Keep Your System Flowing

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May/June 2024

PUZZLER

Stock Picker

One day, you get a call from a random stock advisor.

"Next week, ABC stock is going to move up," he tells you. "I'm not asking you to buy any stock from me, but just take a look."

You do. (Why not, it can't hurt...) He was correct.

The following week you get another call from the "Lucky Guesser". His pick? "DEF is going to go down." Guess what! He was right again!

For five weeks, this guy predicts the behavior of stocks. The sixth time he calls, he says, "I've been right the past five times. This time I have a stock for you and I want you to buy some shares through me."

What do you say? Do you buy shares from this guy?

See answer here

Keep Your System Flowing

Identify and Fix Common Rotary Airlock Valve Problems

Rotary airlock valves are workhorses in many industrial applications, but like any mechanical device, they can experience problems. Here's a guide to help you identify and fix common rotary airlock valve issues, keeping your system running smoothly.

Identify the Problem

Air Leaks

A small amount of leakage is normal, but excessive air escaping from the valve indicates worn blades or increased clearance. Listen for hissing sounds and check for material dust escaping. If your valve’s air leakage is excessive, you’ll notice symptoms such as a drop in material throughput or an increase in the conveying system’s air requirement.

Jamming

Material buildup between the rotor blades and housing can cause jamming. This can happen due to improper valve sizing, incorrect material characteristics, or worn bearings. Material buildup can overload a motor, break a chain or bend the rotor to the point that it breaks. Jamming is more common in certain applications, such as when conveying sugar or other sticky or powdery materials. Moist or humid conditions can cause those materials to stick inside the rotor. Also, some materials are more susceptible to jamming. These include stringy or fibrous materials, such as wood fibers, hard materials, like some plastic pellets and large, chunky materials.

Strange Noises While some noise is normal during startup, unusual grinding or clanging noises may indicate bearing wear, misalignment, or debris caught in the valve.

Insufficient Throughput If the valve isn't handling the expected amount of material, check for excessive air leakage. Other causes include improperly sized valves, clogs, worn blades or incorrect speed settings.

Explore Solutions

Air Leaks

The solution depends on the severity. Minor leakage might require adjusting clearances or replacing gaskets. For significant leaks, worn blades might need replacement.

Ways to minimize air leakage

Install flexible seal strips to reduce clearances
Select a valve with more rotor blades
Install a housing or headplate vent
Install a vent adaptor at the material inlet

Jamming Stop the valve and clear any blockages.

Check the valve's rotation. Is it turning in the direction the manufacturer recommends? (View the rotation from the driven end). Correct valve rotation is especially important when utilizing beveled tips. With beveled tips, the wrong rotation can cause excessive drag and force between the rotor and housing. This can result in a failure of weld between the vane and rotor hub even to the point of the vanes separating from the rotor hub.
Does the rotor turn smoothly without contacting the housing or headplates?
Does the valve shudder? Shuddering can indicate material is jammed between a blade tip and the housing.
Is your valve undersized? Material must fit comfortably in the rotor pocket.
Has a foreign object entered the valve?
Are changes to the material's properties affecting the flow?
Is the material temperature higher than expected?

Remedies

Bevel blade tips to ease flow between the blades and housing or headplates.
Install flexible seal strips.
If water vapor reaches your material and causes it to lump, vent moist air before it reaches the valve.
Higher than expected material temperature may cause valve components to expand, reducing valve clearances. Ideally, reduce material temperature. If not possible, valve clearances may need to be increased.

Strange Noises Investigate the source of the noise. Bearings might require lubrication or replacement. Misalignment might require readjustment. Shut down the valve immediately if debris is caught to prevent further damage.

Ensure the rotor is running in the right direction and doesn't contact the housing or headplates.
Was the valve properly stored? If not, check for rust. Rust can reduce the clearances inside the valve.
Build up inside the valve can cause noises. Material, especially hygroscopic material, can build up on the housing and headplates. Coating the valve interior with nickel or chrome often prevents material buildup. Or, try venting moist air before it reaches the valve.
Use beveled rotor blade tips to reduce drag.
You could have a mechanical problem with the drive chain or drive shaft.

Insufficient Throughput Check for excessive air leakage. Clean out any clogs. Check for worn blades or improper speed settings. Ensure the chosen valve size can handle the required material flow rate.

If the problem persists, you may need to re-examine and validate the operating conditions, environmental factors, and material properties you originally specified for your application. If the conveying system’s operating speed has dropped or your material’s properties have changed since you installed the valve, you may need to install a smaller or larger valve. Your TEC engineer can help you determine which valve size can improve your material throughput or suggest appropriate field-applied modifications to your valve that will improve throughput

Preventive Maintenance:

Regularly inspect the valve for wear and tear.
Conduct routine cleaning to prevent material buildup.
Lubricate bearings according to the manufacturer's recommendations.
Monitor differential pressure to detect potential blockages.
Consider using a bypass system to isolate the valve for easier maintenance.

By recognizing the signs of trouble and taking preventative measures, you can keep your rotary airlock valve functioning optimally and avoid costly downtime. If you're unsure about how to fix a specific issue, consult the valve's manual or contact your TEC engineer

WARNING

Before performing any maintenance step, always make sure you understand the applicable safety precautions. Observe all warnings and instructions on the equipment and in the operating manual. For maximum safety, workers should electrically lock out the rotary airlock valve before performing routine maintenance, repair or replacement.

For more information on sizing and selecting rotary airlock valves, contact your TEC representative or visit Meyer Industrial.