Most articles about belt weighers talk about calibration. This one is about the things that quietly destroy the electronics before calibration ever comes into it. The integrator is the brain of the weigher, and on an Australian site it lives a hard life: sitting at the end of long cable runs, bolted to a vibrating structure, baking in the sun, breathing dusty air, and copping washdown water and every storm that rolls through. None of that shows up on a calibration report until the day the integrator will not power up, the display has gone black, or the readings have turned to noise. The good news is that the protection is cheap and mostly common sense. This guide covers what actually kills belt weigher electronics in the field, and the simple things that keep them alive.
Why are belt weighers such surge magnets?
A belt weigher is unusually exposed to electrical surges, and it is worth understanding why. The integrator sits in a cabinet, but its senses reach out along load cell and speed sensor cables that can run for hundreds of metres, strung the length of a steel conveyor. Those long cable runs act like an antenna. When lightning strikes anywhere nearby, even without a direct hit on the plant, the discharge throws out a powerful electromagnetic field, and that field induces a voltage spike into every long conductor within reach. The longer the cable and the closer the strike, the bigger the spike. It travels straight down the cable into the integrator's delicate input circuitry, and that is often the end of the input, the board, or the whole unit.
This is why some sites lose an integrator almost every storm season, while a similar unit indoors somewhere sheltered runs for a decade untouched. Exposed overland conveyors, high ground and the long wet-season storm run all raise the odds. The damage is rarely a dramatic bang; more often the unit simply behaves oddly or dies quietly, and the cause is only obvious once you know to look for it.
How do surge protection and earthing work together?
Work on or near a conveyor, or inside an electrical enclosure, needs isolation under your site’s procedures and trained, authorised people. If that’s not you, stop and call us on 1300 101 666.
Two things reduce surge damage. The first is surge protection devices: a component fitted on the incoming supply, and on signal lines where the exposure warrants it, that clamps a spike and diverts its energy away from the electronics before it reaches them. The second, and by far the more important, is earthing done properly. A surge protector has to send that diverted energy somewhere, and if the earth path is poor, corroded or missing, the protection cannot do its job. Solid bonding and a genuine low-resistance earth path are what actually save the equipment.
There is a trap here worth naming: the earth loop. If the conveyor structure is earthed at one point and the integrator cabinet is earthed at another, and the two earth points sit at slightly different electrical potentials, current can flow between them through the signal wiring itself. That shows up as noise, drift and erratic readings that no amount of recalibration will fix, and it makes surges worse. Getting the earthing arrangement clean and consistent removes a whole family of problems at once.
One more point that surprises people: surge protection devices wear out. Every spike they absorb, even a small one, does a little permanent damage inside them, and eventually a device that looks fine and may still show a green status light is no longer protecting anything. They fail silently. A surge protector fitted years ago is not a job done forever, and its condition is one of the things worth checking.
How does water get into belt weigher electronics?
Water gets into belt weigher electronics in more ways than people expect, and it does its damage slowly. The common paths in are:
- Washdown aimed the wrong way. A hose pointed straight at a cabinet or a junction box will drive water past seals that would happily shed rain.
- Glands never tightened. A cable gland that was never properly done up lets water track down the cable and into the enclosure.
- Lids left loose. A junction box lid not resealed after a speed sensor swap invites the next downpour straight in.
- Condensation from breathing. Even a sealed cabinet is not immune. As it heats through the day and cools overnight the air inside expands and contracts, drawing in humid air that condenses onto cold metal and boards each morning.
The fixes are all cheap and all about discipline: cable glands done up properly and facing downward, drip loops so water runs off the cable rather than following it into the box, and door and lid seals that are actually intact rather than perished and flattened. Junction box moisture is one of the most common causes of erratic weigher behaviour, covered from the fault side in common belt weigher faults, and it is nearly always cheaper to keep the water out than to chase the symptoms it causes.
What harm does conveyor dust do inside an enclosure?
Conveyor dust is relentless, and it finds its way into any enclosure that is not properly sealed. On its own a light coating of dust is a nuisance; the real harm is that dust is hygroscopic on many sites, meaning it holds moisture against the boards and terminals long after the air has dried out. Damp dust packed onto a circuit board bridges connections, corrodes tracks and traps exactly the moisture you were trying to keep out. The discipline is simple and unglamorous: keep cabinet and junction box doors shut, replace seals when they perish rather than when they fail, and do not leave an enclosure open on a dusty belt while you go for a part.
What do heat and direct sun do to an integrator?
A steel cabinet standing in full Australian sun is an oven, and the electronics inside it are cooking. Sustained heat shortens the life of every component, including the surge protection devices mentioned above, and it is a common reason a display fades, goes unreadable, or blanks out entirely on a hot afternoon and comes back once things cool. You do not need refrigeration to fix this. Shade is remarkably effective: a simple sun hood or a cabinet positioned to face away from the worst of the afternoon sun runs far cooler. Where a cabinet has vents or a filtered fan, keeping those clear so warm air can escape does the rest. These are among the cheapest reliability improvements available, and they are routinely overlooked.
How does constant vibration cause intermittent faults?
An integrator or junction box mounted straight onto the conveyor structure feels every bit of the vibration that structure carries, hour after hour, for years. Over months that constant shaking works terminal screws loose, fatigues wiring where it flexes, and wears connectors. The result is intermittent faults that come and go with no obvious pattern, which are miserable to chase. Two things help: sensible mounting that isolates the electronics from the worst of the vibration rather than bolting them rigidly to the source, and periodic checks that re-tighten terminals and inspect connections before a loose one turns into a callout. For the load cell wiring in particular, where vibration and moisture both take their toll, see the belt weigher load cells guide.
What do we look at on service visits?
Electronics protection is part of every service, not a separate job. While we are on site we look at:
- Glands and seals. Whether cable glands are tight and facing the right way, and whether door and lid seals are intact or perished and flattened.
- Earthing condition. Whether the earth path is clean and sound, and whether an earth loop is quietly injecting noise into the readings.
- Surge device state. The condition of any surge protection devices, because they age silently and a tired one gives false comfort while showing a healthy light.
- Cabinet interiors. We open the enclosures and read what is inside: dust staining, water tracks and corrosion tell the story of what has been getting in and where, often long before it has caused a fault.
Catching a perished seal or a loose gland at a routine visit is a five-minute job; catching it after it has killed an integrator is a very different day. How this fits into the wider care of your weighers is on our asset management page.
Frequently asked questions
Our integrator dies every storm season. Why does this keep happening?
Almost certainly induced surge coming in on the long load cell and speed sensor cables. A nearby lightning strike induces a voltage spike into those long runs without ever touching the plant, and it travels down the cable into the integrator. Repeated seasonal failures usually mean surge protection is absent, or was fitted years ago and has quietly worn out, and often that the earthing needs attention as well. It is worth having the surge protection and earthing looked at as a package before the next wet season, not after the next failure.
Can we hose down the scale area?
Yes, with a bit of care. The mechanical parts are built to get wet, but do not aim a hose directly at the integrator cabinet, the junction boxes or the cable glands. A jet driven straight at a seal will get past it in a way that rain never would. Keep the nozzle off the enclosures, and it is worth confirming the glands are tight and the seals are sound before washdown becomes routine, because water forced in during cleaning is one of the most common causes of electronic faults on wet sites.
Do surge protectors actually wear out?
Yes, and this is the part people miss: they wear out silently. Every surge a protection device absorbs does a little permanent internal damage, and over time it degrades until it is no longer protecting anything, often while still showing a healthy status indicator. A surge protector is not fit and forget. It has a service life and needs checking, and replacing periodically, as part of routine maintenance.
There is water inside a cabinet that never gets hosed. Where is it coming from?
Most likely condensation. A cabinet breathes as it heats and cools between day and night, drawing humid air in and condensing it onto cold metal and boards. Good seals slow it, and keeping the enclosure genuinely closed and the dust out helps, but some thermal breathing is normal. It is one reason we check cabinet interiors for water tracks and corrosion at every service, even on cabinets that look perfectly dry from outside.
Should the integrator be mounted somewhere out of the weather?
Where practical, yes. An integrator in shade, out of the direct washdown line and away from the worst of the vibration will outlast an identical unit sitting exposed by years. It is not always possible to move an existing installation, but shade hoods, better seals and sensible mounting achieve most of the benefit without relocating anything. If the numbers upstream matter, the electronics that produce them are worth protecting, and the same signals feed into any PLC or SCADA connection the site relies on.