Capacity Calculation Of Compression Machine Hoppers

Compression machines are used in pharma industries for manufacturing tablets by compressing powders or granules using a specific tooling.

Tablet compression machine has different components that play an important role during tablet compression but in this article we will only discuss initial component of tablet compression machine which is known as hopper. If you want to read all components in dedetailead following article,

Components Of Tablet Compression Machine 


Hopper of compression machine


Image Credit

Image Source – Google | Image By – NATOLI

Compression Machine Hopper Whenever we want to compress any product, the first part of the compression machine which comes in direct contact with the product is the hopper of the compression machine.Hopper of compression machines act as a storage medium or reservoir where powder or granules are added & delivered to the dies by feeding system of compression machine.

Material Of Construction

As we discussed earlier the hopper comes in direct contact with the product so it is made of stainless steel grade 316L.

Capacity Of Hopper 

Really we are talking about the capacity of hoppers?Many of us never think about it because this concept is not very common.

Not many of us in pharma discuss hoppers, as it is just a storage medium for a compression machine but to understand its capacity is as important as the capacity of the compression machine itself.

Facts About Hopper Capacity

Most of the people when talking about a hopper they take its capacity in kilograms even the operator said it is a 7 kilogram hopper or it is a 10 kilogram hopper etc but reality is opposite to kilograms.

The capacity of compression machine hoppers means how much powder can be added in a hopper depends on the volume of the hopper so it is calculated in terms of  liters not in kilograms.

Whenever you will read the manual of a compression machine it will clearly mention the hopper capacity in liters like 16 liters ,20 liters etc.

How To Measure Hopper Capacity

Now we are familiar that hopper capacity is in litter but the question is 

  • How to calculate or verify the volume in liters if you have no compression machine manual


    • How can we calculate the amount of powder added in hoppers in kilograms from litters?


Suppose we have a compression machine & we don’t have its URS or manual & we want to calculate the capacity of its hopper.

Follow the following steps

    • Remove the hopper from the compression machine.
    • Close the bottom butterfly valve tightly.
    • If the hopper does not have a butterfly valve,close the lower side tightly with tape.
    • Add a measured quantity of water in the hopper using a jar or beaker.
    • Ensure there should be no leakage of water from the lower side.
    • Fill the hopper with water till it’s Brimful capacity & note down the volume of water added into it.
    • Suppose 16 liter water is added in the hopper so the capacity of that hopper will be 16 liter. 

As we have calculated the capacity in liters now it will help us to measure powder added into hoppers in kilograms.For this we will have to measure the bulk density of that product.

How To Calculate In Kilograms?

If you don’t know how to calculate the bulk density of a product read following article,

Blender Capacity & Bulk Density Calculation

Example #1

Suppose we have a product with bulk density 0.5 g/ml & our hopper capacity is 16 liters.

Use following formula to calculate hopper capacity in kilograms for the product having bulk density 0.5 g/ml

    • Volume of hopper (liter) × Bulk density of product 

Add values

    • 16 liter × 0.5 g/ml = 8.0 kg

The answer is 8.0 kilograms.

Meaning we can add 8.0 kilograms of that material whose bulk density will be 0.5 g/ml.

Example #2

Suppose, again we have a product with bulk density 0.75 g/ml &  hopper capacity is 16 liters.

The amount in kilograms will be

    • Volume of hopper (liter) × Bulk density of product 

Add values

    • 16 liter × 0.75 g/ml = 12 kg

The answer is 12.0 kilograms.

Meaning we can add 12.0 kilograms of a product having bulk density of 0.75 g/ml.


The capacity of a compression machine hopper is calculated in liters not in kilograms because products with different bulk densities will occupy different volume in the hopper.

The capacity of same hopper will be less in kilograms for those products which are lighter with low bulk density & will be high for denser products as in above example the product with 0.75 g/ml bulk density is denser so we can  add maximum of 12 kilograms of that product in hopper whereas we can only add 8 kilograms of the lighter product having 0.5 g/ bulk density.

Also Read

  1. Working and Principle Of Tablet Compression Machine
  2. Function Of Blank Dies In Compression Machine
  3. Advancements in tablet compression machines.
  4. Calculation of compression machine capacity.