**How the requirement of carbon dioxide in a ship’s installation is calculated.**

Regulation stipulates the requirements of CO2 onboard ships as follows

>For cargo space, 30% of gross volume of largest cargo space

>CO2 of sufficient amount to give minimum value of free gas equal to larger of following volumes

I. 40% of gross volume of largest machinery space excluding casing

II. 35% of gross volume of largest machinery space protected including casing

Regulation also states that, for machinery space, piping arrangement should be such that 85% of the gas can be discharged into the space protected including the casing with in 2min.

The following information about CO2 is important

Volume of free CO2 should be taken as 0.56m3/Kg (inverse of density)

CO2 content in a bottle is 45.4Kg (standard)Water capacity of the bottle = 65.1 liters (standard)

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>Solas Requirement For Fixed Co2 System And Co2 Bottles

For example, consider a ship in which

a. Engine room gross volume (to upper deck) = 4658m3

b. Engine room gross volume to top casing = 5358m3

c. Volume of the largest cargo hold = 6849m3

Calculation of the CO2 cylinder required as per the regulations for the volume of the air reservoir = 375m3

Therefore, for engine room the CO2 bottle requirement is calculated as

For gross volume excluding casing,

(4658+375)*0.4/ (45.4x0.56) = 80 cylinders

For gross volume of engine room including casing,

(5358+375)*0.35/ (45.4*0.56) = 79 cylinders

For cargo hold, requirement is calculated as

(6849*0.30)/(45.4*0.56) = 81 cylinders

The requirement is the largest of the above values, which is 81 cylinders

why it is 30% and 40% why not 20%

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