Cracking in a dryer shell can cause alarm and anxiety. How will the cracking affect the life of the dryer? Just like a small chip in a car’s windshield, there is concern that high stress on a weakness in a rotary dryer shell could grow into a bigger crack.
With the technical experience of the Louisville Dryer’s field engineers on your side, there is no need for stress. Dryer shell cracks do not always mean that the shell is on the verge of catastrophic failure. We can assess the status of your existing equipment and take the necessary steps to keep you operating efficiently.
Why Do Dryer Shell Cracks Occur?
Cracking generally occurs at high-stress locations and surfaces slowly. They are typically caused by the cyclic loading and unloading at these high-stress locations.
There are four common shell crackings, which we have outlined for you. The causes and concerns vary, as do the repair solutions. We are providing a broad overview of these common cracks to help you assess your needs. Please keep in mind that this is not inclusive of all shell cracks, and we always recommend a professional assessment by a knowledgeable rotary dryer specialist.
Four Common Dryer Shell Cracks | Causes & Solutions
# 1. Shell cracking that moves away from support points.
Identification: Cracks forming lengthwise near the middle of the shell.
Common Cause: Continual overloading or an abrasive or corrosive product that has worn away the thickness of the shell plate.
Common Concern: In this scenario, the shell has started to exceed the limit of its bending stress due to a reduction of shell plate thickness, or excessive weight. At this point, the cracks will continue to get worse, and sometimes at an alarming rate.
Typical Solutions: Wrapping or lining the shell can provide a temporary fix, but it does not add full rigidity back to the unit. A longer-term solution might require cutting that section of the dryer out and installing a new section. If the contributing factor is abrasion or corrosion, then the next step is to identify and mitigate that cause.
# 2. Cracking near the support pads of the riding tires.
Identification: Cracks forming near the tires.
Common Cause: Continuously overloading the unit by running material loads considerably past design.
Common Concern: All components of the rotary are designed with a certain amount of service factors, but those factors can be exceeded. When higher throughput is introduced, the excess stress causes the tires and support pads to transfer that pressure to the shell which can cause a small weakness to increase in size and vulnerability.
Typical Solutions: If you notice this type of cracking, act quickly. Start by reducing the amount of material passing through the unit. Cracks that are not excessive can typically be ground out and rewelded for a cost-effective and simple fix.
# 3. Cracking emanating from the corners of support pads.
Identification: Cracking of this nature typically occurs at support pads with sharp corners.
Common Cause: If the tire pads have sharp terminating corners, then the stress at these locations are exponentially higher than when the pads have rounded ends. It’s like the difference between pressing against something with a knife versus with the back of a spoon.
Typical Solutions: Stress riser induced cracks can be ground out and rewelded. In addition, the sharp corners of the support pads should be removed or the pads should be replaced entirely.
# 4. Cracks around steam tube support bundles.
Identification: Cracks between the supports and shell.
Common Cause: Steam tube supports should be designed to flex with the shell, and not act as a rigid, unforgiving inside stiffener. When supports are stiff, cracking can occur at the welded connections between the supports and shell.
Typical Solutions: Cracks can be ground and welded. U-style support stiffeners should also be installed on the shell externally to reduce stress from the tube support to the shell.
Protect Your Investment
Your dryer is a key piece of your operation and requires the best service from reputable experts. Louisville Dryer has been synonymous with rotary drying equipment for over a century. Our in-house team of engineers has the expertise to respond to any of your needs.
Over our extensive history, we have built, installed, and serviced rotary equipment that processes nearly every imaginable kind of material. No problem is too big or too small for you to contact us. We can help you assess any cause or concern, from small cracks and weaknesses to larger malfunctions and threats to your productivity. You can rest assured you will receive effective solutions that keep your production moving on time and on budget.
The Louisville Dryer team is open and willing to share our knowledge with you. It starts with making a phone call to us at (800) 735-3163 or by taking a moment to fill out our online contact form.