Tube Dryers

As part of our lifelong learning, Louisville Dryer Co. engineers regularly interact directly with processing industry customers and continue to make discoveries. Most recently, with changes in legislation for the burgeoning hemp industry and as the quantity of hemp to be processed has skyrocketed, entrepreneurs have reached out to technical experts in drying sciences and technology to help them explore their options for cost-effective solutions.

Hemp processors who were wanting to reduce their drying times by accurately controlling the drying environment consulted with Louisville Dryer Co. applications engineers.

As part of this endeavor, using our production-worthy scaled-down dryers in our Research & Development/Testing laboratory, we have engaged in leading-edge testing to determine which of their methods of processing and drying would perform the best for handling hemp.

In our Research & Development/Testing Laboratory, we use production-worthy scaled-down dryers to assist companies in developing new products such as wood composites, airbag propellants, rocket fuel, algae-derived oils, and more.

For an organic material such as hemp, a steam tube dryer is typically the ideal choice for the process since it allows for slow, even heating to remove internal moisture without scorching. Historically, a separate necessary step is the activation of the CBD-A as it exists in the hemp plant so that it is converted into the usable form CBD. This process is called activation or decarboxylation and makes the hemp’s chemical properties accessible for human bodies to process. The original understanding was that drying and decarboxylation were two separate steps and that they would need to take place in separate pieces of equipment to optimize each process.

Through hemp R&D experiments in our own testing laboratory, Louisville Dryer Co. engineers discovered that hemp dried in their Steam Tube Dryer went through the decarboxylation process: which is the necessary reaction where the organically present THCA or CBDA (from the cannabinoid-rich oil extracts) is converted into THC or CBD, which provides the consumer with the desired medicinal effects of the product.

What Louisville Dryer engineers observed in their laboratory and confirmed through independent testing was that decarboxylation can take place inside the steam tube dryer and is dependent upon the temperature and residence/dwell time of the material. In one of the tests, material was hand-harvested from a small local hemp farm and immediately taken to Louisville Dryer’s facility for processing.

Upon arrival, one of the first goals was to get the material to a manageable size that would make it through the steam tube dryer. Although a commercial unit can handle larger particles than the lab dryers, it is still valuable to know successful techniques for particle size reduction for instances when entire plants are being harvested.
Using a woodchipper, hemp flowers with some stems were chopped and collected. The resulting feed material was manually weighed and fed into the pilot steam tube dryer by hand. Through product material evaluation and testing, it was discovered that dryer material indicated a higher level of decarboxylation since lower product discharge moisture indicates higher material temperature. One of the major benefits is that the material can be activated and ready for use without it needing to be burned or further processed for decarboxylation to occur.
As hemp production needs increase, the next logical step for processors is to minimize the manual labor historically involved in smaller scale operations. For example, we have spoken with customers who still hang hemp in barns to dry in a similar manner to tobacco. This may work sufficiently for very small farms and acreage, but very quickly the costs and headaches of manually harvesting and hanging material become apparent on a larger scale.
In addition, there have been reports of improper ventilation that has led to product loss through molding. Another issue is the large footprint required for barns or similar buildings to hang hemp especially as the quantity to process increases. The steam tube dryer allows for material drying to take place in minutes and hours instead of days and weeks as with more traditional methods and naturally helps to prevent contamination of the hemp because of this and through less time spent handling/re-handling.

With decades of experience in the agricultural processing industry, Louisville Dryer Co. manufactures direct heat dryers for processing hemp and steam tube dryers with a range of capacities to dry wet hemp biomass with an output moisture content between 10-12%.

To learn which processing technologies would be optimal for your material and application, contact our team of Applications Engineers at (800) 735-3163 or fill out our online contact form.

Drying Distillers Grains: Steam Tube Dryer vs. Direct Heat Dryer

Drying Distillers Grains: Steam Tube Dryer vs. Direct Heat Dryer

Consider a drying system to process 20 tons per hour of combined wet cake and syrup produced in an ethanol plant or distillery. At 66% combined feed moisture dried to 10% moisture content, the mass balance would be as follows:

Feed MaterialDischarge Material
Dry Solids13,600 LB per Hour13,600 LB per Hour
Moisture26,400 LB per Hour 1,511 LB per Hour
Total40,000 LB per Hour15,111 LB per Hour

Evaporation:                     24,889 LB per Hour

The heat requirement for drying is approximately 27.2 MMBTU.

Direct Heat Dryer

Using a direct heat dryer system for the process above, the system schematic would be similar to the one shown in Figure 1. Note that the dry material recycle loop is not shown since it would be identical for either dryer.

Drying Distillers Grains Direct Heat Dryer

The direct heat dryer in the example is equipped with a combustion system having a dryer inlet gas temperature of 1,000 F. Based on this system, the dryer exhaust gas discharge volume would be 53,000 ACFM. The system is provided with a flue gas recirculation system. This is included for two reasons:

  • Since the gas is laden with water vapor and combustion products (from having passed through the burner), it lowers the amount of oxygen present in the drum in order to prevent combustion from occurring inside the dryer.
  • It reduces the amount of gas having to go to the thermal oxidizer for destruction of VOC.

    This operating cost of the system is not just the drying but also the cost to operate a thermal oxidizer. This type of system also requires two additional fans, which cause increased horsepower requirements and exponential complexity of process control.

    Steam Tube Dryer

    Using a steam tube dryer system for the process above, the dryer system schematic would be similar to the one shown in Figure 2.

    Drying Distillers Grains Steam Tube Dryer

    Because the steam tube dryer employs steam to do the work, very little air is required. Typically, the dryer is run under slight negative pressure and a small amount of air is vented into the dryer to offset dust from puffing out. Thus, the primary content in the exhaust stream is water vapor instead of air.

    Since water is condensable, the exhaust gas goes through a condensing scrubber where a great deal of the water is collapsed back to liquid phase and removed. The remaining saturated air stream is taken back to the boiler and used as combustion air. The boiler acts as the VOC combustor – potentially negating the need for an RTO.


    Employing a steam tube dryer for processing DDGS may initially appear to be a more costly system (because the dryer itself is more expensive, and a boiler is required).

    Yet, for true comparison, the following factors of the overall system also need to be considered:

      • Steam tube dryers do not require heated air to operate.
      • Steam tube dryers do not require recycle gas stream for fire prevention.
      • Steam tube dryers are easily controlled by simple modulation of a steam valve.
      • Steam tube dryers do not require a thermal oxidizer system for most biomass systems. If an RTO is required, it is 75% smaller than with direct heat.
      • Steam tube dryers have an atmospheric environmental impact a fraction of direct heat dryers.
      • Considering the cost of an RTO verses a boiler, the steam tube dryer system may have a smaller initial cost.
      • Since the boiler for a steam tube dryer system may act as a thermal oxidizer, the operating cost is much lower.

    Learn more about When you would need a Steam Tube Dryer vs. a Direct Heat Dryer.

    Contact our Application Engineers to discuss your operation’s specific needs and how we can help you achieve The Lowest Cost per Revolution.