Palm Fruit Threshing Problems: Why Do Fruits Remain Attached?

When palm fruit bunches come out of a palm fruit threshing machine with too many fruits still attached, the immediate assumption is often that the thresher needs a higher drum speed or stronger mechanical action.

In reality, unstripped fruits can have several causes.

The condition of the bunches before threshing, the time between sterilization and threshing, feeding stability, raw material differences and the condition of the machine can all affect fruit detachment.

That is why troubleshooting should start with the complete operating situation rather than focusing only on the palm fruit threshing machine.

What Causes Unstripped Fruits During Palm Fruit Threshing?

Several factors can produce similar threshing symptoms.

1. Inadequate sterilization

If palm fruit bunches have not been adequately sterilized, the fruits may remain firmly attached to the bunches.

In this situation, increasing the threshing intensity may not solve the real problem because the material entering the thresher has not been properly prepared.

For reference, Glory Oiltech uses steam sterilization at 145°C for 60–120 minutes, depending on fruit maturity and equipment design. Different sterilizer types can require different cycle times, so this should be treated as a reference rather than a universal setting.

When unstripped fruits increase, checking sterilization conditions should therefore come before making major changes to the thresher.

2. Too much time between sterilization and threshing

Material flow also matters.

Even when sterilization has been adequate, a long delay before threshing can affect fruit detachment. Sterilized bunches should not be left accumulating unnecessarily before they enter the threshing stage.

A stable flow between sterilization and threshing makes it easier to maintain consistent operating conditions.

This is also why sterilization and threshing should be considered together when designing or troubleshooting a palm oil processing line.

3. Excessive or unstable feeding

A palm fruit thresher needs an appropriate and stable feed.

When too much material enters the drum at once, the threshing action can become less effective. Uneven feeding can cause similar problems because the machine load keeps changing.

A simple observation can help identify this cause.

If the amount of unstripped fruit increases when the feeding rate becomes heavier, correct the feeding condition before changing other machine settings.

Equipment selection should also consider the complete material flow instead of looking only at the nominal capacity of the thresher.

For reference, Glory Oiltech's simple-type palm fruit thresher is designed for 1–2 tons of palm fruit bunches per hour, while its drum-type models cover 1–15 tons per hour.

The appropriate machine therefore needs to match the actual processing scale, feeding condition and incoming FFB.

Raw Material Can Affect Threshing Results

The incoming palm fruit bunches are not always identical.

Differences in bunch size, maturity and physical condition can affect how readily fruits detach.

This is especially important when the problem occurs mainly with particular batches.

If one batch produces more unstripped fruits than another, continuously increasing the machine intensity may not be the best approach. Instead, compare the raw material condition and operating records.

Keeping the main operating conditions stable makes these differences easier to identify.

When Should You Inspect the Threshing Machine?

If sterilization, waiting time and feeding conditions appear normal but unstripped fruits continue to occur, then the palm fruit threshing machine itself should be inspected.

Relevant components should be checked for:

Wear
Damage
Looseness
Incorrect adjustment
Relevant clearances, where applicable

A worn or incorrectly adjusted component can weaken the mechanical action used to detach fruits.

If a component is simply incorrectly adjusted, adjustment may solve the problem. If it is badly worn or damaged, replacement may be required.

It is better to make one controlled change at a time where practical. Changing feeding rate, drum speed and component adjustment simultaneously makes it difficult to determine which change actually affected the result.

What About Drum Speed?

Drum speed should be treated as a machine-specific parameter.

For example, Glory Oiltech's simple-type palm fruit thresher operates at 480 r/min. This is a reference for that corresponding machine model, not a universal drum-speed standard for all palm fruit threshers.

Using a speed value from another machine without considering its design can therefore lead to misleading conclusions.

How Should Threshing Performance Be Measured?

A measurable result is more useful than simply saying that threshing performance is “good” or “poor.”

A practical project-specific indicator is:

Unstripped fruit rate = Weight of unstripped fruit ÷ Total fruit/bunch material evaluated × 100%

The same evaluation method should be used when comparing different tests.

Record:

Amount of material evaluated
Amount of unstripped material
Raw material condition
Sterilization conditions
Approximate waiting time
Feeding condition
Machine operating conditions

This makes it easier to determine whether a change actually improved the result.

Glory Oiltech's simple-type palm fruit thresher has a fruit stripping rate of up to 98%, while its drum-type model can achieve over 99%. These figures apply to the corresponding equipment models and should be used as reference values rather than universal industry standards.

What Information Should You Give an Equipment Supplier?

If the problem continues after basic checks, avoid sending only a message such as “the thresher leaves too many fruits.”

The supplier will be able to assess the situation more effectively if you provide operating information.

Useful information includes:

Type and condition of incoming FFB
Processing capacity or actual feeding rate
Sterilization method and actual conditions
Approximate time between sterilization and threshing
Current machine model and operating conditions
Drum speed, if available
Recent changes, repairs or component replacements
Photos or videos of the unstripped bunches
Measured unstripped-fruit rate, if available
Adjustments already tried and their results

This information helps separate an upstream problem from a machine problem.

A Practical Troubleshooting Sequence

When unstripped fruits appear, a useful sequence is:

Step 1: Check sterilization.

Step 2: Check the time between sterilization and threshing.

Step 3: Check feeding rate and feeding stability.

Step 4: Compare the condition of different FFB batches.

Step 5: Inspect threshing components.

Step 6: Make one controlled adjustment at a time.

Step 7: Measure the result before and after the adjustment.

This approach is generally more informative than immediately increasing drum speed.

Palm Oil Processing Projects as Practical References

Glory Oiltech's documented project experience includes a 2 TPH small-scale palm oil mill in Nigeria, completed on May 23, 2025, and a 5 TPH automatic small palm oil mill in Liberia, completed on April 1, 2024.

These projects provide practical references for looking at sterilization, threshing and the wider palm oil processing line as connected stages.

The company provides palm oil processing equipment and solutions, including palm fruit sterilizers and palm fruit threshers.

Final Takeaway

Unstripped fruits after palm fruit threshing do not automatically mean that the palm fruit threshing machine has failed.

The cause may be related to sterilization, the time before threshing, feeding conditions, raw material differences, machine operation or component condition.

The most practical approach is to identify the limiting factor first, make controlled changes and measure the result.

If you are planning a new palm oil processing line or troubleshooting an existing threshing system, Glory Oiltech can provide equipment selection, technical guidance, commissioning and after-sales support based on the actual processing conditions.

Full guide:
https://www.palmoilextractionmachine.com/FAQ/palm_fruit_threshing_1376.html

Official websites:
http://www.palmoilprocessingmachine.com
http://www.palmoilextractionmachine.com

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