Liquid natural oils, fats


and fatty products The products dealt with below include crude vegetable, animal and marine oils as well as fats. Some of the oils are edible and others are used in the production of soap, paint, lacquer, cosmetics and medicines. Occasionally, refined vegetable oils are shipped. When these products are transported by sea, a variety of difficulties may be encountered, the cause of which generally fall into two categories.


● Handling (basically temperature control) ● Contamination.


Handling


Claims still frequently arise which involve allegations of unsatisfactory handling by ships. It is sometimes necessary to apply heat to these cargoes, since during a sea passage, the temperatures encountered are likely to be lower than those recommended by the shippers. Many products of this type are adversely affected by heating so that some deterioration is inevitable, with the extent of the damage depending on the nature of the product and length of the voyage. Unsatisfactory temperature control can cause additional deterioration, usually because the carrying temperature has been too high for all, or part of the voyage. It is possible for experts to estimate the level of unavoidable damage and hence the extent of any further damage caused by poor temperature control.


Damage may also result if the carrying temperature is allowed to fall below that recommended by the shippers. The normal procedure for heating this type of product is by heating coils at the tank bottoms and lower sides, with heat being transferred throughout the oil, mainly by convection current. The heat transfer becomes progressively less efficient as viscosity increases. The viscosity of liquid natural fatty products is greatly affected by temperature and a reduction in temperature of only a few degrees can have a serious effect. If the heating process is inadequate to the maintenance of sufficient fluidity within the bulk of cargo, then the liquid in the vicinity of the heating coils can become overheated.


During the discharge of cargo, if the environmental temperatures are very low, further problems may arise as a result of solidification, which most commonly occurs when a tank is almost empty and the liquid level has fallen below the level of the heating coils. Under such circumstances, the final residues may be removed by sweeping or by steam stripping, provided the


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More recently, traders and governmental authorities have taken a serious view of the contamination of edible products by traces of chemical substances. Often, but not invariably, these contaminants have come from residues of previous cargoes.


It is normal practice for samples to be drawn by independent surveyors during loading, or immediately after loading, and for at least one set of these samples to be given to the ship. It is important that the ship has a set of loading samples, since most claims are based upon differences in analytical parameters in samples drawn at loading and discharge. If the master is instructed to deliver a set of samples to the receivers on arrival at the discharge port, it is recommended that he requests that the shippers provide a second set of samples for the use of the shipowners. Any such samples handed to the ship should be properly stored during the voyage, preferably in a refrigerated store.


At the time of discharge, samples are always drawn by the receivers or their surveyors. Normal analyses conducted at both load ports and discharge ports are quite straightforward and the typical parameters determined are water, free fatty acid, unsaponifiable matter and odour. If there is evidence or suspicion that on delivery the cargo does not conform to either a specification or to the loading samples, more detailed chemical analysis may be performed. There are now reliable and effective procedures available for determining traces of chemical contaminants. Certain contaminants can be identified and determined at levels as low as 10 parts per billion (ppb). Contamination at this level will result from admixture of 10 grams of contaminant, with 1000 tonnes of cargo. Most chemical contaminant can be identified and determined at levels of 100 ppb or 100 grams per 1000 tonnes of cargo.


receivers are able to accept the fat and water mixture which is produced. Ship’s officers responsible for discharging heated products in cold climates should ensure that the maximum pumping rate is maintained and that there are no interruptions during discharge, shore operations permitting.


Contamination


In the past, the most common contaminant, resulting in claims, was water, originating from shore or ship tanks, pumps or lines at the time of loading, or introduced by mistake, or due to leakage. Some products contain a significant quantity of water when shipped, but the presence of excess water in others may accelerate deterioration. Experts can frequently estimate the damage due to contamination with excess water.


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