How to Inspect the Dryer at Your Asphalt Batch Plant

Stansteel Hotmix Parts & Service shares best practices to inspect the dryer at the batch plant

Assessing components at the hot-mix asphalt (HMA) plant is only one step in the overall picture of plant health. This month, the plant maintenance series from Stansteel Hotmix Parts & Service, Louisville, Kentucky, focuses on the batch plant, showcasing the dryer specifically.

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Safety Notes

The first step with any plant maintenance, whether a continuous drum mix facility or a batch plant, is to make sure all inspections, markings or repairs happen while using proper OSHA Lockout/Tagout procedures. Ensure you have complete power disengagement before performing any inspections or repairs. For observations that require fans, motors or other components to be operating, listen or watch for vibration and noises from a safe distance or rely on your controls system to provide feedback on specific parameters. In this situation, you will observe and document, but do not touch the operating equipment.

For this series on assessing your asphalt plant for repairs and to avoid unplanned downtime, plant owners are reminded that only fully trained personnel should be allowed to conduct work on or around the equipment. For safety’s sake, the worker(s) should be fully trained on and act in accordance with all federal, state, county and local laws and regulations, and that includes OSHA and MSHA laws. You want your workers to be familiar with and act in accordance with the equipment specifications and manuals as well as your site-specific safety rules and regulations.

Workers have to take responsibility for their own actions, inactions, consequences and results, but you can ensure the best possible outcome for their safety and your operation’s success when you take the time to train and educate each worker who has access to the equipment and material at your facility.

Always utilize OSHA Confined Space procedures.

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Before You Power Down

While the dryer is still running, from a safe distance, observe the following:

• Are motors operating at normal temperatures? (Non-contacting infrared temperature guns work well and from a safe distance.)
• Is there excessive noise or vibration during motors’ operation?
• Do you smell any unusual odors during operation?
• Are bearings operating at normal temperatures?
• Is there excessive noise or vibration during operation of the bearings?

Observations from a safe distance while the dryer is running will give you some information at the beginning of your inspection. With the power off and proper lockout/tagout procedures in place, you can get closer to the motors, reducers, sprockets and guards for a full inspection. All photos courtesy of Stansteel Hotmix Parts & Service

Start With the Big Picture

With proper lockout/tagout procedure in place, perform a visual inspection of the complete dryer system. You’re looking for noticeable issues—any areas that might be damaged or in need of immediate repair or replacement. Depending on what damage you see, you may circle it with spray paint, paint or mark with a Sharpie to indicate exactly where the problem is, or place some other type of tape or marker where the mechanic or grounds crew can find and fix the damage efficiently. You will also record the damage or problem in your company’s log, whether that’s a paper worksheet or an app on the Tablet you carry into the field.

Also look at the dryer seals. You’re looking for cracked seals or missing sections. Make a note of these for repair or replacement.

While still outside the dryer, perform a shell thickness test in multiple areas. It’s helpful to “map” your drum with not only a thickness profile down the length of the drum, dryer or rotary mixer, but also to capture a temperature profile while in operation and note operational details such as tons per hour, percentages of reclaimed material being used, fuel used, etc. This can help to identify flighting problems or poorly tuned burners in the future.

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Inspect Inside

Following OSHA standards for Confined Space entry, it’s time to look inside the dryer.

• Are there any missing flights?
• Are there any broken flights?
• Are there any bent flights?
• Are there any heat-distorted flights?
• Are there any missing flight clips?
• Are there any missing or damaged materials dams?
• Inspect the inlet spiral flights and make notes for repairs.
• Inspect shell integrity, looking for excessive wear throughout.
• Check the combustion flight zone, where excessive heat from the burner flame exists; perform shell thickness tests in this area.
• Take photos of the interior, of the flights and of the burner area and date them.

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Inspect Discharge Area

You want to give special attention to the discharge paddles and check for the following:

• Are there any missing discharge paddles?
• Are there any bent discharge paddles?
• Are there any missing connection bolts?
• Inspect the discharge paddle ring and wear bars.
• Inspect the discharge chute for visible wear.
• Inspect the discharge chute for missing or worn liners.

Inspect Drive Components with Power Off

The observations while the dryer was running gave you some information at the beginning of the inspection. Now with power off and proper lockout/tagout procedures, it’s time to get closer to the motors, reducers, sprockets and guards.

• Are all motors properly ventilated? (Is heat dissipating; fins clean?)
• Are all motors connected to drive coupling with no signs of misalignment?
• Check and maintain proper oil levels in motors/reducers.
• Double-check that oil samples have been taken and that recommended oil changes have occurred.
• Are drive or driven sprockets showing signs of wear?
• Are there any visible cracks in shafts?
• If you have drive belts, are any cracking? Are they tensioned properly?
• Are sheaves showing signs of wear?
• Is the drive chain showing signs of wear?
• If you have a cradle chain drive, is there chain shoe wear?
• If you have a cradle chain drive, inspect the drive/driven sprocket.
• If you have a cradle chain drive, inspect the circumferential sprocket.
• If you have a ring gear drive, inspect the ring and pinion gear.
• If you have a trunnion drive, inspect the trunnion and tire faces as they can provide indications of poor wear patterns before excessive damage occurs.
• Are bearings properly lubricated?
• Is there visual abnormal coloration? (blackened grease)
• Is there excessive grease or oil escaping the bearings?
• Are bearing mounting bolts tight?
• Are there any cracks in bearing housings?
• Inspect tires for misaligned wear, as well as making sure all tire rigging is intact.
• If any rigging bars are missing, note for immediate repair and replacement.
• Check and measure the gap between the tire inner diameter and the surface of the support rigging. This is most important at the 12 o’clock position. Note if the drum is cool or hot.

Inspect Trunnions

The trunnion alignment and maintenance is so important that AsphaltPro Magazine has included several articles about this topic over the years. If you see excessive wear on trunnions and tires, this could be because of improper trunnion alignment. Stansteel Hotmix Parts offers the T-Trac Alignment System that is designed to establish a properly skewed trunnion roller setting to thrust the drum/dryer/rotary mixer in the uphill direction to its desired neutral thrust operating position. This can save thousands of dollars in premature trunnion and tire wear. Make sure you inspect and note the trunnion for immediate repair and replacement, if needed. Also inspect the thrust rollers and bearings for excessive wear as well as spacing.

If you have comments on any of the dryer elements you’ve inspected, make those notes for your grounds crew or mechanic and set a date by which you’ll check back on the progress of repairs. A well-maintained and properly functioning dryer is integral to the success of your batch plant. Keeping it in good working order keeps your operation safe as well as efficient.