A conveyor metal detector watches the material on the belt for stray metal and reacts before that metal reaches the crusher or slits the belt. We service and support conveyor metal detection equipment on site across Australian mining and quarrying, including the ADS SurroundScan Protector range and Saimo detectors. This page covers what a detector protects, how it works in practical terms, how it sits alongside magnets, and what a service visit covers.
Why do sites fit a metal detector?
Tramp metal is the loose steel that has no business being in the material: broken bucket teeth, bore crowd and ground-engaging wear parts, lengths of bar and reo, dropped hand tools, chain, and weld offcuts. One item through a crusher or sizer can smash liners and cost a shift of production. A sharp piece can slit a belt lengthways, and heavy scrap can carry through to a screen, a mill, or a saleable product. A detector is cheap insurance against events that cost far more than the detector ever will. The classic loss is a digger tooth through a crusher, a bar jamming a sizer, or an offcut opening up a belt.
That is why detectors usually sit on a straight, troughed run of belt just ahead of the gear they protect, such as before a crusher or a transfer point, where there is a clean length of belt to mount the coils and enough belt left after the trip to stop the conveyor before the metal reaches the machine.
How does a conveyor metal detector work?
At a practical level, the detector is a coil arrangement built around or under the belt that sets up a field the material passes through. When a piece of metal moves through that field it disturbs it, and the detector picks up the disturbance. What happens next depends on how the unit is set up. It can trip the conveyor to a stop, fire a marker system such as a paint spray or a flag so the spot is easy to find, or do both, so the metal can be located and pulled out of the stopped burden by hand.
How readily a detector responds to different metals depends on the design. Ferrous items are generally the easiest to pick up, while non-ferrous and weakly magnetic items such as manganese steel teeth behave differently and are caught to a different degree. The right balance between catching small items and living with nuisance trips is set on site against the material actually running, not from a brochure.
The marker side matters as much as the detection. Stopping the belt is only half the job; someone still has to find the item in a stationary heap of material. A marker that lays paint or drops a flag at the right point turns a long dig through the burden into a quick, targeted pull, which is why we treat the marker timing as part of the service rather than an afterthought.
How do detectors, magnets and TMDs fit together?
"Tramp metal detector" (TMD) and "conveyor metal detector" describe the same device. It rarely works alone. On a well-protected conveyor an overband or suspended magnet removes the bulk of loose ferrous tramp continuously, with no belt stop, and the detector sits downstream as the backstop that catches what a magnet cannot: non-magnetic and manganese items, stainless, and metal buried too deep in the burden for a magnet to lift. The magnet keeps the belt running by clearing the easy ferrous stuff, and the detector reserves its belt stops for the genuine problem items.
For the full comparison, including when a site needs a magnet, a detector, or both, see our companion guide to tramp metal detectors vs magnetic separators.
Because the pieces work as a chain, they are best kept on the one schedule. A magnet that has clogged and stopped clearing tramp quietly hands more work to the detector downstream, and a detector that has drifted lets through what the magnet already missed. Servicing them together, on the same conveyor and the same visit, keeps the whole chain honest.
Which detector brands do we see in the field?
We supply and service ADS (Advanced Detection Systems) detectors, and our manuals and training library covers the SurroundScan Protector range: the Protector HD, the Protector HD Ultra, and the low-profile Protector LP, used on aggregate and mining conveyors. We also come across Saimo metal detectors installed alongside Saimo belt scales. Where a Saimo scale is on the same conveyor, see our Saimo belt weigher service page.
These units live outdoors on a moving conveyor in dust, wet, and vibration, so the enclosures, coils, and field wiring take a beating over time, and that is where most of the service work ends up. Across brands the working principle is the same, so a mixed-brand plant can have its detectors, magnets, and belt scales looked after by the same service technicians on the one visit rather than several separate call-outs.
What service issues do we see on conveyor metal detectors?
Most detector problems trace back to the belt, the wiring, or a setting that no longer matches the job:
- False trips from the belt itself. Metal clips or splices in the belt, and damage to a steel-cord belt, all look like tramp moving through the coil. If the setup does not account for them, the belt triggers the detector every revolution and someone eventually turns the sensitivity down until it catches nothing.
- Sensitivity set wrong for the burden. Too high and the unit cries wolf all shift; too low and real tramp sails through. A setting that suited a thin, slow load can be wrong once the burden depth or belt speed changes.
- Marker systems that fire late or not at all. If the paint or flag lands in the wrong place, or the marker is out of consumable or jammed, the detector trips but the metal cannot be found on the stopped belt, which defeats the point.
- Mistracking belts. A belt wandering off centre changes the geometry through the detector and can shift how it responds or nudge the coils.
- Junction box moisture and loose terminals. Water ingress and terminals worked free by conveyor vibration cause intermittent and lost signals. These are the same field-wiring faults that plague belt scales; see common belt weigher faults.
What does a metal detector service visit cover?
A routine service proves the detector still does its job and leaves a clear record:
- Verify detection with a test piece. We pass a known metal test piece through on the running belt to confirm the unit still triggers as it should, because a detector that has quietly drifted or failed gives false confidence, which is worse than none.
- Check trip and marker timing. We confirm the belt stops or the marker fires at the right moment, so the metal can actually be found and removed.
- Inspect the coils and wiring. Coil enclosures, cable runs, glands, and the junction box get checked for damage, moisture, and loose terminals.
- Confirm the interlocks. We check that the trip signal genuinely stops the conveyor, not just lights a lamp on the panel.
- Document as-found and as-left. We record the settings we found and the settings we left, so the site has a clear before-and-after, and they go into AIMM, our asset management system, with the detector's next service date.
Looking for the SurroundScan Protector or Saimo detector manual?
Start at the nameplate rather than the search box. The Protector HD, the Protector HD Ultra and the low-profile Protector LP are three different units behind three similar names, and the marker and interlock wiring is the part that most often differs between them, so the first PDF a search turns up is usually written for somebody else's coils. Saimo paperwork is harder again, because the detector book often arrived bundled with the belt scale documents for the same conveyor rather than on its own. We do not host either maker's manuals, and the copy that matches your unit sits with the maker or with whoever supplied and installed it.
Send us the model and whatever is stamped on the plate, serial number and any board or firmware version included, and we will work out with you which document you are actually chasing. Often it turns out you did not need the PDF at all: our service technicians work from the full documentation for the detectors we look after, and we record as-found and as-left settings on every unit, so a detector that has been reset, rewired or swapped is a reload rather than a set-up from scratch on the day. Ring 1300 101 666, email admin@accurateindustries.com.au, or contact us.
Frequently asked questions
Why does it keep false tripping?
The usual causes are the belt itself, metal splices or clips, or steel-cord damage reading as tramp, or a sensitivity set too high for the burden. A mistracking belt or a wet junction box can do it too. We work through each on site rather than just winding the sensitivity down, which would leave real tramp uncaught.
Detector, magnet, or both?
They do different jobs. A magnet removes ferrous tramp continuously with no belt stop; a detector catches what the magnet misses, including non-magnetic and deeply buried items, and stops the belt so it can be pulled out. Many conveyors run both. The detector vs magnet guide walks through the choice.
Will it catch digger teeth and non-ferrous scrap?
A detector can pick up items a magnet will not, including weakly magnetic manganese teeth and stainless, though how readily depends on the unit and its setup. That backstop role is a big part of why detectors earn their place.
Do you only service ADS detectors?
No. We service and support conveyor metal detection equipment across brands, including the SurroundScan Protector range and Saimo detectors, from field experience on the same conveyors as the belt scales and magnets around them.
How do we know it is actually working?
That is exactly what the test-piece check proves. A detector can sit on a conveyor for months looking healthy while catching nothing, so periodic proving with a known metal piece is the only honest confirmation.