AlexeyChepok

Friday 17 February 2012

Ingress volumes - how much water flows into a damaged compartment

SOLAS CH II-1 Regulation 19 requires that each ship to be provided with the damage control information. Very often it is a thin file with the general arrangement plan showing boundaries of the watertight compartments with the openings and their means of closure, position of controls thereof, arrangements for the correction of any list due to flooding; watertight doors arrangement, general and specific precautions considered by the Administration to be vital to the survival of the ship, passengers and crew (i.e., closures, security of cargo, sounding of alarms, etc.).

Frankly speaking, on some ships I found it of just an illustrative use.

The same regulation says:

In case of ships to which damage stability requirements of part B-l apply, damage stability information shall provide the master with a simple and easily understandable way of assessing the ship's survivability in all damage cases involving a compartment or group of compartments.

"simple and easily understandable way" - unfortunately I have never seen such even on the big brand-new ships.

What about taking decisions? when there is no time? Best of all when you have the knowledge a priori. For instance, when you have the idea of how much time is left to flood the compartment. In order to know that, we need to know how much water floods in.

Source: National Geographic

Ok, imagine the situation: Ship is flooding and you, calculator in your hand, are look through your books searching for a formulae.
Or otherwise: You have a breach of 2m² below the waterline and still hope to pump it out with the bilge pump.

In such cases having an evaluation before any similar emergency breaks out is much better.

The table below shows the estimated volumes of water ingress (m³/h) into a damaged compartment.

WATER HEAD (metres below WL), m	AREA OF THE BREACH, m²
	SMALL		AVERAGE				LARGE
	0,01	0,05	0,10	0,15	0,20	0,50	0,75	1,00	1,50	2,00
1	104	518	1037	1555	2074	5180	7780	10370	15550	20740
2	147	726	1470	2200	2940	7260	11000	14700	22000	29400
3	180	898	1795	2695	3590	8980	13550	17950	26950	35900
4	208	1037	2075	3110	4150	10370	16550	20750	31100	41500
5	232	1160	2325	4650	5260	11600	17400	23250	34850	46500
6	254	1265	2540	3820	5080	12650	19100	25400	38400	50800
7	275	1370	2750	4130	5500	13700	20650	27500	41300	55000
8	294	1460	2940	4410	5870	14600	22000	29400	44100	58700
9	311	1555	3110	4670	6220	15550	23350	31100	46700	6220
10	318	1590	3180	4770	6360	15900	23850	31800	47700	63600

To estimate the time left to flood the compartment, divide the volume of the compartment by the figure taken from the table, then multiple it by the permeability factor (roughly 0.85 for E/R and 0.90 for cargo spaces).

A.O. Chepok