How to calculation of using amount of the container desiccant during the shipping,according to the Japanese Industrial Standard Method of moisture-proof Packaging JIS Z 0301-1989
The formula as the following:
W=Amount of desiccant used(g)
R=barrier film moisture transmission(g/m2-24H)
A=barrier film surface area(M2)
t=transportation and storage period(days)
h1=average humidity of outside air during the packing period(%)
h2=average humidity (relative humidity) of inside air during the packing period(%)
K1=coefficient determined by barrier film type
C1=moisture absorbing rate of desiccant when starting use(%)
C2=moisture absorbing rate of desiccant when respect to maximum limit of relative humidity permitted within packing
K2=coefficient determined by moisture absorbing rate of packing material with moisture absorption within packing
D=weight of packing material with moisture absorption within packing(g)
Conditions set for example calculation(calcium chloride desiccant)
After humidity-proof packaging the 12pieces of corrugated fibreboard box of 40cm*30cm*25cm put in with products and accessories,by packaging with low density polyethylene film of 0.2mm in thickness and when packaged in wooden box, when carrying out the calculation of amount of desiccant agent of calcium chloride for packaging required for keeping the inside of package at not more than 40% in humidity according to the above formula and the formula
K2=C4-C3/C2-C1
Notes:
content of anhydrous calcium chloride(Cacl2)=15%
Initial moisture absorption rate=32%(Cacl2 base)-moisture absorption rate
Maximum moisture absorption rate
Capable of keeping at not more than 40%in humidity=87%(Cacl2 base)--moisture absorption rate of saturated solution(40℃）
R=2.4G/M2·24H C1=32% C2=87% A=3.06M2
t: θ℃=20℃，h1=70%, h2=35% in 60days, K1=0.0018
θ℃=35℃，h1=90%, h2=35% in 30days, K1=0.0070
K2: C1=32% C2=87% C3=5.0% C4=9.5%
D: Mass of one piece=300g, 12 pieces:3600g
W1=2.4*3.06*60*(70-35)*0.0018/(87-32)*10-2=50.5g
W2=2.4*3.06*30*(90-35)*0.0018/(87-32)*10-2=154.2g
K2D=C4-C3/C2-C1=(9.5-5)/(87-32)*3600=294.5g
W=W1+W2+K2D=50.5+154.2+294.5=499.2g
Using amount of desiccant agent containing 15% of anhydrous calcium chloride is
499.2/0.15=3328g
