Gravimetric Filling: How It Works and When to Use It
Gravimetric filling measures the product you put in a container by its weight, not by its volume. A load cell under the container (or under a supply hopper) reports mass to a controller, and the controller closes the filling valve when the target weight is reached. Because mass does not change with temperature, foam or air pockets, it suits viscous, foaming, expensive, hazardous and bulk products, and any product sold by weight in Australia. This guide explains how it works, how it compares with volumetric filling, and how to decide whether it belongs on your line.
TL;DR
Gravimetric filling weighs the product as it goes in, so density, temperature and foam have far less influence on the fill than they do with volume-based methods.
It is the natural choice for products sold by weight, thick or foaming liquids, valuable chemicals and bulk containers such as IBCs, drums and jerrycans.
Volumetric filling is usually simpler and quicker for thin, consistent liquids in small containers. The right answer depends on your product, your container and your throughput.
Accuracy depends on the whole installation: load cell, vibration, air movement and how the pipework is supported, not just the controller.
Australian trade measurement rules apply to pre-packaged goods sold by measure, so your filling method must support compliant net quantities.
Table of Contents
What gravimetric filling means
In a gravimetric system the quantity is defined by mass. You set a target in grams or kilograms, and the machine fills until a scale says the target has been reached. The word comes from the same root as gravimetric analysis in chemistry, where a substance is quantified by weighing it.
The method also sits at the top of the measurement world. EURAMET’s guidance on uncertainty in volume calibration identifies the gravimetric method as the standard for calibrating volume instruments at the highest level of the traceability chain: the liquid is weighed and its mass converted to volume at a reference temperature. Put simply, when laboratories need to check a volume, they weigh it. A filling machine that weighs the product is borrowing the same principle for production.
How a gravimetric filling machine works
Most gravimetric fillers share four building blocks:
A weighing platform with load cells. The container sits on it (net-weight filling), or the supply vessel sits on it (loss-in-weight filling).
A feed device. This is a valve, pump or screw that moves product into the container, with a filling nozzle or lance matched to the liquid.
A controller. It reads the weight, decides when to slow down and when to stop, and stores recipes.
Data outputs. These connect the filler to your line controls, batch records or reporting.
A typical filling cycle
A well-set-up cycle usually runs through the same stages every time:
Tare. The empty container is weighed so only the product is counted.
Coarse feed. The valve opens fully for most of the fill to save time.
Fine feed. Flow is reduced as the weight nears the target, which allows an accurate cut-off.
Settling and checking. The scale waits for the reading to stabilise, then confirms the final weight.
Correction. The controller compares the result with the target and adjusts the cut-off point for the next container, compensating for product still in flight between the nozzle and the container.
That last step is what separates a good gravimetric filler from a simple scale with a valve. The controller learns from each completed cycle and trims the next one, so small drifts in viscosity or flow rate are absorbed rather than passed on to your customer.
Net-weight and gross-weight filling
In net-weight filling each container is tared and the product alone is weighed. This is the most accurate arrangement for bottles, pails and cans. In gross-weight filling, the container’s full weight is measured and the empty weight is assumed or subtracted. It is common on heavy bulk containers, where the scale must carry a large load and the container weight can be recorded beforehand.
Gravimetric vs volumetric filling
Volumetric filling dispenses a set volume using a piston, gear pump, time-pressure arrangement or flowmeter. It is fast, mechanically simple and very good at repeatable volumes. Our own guide to how volumetric filling works and when to use it covers it in detail. The two methods answer different questions.
Factor | Gravimetric | Volumetric |
What is measured | Mass of the product | Volume delivered |
Effect of density change | Largely removed | Fill weight changes if density changes |
Effect of temperature | Small | Volume shifts with temperature, so weight does too |
Foaming products | Handled well, since foam adds little mass | Foam can distort the volume |
Product sold by weight | Direct match | Needs density to be stable and verified |
Changing fill size | Change the setpoint | Often a stroke or timer adjustment, sometimes change parts |
Speed on small containers | Slower, as the scale needs to settle | Usually faster |
Typical sweet spot | Bulk, viscous, high-value, hazardous | Thin, consistent liquids at high speed |
The practical rule: if your product is sold by weight, or if its density moves around, weigh it. If your product is thin, consistent and sold by volume at high speed, volumetric is often the better fit. Many plants run both.
The advantages of gravimetric filling
Accuracy that does not depend on the product staying the same. A batch of sauce that is slightly thicker or warmer than yesterday’s still ends up at the same weight. This matters for giveaway: every gram over target is product you paid to make and did not sell.
A direct match to how many products are sold. Oils, chemicals, concentrates and many foods are labelled by mass. Filling by mass removes a conversion step and a source of error.
Good control with difficult products. Foaming liquids, products with particulates and viscous fluids are awkward for volume-based systems. Weight keeps counting regardless of what the product is doing as it flows.
Built-in records. Because the controller sees every fill weight, it can store them. That helps with batch traceability and with showing that your process holds its target over time.
Fast changeovers between sizes. Changing from a 5 kg to a 20 kg target is generally a recipe change on the controller, rather than a mechanical adjustment.
Safer bulk handling. Filling into IBCs, drums and jerrycans by weight lets the machine stop the fill at a known mass, which reduces the risk of overfilling a large container of chemical or flammable product.
The limits to plan around
Gravimetric filling is not magic, and a good installation plans for its demands.
The scale needs a stable environment. Accuracy depends on the load cell, material in flight, vibration and air currents. A filler placed beside a pounding press or in a draughty doorway will struggle.
Pipework can push on the scale. Rigid hoses or pipes connected to a weighed vessel can transmit force into the load cell and corrupt the reading. Flexible connections and independently supported discharge lines solve this at design stage.
Settling time costs seconds. On very small containers at very high speeds, the wait for a stable reading can limit throughput. Multi-head machines and good coarse and fine feed tuning narrow the gap.
Scale capacity must suit the container. A scale built for a 1000 kg IBC is the wrong tool for a 250 mL bottle. Resolution matters as much as capacity.
None of these is a reason to avoid weight-based filling. They are the checklist an experienced supplier works through before the machine is built.
What affects accuracy, and how it is kept
Three layers decide how close each fill lands to its target.
The weighing hardware. Load cell quality, resolution and the stiffness of the frame set the floor. Products intended for trade use are built to recognised standards.
The control strategy. Coarse and fine feed, a sensible cut-off point and self-correction from completed cycles keep the average on target and the spread tight.
Checking downstream. Inline checkweighing verifies the weight of every pack. According to Mettler-Toledo’s Australian product inspection page, checkweighers can feed results back to the filling system in real time, helping avoid overfilling and underfilling in line with relevant weighing regulations. Pairing a gravimetric filler with a checkweigher gives you two independent confirmations that the pack is right.
Which products suit gravimetric filling
The method earns its place when the product or the container makes volume unreliable, or when value and compliance raise the cost of error.
Sauces, pastes and syrups. Viscous and sometimes with particulates, their density can change with temperature and recipe.
Oils. Often sold by weight, and a small overfill across thousands of containers adds up quickly.
Chemicals and concentrates. High-value or hazardous products where overfilling is costly or unsafe.
Foaming products. Detergents, cleaners and some beverages and personal care liquids.
Flammable liquids. Weight-controlled filling can be built into equipment designed for hazardous areas.
IBCs, drums and jerrycans. Bulk containers where a few percent of error means many litres.
For thin, free-flowing liquids in small bottles at very high speed, volumetric or flowmeter-based filling often wins on throughput. If you are unsure, run a trial with your own product. Samples, not brochures, settle the question.
Australian rules: filling and trade measurement
If you sell pre-packaged goods by measure in Australia, your fill method has to deliver compliant quantities. The Department of Industry, Science and Resources’ Guide to the sale of pre-packaged goods explains that national trade measurement legislation requires accurate net measurement markings that exclude the weight of any packaging. The same guide notes that some desiccating goods, such as mushrooms and soap, are allowed a greater permissible deficiency after packing to reflect moisture loss.
This is where gravimetric filling helps in practice. A net-weight filler tares the container and reports the product mass directly, which lines up with how the marking is defined. It also gives you fill records to support your own quality checks. Confirm your obligations, including any packer or average-quantity requirements for your product and pack size, against the official guide or with the trade measurement authority before you commission a line.
Choosing a gravimetric system: a short checklist
Before you talk to any supplier, write down:
Product. Viscosity range, foaming behaviour, particulates, temperature, and whether it is flammable or corrosive.
Containers. Type, material, size range and neck or opening style.
Fill targets and tolerance. In grams or kilograms, with the tolerance your customers and the regulations require.
Throughput. Containers per hour now, and where you expect to be in three years.
Environment. Washdown, hygiene requirements, hazardous area classification, vibration and floor condition.
Integration. Conveyors, cappers, labellers, checkweighers and the data you want captured.
Support. Who commissions, trains your team, supplies spares and answers the phone when something drifts.
A short, honest brief like this lets a supplier propose the right configuration the first time. Our guide on choosing an IBC filling machine walks through the same questions for bulk containers, and the article on user-friendly filling solutions covers operator controls and recipes.
Perspective
Most filling problems we see are not machine problems. They are measurement problems. A product that changes thickness between summer and winter, a sauce that carries air, a chemical that is too valuable to overfill: volume alone cannot keep up with those. That is why we build weight-controlled filling into our bulk systems and offer customisable filling technologies across our ranges. We would rather match the technology to your liquid than push one method onto every product. Semi-automatic fillers suit growing businesses that need accuracy without a full line. Fully automatic systems suit plants where continuous operation and low error rates pay for themselves. Our advice is simple. Weigh what you sell by weight, keep the scale isolated from vibration and rigid pipework, and test with your actual product before you commit. Accuracy is a result of good design and good support, and we put both behind every machine we supply in Australia. Sandeep
Weight-controlled filling from Optima Weightech
Optima Weightech supplies liquid filling machines to Australian food and chemical manufacturers, with configurations built around your liquid’s viscosity, foaming, particulates and hazard class. Our IBC, drum and jerrycan filling machines use weight-controlled filling for bulk containers, and our fully automatic liquid filling machines are designed for continuous production with advanced control systems. If you are earlier in your growth, the semi-automatic range gives you a precise, scalable starting point.
Tell us what you fill, what container you fill it into and how many per hour, and we will recommend a configuration. Start from our liquid filling machines overview or contact the team through the Optima Weightech home page.
Where gravimetric fits in a wider filling strategy
Gravimetric filling rarely stands alone. A food manufacturer might fill sauces by weight into pails and jars while running thin dressings on a volumetric line. A chemical producer might weigh concentrates into jerrycans and drums while using flowmeters for large transfer. The point is to treat measurement as a decision for each product, not a company-wide standard.
If you are building the case for new equipment, the benefits of liquid filling machines and the guide to boosting efficiency with a liquid filling machine show where the savings usually come from: less giveaway, fewer rejected packs and less operator intervention. For food producers, top liquid filling machines for food manufacturing covers hygiene and product-specific considerations.
FAQ
What is the difference between gravimetric and volumetric filling?
Gravimetric filling weighs the product and stops at a target mass. Volumetric filling delivers a set volume using a piston, pump or flowmeter. Gravimetric is less affected by density, temperature and foam, while volumetric is generally simpler and faster for thin liquids in small containers.
Is gravimetric filling more accurate than volumetric filling?
For products whose density, temperature or foaming changes, it usually is, because the scale measures what the customer actually receives. For stable, thin liquids a well-maintained volumetric filler can be very repeatable. The best way to settle it is a trial with your own product and container.
Can gravimetric filling handle thick or foaming products?
Yes, these are among its strongest uses. Weight keeps counting whether the product is viscous, foamy or carries particulates. The nozzle, feed device and fine-feed settings still need to suit the product, which is why we configure each system around the liquid being filled.
Does gravimetric filling help with Australian trade measurement compliance?
It can support it, because a net-weight filler tares the container and reports product mass, which matches how net markings are defined. Compliance still depends on your whole process and pack type, so check your obligations against the Department of Industry, Science and Resources guide before you commission.
What can reduce the accuracy of a gravimetric filler?
Vibration, air currents, rigid pipework pushing on the weighed vessel and a scale of the wrong capacity are the usual causes. Good installation, flexible connections and a correction routine that adjusts the cut-off from previous fills keep the results tight.
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