Indonesian Vegetables: Metal Detector & X-Ray 2025 Guide

A practical, field-tested playbook to cut metal detector false rejects on wet/salty vegetables, tune frequency and phase for product effect, size your aperture right, and know when to move to X-ray. Built from our Indonesia-Vegetables Team’s day-to-day work on export lines across Indonesia.

We cut false rejects by 72% in 90 days on vegetable lines using this exact playbook. That’s on brined cucumbers for acar, salty chili pastes for sambal, and IQF frozen packs where ice crystals make detectors “hear ghosts.” Here’s what actually works in 2025, without overspending or compromising sensitivity.

The 3 pillars of stable metal detection on vegetables

1. Control the product effect. Wet, salty, acidic, or still-warming products behave like metal. Your detector sees conductivity and moisture as a signal. We minimize and offset that signal.

2. Engineer the aperture and handling. The single biggest lever on sensitivity is aperture size. The second is how the pack passes through the field. Orientation and spacing matter.

3. Validate and document. Sensitivity targets are useless if you can’t pass them during production. We set realistic targets, prove them with certified wands, then lock the setup with records that survive buyer and BRCGS audits.

This leads us to a practical rollout timeline.

Weeks 1–2: Baseline and validation (tools + templates)

• Map your SKUs and worst-case packs. High-risk examples in our world: brined Japanese Cucumber (Kyuri), sambal with Red Cayenne Pepper (Fresh Red Cayenne Chili), and IQF like Frozen Mixed Vegetables with ice crystals.
• Establish achievable targets by pack size and aperture. Typical 2025 conveyor targets we sign off on:
  • 2.5 mm ferrous
  • 3.0 mm non-ferrous
  • 3.5 mm stainless 316 For 1 kg bags and tall packs, 4.0 mm 316 may be realistic depending on aperture height.
• Verify your test pieces. Use certified 2025-dated wands or spheres in Fe, Non-Fe, and 316. Test in product, at the geometric center and edges. Don’t rely on air tests.
• Record product temperature, salinity, and pH. Product effect rises with conductivity and temperature. If your acar brine swings 4–6°C through the shift, detector stability will suffer.

Takeaway: You can’t tune what you don’t baseline. Build a one-page spec per SKU that includes pack dimensions, temperature range, and initial sensitivity passes/fails.

Weeks 3–6: Tuning frequency, phase, and the mechanics

Here’s the thing. Most “metal detector false rejects vegetables” issues are not electrical problems. They’re product effect and presentation problems.

• Frequency selection and dual-frequency. Wet product metal detection usually improves at lower frequencies (50–150 kHz) because they’re less sensitive to conductivity. But stainless 316 detection benefits from higher frequency (300–800 kHz). That’s why 2025 dual-frequency systems that run both simultaneously generally win on brined vegetables. We start with low/high pairs (e.g., 90 kHz + 340 kHz) and let auto-learn build a product signature.

• Phase angle adjustment and product effect compensation. Use “phase teach” or “product learn” with a full belt of stable product to capture the phase of the brine signal. In my experience, two learns are better than one: do a learn at the coldest and warmest expected product temp. Many current models can interpolate between these.

• Aperture size sensitivity. Sensitivity declines as aperture height increases. As a rule of thumb, halving the height can improve detectable sphere size by 25–35%. For 1 kg vegetable bags, run the smallest practical aperture height. Use pack compression or orient narrow-edge-first so the “presented height” is minimized.

• Belt speed and spacing. Slower belts increase dwell time and can add 10–15% detection performance. But the bigger win is spacing. Only one pack should be in the aperture at a time. Use a 1.5x product length gap as a starting point.

• Orientation and seams. Metallized film seams and clip areas can spike signals. If you must run metallized packaging, use “foil mode” and accept that you’ll only catch ferrous at the surface. Otherwise, plan to move to X-ray.

• Environment. Electrical noise, vibrating conveyors, and nearby VFDs add instability. Ground the frame properly. Shield and separate detector cables from motor power. If rejects spike when a chiller or sealer kicks on, you’ve found a noise source.

Practical test: After tuning, run 100 consecutive packs. Track false rejects and pass/fail for each sphere type. You want zero false rejects over that run with spheres detected in at least three positions in the pack.

Why does my metal detector reject brined vegetables when there’s no metal?

Because salty brine changes the electromagnetic field. The detector reads that changing “product signal” as if it were metal. Phase teach, lower frequency, consistent product temperature, and tight aperture all reduce the effect. If your brine is hot or varies batch to batch, retune after each changeover.

What frequency and phase settings reduce product effect on wet vegetables?

Start low frequency (50–150 kHz) to calm product effect. Pair with a higher frequency (300–500 kHz) if you need better stainless 316 detection. Use auto-learn to lock product phase, then fine-tune phase angle manually if your unit allows. We typically land near the vendor’s default phase for “wet protein” profiles, then tweak 5–15° to eliminate drift.

Can a dual-frequency metal detector catch 316 stainless in salty vegetables without constant false rejects?

Yes, if you combine dual-frequency with tight aperture, phase teach at temperature extremes, and consistent pack presentation. Stainless 316 is the hardest to detect. It often needs 3.5–4.0 mm spheres on larger packs. If you must hit 2.5–3.0 mm 316 inside a 1 kg brined pack, you’re likely in X-ray territory.

Weeks 7–12: Scale, verify, and lock for audits

• Build a product library per SKU. Save separate learns for frozen, chilled, and ambient variants. For IQF items like Premium Frozen Sweet Corn or Premium Frozen Okra, ice crystals change over time. Relearn after 30–60 minutes if surface melt begins.
• Intermittent rejects on IQF. Ice bridges act like conductive paths. Keep product at a stable subzero temperature and reduce belt vibration. In my experience, this single step halves nuisance rejects.
• Validation and verification records. For BRCGS and buyer audits:
  • Validation: Prove the setup works. Document test piece type/size, location in pack, belt speed, aperture size, frequency/phase, and 100-pack challenge results.
  • Verification: Hourly metal checks with certified wands. Do all three metals at start, middle, and end of the aperture, and through-pack at least once per shift. Trend results by SKU and operator.
  • Change control: When you tweak frequency, phase, speed, or reject timings, note it in a controlled log with reason and approver. Auditors love clear version histories.

Need help with a stubborn line or audit-ready templates we use in our own facilities? You can Contact us on whatsapp.

X-ray vs metal detector: when to switch in 2025

• Use X-ray when:
  • You run foil or metallized film routinely.
  • You need sub–3.0 mm stainless 316 detection inside wet, salty packs.
  • You also care about glass, stones, or dense plastics.
• X-ray detection limits. For uniform-density vegetable packs, 2.0–3.0 mm stainless is realistic. Retort pouches and dense sauces vary; run a feasibility test.
• Cost comparison in Indonesia. Metal detectors: roughly USD 6k–25k installed. X-ray: USD 35k–90k. X-ray OPEX is higher. You’ll need radiation safety procedures and periodic certifications.
• Throughput. Modern X-ray handles high speeds well. But for viscous lines like sambal, a pipeline metal detector upstream of the filler is often the most cost-effective CCP.

Takeaway: If metallized packaging or ultra-tight 316 sensitivity is non-negotiable, X-ray pays for itself in reduced rework and fewer false rejects.

How do pack size and aperture height cause false rejects on 1 kg vegetable bags?

Large packs need taller apertures. Taller apertures are less sensitive and more susceptible to product effect drift across the field. If the pack “fills” the aperture inconsistently, the baseline shifts and trips the reject. Shrink the effective height with compression guides, orient the narrow side first, and keep only one pack in the field at a time.

Which test pieces should I use to validate detection on Indonesian vegetable lines in 2025?

Certified Fe 2.5 mm, Non-Fe 3.0 mm, and SS 316 3.5 mm spheres in rigid wands. For bigger packs or taller apertures, validate to 4.0 mm 316 if justified by risk assessment. Always challenge in the product, centered and edge positions, and at real belt speed.

How do I document tuning changes to satisfy BRCGS or buyer audits while reducing false rejects?

Use a controlled “Detector Setup Sheet” per SKU: product, pack size, aperture, frequency pair, phase angle, belt speed, reject timing, temp/salinity window, and reference photos. Attach validation data and change-control entries with date, reason, approver, and post-change verification results. Keep 12 months of hourly metal check records and trending charts.

5 mistakes that keep vegetable lines stuck in false-reject purgatory

1. Chasing maximum sensitivity that your process can’t sustain. Set targets that pass during production, not just at commissioning.
2. Learning the product once at startup temperature. Then production warms up and everything drifts. Teach at both ends of the temperature window.
3. Oversized apertures “just in case.” Engineer the aperture to the tallest pack actually run. Extra headroom costs you sensitivity.
4. Running two packs inside the field. Space them. Put a pacing roller upstream if needed.
5. Ignoring packaging seams and clips. If you must stay with metallized film, consider X-ray. Or rotate the pack to present the seam consistently.

Field examples from our exports

• Pickled cucumbers for acar: Dual-frequency with phase teach at 4°C and 10°C cut false rejects 68%. Tightened aperture from 150 mm to 120 mm and oriented packs narrow-edge-first.
• Sambal base with red cayenne: Pipeline detector upstream of the filler achieved 3.0 mm 316 with stable performance. Downstream conveyor detector was retired as CCP and used as an extra PRP.
• IQF mixed veg: Stabilized product at −18°C, slowed belt from 35 to 28 m/min, and increased pack spacing. False rejects dropped to near zero while meeting 3.5 mm 316.

If you’re exploring new SKUs or packaging formats, browse what we export and how we grade and pack for quality. View our products.

Quick troubleshooting checklist

• Confirm certified test pieces and do through-pack tests.
• Verify product temperature and salinity are within the learned range.
• Reduce aperture height or change orientation to minimize presented height.
• Relearn at two temperatures. Use dual-frequency if available.
• Slow belt slightly and ensure one pack in the field at a time.
• Check grounding, cable routing, and nearby electrical noise sources.
• If packaging is metallized or targets are sub-3.0 mm 316 in brine, run X-ray feasibility.

The reality is, stable detection is a process, not a setting. When we tune frequency and phase to the product, engineer the aperture, and document rigorously, false rejects drop and buyer confidence rises. That’s the standard we run in Indonesia, and it’s what your line can run too.