Tank, Silo and Hopper Weighing with Load Cells: Worked Examples

To weigh a tank, silo or hopper, you support the vessel on three or four load cells, add up their signals and subtract the weight of the empty vessel, so the display shows only the contents. The cells are usually shear beam, compression or canister types, fitted with mounting hardware that lets the vessel expand and contract without binding. The vessel itself must be free to move a tiny amount, which means flexible pipe connections and no fixed supports sharing the load. This guide walks through how it works, how to size the load cells with worked examples, and how to avoid the mistakes that cause drifting or wrong readings.

Why weigh a vessel instead of measuring level?

Level sensors tell you how high the product is, not how much it weighs. Weight tells you the real quantity, whatever the product’s density, how packed it is, or how it piles up. That matters in several situations:

• Powders and grains: they form cones and bridges, so level readings can be misleading.
• Liquids that change density: temperature and concentration change how much a litre weighs.
• Batching: recipes are usually written in kilograms, not litres.
• Stock control: you can see exactly how much is left, and prove how much was delivered.

How a weighing vessel works

1. The vessel sits on three or four load cells, usually under its legs or lugs.
2. Each cell measures its share of the total weight.
3. A junction box combines the signals.
4. An indicator or transmitter converts them into a weight reading, which can be shown on a display or sent to a control system.
5. When the vessel is empty, the reading is set to zero. From then on the display shows only the contents.

The ideas are the same as for a platform scale. The difference is that a vessel is tall, can be exposed to wind, and has pipes attached to it, all of which affect the result.

Choosing the load cell type

Examples from our range include the Sensortronics 65016-W (1,000 to 100,000 lb, stainless steel, IP67, designed for tank and bin weighing), the Sensortronics 60063 S-type for hanging hoppers, and the Revere RLC ring torsion cell for low-profile hoppers. For more on matching types, see load cell types. For mounting hardware, see the Revere ASC-DSC mounting assemblies in our accessories.

Worked example 1: a four-leg liquid tank

A food business has a stainless steel mixing tank on four legs.

• Empty tank weight (dead load): 1,200 kg
• Maximum contents: 8,000 kg
• Total at maximum: 9,200 kg

Step 1: Share the load. With four cells, each carries about 9,200 divided by 4, which is 2,300 kg at full load.

Step 2: Add a safety margin. Wind, agitators, filling surges and uneven legs mean the load will not be shared perfectly. A margin of 1.5 times is a common starting point, which gives 2,300 × 1.5 = 3,450 kg per cell.

Step 3: Choose the next standard size up. Load cells come in standard capacities. A 5,000 kg (5 t) cell is the sensible choice here.

Step 4: Check the resolution. Four 5 t cells give a total capacity of 20 t. Weighing 8 t of product on a 20 t system is fine for many batching jobs, but if you need to measure to a few kilograms, discuss the accuracy needed with your supplier, because oversized cells give less signal per kilogram. Our guide to choosing the right load cell explains this trade-off.

Worked example 2: a three-leg grain bin

A farm has a grain bin on three legs.

• Empty bin: 2,500 kg
• Maximum grain: 20,000 kg
• Total: 22,500 kg

Each cell carries 22,500 divided by 3, or 7,500 kg. With a 1.5 times margin that is 11,250 kg per cell. The next standard size is likely 15 t or the closest available capacity, and the supplier will confirm the right choice. The bin is outdoors, so choose stainless steel, sealed cells (IP67 or better), add lightning and surge protection, and fit restraints so wind cannot lift or push the bin off the cells.

Why three legs help. Three points always touch the ground. A four-legged structure can rock slightly on uneven surfaces, so one cell may carry more than its share. With three cells the load is shared in a predictable way. If your vessel has four legs, shim and level it carefully, or consider whether three cells suit the design.

Worked example 3: a hanging hopper

A small plant has a 500 kg hopper suspended from a frame, with contents up to 1,500 kg.

• Total at maximum: 2,000 kg
• Supported on three hangers, so each carries about 667 kg
• With a 1.5 times margin: about 1,000 kg per cell

A 1,000 kg S-type tension cell, such as the Revere 9363 (50 to 10,000 kg), would suit, with rod ends or swivels so that the cell hangs freely and pulls straight.

Mounting: let the vessel move a tiny bit

Vessels grow and shrink with temperature. If they are held too tightly, the cells will twist, and the readings will drift. Good mounting does three jobs:

1. Carries the weight straight down through the centre of the cell.
2. Allows small movement sideways, so that expansion does not bind.
3. Stops the vessel falling in extreme events, using check rods or restraints set with a small gap, so that they do not touch in normal use.

Self-aligning mounting assemblies do much of this for you. See load cell installation for mounting methods by type.

Pipes, hoses and cables: the hidden problem

A stiff pipe attached to the tank acts like a second support. It carries part of the load, pushes on the tank as it moves and gives false readings. To avoid it:

• Use flexible connections (hoses, bellows or flexible couplings) on all pipes.
• Run pipes horizontally from the tank for a distance before they are fixed.
• Keep the connections the same height as the load cells where possible.
• Do not let walkways, ladders or cable trays touch the vessel.
• Support cable runs so they do not pull on the vessel.

Wind, agitators and sloshing

• Wind: pushes sideways and can lift one side of a tall tank. Use restraints and consider enclosing outdoor installations.
• Agitators and pumps: shake the vessel. Use averaging or filtering on the indicator to steady the reading.
• Sloshing: moving liquid changes the reading. Wait for the surface to settle before recording a weight.

Calibrating a vessel

After installation, the system must be calibrated so that the display shows real kilograms. There are two common ways:

• Test weights: place known weights on the vessel. This is the most direct method for smaller vessels.
• Substitution: add a known amount of material, such as water measured through a calibrated flow meter or by weighing deliveries on a weighbridge.

Zero the display with the vessel empty and record the result. See load cell calibration for details.

Troubleshooting a drifting tank scale

For deeper fault finding, use load cell troubleshooting.

Safety and compliance

Weighing vessels may contain dust, flammable liquids or hot products. Where explosive atmospheres are possible, use equipment suitable for the zone. See hazardous area load cells. If you sell product by the weight shown on the vessel, trade measurement rules may apply. See legal for trade weighing in Australia.

Frequently asked questions

How many load cells does a tank need?

Three or four in most cases, one under each support. Very large or long vessels may need more.

Can I weigh an existing tank?

Yes. The tank is lifted slightly, or the cells replace the existing support pads, with proper mounting hardware.

Do I need to empty the tank to install?

For safety and accuracy, it is best to install and zero with the tank empty.

What accuracy can I expect?

It depends on the cells, mounting, environment and electronics. Real vessel systems are often less accurate than a bench scale, because of pipes, wind and temperature. Discuss your target with your supplier.

Where can I read more?

Start at our complete load cell guide, or see load cells in batching and filling systems.

Get help with your vessel

Send us the vessel weight, maximum contents, number of supports and the environment through our contact page, and we will suggest suitable cells from our double ended shear beams, canister load cells and S-type load cells.