Moisture Damage

For many years, thousands of containerized cargoes are damaged by moisture problems. When the containers arrive at the destination, metal is found to be rusty or oxidated, cartons become soft and moldy, bulk coffee, cocoa, beans may be damp, musty…,such losses sometimes costs several million dollars. It is caused by two main reasons: Container Rain and Cargo Sweat.

Four Areas of container moisture damage:

1. The ceiling and inner walls of the container, the condensation is known as “Container Rain”

2. The surface of cargo, the condensation is known as “Cargo Sweat”

3. The container floor. There are two kinds, iron floor is cold, wooden floor contains moisture inside. They both easily make the pallets moldy.

4. The container doors. The outside wet air easily goes through the crack of the container door and causes high relative humidity.

Water vapor content in the air at different temperature and RH

RH T(℃)	100%	90%	80%	70%	60%	50%	40%	30%	20%	10%
65	160.3	144.3	128.2	112.2	96.2	80.2	64.1	48.1	32.1	16.0
60	129.6	116.6	103.7	90.7	77.8	64.8	51.8	38.9	25.9	13.0
55	103.9	93.5	83.1	72.7	62.3	52.0	41.6	31.2	20.8	10.4
50	82.7	74.4	66.2	57.9	49.6	41.4	33.1	24.8	16.5	8.3
45	65.2	58.7	52.2	45.6	39.1	32.6	26.1	19.6	13.0	6.5
40	50.9	45.8	40.7	35.6	30.5	25.5	20.4	15.3	10.2	5.1
35	39.2	35.3	31.4	27.4	23.5	19.6	15.7	11.8	7.8	3.9
30	30.0	27.0	24.0	21.0	18.0	15.0	12.0	9.0	6.0	3.0
25	22.8	20.5	18.2	16.0	13.7	11.4	9.1	6.8	4.6	2.3
20	17.1	15.4	13.7	12.0	10.3	8.6	6.8	5.1	3.4	1.7
15	12.7	11.4	10.2	8.9	7.6	6.4	5.1	3.8	2.5	1.3
10	9.3	8.4	7.4	6.5	5.6	4.7	3.7	2.8	1.9	0.9
5	6.8	6.1	5.4	4.8	4.1	3.4	2.7	2.0	1.4	0.7
0	4.8	4.3	3.8	3.4	2.9	2.4	1.9	1.4	1.0	0.5
-5	3.2	2.9	2.6	2.2	1.9	1.6	1.3	1.0	0.6	0.3
-10	2.1	1.9	1.7	1.5	1.3	1.1	0.8	0.6	0.4	0.2
-15	1.4	1.3	1.1	1.0	0.8	0.7	0.6	0.4	0.3	0.1
-20	0.9	0.8	0.7	0.6	0.5	0.5	0.4	0.3	0.2	0.1
According to the above table we can calculate moisture content in the air in the containers/cartons before shipment. Total water vapor= unoccupied space in the container* = water vapor in every cubic meter air at relevant temperature and RH(from the table it can be found) Statement: The calculation simply tells how much water vapor in the container/carton before shipment. It does not include the water vapor from other sources(such as cargo, container wood floor, pallets and the packaging material inside the container.)

Temperature, Rainfall and Rainfall Days Records

BEIJING					SHANGHAI
	Temperature		Total	Days		Temperature		Total	Days
Month	Lowest	Highest	Rainfall	Rainfall	Month	Lowest	Highest	Rainfall	Raining
	/day	/day	mm	Days		/day	/day	mm	Days
Jan	-9.4	1.6	3	2	Jan	0.5	7.7	39	9
Feb	-6.9	4.0	6	3	Feb	1.5	8.6	59	10
Mar	-0.6	11.3	9	4	Mar	5.1	12.7	81	13
Apr	7.2	19.9	26	5	Apr	10.6	18.6	102	13
May	13.2	26.4	29	6	May	15.7	23.5	115	13
Jun	18.2	30.3	71	9	Jun	20.3	27.2	152	14
Jul	21.6	30.8	176	14	Jul	24.8	31.6	128	12
Aug	20.4	29.5	182	12	Aug	24.7	31.5	133	10
Sep	14.2	25.8	49	7	Sep	20.5	27.2	156	12
Oct	7.3	19	19	5	Oct	14.7	22.3	61	9
Nov	-0.4	10.1	6	3	Nov	8.6	16.7	51	8
Dec	-6.9	3.3	2	2	Dec	2.4	10.6	35	7

GUANGZHOU					XIAMEN
	Temperature		Total	Days		Temperature		Total	Days
Month	Lowest	Highest	Rainfall	Lowest	Month	Lowest	Highest	Rainfall	Lowest
	/day	/day	mm	/day		/day	/day	mm	/day
Jan	9.8	18.3	43	8	Jan	9.7	16.8	37	8
Feb	11.3	18.4	65	11	Feb	9.8	16.5	65	13
Mar	14.9	21.6	85	15	Mar	11.9	18.8	99	17
Apr	19.1	25.5	182	16	Apr	16.1	23	147	16
May	22.7	29.4	284	18	May	20.3	26.7	152	16
Jun	24.5	31.3	258	19	Jun	23.3	29.4	196	14
Jul	25.3	32.7	228	16	Jul	25.3	32.4	140	10
Aug	25.2	32.6	221	16	Aug	25.2	32.2	155	10
Sep	23.8	31.4	172	13	Sep	23.8	30.7	117	11
Oct	20.5	28.6	79	7	Oct	20.5	27.4	29	3
Nov	15.7	24.4	42	6	Nov	16.4	23.4	37	5
Dec	11.1	20.5	24	5	Dec	11.7	19.1	25	4