misalignment of rotary dryer

question of the week: what causes rotary dryer misalignment?

Rotary dryer misalignment is oftentimes the result of improper base installation. Misalignment in the base will quickly spread through the rest of the drum, causing wear and damage to other drum components. In addition, misalignment can occur naturally over time as part of normal rotary drum wear and tear.

It is important to routinely have the dryer inspected and re-aligned as needed. This routine, preventative maintenance is an imperative part of keeping your drum running smoothly, prolonging its life, and minimizing the potential for damage and downtime.

the importance of rotary drum alignment

Misalignment is one of the most common problems faced when working with rotary drums. Though aligning a drum is a simple solution, leaving a drum out of alignment can result in major problems. Routinely having a rotary drum re-aligned is an important part of preventative maintenance, and the overall longevity of a rotary drum.

A misalignment is often the result of an improper base installation. Proper drum base installation will help to ensure that the drum properly floats between thrust rollers. Misalignment in a base will propagate through the drum, causing wear and damage to other drum components, such as trunnion wheels, tires, drive components, and thrust rollers.

Misalignment also occurs naturally, as a drum experiences normal wear and tear, causing the drum to gradually fall out of perfect alignment. For this reason, it is important to routinely have a drum re-aligned.

Misalignment causes a drum to ride harder against the thrust roller, therefore wearing faster on the tire sides. This excessive riding can result in grooves and/or gouges on the face of the tyre. There are several tell-tale signs that can be a good indication that a rotary drum is out of alignment:

In addition to this, watching a drum run can indicate that it is time for a re-alignment. A working drum that is properly aligned should have little to no contact with thrust rollers. Drive components should run smoothly, without excessive chatter or vibrations.

Ensuring proper alignment of your rotary drum is an integral part of preventative maintenance, and a rotary drum that stands the test of time. Regular maintenance and inspection of your rotary drum will only help in prolonging the life of your drum, and ultimately minimizing maintenance costs and down time.

industrial dryer system maintenance tips - thompson dryers

Most of the problems encountered around the drum can be remedied or lessened by making your drum rigid, round and aligned. Among other benefits, a rigid drum will eliminate flexing and the problems caused by cyclic loading. A round drum will improve the effectiveness of the seals, and reduce bearing failures caused by impact loading. An aligned drum will improve the life of the trunnion wheel and tire surfaces as well as the health andwell-beingof the trunnion bearings.

Rotary drum dryers are the workhorse of the industrial drying industry. But even workhorses can have maintenance problems. However, they tend to boil down to a few core issues involving the following equipment: 1) trunnion wheels & shafts, 2) trunnion bearings, 3) drum tires, 4) drum shell and head plates, and 5) seals.

Performing daily inspections go a long way to benchmark what is normal in your plant. With the aid of daily inspections, the dryer operator is the first line of defense against problems because they typically know what is normal, and when somethings just not right. It is much easier and quicker to spot when something is out of place, such as vibrating worse than usual, new or worse leaks, new sounds, etc. when performing daily inspections.

Immediate Action: A surface problem, such as a rough surface, crowning, or tapering, needs to be reground or machined. You need not remove the wheel to perform this action. However, if the wheel surface becomes rough or gouged soon after resurfacing, something else is going on and you will want to call in the dryer experts. If a trunnion shaft breaks, shut the dryer down and call in the experts immediately. Something is going horribly wrong.

Proactive Action: Schedule resurfacing of trunnion wheels and drum tires at the same time as a precision alignment check, about every year or 2, and directly after any trunnion wheel or bearing replacements.

Purpose. Trunnion bearings support the trunnion wheels. They must also be quite stout, as 2 bearings support each trunnion wheel. To be effective and long-lasting, a trunnion bearing must be able to handle some misalignment and thrust. The symptoms displayed at your plant will determine whether you need to focus on a self-adjusting bearing or a double taper lock bearing.

Immediate Action: Change the bearings. Again. Most of the rotary dryer systems that have trouble with bearings have bearings that dont properly handle thrust and/or misalignment. Typically, if you are plagued with bearing problems, you can experiment by changing the bearing type. Changing greasing frequency may help.

Proactive Action: Investigate root cause of trunnion bearing failure and act accordingly. If your primary problem is thrust, which manifests as external failure, you will want to focus on a style of bearings that uses a concentric lock mechanism (or double taper lock). If misalignment is the primary issue, which usually manifests as an internal bearing failure, choose a self-adjusting bearing with more than 2 misalignment capability.

Trunnion bearings used with rotary drum dryers in the ethanol industry tend to fail regularly, but if one calculates their expected life (calculations are usually available on your bearing manufacturers website), they will discover that the trunnion bearings commonly used in the dryer industry should last 20 years or more. Instead of following the typical recommendation of replacing trunnion wheels and bearings every 2 years, the better solution is to find the root cause and deal with it. You can get an early warning sign by using an infrared camera, such as a Flir, which will show heat generated by friction. Every time a wheel and/or bearing is replaced, the drum and trunnions will need to be re-aligned and resurfaced. A drum running out of alignment, for whatever cause, could do more damage than not replacing the trunnions and bearings every 2 years.

Purpose. The tire provides a reinforced surface for the drum to roll on the trunnions. Without the tire, the whole shell would have to be much thicker to withstand this pressure. The longest lasting tires with least amount of maintenance necessary are rigid, round, and aligned. A rigid tire will eliminate flexing and the problems caused by cyclic loading. A round tire is the first step in achieving a round drum. An aligned drum will improve the life of the trunnion wheel and tire surfaces.

Immediate Action: Replace and/or redesign shims, if they are falling out; then have the drum and trunnions precision aligned and resurfaced. If the tire and shims have worn out to the point that the tire is moving back and forth on the shell, you need to call the experts immediately. You may also want to call in the experts if you have long grooves in the tire, or the surface gets rough soon after resurfacing. Daylight between the wheel and tire may only mean there are surface imperfections on the trunnions and tire, such as a crown. A precision alignment will determine if this is the case.

Proactive Action: Test your drum for walking (see sidebar). Make your drum rigid, round, and aligned. This includes shimming the tire such that it no longer walks, which likely involves a redesign of the shims. Schedule resurfacing of trunnion wheels and drum tires at the same time as a precision alignment , about every year or 2, and directly after any trunnion wheel or bearing replacements.

Walking Test If there are shims between your drums shell and tire, you will want to test the tire for walking, which means it rotates at a different rate than the drum. Over time the outside of the shims and the inside of the tire can wear down, allowing the tire to walk. You can perform this test while the drum is running by using a piece of chalk or spray paint and marking the side of the tire and where it lines up on the shell/shim. Check on it throughout the day to see if the lines still match up. Do this again when shutting down and starting up to see if you get the same results. If the marked line remains lined up, the tire is providing support to the shell, and likely not the source of any problems you may be experiencing. If it does not line up, the tire is likely causing stress to the shell and shims and may be causing other problems in the drum as well.

Purpose. The dryer drum is where the wet material is showered through the hot drying gases to evaporate water. The drum is the most important part of a rotary dryer system. Drums that are rigid tend to last longer than those that are not. A rigid drum reduces flexing and the problems caused by cyclic loading.

Immediate Action: Cracks anywhere in your drum should be fixed immediately. However, if similar cracks keep coming back over and over again, you have something else going on potentially caused by drum flexing that needs to be investigated by your dryer expert. Use the test described in But why is my drum cracking? sidebar to determine if your drum is flexing. If your drum broke in half and is now sitting on the floor, you are a bit late on reading this article, or I was a bit late writing it.

Proactive Action: Make your drum rigid, including eliminating the tire from walking. A rigid drum will eliminate flexing and the problems caused by cyclic loading. Schedule regular inspections for cracks by plant personnel and dryer experts. It is recommended to have a structural drum inspection by a dryer expert once every year or two, depending on the history of your drum.

But why is my drum cracking? Most cracks develop over time as the drum flexes, which can only rarely be seen by the naked eye. But, for a visual image of whats going on, think about what a water balloon looks like if you fill it up and then roll it down the sidewalk. It will always be wider than tall, but the exact points that are furthest and nearest are always changing as it rolls.

Determine whether your drum is flexing or not by taking internal measurements while the dryer is down. Mark off 4 spots 2 each on the horizontal and vertical axes. Measure from 1 to 3, the vertical axis, and then 2 to 4, the horizontal axis, as shown in the picture. Rotate the drum 90 and measure from 1 to 3, which is now on the horizontal axis, and 2 to 4 which is now on the vertical axis. If the first measurements of 1 to 3 v. the second measurement of 1 to 3 differ, the drum is flexing. Likewise on the measurements of 2 to 4. Any flexing will reduce the life of your dryer, but if the measurements differ more than , you will have problems with cracks sooner than later, if you do not already.

Flexing causes cyclic loading two cycles at every point for every rotation. At this rate, the fatigue limit is reached within the first 5 years of a stainless steel drums life if it is flexing. Carbon steel acts different under cyclic loading than does stainless steel. Stainless steel has a significantly lower fatigue limit than does carbon steel. Special care should be taken when inspecting for cracks and flexing when you have a stainless steel dryer drum.

Purpose: Since most rotary dryer systems are setup to be negative pressure, the seal is mainly keeping transient air out of the system. Excess transient air can make fires or explosions more likely as well as cool the ductwork and lower the wet bulb temperature to make buildup on the inside of the ductwork worse. It can decrease the effectiveness of cyclones, baghouses, thermal oxidizers, etc., because of the higher gases volume. Good seals enhance personnel safety and dryer efficiency and should be maintained accordingly.

Immediate Action: Replace your seals. Again. Also, resurface the sealing surfaces. The sealing surfaces get rough like trunnions and tires. If you already use an outside company to resurface your tires and trunnion wheels, you can usually schedule this activity at the same time.

Proactive Action: Probably need to change your seal style altogether and add a heat shield. Plus, make your drum rigid, round, and aligned. When the drum is not round, there will be intermittent gaps between the seal and the sealing surfaces that allow in transient air. If its not rigid, theres no hope of getting the sealing surfaces round. And if the drum is not aligned, the seals could be getting damaged by excess wear against the constantly moving sealing surfaces.

Seal material needs to be flexible, airtight or almost airtight, rated for high temperature, and durable. Thompson Dryers recommends a high temperature rubber belting. However, high temperature for these rubber belts is only about 400F. The gases at the front of the drum can be in excess of 1000F, which will burn up a seal in a matter of hours after installation without a heat shield. There is a sealing material made of kevlar that is commonly used in dryer applications. It doesnt burn up as fast, but still must be replaced quite often. A heat shield will prevent hot gases and/or radiant heat from destroying the seal. With a well-designed heat shield, your high quality rubber belting could last a year or two before needing to be replaced.

Dryer personnel should be performing daily inspections as a way to benchmark what is normal in your plant. That way, it is much easier to spot when something is wrong. The most common problems occurring in rotary dryers can be solved by making your drum rigid, round and aligned. Among other benefits, a rigid drum will eliminate flexing and the problems caused by cyclic loading. A round drum will improve the effectiveness of the seals. An aligned the drum will improve the life of the trunnion wheel and tire surfaces as well as the health and wellbeing of the trunnion bearings.

If you are in the middle of an emergency, take the immediate action to get up and running as quickly as possible. But, to prevent emergencies in the future, take a look at the proactive actions and try to incorporate viable solutions into your preventative maintenance program.

tire and trunnion grinding: critical rotary drum maintenance

A rotary drum in any industrial process setting, whether it is serving as a dryer, cooler, kiln, or agglomeration drum, is a critical component in the process loop; in most cases, if the rotary drum is offline, the remainder of the process must go down as well, resulting in downtime and lost production. In order to minimize downtime and circumvent potential issues, operators must regularly inspect the drum and carefully follow preventative maintenance procedures.

One of the easiest and most effective preventative maintenance procedures is tire and trunnion grinding the practice of resurfacing the tire (riding ring) and trunnion wheel components to like-new condition. Since damage to these components has a compounding effect on the rest of the drum, keeping tires and trunnion wheels in good condition is the starting point for avoiding more severe issues.

As the drums foundational support, problems that start in the tires and trunnion wheels work their way to other parts of the drum if not promptly addressed. When left untreated, the resulting stress on other components continues to build, exacerbating existing issues and promoting more severe damage.

Rotary drum alignment is a primary contributor to overall drum performance and longevity. Much like tires and trunnion wheels, the alignment of a drum affects several components, and when allowed to run out of alignment, can result in a wide range of problems.

While there are many potential consequences of misalignment, one especially challenging result is the lack of control over axial thrust. The inability to properly manage axial thrust promotes excessive wear on one of the thrust rollers, which has the potential to cause thrust roller bearing failure. In turn, bearing failure can lead to the drum dismantling the thrust roller shaft. If dismantling of the thrust roller shaft occurs, the drum is able to roll off the trunnion rollers, causing catastrophic failure and severe damage to breechings, seals, trunnion base weldment, concrete piers, gears (or chain and sprocket), tires, and the drum shell.

Drum vibration amplitude should be kept at a minimum in order to keep the drum running as smoothly and efficiently as possible, minimizing stress on all components. Excessive vibrations not only cause undesirable chattering, but they also quickly propagate to the rest of the drum, causing:

Allowing a drum to run with an increased vibration amplitude will eventually lead to catastrophic failure. A vibrations study can be performed to measure the vibration amplitude (peaks) and determine how aggressive the vibrations are. Vibration amplitude assesses the amount of displacement occurring, measured in micrometers (m).

A rotary drum is supported at four points where the tires (riding rings) meet the trunnion wheels. These four points of contact bear the weight of the drum and must be carefully balanced to provide even weight distribution and avoid putting excess strain on any of the components.

Additionally, wear may also be indicated by a chattering or vibrational sound. Furthermore, wear on one component (the tire or trunnion) is typically mirrored on the corresponding component, but this does not hold true in all settings. Any sign of wear, whether on one or both surfaces, should be immediately addressed.

Sometimes called reconditioning, tire and trunnion wheel grinding is a relatively simple process in which trained technicians use a specialized grinding machine to remove any surface wear to reveal the undamaged surface underneath.

Depending on the severity of the wear and the diameter of the wear surface, this process may take anywhere from a few hours to a few days. In many cases, the drum can remain in operation during the grinding process, so production need not be affected.

If wear exceeds greater than 10% of the original diameter, FEECO recommends replacement of the component to avoid problems associated with an altered slope, which can have greater ramifications on the overall process.

If the drum were not aligned following grinding, the misalignment of the drum, however minuscule, would immediately begin causing wear to tires and trunnion wheels, bringing them back to their pre-grinding condition.

While manual methods are available, rotary drum alignment is typically carried out using a laser alignment system. This advanced system reduces potential for human error, improves accuracy, and speeds up the alignment process.

Tires and trunnion wheels serve as the support system for a rotary drum, and as such, have a compounding effect on the system if allowed to wear. Tire and trunnion wheel grinding is a critical preventive maintenance tool in prolonging rotary drum life and promoting efficiency.

FEECO is a leader in rotary drum maintenance for dryers, kilns, coolers, and agglomeration drums. Our experienced technicians can assess damage to load-bearing surfaces and resurface tires and trunnions quickly and accurately. Technicians can then realign the drum for optimum mechanical stability. FEECO can also provide replacement tires and trunnions in cases of severe wear. For more information, contact our Customer Service Team today!

laser alignment

Whether you are running a rotary dryer, cooler, agglomerator, kiln, or other rotary equipment, proper alignment is key to extending equipment life and maintaining operational efficiency. A misalignment issue can quickly spiral into major equipment damage and downtime, if left untreated. A rotary drum will naturally fall out of alignment over time, making routine realignments an integral part of any preventative maintenance program.

FEECO utilizes a highly advanced laser tracking system to perform alignment services. This means our service technicians can perform alignments faster than ever, and with precision accuracy. Benefits of utilizing this system include:

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o'connor kiln & dryer, inc

Most problems with rotary equipment stem from the drum being misaligned. When it is not set to the right slope or is not paralleled, problems may occur. When we align a drum, first we review the drawings to determine the design slope and locations of the tires, trunnion rollers, and complete unit. We measure the diameters of the tires and trunnion rollers. Then our crew will use a Non-Reflective Total Station Instrument that measures angles and distances (Electronic Distances Measuring) to perform the following alignment procedures:

By using the Non-Reflective Total Station Instrument, we maximize the accuracy of our measurements. The instrument measures directly to surfaces, it does not require a prism, target, or scale to be held in place. Anytime a target must be located and held by a person or stand, it introduces additional chance for error in the measurement.

Once the laser in our instrument is directed onto the desired surface, the instrument takes the measurement. It is not necessary for the operator to read a scale or make a judgment call, and record a value. The instrument measures the angle and distance, then displays the values and saves them in memory.

how to diagnose rotary drum malfunctions and perform maintenance to avoid them | 2016-04-01 | process heating

While checking for internal cracks in a dry distillers grain soluble (DDGS) dryer drum, a dryer design engineer uses a Swiss army knife. Due to the size of the crack, the blade can be fully inserted into a crack between the shell and head plate. If cracks of this size are not fixed, they will continue to grow until the drum fails, perhaps catastrophically.

Do you know how much misalignment your bearings can handle? Misalignments are additive, so if they are not parallel in all planes, you can have some serious issues. I-beams, wide flanges, square tubes, etc. are not precision pieces of metal. Quite the contrary, if the bases are uneven, you will want to make them as level as possible by adding shims. In the figure, you can see how a small measurement difference will give you 1 of misalignment. This is more than most bearings can handle.

Figure for "Why Is My Drum Cracking?" Sidebar To determine whether your drum is flexing, begin by taking internal measurements while the dryer is down. Mark off four spots two each on the horizontal and vertical axes. Measure from 1 to 3, the vertical axis, and then 2 to 4, the horizontal axis, as shown in the figure. Next, rotate the drum 90 and measure from 1 to 3, which is now on the horizontal axis, and 2 to 4, which is now on the vertical axis. If the first measurements of 1 to 3 vs. the second measurement of 1 to 3 differ, the drum is flexing. Likewise, if the first measurements of 2 to 4 vs. the second measurement of 2 to 4 differ, the drum is flexing in that direction.

Rotary drum dryers are the workhorses of the industrial drying industry, but even workhorses can have maintenance problems. Fortunately, most drum maintenance problems center around a few core issues involving specific equipment:

Performing daily inspections goes a long way to benchmark what is normal in your plant. With the aid of daily inspections, the dryer operator is the first line of defense against problems. Those working with the equipment daily come to know what is normal and when something is just not right. It is much easier to spot something out of place increased vibration, new or worsening leaks, or even new squeaks, creaks and groans when performing daily inspections.

You can perform this test while the drum is running by using a piece of chalk or spray paint. Mark the side of the tire and where it lines up on the shell/shim. Check on it throughout the day to see if the lines still match up. Do this again when shutting down and starting up to see if you get the same results.

If the marked line remains lined up, the tire is providing support to the shell and likely not the source of any problems you may be experiencing. If it does not line up, the tire likely is causing stress to the shell and shims. It may be causing other problems in the drum as well.

Trunnions are stout, steel wheels on which a rotary dryer drum rolls. Each must support anywhere from 10 to 20 tons. Trunnions must be smooth and round to reduce vibration, wear and friction. Common symptoms of trunnions issues include a rough wheel surface, crowned surface, tapered surface and shaft breakage. A surface problem such as a rough surface, crowning or tapering must be reground or machined to correct it. Fortunately, the wheel does not need to be removed to perform this action. If the wheel surface becomes rough or gouged soon after resurfacing, however, something else is going on, and you will want to call in the dryer experts.

Proactive maintenance for dryer trunnions includes scheduled resurfacing of the trunnion wheels and drum tires followed by a precision alignment check. This maintenance should be completed every year or two as well as any time a trunnion wheel or bearing is replaced.

Trunnion bearings support the trunnion wheels. Like trunnion wheels, trunnion bearings must be quite stout. Two bearings support each trunnion wheel. To be effective and long lasting, a trunnion bearing must be able to handle some misalignment and thrust. The symptoms displayed at your plant will determine whether you need to focus on a self-adjusting bearing or a double-taper-lock bearing.

The most common bearings-related problems in rotary dryer systems are bearings misalignment and bearings that do not properly handle thrust. If you are plagued with bearing problems, changing the bearing type may help. Another common fix is changing the greasing frequency.

Proactive activities include investigating the root cause of trunnion-bearing failure and acting accordingly. If your primary problem is thrust, which manifests as external failure, switch to bearings that use a concentric lock mechanism or double-taper lock. If your primary problem is misalignment, which usually manifests as an internal bearing failure, choose a self-adjusting bearing with more than 2 misalignment capability.

Trunnion bearings used with rotary drum dryers in the ethanol industry tend to fail regularly. Because bearing failures in this industry are common, some may assume that only a short operating life is possible. If you calculate the expected life of trunnion bearings using tools typically available on bearing manufacturers websites, you will discover that the trunnion bearings commonly used in the dryer industry should last 20 years or more. Instead of following the typical recommendation of replacing trunnion wheels and bearings every two years, the better solution is to find the root cause and deal with it. You can get an early warning sign by using an infrared camera, which will show heat buildup generated by friction.

Every time a wheel or bearing is replaced, the drum and trunnions must be precision aligned and resurfaced. A drum running out of alignment for whatever cause can do more damage than not replacing the trunnions and bearings every two years.

The longest-lasting tires with least amount of maintenance necessary are rigid, round and aligned. A rigid tire will eliminate flexing and the problems caused by cyclic loading. A round tire is the first step in achieving a round drum. An aligned drum will improve the life of the trunnion wheel and tire surfaces.

If drum tire symptoms are present on your dryer, immediate actions include replacing or redesigning the tire shims. Proactive action includes testing your drum for walking (see sidebar). Make your drum rigid, round and aligned. This includes shimming the tire such that it no longer walks, which likely involves a redesign of the shims. If they are falling out, then the drum and trunnions should be realigned and resurfaced.

If the drum tire and shims have worn out to the point that the tire is moving back and forth on the shell, it is time to call in the experts. You also may want to call in the experts if you have long grooves in the tire or if the surface gets rough soon after resurfacing. Daylight between the wheel and tire may mean there are surface imperfections such as a crown on the trunnions and tire. Check this with your laser alignment kit.

Schedule trunnion wheels and drum tire resurfacing at the same time as an alignment check about every year or two. Also, perform resurfacing directly after any trunnion wheel or bearing replacements.

The drum is the most important part of a rotary dryer system. This is where the wet material showers through the hot drying gases to evaporate water. Drums that are rigid tend to last longer than those that are not. A rigid drum reduces flexing and the problems caused by cyclic loading. Typical problems with dryer drums include head plate cracks, shell cracks, cracks in welds, seal leakage, and drums that break in two and collapse on the floor.

Cracks anywhere in your drum should be fixed immediately. Use the test described in the Why is My Drum Cracking? sidebar to determine if your drum is flexing. However, if cracks keep coming back in the same locations repeatedly, you have something else going on that could be caused by drum flexing. In such cases, have a dryer expert investigate the cause of repeated cracking in the drum.

To be proactive, make your drum rigid and prevent the tire from walking. A rigid drum will eliminate flexing and the problems caused by cyclic loading. In addition, you should schedule regular inspections for cracks by plant personnel and dryer experts. It is recommended to have a structural drum inspection by a dryer expert once every year or two, depending on the history of your drum.

Most cracks develop over time as the drum flexes, which can only rarely be seen by the naked eye. But, for a visual image of what is going on, think about what a water balloon looks like if you fill it up and then roll it down the sidewalk. It will always be wider than tall, but the exact points that are furthest and nearest are always changing as it rolls.

To determine whether your drum is flexing, begin by taking internal measurements while the dryer is down. Mark off four spots two each on the horizontal and vertical axes. Measure from 1 to 3, the vertical axis, and then 2 to 4, the horizontal axis, as shown in the figure. Next, rotate the drum 90 and measure from 1 to 3, which is now on the horizontal axis, and 2 to 4, which is now on the vertical axis. If the first measurements of 1 to 3 vs. the second measurement of 1 to 3 differ, the drum is flexing. Likewise, if the first measurements of 2 to 4 vs. the second measurement of 2 to 4 differ, the drum is flexing in that direction. Any flexing will reduce the life of your dryer, but if the measurements differ more than 0.125, you will have problems with cracks sooner than later if you do not already.

Flexing causes cyclic loading two cycles at every point for every rotation. At this rate, fatigue limit is reached within the first five years of a stainless steel drums life. Carbon steel acts differently under cyclic loading. Stainless steel has a significantly lower fatigue limit than carbon steel. Special care should be taken when inspecting for cracks and flexing when you have a stainless steel dryer drum.

Because most rotary dryer systems are set up with negative pressure, the seals are responsible for keeping transient air out of the system. Excess transient air can make fires or explosions more likely as well as cool the ductwork and lower the wet bulb temperature. A low wet bulb temperature can worsen buildup inside of the ductwork. Excess transient air also can decrease the effectiveness of cyclones, baghouses, thermal oxidizers, etc., because of the higher gases volume. In short, good seals enhance personnel safety and dryer efficiency, and they should be maintained accordingly.

Seals that are leaking, tearing, falling off, breaking, burning up or wearing out quickly signify a problem. In these cases, you should immediately replace your seals and resurface the sealing surfaces. The sealing surfaces get rough like trunnions and tires. If you already use an outside company to resurface your tire and trunnion wheels, you usually can schedule this activity at the same time.

Changing your seal style altogether and adding a heat shield would be a proactive action, as would be making your drum rigid, round and aligned. When the drum is not round, there will be intermittent gaps between the seal and the sealing surfaces that allow in transient air. If the drum is not rigid, there is no hope of getting the sealing surfaces round. And, if the drum is not aligned, the seals could be getting damaged by excess wear against the constantly moving sealing surfaces. Seal material needs to be flexible, airtight or almost airtight, rated for high temperature and durable. Some dryer manufacturers recommend a high temperature rubber belting; however, a high temperature belting still should not be used in temperatures higher than 400F (204C). The gases at the front of the drum can be in excess of 1000F (537C), which will burn up a seal in a matter of hours after installation without a heat shield. For these areas, there is a sealing material made of Kevlar that is commonly used in dryer applications. It does not burn up as fast, but it still must be replaced quite often. A heat shield will prevent hot gases and radiant heat from destroying the seal. With a well-designed heat shield, high quality rubber belting could last a year or two before needing to be replaced.

In conclusion, dryer personnel should be performing daily inspections as a way to benchmark what is normal in your plant. Most problems occurring in industrial rotary dryers can be solved by making your drum rigid, round and aligned. Among other benefits, a rigid drum will eliminate flexing and the problems caused by cyclic loading. A round drum will improve the effectiveness of the seals. An aligned drum will improve the life of the trunnion wheel and tire surfaces as well as the health and well-being of the trunnion bearings.

If you are in the middle of an emergency, take the immediate action to get up and running as quickly as possible. But, to prevent emergencies in the future, take a look at the proactive actions and try incorporate viable solutions into your preventive maintenance program.

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what are datscans and why your rotary dryer needs one - optimus solutions

It is a cold drum engineering survey and the rotary dryer or rotary unit must be shutdown to perform this engineering service. A DATscan gives us the baseline measurements to inform our maintenance and repair team to make decisions for your rotary equipment. Whether youre preparing for a plant shutdown or in the middle of one, a DATscan is a great tool to help guide your next steps concerning your rotary unit.

The design and operation of a rotary kiln or dryer are critical to its efficiency. If designed incorrectly or operated improperly, a rotary kiln will inadequately treat materials and drastically increase operating costs. Left untreated, horizontal and vertical misalignment issues on rotary kilns and dryers can lead to unpredictable operation, decreased reliability and cause a complete failure to the unit which could lead to reduced production and/or loss of revenue for the company. When youre experiencing a bearing failure, seal failures, tire-to-roller face contact shifts, and other negative effects, then its an indication that the loads are not evenly distributed to all the piers. This is also an indication that the unit is misaligned or operating outside the design slope. In order to avoid these above issues, DATscan survey is needed to determine the condition of the unit for slope, skew, relationships between tire and roller contact, etc.

Issues with support base structures or its mechanical components may cause excessive wear throughout the unit and/or misalign the unit. Using the TS 16 Leica helps us gather data from our prism location and use this data to determine the slope (position) of the unit and the base slope. This helps us to compare the measured slopes with the designed slope for proper positioning or in the case that theres no designed slope, we can use the measured slopes as established system slopes and base slopes moving forward. A visual inspection is always included in a DATscan. During the inspection, some issues we look for are: wobbling or poor contact between tire and support rollers/trunnions, hot bearings caused by high thrust loads and abnormal wear patterns on support rollers. Checking the feed and discharge seals of the unit is also an important part of the inspection. Were looking for any false air going into the unit, subsequently altering the process by making it less efficient. Air leakage through the seals is possibly a result of abrasion from materials, poor maintenance or product overflow.

Assessment and alignment services help the company to reduce financial risks, increased equipment uptime, lower operating costs and increased profits for stakeholders. It is an excellent first step for both problem solving and as a preventative maintenance tool.

rotary dryer system

A DATscan is a cold drum (performed when a rotary dryer or unit is shut down) engineering survey that measures system alignment. A DATscan gives you baseline measurements to inform your maintenance and repair decisions for your rotary equipment. Whether youre preparing for a plant shutdown or in the middle of one, a DATscan is a great tool to help guide your next steps concerning your rotary unit. This precision engineering survey is checked three ways and boasts an accuracy of +/-0.040.

When the DATscan is performed, each tire (tyre) / riding ring will be surveyed to establish a unit center point, horizontal misalignment, and unit slope. Support rollers / trunnions will be surveyed to establish their relationship to each tire and support roller / trunnion slope and one base at each pier will be surveyed for center reference points. Additionally, a brief visual inspection will be performed on the rotary unit to detect any noticeable problems and recommendations for adjustments will be made.

The DATscan involves the use of optical instrumentation and specially designed software that communicates wirelessly with multiple tools to gather data. It is a cold drum survey engineering survey and the rotary dryer or rotary unit must be shutdown to perform this engineering service.

If you are unsure of your baseline measurements as designed and initially installed, experiencing aggressive or excessive, unexpected wear even after an alignment or as a periodic check of baseline as a measure of your maintenance performance (recommended every two years) and as part of a continuous improvement initiative.

When a rotary unit is "floating," it means the equipment has a natural pull of gravity on it down the slope and is exactly balanced by the combined force of the support rollers / trunnions pushing the shell uphill. Efforts from each support roller should be equivalent. Floats are performed as part of routine maintenance.

An alignment situates the support rollers so that shell flexing is minimized. The beginning of understanding alignment is to know where the support rollers / trunnions are holding the equipment in relation to a straight line. Alignment is best utilized as a preventative maintenance measure. A DATscan provides the data necessary to perform an alignment on your rotary unit.

rotary dryer design & working principle

For evaporating moisture from concentrates or other products from plant operations, Rotary Dryers are designed and constructed for high efficiency and economy in fuel consumption.Whenever possible to apply heat direct to the material to be dried, Rotary Dryers of the Direct Heating Design are used. If it is not possible to apply heat direct to the material to be dried, Rotary Dryers of the Indirect Heating Design can be furnished so that the heated gases will not come in direct contact with the material.

Rotary Dryer is a simple, inexpensive unit for reducing the moisture content of flotation concentrates, as well as chemical and industrial products. Frequently the saving of shipping weight so effected will pay for the dryer in a few months. Difficulties from freezing while in transit are also eliminated. Many industrial projects are now using Dryers for control and production purposes on many materials.

Three main types of Rotary Dryers can be supplied. The direct heat unit is used when it is permissible for the drying gases to come in direct contact with the material being dried. Partition plates increase the heating surface. Drying may be by hot air or exhaust gases from other operations. If this drying gas has a deleterious effect on the product, then an indirect type of dryer can be supplied. A further derivation is the Tedrow Steam Dryer.

Of the different types of dryers that there are the most common is the ROTARY DRUM DRYER/Kiln, This type of drier is common not only in the mining industry but you will find them in fertilizer plants, Cement plants, and peat hogs to name but a few.

The theories behind these machines are very simple, heat an air space up, and then tumble the material to be dried through this space until it is dried. All though it sounds simple there are problems that have to be solved before the required results are met. But first, so you know what we are talking about lets go through the design of a drier.

First is the KILN, this provides the heat, The BURNER is inside this portion. The fuel for the burner is usually diesel although heavy crude oil could be used in some cases. To be able to generate enough heat to dry the concentrate air must be added by way of a BLOWER. In front of the kiln is the point that the wet concentrate enters the drier. It is put into the revolving SHELL. The shell is on a slight incline. As the Concentrate is tumbled through the hot air mass of the drier it travels down this incline to the exit of the drier.

At this exit point the concentrate is either deposited straight into a storage area or taken to the storage area by a conveyor. It is also at this point that there is an EXHAUST HOOD. This provides a controlled escape passage for the fumes and water vapor that is generated by the concentrate drying. This is a very important function and the operator will have to be sure that it is open at all times. If it should become blocked the water vapor will not be able to escape. The concentrate will become wet and sticky which will result in the discharge plugging. The wet sticky concentrate will also lower efficiency level of the drier for an extended period of time. This happens because inside the drier shell are what are termed FLIGHTS these are flat pieces of metal that are bolted onto the shell.

They are there to lift the concentrate up to the top of the shells rotation and drop the concentrate through the hot air. If the water vapor isnt taken away, the concentrate becomes sticky from reabsorbing the water. This sticky concentrate will fill the spaces between the flights.

The concentrate will not be lifted and dropped through the hot air. This results in a long term condition of poor performance even after the initial problem has been cured. These flights will remain buried in concentrate. This removal of the water vapor is one of the functions of the blower. It assists the natural process of air movement as the hot air mass expands. To prevent the buildup of concentrate on the flights there are often CHAINS attached to them. As the drier revolves the chains slap the flights preventing concentrate from building up on dryers walls.

The drier shell is rotated separately from the stationary kiln section. To achieve the rotation a BULL GEAR is attached around the shell section. There are also two flat rings attached to the shell. These provide surfaces for support rollers to roll on. There is another problem that the inclined shell has, the incline causes the shell to want to slide in the direction of the incline. To prevent this additional rollers are attached to the last set of rollers.