122 



IIM)R()l)V\.\Ml(;s 1\ Mill' ni-.SIGN 



Sec. -15.20 



service. Iti'in (12), involving the history of opera- 

 tion, appears to call for about nine proups each, 

 for fresh water anil for s^ilt water, respectively. 

 Table lo.p is a proposal framework for carrying 

 the numerical values in these groups, to be 

 (leterinineil after further study and investigation. 

 The following notes applj' to this table: 



I. Fresh water is defined as that which is suffi- 

 ciently sweet for drinking purposes, even though 

 it may l>e contaminated by microorganisms. This 

 water should be sufficiently free of salts to kill 

 or prevent the growth of adhering marine life. 



II. Salt water is defined as the water found in the 

 oceans and in salt seas, and includes brackish 

 water. It may be expected that the fouling effects 

 in this water will vary approximately in proportion 

 to the salinity or specific gravity, with a specific 

 gravity for average sea water of 1.027, and a 

 corresponding siilinity of 3.5 per cent. 



III. Warm water is that in which the temperature 

 exceeds 77 deg F or 25 deg C. Cool water has a 

 temperature range of from 77 deg F, or 25 deg C, 

 to 41 deg F, or 5 deg C. Cold water is that in 

 which the temperature is less than 41 deg F or 

 5 deg C. Seasonal variations, if any, are taken 

 care of by the variations in water temperature. 



1 \ . lilt he table a ship is a.s.sumed to l)e "stoppetl" 

 if it is moving at 2 kt or le.s.s, relative to the sur- 

 rounding water, slow enough for marine growths 

 to attach thcm.selvcs. 



V. For the approxiiiiati' mu'IIkxI given, the ship's 

 history need be divided into intervals no smaller 

 than 1 day 



^'I. All fouling efTects reckoned in accordance 

 with the tables are additive. 



Concerning item (3) of the summary at the 

 beginning of this .section, the information on 

 fouling rates and fouling cj'des for specific ports 

 appears limited to that given by G. I). Bengough 

 in reference (22) of Sec. 45.21. These data indicate 

 that certain ports and certain areas appear to be 

 excellent for breeding and attaching marine 

 fouling organisms, and that other ports and areas 

 are relatively free of this nui.sance. Ba.sed on data 

 in the reference quoted. Table 45. h is a propo.'^ed 

 guide for determining the relative fouling rates 

 or the locality foulinc/ factor in the ports usually 

 frequented, assuming the ship at anchor (or 

 moving very slowly) and all other conditions the 

 same. This factor is based upon an average rate 

 of fouling in an average port, assumed as unity 

 (1.0). 



TABLE 'IS.!! — Pkoi'oskd Form ok TAnn.ATioN to I'kiimit Selection ok thk IvOcauty Fouung Factok 

 The liBt of port* i.s taken from G. D. Bengough, "Hull Corrosion and Fouling" [NIOCI, 1942-1943, Vol. 59, Talilc 5, 

 |i. 193), with the two left-hand groups interchanged. 



LocALmr Fouung Factors 



