Each Chief Engineer should be given the name of the company of the treatment products which has the

contract furnishing chemicals and service for his particular vessel. It is important that each vessel have the booklet of instructions for the treatment used. Contracts with the company should provide that they will not only furnish the necessary chemicals as requisitioned but that their service engineer will meet each vessel upon arrival in stated ports, collect water samples, test same soonest possible and give a report. This report should include the analyse is of the water samples taken as well as recommendations of actions. The Chief Engineer must see to it that the form provided with the chemical company for recording the feed water and boiler water tests is completely filled out each day of the voyage and that this report is turned over to the chemical company's representative when attending the vessel. In order to counteract the effects of contamination, boiler feed water is treated chemically, to control !" scale formation in the water sides of boilers, #" corrosion, and $" foaming and priming, and it is treated mechanically and by heating to reduce the dissolved o%ygen present in the water. The purpose of the boiler water treatment is& ! To neutrali'e acid forming salts in boiler water, i.e. maintain a slightly alkaline condition. # To provide scale removing and scale preventing chemicals. $ To precipitate impurities into a sludge which can be removed by bottom and surface blows, and ( To prevent corrosion by o%idation. APPLICATION OF BOILER WATER TREATMENT CHEMICALS TO THE BOILER The importance of the correct method of applying treatment chemicals cannot be over) stressed. *dditions of hydra'ine to the feed water into the feed system must be continuous and sufficient quantity to remove the last traces of o%ygen from the feed water and to leave a small e%cess. The e%cess being sufficient to give a small residual in the boiler water to produce sufficient ammonia, by decomposition of the hydra'ine in the boiler, to raise the p+ of the condensate to over ,.-. Continuous application by means of a suitable dosing unit, direct in.ected into the feed line immediately after the /.0. pump. The importance of continuous, #( hours per day, seven days per week, in.ection of hydra'ine and amine should be reflected in the installation of reliable chemical dosing units. The use of unreliable equipment can mean no hydra'ine or amine additions when the unit is out of action. This can lead to the onset of corrosion in the boilers and subsequent repair costs far outweigh the cost of a reliable chemical dosing pump. 1ther chemicals shall be in.ected in the same way. MECHANICAL DE-AERATION 2echanical de)aeration to reduce o%ygen in the feed, is standard practice for all boilers. The need for it, however, depends on various factors, e.g. plant loading, boiler pressure and the evaporation rate. It is advisable to reduce the o%ygen content of the feed water to under 3.3# mg4l for boilers up to (3 bar. 0ith modern de)aerators these levels are easily attainable, if installed. *t atmospheric feed water system with open condensate) filter ) hot well) tanks, the temperature shall be kept as near boiling as possible, also when large quantities of make up water is added. +eating coils in the tank as well as condensate temperature control and alarm should be provided. 5egular testing for o%ygen content of the feed water is necessary. CHEMICAL DE-AERATION *s much of the dissolved o%ygen as possible must be removed by mechanical de)aeration and supplementary chemical treatment used only for the last traces of o%ygen. The feed

temperature should be maintained as high as possible in the feed tank to reduce the o%ygen content of the feed. In open feed tanks, the temperature shall be at least ,-6C or higher". The chemicals used for removal of the residual o%ygen from the feed water are& ! +ydra'ine " The hydra'ine 7#+(" must be continuously dosed into the feed water to react with all the o%ygen present and to produce a small reserve of hydra'ine in the boiler water. The normal level of hydra'ine reserve to be maintained in the boiler water is between 3.! and 3.$ ppm 7#+(. 'he chemical reaction with o%ygen can be e%pressed 7#+( 81#9#+#1 8 7# *s the products of reaction are harmless ) nitrogen as and water, hydra'ine treatment does not increase the dissolved solids content of the boiler water. The e%cess hydra'ine in the boiler breaks down to give ammonia which provides suitable alkaline conditions in the steam condensate system. The reaction can proceed in two ways& * $7#+()))(2+$87# : #7#+())) #7+$87#8+# +ydra'ine for trace o%ygen scavenging is normally recommended for boilers operating above(3 bar but it can also be used in low pressure boilers where corrosion has been e%perienced and it is necessary to avoid any increase in boiler dissolved solids. ;odium sulphite ;odium sulphite is frequently used for removal of traces of o%ygen from boiler feed water. It can be used in marine boilers operating at pressures up to (3 bar. Catalysed sodium sulphite is used in most cases, as the reaction time with o%ygen is e%tremely fast even at ambient temperature. In marine practice, particularly for low pressure shell type boilers, it is usual to add the catalysed sodium direct to the boiler and not continuously into the feed water. This reduces the amount of sulphite required as most of the o%ygen flashes off with the steam and only the small amount in the boiler water has to be removed by the sulphite. This, in turn, limits the increase in boiler dissolved solids resulting from the formation of sodium sulphate. To ensure removal of all o%ygen, a small sulphite reserve is maintained in the boilers, the level of e%cess sulphite varying according to pressure and type of boiler and whether or not the feed water is de)aerated. +ydra'ine, apart from its comparatively slow reaction with o%ygen at ambient temperatures and at a p+ of under <.3 has certain advantages over catalysed sodium sulphite, as follows& * The use of hydra'ine does not contribute to any increase in boiler dissolved solids and this is an important factor in high pressure boilers or in low pressure boilers where any additional dissolved solids must be avoided. : The use of hydra'ine results in a protective magnetic iron o%ide film /e $1(" on the boiler meta= surfaces which acts as an additional protection against o%ygen corrosion. C The e%cess hydra'ine in the boiler breaks down to produce ammonia which has beneficial effects in raising the p+ of the steam4condensate system and thus affords some protection to the system by neutralising any carbon dio%ide