# How to calculate mass balance?

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### #1 qualitymanager

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Posted 03 January 2017 - 01:26 PM

Hello everyone,

I need to calculate the balance mass in our factory but i  don't know how.

we are producing cans and we use for our production these elements as a raw materials: aluminum coil, varnish, ink

Does anyone have an idea how to calculate it in this case?

### #2 TWFUK

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Posted 03 January 2017 - 02:16 PM

Mass balance to me is the concept of checking for an equilibrium. Whether what comes in is the same as what goes out. For that matter you will have to account for your raw materials coming in and how much yiu actually used for the production and estimating or actually calculating for the wastage. Lets say you used 1000kgs of aluminium to make the can out of 1200, then 200 may be either in stock or was wasted. There is an allowable limit for wastage depending on each country i assume. But since its a BRC i guess its universal.

### #3 Foodworker

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Posted 04 January 2017 - 12:33 PM

The mass balances required by most product safety standads are there essentially to prove that your traceability systems work but there can be spin off benefits tp process improvements when you analyse wastages.

In broad terms a mass balance is a percentage based upon the quantity of a raw material received divided by the quantity of that material used to make good product plus the quantity of the material wasted.

In real life it is never that straight forward, but for the aluminium it isn't too difficult.

In the example below, assume that one coil is used to make three different finished products:

Coil Wt

Used on Finished Product

Number of Finished Product cans made

Cup Wt

Waste from Punch Press

Other Process Waste eg trim

x

1

a

W1

P1

O1

2

b

W2

P2

O2

3

c

W3

P3

O3

Mass Balance=           __________________ X

(aW1+aP1+aO1) + (bW2+bP2+bO2) + (cW3+cP3+cO3)     x100

Most can makers will have carried out detailed process capability studies and providing that the can size/design is the same for the three products, unless there is a breakdown on the line, W1,W2 and W3 will be the same value and similarly P1,P2, P3 and O1,O2,O3.

The example assumes that the start of Finished Product 1 coincides with the coil change, which is unlikely, so you will have to understand your own process lines to find the start and end points.

The broad principles are the same for the other raw materials, but I have to say that it will be a nightmare to calculate mass balances on inks. Irrespective of any individual process considerations, the potential error in scaling up from minute ink weights per can to the millions of cans made will make a percentage reconciliation meaningless in my opinion.

### #4 Foodworker

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Posted 04 January 2017 - 12:36 PM

Sorry the table didn't paste properly so I will put it up as an attachment

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