What Should I Check During a Trial Run?
The Trial Run Is the One Step You Cannot Skip
Many people go through the full process of comparing specifications, negotiating prices, and agreeing on terms — then skip the trial run and order directly. This decision is usually regretted after delivery. Output particle size doesn't meet requirements, the feed opening won't accept the primary waste, or the machine frequently overloads when processing your actual material — all of these problems surface during a trial run and are far harder to deal with after installation.
A trial run is not a formality — it is the most important verification step in the purchasing decision.
Preparing for the Trial Run
Bring representative waste samples
This is the most important preparation. The waste you bring must represent what you actually process — not just the easiest material, but including the most difficult, largest pieces, and occasional special batches. If your waste includes more than one material type, bring samples of each. Let the machine process your actual waste mix during the trial, not the supplier's ideal test material.
Prepare a requirements checklist
Compile your specific equipment requirements before the trial: what output particle size do you need; what is your required hourly throughput; is your feed method manual or conveyor-fed; is the output going directly back to process or through a pelletizer first? Verify each item against trial results.
Bring someone who knows your production
The observations and judgments at the trial run site require someone with clear understanding of your plant's operational needs. Do not send only a purchasing person — have a machine operator or production manager attend. When questions arise on site, they can immediately judge the impact.
What to Check During the Trial Run
Feed verification
Does the feed opening size accept your waste? Put your largest pieces into the feed opening and physically confirm they can be smoothly fed — do not judge by eye alone; physically trying it is the only reliable test.
Is feeding smooth? Observe the process of waste entering the granulating chamber. Is there any accumulation, floating, or rough feeding at the feed inlet? Film and light materials are especially prone to floating at the feed inlet. If this problem occurs, confirm whether the machine has a forced-feed design or other solution.
Are there signs of tangling or jamming? Watch the machine's sound and current during feeding for any abnormal load fluctuations. Deliberately feed long strips or high-toughness materials to test for tangling.
Output verification
Does output particle size meet your needs? Collect a quantity of output samples; visually confirm size and uniformity. Measuring tools give more precise data. Non-uniform output (some very fine, some very coarse) indicates the cutting is not ideally effective, or the screen aperture needs adjustment.
Is there contamination or abnormal particles in the output? Metal debris, oversized particles, or abnormally high powder fraction in the sample are all reflections of machine condition.
Is the output rate meeting the expected capacity? At a fixed feed rate, record output volume per unit time and calculate hourly capacity. Confirm it meets your requirements.
Machine operation verification
Is current within the normal range? Watch the ammeter throughout the trial. Record current in idle, light-load, and full-load states. Full-load current should be 75–85% of rated current. If already near or above rated current, the machine is near its limit processing your waste — no headroom.
Are there abnormal sounds or vibrations? Normal operation produces steady shearing sounds without metal contact, abnormal friction, or irregular striking sounds. Slight vibration is normal; clear irregular vibration indicates a problem.
Is chamber temperature rising abnormally? After a sustained trial period, lightly feel the chamber exterior (do not touch high-temperature surfaces directly). Abnormally elevated chamber temperature may indicate insufficient granulating efficiency, excessive material retention time, or a need for supplementary cooling equipment.
Is the safety interlock system functional? Ask the supplier to demonstrate: attempt to start the machine with the hopper open — confirm it cannot start. Confirm the emergency stop immediately halts the machine and the blade shaft comes fully to rest within a reasonable time after stopping.
Operation and maintenance verification
Is blade replacement operationally practical? Have the supplier demonstrate the blade removal and installation procedure; get hands-on experience with the difficulty. Extremely complex blade replacement or requirement for special tools will make future maintenance very troublesome.
Does the screen seat open and close smoothly? High-frequency screen seat operation — confirm smooth action, reliable locking, and operation without excessive force.
How difficult are the various areas to clean? Ask the supplier to explain the standard cleaning procedure. Confirm that areas prone to material accumulation — chamber, screen, feed opening — can be effectively cleaned without dead spots.
After the Trial Run
Request a written trial run report
Trial results should be documented in writing: waste type tested, trial conditions (feed rate, screen aperture), output particle size range, operating current values, and any observations. This record is valuable during subsequent contract negotiation, equipment specification confirmation, and acceptance — and is the supplier's formal confirmation of trial run results.
Compare results against your requirements checklist
Verify trial results against each item on your requirements checklist. For any non-conforming item, before ordering, require the supplier to explain how it will be resolved — or adjust your expectations.
Trial the same waste at multiple suppliers if possible
If time allows, bring the same waste to two or three suppliers for trials. The difference in how different machines handle the same waste often says more than the differences on paper specifications.
Related articles: How to Select a Granulator: Specifications, Site Conditions, and Supplier Evaluation — complete selection evaluation framework; Granulator Blade Replacement Procedure — understand blade replacement procedures, easier to evaluate operational difficulty during trial.