Belt Scale Accuracy in Heavy Industry

Introduction and Relevance

Belt scales with load cells continuously and automatically weigh bulk materials on conveyors. In heavy industry (mining and beneficiation plants, cement plants, etc.), these systems are important for ore accounting, raw material dosing control, and process improvement. Accuracy requirements are high — even a fraction of a percent error can result in significant financial losses due to unaccounted material or deviations in mixture recipes. Therefore, achieving 0.5% or 1% accuracy on belt scales is very important. Modern belt scales, with proper installation and maintenance, provide an error of about ±0.5%, and some models — up to 0.125%.

In the harsh conditions of the mining and cement industries, where conveyors carry tons of abrasive material, to achieve the declared accuracy, many factors must be considered and several rules must be followed.

Article objective: to provide a technical overview of factors affecting belt scale accuracy and methods to maintain high measurement accuracy even with high material flow and in challenging conditions. We will examine the influence of mechanical and operational factors (belt tension, roller geometry and supports, flow uniformity, temperature, vibration, humidity), the role of signal processing, belt scale calibration methods, standard requirements (OIML, ISO, DSTU), and typical installation errors. The summary will include a practical checklist for belt scale installation and setup, a table of typical conditions and corresponding corrections, and examples of economic effects (ROI) from reducing error by 0.5–1.0%.

Factors Affecting Belt Scale Accuracy

Belt scale accuracy is the result of combining many factors. The main ones can be divided into mechanical (geometry and conveyor condition), operating conditions (material feed, environmental conditions), and electronic (signal processing, calibration). Let's examine each factor separately.

Conveyor Belt Tension

Belt tension is one of the most important factors. Variable or excessive tension creates extra forces on the weighing station and understates or overstates readings. It's best if the belt has minimal and stable tension in the weighing zone. Therefore, scales are placed closer to the tail section of the conveyor — where tension is lowest and most stable. It's undesirable to mount scales immediately after tensioning units or near the drive drum, where tension often changes.

During operation, tension fluctuates due to temperature, amount of material on the belt, starts and stops, and other factors. To keep tension constant, it's better to install a counterweight tensioning device. Such a unit automatically eliminates sagging and adjusts tension to conditions, keeping the belt tensioned without noticeable fluctuations. The mechanism moves freely and evenly pulls the belt, compensating for temperature elongation and other changes. Screw (static) tensioners are appropriate only on short conveyors where belt length change is small. Thus, constant tension is the foundation of scale accuracy.

It's important that tension is similar before and after the scales. If a drive or brake is immediately after the weighing section, tension fluctuations occur. The weighing section is placed at a distance from zones with variable tension. If the conveyor route has convex or concave sections (vertical bends), scales should be placed far from places where the belt inclination angle changes: at least 12 m from curvature transition points for concave sections and 6–12 m for convex ones. This way the belt runs evenly on the scale, without additional bending forces.

Consequences of Incorrect Tension

Incorrect tension causes both constant errors (for example, constant overstatement or understatement of readings due to belt pressing against sensors or friction) and unstable zero (when an empty belt gives a "floating zero").

From practice: if you ensure the minimally required tension and keep it constant — for example, with a well-adjusted counterweight tensioner — the error can be significantly reduced. Therefore, an automatic tensioning device is a mandatory condition for 0.5% accuracy class.

Temperature and Tension

With strong temperature fluctuations, the belt length changes, and without counterweight, tension noticeably "walks". Readings can drift throughout the day: some in the morning, others at noon. The solution is a tensioner with counterweight that compensates for temperature elongations.

On long conveyors, a loop tensioner can be installed, which helps keep tension independent of temperature, wear, etc.

Conclusion: stable correct tension is a mandatory condition for high accuracy. Check if the conveyor has an appropriate tensioning mechanism and if it works properly.

Geometry and Alignment of Roller Supports

Roller supports in the weighing zone are essentially the scale platform. Their geometry and installation determine what signal the load cells receive. The main things: level installation, identical elements, and sufficient length of the weighing section.

Skews or different roller heights lead to part of the weight going to neighboring supports or extra vertical or horizontal forces appearing. Precise alignment is very important here.

At least two supports before and two after the weighing (for better accuracy — three or more on each side) should be set level with the weighing station. In practice, this is checked with a taut wire or laser level along the top edge of the rollers. They are aligned with shims under the support posts.

All roller supports in the scale zone must be of the same type: same design, roller diameter, trough angle, and preferably one manufacturer. If you mix supports with different angles, the load distribution will change and calibration will be inaccurate. The distance between supports must be the same so the platform is symmetrical.

Self-centering supports (which align the belt) are not placed close to the scales, otherwise their movements will affect the readings.

Weighing Platform Length

The longer the belt section on load cells, the more stable the readings. Simple models have one roller support (short base), more accurate ones have 2, 3, or more. Multi-roller scales even out the load, so local belt irregularities or individual lumps have less effect on error. With proper installation, such scales give more stable readings and maintain 0.5% class even on large flows.

During installation, ensure the belt lies tightly on all weighing rollers. If there's a gap or the belt lags (due to stiffness or route shape), part of the mass is not weighed.

Effect of Rollers on Zero

Before startup, check that roller supports don't create extra efforts and skews. The weight of the empty belt is compensated automatically (auto-zero) or zero is set manually. If any support jams (bearings don't turn) or there's dirt under it, zero displacement occurs and zero "floats". Therefore, rollers must be clean, lubricated, and rotate freely.

Summary

The weighing section must be prepared carefully. Make sure that:

all supports are level and identical;
the belt lies symmetrically, without skews;
there are no extra contacts near the scales — scrapers, sides, guides, etc., that add resistance.

Then the load cells will measure only the weight of the material — as needed.

Stability and Uniformity of Material Feed

Uniform flow on the conveyor is an important condition for accurate weighing. The principle is simple: weight on belt × speed. When feeding is jerky or with large fluctuations, oscillations appear: during peaks, belt tension increases, support vibration occurs, and the controller doesn't have time to correctly process rapid changes.

For maximum accuracy, uniform belt loading must be ensured. This is done by:

installing feeders (dosers) with adjustable feed;
mounting flow guides or splitters above the belt to distribute material in an even layer.

The scale is placed at a distance from the loading point — at least one step between roller supports after the material drop point. Over this distance, the material has time to distribute evenly across the width and settle.

If you mount the scale right under the loading, readings will be unstable: impact loads, chunk bouncing, material hasn't "settled" yet.

Rule: scales are installed on a horizontal section after loading, where material lies evenly and calmly.

Uneven Flow and "Non-linearity" of Readings

When flow changes abruptly, readings may change not proportionally to consumption. The scale is calibrated at one productivity, but at significantly higher rates the belt behaves differently (different tension, friction, etc.) — hence additional error.

To avoid this, it's useful to do calibration at several flow points, for example at 50% and 100% of maximum. This way the controller accounts for how readings change with increasing flow. In more complex systems, real-time speed compensation and simple loading profile corrections are added.

If you can't even out the feed (for example, the conveyor receives material in uneven portions from an excavator), smoothing algorithms in the controller will help. But first — mechanics, then filters. From experience, intermediate dosing bins, levelers (combs), flow splitters, and other simple solutions significantly improve accuracy and repeatability of readings.

Effect of Temperature, Vibrations, and Humidity

Belt scales are sensitive to operating conditions. In workshops and quarries there are often very low or high temperatures, vibrations, dust, and humidity. This affects accuracy. Below — how to reduce this effect.

Temperature

Most scales with load cells operate within approximately −20 to +60°C. There's temperature compensation, but sharp changes still cause zero shift and sensitivity change. Metal slightly changes dimensions, sensors also react to cold and heat.

After switching on, let the system run without load for 15–30 min, then set zero.
If the temperature range is very wide, do seasonal recalibration (in cold and warm periods).
Protect electronics from direct sun: canopy, housing, ventilation.

Vibrations

Vibrations from drives, crushers, and impact zones add noise to the signal and "shake" the zero.

Place the weighing section on a rigid foundation, away from impact areas of the route.
Don't place scales close to the drive, brake, and material drop point.
Use dampers or rubber pads on auxiliary supports (not under load cells).
Run cables separately from power lines, ensure reliable grounding.
In the controller, turn on moderate time averaging to remove trembling without "smearing" the signal.

Humidity and Dust

Condensation, water, and dust harm electronics and mechanics, cause corrosion and current leaks.

Use sensors and boxes with protection class not lower than IP65, better IP67.
Install sealed cable entries, make drainage, put silica gel in junction boxes.
Keep detachable connections above the dust and water zone, make "drip protection" on cable loops.
Cover the weighing section with housings. Install scrapers for belt cleaning.
Regularly remove buildup from rollers and under the platform. Follow cleaning schedule.

Briefly

Stable temperature, less vibrations, and dry, clean zone — more accurate readings.
First bring order to mechanics and conditions, then select filters and settings.

Vibrations

Belt scales measure force from material mass, so any external forces from vibrations distort readings. Sources of vibrations: crushers, screens, conveyor drives, belt joints, worn or dirty rollers.

During installation, avoid zones with strong oscillations. Place the weighing section on a rigid frame that doesn't "play" and doesn't resonate with neighboring equipment. If the scale is on a separate section — check the fastening: bolts tightened, no play, frame intact.

Some scales have dampers or rubber inserts that separate the weighing platform from the frame. Use them on auxiliary supports (not under load cells) to not transmit oscillations to sensors.

High-frequency vibrations give noise in the load cell signal. The controller, averaging noise, can also "smooth" the useful signal — delay and additional error appear. For belt scales, the signal-to-noise ratio is worse than for static ones because mass is distributed along length, so vibration protection is especially important.

How to Reduce Vibration Effect

Place scales away from drive, brake, and impact loading points.
Ensure frame rigidity, support alignment, and correct belt tension.
Replace worn rollers, remove buildup, align belt joints.
If necessary, apply dampers on auxiliary supports and isolate cables from vibrating parts.
In the controller, turn on moderate smoothing (averaging, median filter) to remove trembling without major delay.

Conclusion: minimize mechanical oscillations, and use filters as an addition when completely removing vibrations is impossible.

Wind and Drafts

On open conveyors, strong wind can lift the belt, press on material, and cool sensors differently. This adds error.

Cover the weighing section with housing or wind shields.
If possible, place scales in a protected area of the route.

Indoors, drafts are rarely critical, but it's better if the scale zone is stable and isolated from air flows.

Humidity and Buildup

High humidity usually doesn't harm electronics if there's normal protection (about IP53–IP65). The problem is wet material and condensation.

Wet raw material sticks to the belt and rollers, gives zero shift and "adds" extra mass.
Install scrapers before and after scales. Regularly clean the weighing section.
In harsh conditions, use air blowing or heating so the belt stays clean.

Condensation and Contact Corrosion

Condensation in junction boxes or on boards causes electrical noise and failures. To prevent this, seal all connections and use sealed cable entries that don't let water in. In environments with aggressive vapors (cement dust, fertilizers), protect contacts from corrosion: use anti-corrosion coatings, sealed connectors, gaskets, periodically inspect and renew contact lubrication.

Place junction boxes above water and dirt zones, make "drip protection" on cable loops.
Provide drainage or valve for moisture removal.
Keep cables separate from power lines, ensure reliable grounding.

Summary

Environmental conditions significantly affect accuracy. Most problems can be prevented:

vibrations — by proper scale placement and dampers;
buildup — by scrapers and regular cleaning;
temperature shifts — by competent calibration and thermal compensation;
wind and moisture — by housings, sealing, and connection protection.

The main thing is to know weak points and minimize their impact in advance.

Algorithmic Filters and Signal Processing

Scales like VKM-2T have digital filters. They remove noise and vibrations, smooth short oscillations, and increase reading reliability. Use them moderately: it's important to understand what each filter is for.

The main signal is the load per unit belt length (kg/m) multiplied by speed. The signal is "live": each piece of material, passing through the weighing section, gives its triangular pulse. When there are many such pulses, fluctuations appear. The controller sums them at high frequency (hundreds of measurements per second), so integration itself partially filters small oscillations.

Smoothing (Low-Frequency Filters)

To reduce the effect of vibrations and random jumps, time or belt length averaging is used. For example, displaying productivity as an average over the last 5 seconds — this way random peaks disappear. Strong smoothing gives calm readings but adds inertia; weak — readings are "lively" but with more noise.

Adaptive Filters

More complex methods are adaptive filters. For example, a Kalman filter can distinguish noise from useful signal and correct readings. There are examples where such an approach reduced scatter and improved accuracy during flow changes.

Another approach is filtering by belt rotation cycle. If a full rotation takes, say, 60 seconds, you can track repeating surges (for example, a heavy joint repeatedly) and remove them programmatically.

Important Limitation

Digital filters don't cure systematic errors and installation flaws. They only reduce random noise. If readings "drift" over time (buildup, slow sensor change), auto-zero and maintenance are needed, not stronger filtering.

Auto-Zero

Auto-zero is activated on schedule or when shift is detected. This allows the controller to correct zero readings if they shift due to temperature changes, buildup, or other factors. For example, if the weight of an empty belt shows some value.

Practical Filter Setup Tips

First bring order to mechanics and feed, then adjust filters.
Start with a short smoothing window and increase gradually so as not to "squeeze" the signal.
If there's a choice, set smoothing both in seconds and in belt meters.
Set up filtering separately for indication and separately for 4–20 mA and Modbus outputs: output usually gets less smoothing.
After filter changes, check scale readings in operation.

Briefly

Mechanics and uniform flow are priority; filters are supplementary.
Adaptive methods are useful when noise has a repeating character or conditions change frequently.

Filter Conclusion

Use all useful controller functions: smoothing, calibration, testing.

Proper smoothing settings noticeably improve accuracy.

Important balance: too much smoothing slows response to real flow changes.

Select parameters in practice so that:

scales don't react to random vibration peaks;
and at the same time quickly react to real load increase or decrease.

Belt Scale Calibration Methods

Calibration is adjusting coefficients so readings are correct. Calibrating belt scales is more complex than static ones: you can't just put weights on a platform and immediately know the exact mass. Belt tension, speed, flow dynamics, and other factors must be considered. For proper calibration, follow manufacturer instructions.

There are several belt scale calibration methods:

Direct Calibration with Real Load

The most detailed method: a certain batch of material is passed through the scales, then this same batch is weighed by another, control method (for example, on railroad scales or in a bin of known mass). The difference between readings gives a correction. The method well imitates real operation, so it's considered most accurate.

Pros: high reliability, accounts for real conditions.
Cons: complex and long to perform; requires organizing a control sample and third-party weighing, which is hard to do without stopping the process.

Indirect Methods

Static Calibration with Weights

Standard weights (or loads of known mass) are installed on the weighing section — directly on the belt or through special levers that press on the frame. Weight mass is taken considering maximum mass. Simply: they imitate the load expected in operation.

Pros: quick and convenient; no need to stop production for long.
Cons: static loading doesn't account for conveyor dynamics — belt tension, friction, movement. Because of this, scales can be accurate on the bench but give deviations during movement.

To reduce error, additional calibrations with the conveyor running are performed.

Calibration with Load Hoist ("Lifter")

Some scales have a stationary mechanism that lowers a known load onto the frame through a lever. At rest, the load is raised; for checking — it's lowered and creates a set force on the weighing section.

Pros: quick regular checking with one button press; easy to notice if settings have "drifted".
Cons: this is essentially static loading; doesn't account for belt movement dynamics, so doesn't suit as basic calibration.

Conclusion: "lifter" is convenient for repeatability control, and basic setup is better done with material.

How Often to Calibrate

After installation, new scales are mandatorily calibrated and pass verification. Then — according to production requirements: usually verification once a year, and between it — checks and adjustments as needed.

Practical Schedule

Daily (quick check): empty run — see if mass "accumulates". This is a sign of zero shift; fix with auto-zero or manually.
Periodic: verification for commercial accounting and full calibration. If needed — light coefficient correction.

When to Do Unscheduled

after belt, roller, drive replacement or frame repair;
after moving scales or changing conveyor angle/speed;
after incidents (impacts, significant buildup, flooding, overheating).

Typical Installation and Operation Errors

Below are common errors that reduce accuracy. Avoid them during installation and operation.

Wrong Installation Location

Scales are placed "where convenient", not "where needed": right after loading or on a bend. There the belt is unstable and tension is variable. Solution: level horizontal section closer to tail drum, away from transfers and bends.

No Tension Compensator

Without a tensioning device or with an incorrectly adjusted tensioner, readings "float" with temperature and loading changes. A counterweight is needed; if impossible — at least seasonally adjust screw tension. Without stable tension, 0.5% class is unattainable.

Uneven or Broken Roller Supports

"Screwed on by eye" — got skew. Or the weighing section stands where neighboring rollers have sagged. Part of the weight goes to neighbors — scales understate readings. Solution: precise support alignment before calibration, replacement of worn rollers.

Different Roller Types in Scale Zone

Weighing support with 20° trough angle, neighboring ones — 35°, or different roller diameters. Belt profile becomes uneven — mass distribution is distorted. Solution: all rollers around scales — same type and model.

Closely Placed Self-Centering Supports

Rotating (self-centering) supports transmit their movements to the weighing section and add fluctuations. Keep them at a distance.

Poorly Secured Frame, Vibration

If the section with scales isn't rigidly connected to the conveyor frame, it can sway. During heavy batch passage, the frame bends — readings are understated.

strengthen the frame, install braces;
anchor to foundation;
use anti-vibration pads (not under load cells).

Electrical Interference

Cables from load cells and encoder, laid next to power ones, catch induced noise — jumps and drift appear.

run signal cables separately from power ones, in metal pipes or trays;
use shielded cables, ground shield and housing at one point;
avoid "ground loops", make reliable terminal connections.

Incorrect Speed Sensor Installation

The encoder must read real belt speed. On the drive drum, slipping is possible; on a broken roller — trembling.

place sensor on clean, non-lagged drum (often tail) or on separate pressure wheel without slipping;
if using cart with wheel on lower run — make spring pressure and place near support so wheel doesn't bounce;
ensure coaxiality, reliable fastening, correct pulse polarity.

Ignoring Zero and Taring

After installation or cleaning, the scale must be zeroed on empty belt. Otherwise, initial error goes into each reading. Material residues act as permanent tare.

run empty belt at least one full cycle and verify readings ~0;
if zero "floats" — perform zero setting (auto or manual) and find the cause.

Disabled or Unconfigured Auto-Zero

Without auto-zero, sensor drift accumulates. Turn on and configure auto-zero: intervals, tolerances, trigger condition on empty belt.

Briefly

rigid frame and absence of resonances;
separate routes for power and signal cables, single-point grounding;
correct encoder location — without slipping and bouncing;
regular zeroing and zero control.

The list is not complete, but here are the most common errors. Many maintenance people will recognize their situations.

The main thing: belt scale accuracy is established during installation. Then it's maintained by proper operation and care.

In the next section will be a simple checklist for installation and setup — it will help quickly check all critical points.

Checklist for Proper Conveyor Scale Installation and Setup

Use this list during belt scale installation and startup to achieve maximum accuracy.

Scale Location

Horizontal straight section, closer to tail drum (where tension is minimal).
After loading point — at least one span between roller supports, so material "settles".
Not on profile bends; maintain ≥6–12 m to route angle change points up/down.

Conveyor Belt

Belt is serviceable, without significant joint thickening.
If possible — joints covered by vulcanization; mechanical splice thickening removed/ground.
Scale zone is clean: no buildup on belt and rollers.

Belt Tension

There's a working tensioning device; priority — counterweight (gravity).
Counterweight moves freely, removes sagging; nothing jams.
If only screw tensioner — seasonally adjust (temperature, wear).

Roller Supports in Scale Zone

Align all weighing and neighboring supports in one plane.
Check with taut wire or laser level.
Ensure supports are identical by model, roller diameter, and trough angle.
Secure supports rigidly, remove play.

Weighing Section Length

For multi-roller scale, verify belt fits tightly to all rollers; if needed, set required sag.
For single-roller, ensure at least two supports before and after in one plane for belt stabilization.

Auxiliary Devices on Belt

Place scrapers and cleaners before weighing section; in scale zone they don't touch belt.
Self-centering (rotating) supports — no closer than two spans to scales.
Secure sides and covers firmly; nothing presses from above or rubs against belt.

Speed Sensor

Install on tail drum or separate pressure roller with contact without slipping.
Check absence of sliding; if needed, use spring pressure wheel.
Avoid vibration areas; preferably mount on smooth (not ribbed) drum.
Make sensor connection reliable, without play and protected from impacts.

Electrical Connection

Use shielded cables for load cells and encoder.
Route them separately from power lines, preferably in metal pipes or conduit.
Ground cable shields.
Check contact reliability in terminal boxes and presence of moisture protection.

Calibration

Perform calibration by chosen method — preferably standard chain or real material.
Enter obtained coefficients.

Zero Setting

After installation, run empty belt for 1–2 full circles and perform zeroing.
Ensure zero is stable (deviation no more than allowable).
If possible, make several control runs with known mass (or with chain) at different flow levels. And recheck calibration coefficients.

Testing

Start conveyor with material and compare readings with control measurement (if available) or expected data.
Ensure readings are stable, without large oscillations and shifts.
Track one belt cycle and check for periodic peaks (may indicate joint or roller problem).

Documentation

Record calibration results and entered coefficients.
Make short "as installed" table to track accuracy changes later.

Use this checklist to systematically check all important installation details. Most errors appear when one or several such points are ignored. Don't rely on "maybe" or only on declared 0.5% class — conditions for this accuracy must be ensured on site.

"Condition → Correction" Matrix for Accuracy Improvement

Below is a matrix of typical problematic conveyor scale operating conditions and corresponding actions. It will help quickly determine what exactly worsens accuracy in your conditions and suggest how to fix it:

Problem condition / factor	Possible correction / solution
Unstable belt tension (changes with load and temperature)	Install or adjust counterweight tensioner for automatic sag compensation. Reduce span between drums or add intermediate tensioning drum.
Joint thickening (mechanical splice)	Ensure even belt thickness: use vulcanized joint without thickening or calibrate accounting for joint. If effect is significant — position scale so joint doesn't always hit weighing zone with material, or increase number of weighing rollers for averaging.
Crooked roller installation (skewed weighing support)	Realign roller supports: use wire or laser, set in one plane. Place adjustment plates under support legs. Check level after bolt tightening.
Strong structure vibrations (nearby heavy equipment, conveyor resonates)	Move installation location away from vibration source; install damping pads or shock absorbers under weighing section; verify frame is rigidly secured without play; if needed, add moderate digital smoothing in controller.
Uneven material flow (jerks, large pieces)	Add flow stabilization: feeder-doser, vibratory chute or other dosing device; install distribution combs/deflectors for even layer across width; increase integration constant (more time smoothing), considering slower reading response.
Zero drift over time ("growing" empty mass)	Check and remove buildup on belt and rollers; turn on auto-zero during work pauses; ensure load cells aren't overloaded and electronics are warmed to stable temperature before measurement.
Daily/seasonal temperature fluctuations	Use scales with specified temperature compensation; do control calibrations/verifications with significant temperature changes; protect weighing section from direct sun; ensure counterweight tensioner for temperature elongation compensation.
High humidity, buildup (wet material, moist belt)	Install quality belt cleaners before and after scale, regularly clean weighing support. Consider conveyor covering for precipitation protection. If material is hygroscopic — monitor its moisture, as moisture change changes dry matter mass (important for mass balances).
Incorrect speed sensor operation (slipping, jerks)	Check sensor mounting and contact with belt/shaft without slippage. If needed — pressure wheel with greater force or high-friction rubber. Check encoder cable shielding and eliminate electrical interference. Set "pulse value" in controller by actual belt circle length.

The matrix doesn't cover absolutely all cases but includes the most common problems. Under special conditions (for example, aggressive chemistry, explosive dust zones), additional measures are needed — this is more about equipment reliability than metrological accuracy.

Using "condition → correction" advice, you can quickly find the cause of scale performance deterioration and take needed corrective actions in time.

ROI Examples: Economic Effect from Accuracy Improvement

Costs for accurate scales pay back quickly, especially on large productions. Below is a conditional but close-to-reality example to calculate savings even from reducing error by fractions of a percent.

Input Data

A mining plant accounts for ore with belt scales. Conveyor productivity — 200 t/h, operation — 16 h/day, about 300 days per year. Annual flow — 960 thousand tons. At cost of $20/t this is ≈ $19.2 million per year of material.

If Accuracy is 5% (accuracy class worse than 2)

Unaccounted mass can reach up to 48 thousand t/year. In money — about $960 thousand yearly. These are direct losses from inaccurate accounting.

Improvement to 1% (class 1)

Losses decrease to ≈ $192 thousand per year. Savings — approximately $768 thousand yearly. Compared to quality weighing system cost, this amount is several times larger — meaning investment pays back very quickly.

If applying newest solutions and achieving 0.5% error (class 0.5), annual losses will be only ≈ $96 thousand, and savings compared to 5% — $864 thousand. Even transition from 1% to 0.5% gives about $96 thousand more savings per year for this scale.

Cost Dependence on Accuracy Class (for given example)

Class / accuracy	Daily error, t	Annual error, t	Annual losses	Savings vs 5%
5.0% (class >2)	~160 t	~48,000 t	$960,000	–
1.0% (class 1)	~32 t	~9,600 t	$192,000	$768,000
0.5% (class 0.5)	~16 t	~4,800 t	$96,000	$864,000
0.25% (class 0.2)	~8 t	~2,400 t	$48,000	$912,000

Example of error cost calculation for 960 thousand tons/year at $20/t (according to Siemens data)

Each accuracy improvement directly reduces material losses. For a cement plant or quarry, this gives not only direct financial effect (less raw material "goes nowhere"), but also additional benefits: more stable mixture composition, better product quality, fulfillment of contract mass conditions.

ROI for 0.5% accuracy systems is usually counted in months, not years. For example, transition from class 2 (±2%) to class 0.5 (±0.5%) can save ≈ $800 thousand per year. If modernization cost $100 thousand, payback is less than 2 months. Add fewer downtime (less frequent readjustments and stops needed) — and effect becomes even more noticeable.

Conclusion: accuracy is not only about measurement, but also about money. Reducing error by 0.5–1% on high-productivity conveyor gives hundreds of thousands of dollars savings. So it's worth investing in maximum accuracy of belt tension scales — these investments pay back many times over.

Conclusions

Achieving high belt scale accuracy in heavy industry is realistic, though the task is multi-faceted. We outlined key factors and practical steps that allow reaching 0.5% class even on lines with high flow of abrasive materials. Main advice:

Mechanics and installation — priority. Correct location (level section, stable tension), precise roller alignment and uniform support geometry — basis of accuracy. Most errors come from mechanical flaws.
Belt tension — critical. Install gravity tensioner and monitor its operation. Tension must be constant and minimally sufficient, otherwise stable 0.5% is not achievable.
Environmental control. Protect scales from extra vibrations (mechanically and with filters), keep belt and rollers clean (fight buildup), compensate temperature effects (auto-zero, counterweights, regular verification). Don't let "noise" override material weight.
Smart functions help. Use digital smoothing, auto-zero, multi-point linearization, angle compensation. Properly configured integrator removes random oscillations without sensitivity loss.
Calibration must be quality. According to instructions. With mandatory periodic reviews. Check scales regularly, don't wait for large error accumulation.
Documentation and personnel training. Keep scale setting log and train operators to read indications (what jumps or drift mean). Culture of proper operation ensures long-term accuracy.

Summary

Following this advice, conveyor strain gauge scales like VKM-2T and their analogs will work maximally effectively and stably maintain 0.5–1.0% class even in harsh conditions of mining and cement plants. Accuracy is not luxury but necessity, ensured by engineering approach, regular control and attention to details.