Sunday, November 21, 2010

VEGETABLE OILS AND FATS ON CHEMICAL TANKERS -- CAPT AJIT VADAKAYIL






 VEGETABLE AND PALM OILS ON CHEMICAL TANKERS-- CAPT AJIT VADAKAYIL

The vegetable oil trade represents close to 60 million tonnes.  It is 1/3 of the chemical tanker trade.

High melting point palm oils like palmitic acid, stearic acid , fatty acids etc must never be allowed to freeze in the cargo pipelines. Discharging high MP palm oils in cold freezing weather requires clear action plan—in case 
of barge change over, for efficient sweeping etc.  Cargo inside the pipelines must be immediately blown down hill ( trim ) before it freezes. 

Sweeping high MP palm oils heated to high dischg temperature requires close supervision . Sweeping equipment and waders must be kept in readiness and tank dry surveyor must be available to declare when enough is enough.  Remember once the cargo falls below the level of steam coils things must happen the way it is desired, before it solidifies.

When vessels are carrying solidifying products it is important that the products are at the maximum discharge temperature (or slightly above) at least one week prior to arrival at the discharge berth. Also during this period once the product is up to required temperature, soundings must be made in each tank using a rod and line to determine if there are any solid products on the tank bottom.

In addition, any ballast in double bottom tanks beneath the cargo tanks must be lowered so that there is no direct contact between the ballast and the cargo in adjacent tanks. If there isn a suction pit under the impeller of the deepwell pump, there is every chance that the impeller is stuck---in which case the pit ( cold pocket ) may have to be steamed from underneath.

The Internationally recognised heating instructions for the various products are as follows, the product should be up to the maximum temperature indicated at least seven days before arrival. Following is just a guide line as shippers will give clear heating requirements for voyage heat and discharge heat.

Product Voyage Temp 
°C Disch Temp °C

Crude Palm Oil 32/40 50/55
Neutralised Palm Oil 32/40 50/55
Neutralised Bleached Palm Oil 32/40 50/55
RBD Palm Oil 32/40 50/55
NBD Palm Oil 32/40 50/55
Crude Palm Olein 25/30 32/35
Neutralised Palm Olein 25/30 32/35
Neutralised Bleached Palm Olein 25/30 32/35
RBD Palm Olein 25/30 32/35
NBD Palm Olein 25/30 32/35
Crude Palm Stearin 40/45 60/65
Neutralised Palm Stearin 40/45 60/65
Neutralised Bleached Palm Stearin 40/45 60/65
RBD Palm Stearin 40/45 60/65
NBD Palm Stearin 40/45 60/65
Palm Acid Oil 42/50 67/72
Palm Fatty Acid Distillate 42/50 67/72
Crude Palm Kernal Oil 27/32 40/45



PALM OIL ABBREVIATIONS:

CPO/ crude palm oil
NPO/ neutralised
B/ bleached
RD/ refined , deodourised
L/ olein
S/ stearin
A/ acid
FD/ fatty distillate
K/ kernel
LC/ low colour
DF/ double fractionated
ME/ methyl ester
IV/ iodine valuse
PU/ poly unsaturated

In case of palm oils sudden rise of temperatures due to indiscriminate heating can cause release of FFA and make cargo off spec.

Acid value: AV is the number of  grams of KOH required to neutralise 1 kg of product.

FFA: AV is generally twice the FFA number.

FATTY ACIDS:
ALIPHATIC ( oleic, palmitic , stearic ),
AROMATIC ( phenyl stearic ),
AMINO ACIDS

Risk assessment form prior sweeping cargo—wrt oxygen deficiency, burns to crew, and toxic/ health  dangers

VEG OIL CARRIAGE

Three types of deterioration can occur in oils and fats

Oxidation

Contact of oils and fats with oxygen, present in the atmosphere, causes chemical changes in the product which downgrade the quality. Much can be gained by reducing the amount of air contact . Oxidation proceeds more rapidly as temperature increases, so each operation should be carried out at the lowest practicable temperature. The rate of oxidation is greatly increased by the catalytic action of copper or copper alloys, even when trace amounts (ppm) are present. Because of this, copper and copper alloys must be rigorously excluded from the systems--seals, valves,  strainers, pumps, temperature gauges or in sampling apparatus. Prolonged contact with mild steel can also cause oxidation.

To prevent aeration-- It is preferable to clear the pipe line leading to the tank by a “pigging” system and/or by the use of inert gas. However, if air is used, a suitable means must be provided to prevent it being blown into the oil in the tanks.

Hydrolysis
The breakdown of fats to fatty acids is promoted by the presence of water particularly at higher temperatures. Hydrolysis is also promoted by the action of certain micro-organisms. Tanks in which the oil is being stored or shipped should always be clean and dry before use.

FFA

FFA of certain heating cargoes cargoes will increase if the moisture content is too high. Veg and animal oils have different SG at different levels after long storage. FFA of the layer closest to the coils increases faster and cause damage to the bottom—so recirc  Vegetable oil and Animal oil in coated cargo tanks. Advantages are less manual labour for squeezing after discharge  and not allowing a difference in the FFA content between the lower and upper levels in the tanks.

Fat is combined with glycerine and fatty acid. When the fat is hot , it get decomposed to FFA and
glycerine ( hydrolysis ). Increase of FFA means the cargo will become worse in quality. The quality
of vegetable oils and animal fats is largely determined by their AV acid value. A fresh oil or fat has
low AV. Parcels having different FFA shall not be commingled .Rapid heating results in increase
in FFA content or discolouration of the cargo.


Vegetable oil and Animal oils have a FREE FATTY ACID content (FFA).If hot prewashed FFA will increase rapidly to a level, which will coagulate the albumen in the Vegetable/Animal oil. This damages the surface of the zinc silicate lining.

Contamination

Undesirable contamination may be from residues of a previous cargo or sea water . Previous cargoes not on the  Lists of Acceptable or Banned cargoes are only to be used if agreed upon by competent authorities of the importing countries.

HEATING:

All ships should be equipped with temperature sensors and control devices to prevent overheating of oil in the tank and associated lines.

In temperate and cold climates, pipelines used for oils and fats which may solidify at ambient temperatures should preferably be lagged and also provided with heating, for example by steam tracing lines or electrical heating tape. When clearing pipelines in such climates, steam may be used.

Heating should start at a time calculated to give the required pumping temperature without ever exceeding the maximum rate of 5°C over a 24 hour period

To prevent excessive crystallisation and solidification during short-term storage and shipping, oil in bulk tanks should be maintained within the temperature ranges given in Table 1.

The temperatures apply to both crude and refined oils in each grade.

The temperatures are chosen to minimise damage to the oil or fat. Some crystallisation will occur, but not so much as to require excessively long heating before delivery. Thus palm oil stored at 32°C - 40°C will require about three days heating at 5°C over a 24 hour period to bring it to transfer temperature. Long term storage of all soft oils should be at ambient temperature and heating should be completely turned off. If the oil then becomes solid, extreme care should be taken during the initial heating to ensure that localised overheating does not occur.

Temperature at loading or unloading should refer to the average of top, middle and bottom temperature readings. Readings should be taken not less than 30 cm away from the heating coils.
Under cold weather conditions discharge temperatures should be at the maximum of those shown in Table  to prevent blocking of unheated pipelines

Where a number of products are transferred through a common pipeline system, the system must be cleared completely between different products or grades. The order of loading and discharge should be carefully chosen to minimise adulteration.

The following principles should be observed:
Fully refined oils before partly refined.
Partly refined oils before crude oils.
Edible oils before technical grades.
Fatty acids or acid oils should be pumped last.

Special care should be taken to prevent adulteration between lauric oils and non-lauric oils.
The first pumpings of each grade should be collected where possible in separate tanks for quality checks

TEMPERATURES DURING STORAGE, TRANSPORT, LOADING AND DISCHARGE


Storage and bulk shipments
Loading and discharge
Oil or fat
Min °C
Max °C
Min °C
Max °C
Castor oil
20
25
30
35
Coconut oil
27
32
40
45
Cottonseed oil
Ambient
Ambient
20
25 (2)
Fish oil
20
25
25
30
Grapeseed oil
Ambient
Ambient
15
20 (2)
Groundnut oil
Ambient
Ambient
20
25 (2)
Hydrogenated oils
Various
-
Various
- (1)
Illipe butter
38
41
50
55
Lard
40
45
50
55
Linseed oil
Ambient
Ambient
15
20 (2)
Maize (corn) oil
Ambient
Ambient
15
20 (2)
Olive oil
Ambient
Ambient
15
20 (2)
Rapeseed/low erucic acid rapeseed oil
Ambient
Ambient
15
20 (2)
Safflower oil
Ambient
Ambient
15
20 (2)
Sesame oil
Ambient
Ambient
15
20 (2)
Sheanut butter
38
41
50
55
Soyabean oil
Ambient
Ambient
20
25 (2)
Sunflower oil
Ambient
Ambient
15
20 (2)
Tallow
45
55
55
65

Notes
Hydrogenated oils can vary considerably in their slip melting points, which should always be declared. It is recommended that during the voyage, the temperature should be maintained at around the declared melting point and that this should be increased prior to discharge to give a temperature of between 10° C and 15°C above that point to effect a clean discharge.

It is recognised that in some cases the ambient temperatures may exceed the recommended maximum figures shown in the Table.

FOSFA HEATING INSTRUCTION:

Shippers shall ensure that the temperature of the oil during delivery into the tank(s) of a
ship is that at which the oil is usually handled and where heat is applied that the
temperature in no case exceeds that given in the appropriate table.

Master shall supply to cargo receivers a statement showing the cargo temperature at
loading and a chart on which the daily temperatures after loading have been recorded.
The charts hall be signed by the Master or authorized officer.

Shippers shall supply the following instructions with regard to heating of oil during the
Voyage for ship's tanks fitted with heating coils :--

1.On completion of  loading ship's steam coils shall be completely covered with oil.

2.Heating shall be effected by hot water or, where this is impracticable by low pressure
saturated steam. Pressures shall not exceed 1 .5 bar gauge.

3.During the voyage the oil shall be maintained in accordance with the temperatures set
out in the Heating Recommendations.

4.In sufficient time prior to arrival at port of discharge heat shall be applied gradually to
ensure that the temperature of the oil at time of discharge is in accordance with the
temperatures set out in the heating recommendations  The cargo shall be maintained
within this range of temperatures throughout the discharge.

5.ln order to avoid any damage to the quality of the oil it is essential that heat is applied
gradually . A sudden increase in temperature must be avoided as it will almost certainly
result in damage to the oil.

6.The increase in temperature of the oil during any period of 24 hours shall never exceed
5'C.

7.As far as practicable top and bottom temperature shall be maintained at equal levels;
the difference between these two temperatures shall never exceeds 5 deg C.

8.The temperatures referred to above are the average of top, middle and bottom readings.
The top reading shall be taken at about 30 cm (one foot) below the surface of the oil.
The bottom readings shall be taken:
In tanks which have bottom coils at 30 cm (one foot) above the level of the coils;
In tanks which have side coils but no bottom coils, at a point about two feet (60
c) from the bottom of the tank and about 30 cm (one foot) from the side coils.

9.The temperature indicated in 4 above are applicable under normal conditions ruling
at port of discharge. ln the event of abnormal conditions( such as extremely low air or
water temperatures) receivers either directly or through their appointed representatives,
may vary the temperatures stated and instruct shipowners or their agents accordingly.
Details of any such variations shall be duly recorded and advised to shippers or their
representatives  If there is more than one receiver of the oil ex one ship's tank:

All receivers from that tank should be in agreement to the proposed variations in
the temperature stated in 4 above;
Shipper's representatives at port of discharge shall endeavour to reconcile
requirements of the individual receivers.

The acid value of an oil may be used as a measure of quality. However, the acid value of the oil must not be too high, as this denotes an excessively high content of free fatty acids, which causes the oil to turn sour. Discoloration may also occur.

Oils and fats spoil by readily becoming rancid. Rancidity is promoted by light, atmospheric oxygen and moisture and leads to changes in odor and taste. Thus, the tanks  must be filled as full as possible, taking into consideration the coefficient of cubic expansion  so that as little ullage space as possible is left above the cargo. Do not load rancid oil, since it does not meet quality requirements.
If the oil solidifies in the tanks, it cannot be liquefied again even by forced steam heating. In the vicinity of the heating coils, the oil melts, scorches, discolors and becomes rancid.

Pumping out may be difficult in cold weather. The oil may cool too rapidly in the long lines and solid deposits form on the outer walls, which cannot be pumped out and prevent the still liquid cargo from reaching the suction valve. This problem can be solved by appropriate voyage heating. Chill haze (separation) begins if cooling causes the temperature of the oil to approach solidification point, the oil becoming ointment-like and finally solid, such that it is no longer pumpable.
All fats and oils have a particular density (approx. 0.9 g/cm3). With a rise in temperature, however, density diminishes, thereby leading at the same time to an increase in volume. This behavior is described by the coefficient of cubic expansion and is known as thermal dilatation.

The coefficient of cubic expansion amounts to: g = approx. 0.000746°C-1

As a rule of thumb, oils may be expected to increase in volume by 1% of their total volume for each 14°C temperature increase

Fats and fatty oils are insoluble in water. However, contact with water may give rise to soluble lower fatty acids and glycerol, which cause rancidity together with changes in color (yellow to brown), odor and taste as well as gelling and thickening. For this reason, the tanks must be absolutely dry after cleaning

Ventilation must not be carried out under any circumstances, as it would supply fresh oxygen to the cargo, which would promote oxidation processes and premature rancidity.

Before anybody enters an empty tank for squeezing , it must be ventilated and a gas measurement carried out. Oxidation processes may lead to a life-threatening shortage of O2.

Of considerable significance with regard to tank cleaning is the iodine value, which is a measure of how strong a tendency the oil has to oxidation and thus to drying. Drying is particularly detrimental to tank cleaning, as the oil/fat sticks to the walls and can be removed only with difficulty. On the basis of drying capacity, oils are divided into nondrying, semidrying and drying oils. Drying oils have  iodine value >130 while non drying oils/ iodine value have Iodine value less than100

With an iodine value of 118 - 144, sunflower oil is a drying oil, which means that it is subject to severe drying on contact with atmospheric oxygen, so considerably complicating cleaning of the tanks. In addition, considerable weight losses sometimes occur.

Drying , semidrying vegetable oils and animal oils ( or if you are in doubt )  must be cold prewashed assoon as possible after discharge  . A thin drying oil film like soyabean absorbs oxygen from air and polymerises to form a tough elastic film.  

The drying ability is expressed by its iodine number. Non drying oils have least capacity for iodine. It is a measure of saturation. Unsaturation of veg oils range from 78% for safflower to 10% for coconut oil.

Examples of drying oils are—
Soyabean oil, saffloweroil, tall oil, tung oil, linseed oil, mustard seed oil, poppyseed oil, walnut oil etc.


OXIDATIVE AND HYDROLYTIC RANCIDITY OF VEG OILS


Changes in  quality  of  the  fats  and  oils  during shipment occur due to hydrolysis and oxidation and this loss in quality is taken into account when edible fats and oils are processed further into food during refining.

The term edible” includes fats and oils which are destined for the oleo-chemical industry for use in personal care products and cosmetics.

      Residue of a previous cargo in tank , before loading a veg oil or fat should not result in adverse human health effects.   The previous cargo  should not be a known allergen.
       
        It is quite probable that some residue from the previous cargo can remain in the tank and its associated pipework after cleaning and also may also be absorbed onto the tank bulkheads.

      Oxidation and hydrolysis are considered as changes in quality.  Persistence and bioaccumulation are implicitly covereby the ADI (oTDI).

Solubility and vapour pressure should be taken into account when deciding on the appropriate cleaning procedures.

The Federation of Oils, Seeds and Fats Associations (FOSFA International) is a professional international contract-issuing and arbitral body concerned exclusively with world trade in oilseeds, oils, fats and edible groundnuts. About 85 percent of ships carrying oil cargoes operate under a FOSFA contract. The other 15 percent have equivalent contracts, but with other organizations.

A standard FOSFA contract is a “banned list terms” contract. This means that the buyer will accept delivery of the oil as long as the previous cargo in the ship’s tank was not on the banned list. The contract can be converted into an “acceptable list terms” contract by the inclusion of an optional clause within the contract, as agreed by both parties.

Although some regions and countries (e.g. European Union and United States) have adopted the acceptable list terms into their national legislation, the majority of countries have carried out a government or industry risk appraisal and acceptethat the banned list terms are satisfactory.

Thus, the majority of the edible fats and oils traded worldwidhave had a previous cargo which is on neither list. The main reason for using an acceptable terms contract is to reduce the potential risk to the product from any residue of the previous cargo.

OS products are deemed to present no harm to the marine environment and are therefore not regulated.

Edible fats and oils are carried in ship types 2 or 3, and these ships may carry each of the pollution categories X, Y, Z or OS.

The viscosity of a liquid is defineas a measure of the forces that work against a flow when a shearing stress is applied.  At higher temperatures, the viscosity becomes lower .

Temperature/viscosity relationship


20°C
40°C
60°C
Viscosity
Water:
1.00
0.66
0.47
(mPa.s)
Castor oil:
986
231
80


The viscosity of a cargo is a very important parameter when considering carriage by sea. The revised IMO regulations state that a cargo is considered to be a “high viscosity cargo” if its viscosity exceeds 50 mPa.s at 20°C.

IMO requires that the Master be informed of the viscosity of the cargo at 20°C prior to loading. If the viscosity is greater than 50 mPa.s, the Master must be informed of the temperature at which it drops below 50 mPa.s. 

If the cargo is discharged at a lower temperature, the first washings of the tank cannot be pumped to sea, bumust be pumped ashore for disposal. Most vegetable oils are loaded and discharged at 10° to 15°C above their melting point .

Microbiological growth  requires  the  righ combination  of  conditions:  moisture, temperature and nutrients. Edible fats and oils contain very low levels of proteins and carbohydrates, if any. In addition, a 1 000-tonne tank of most edible fats and oils will contain about 500 kg of water, but this is well dispersed and does not promote microbiological growth. As edible fats and oils are low in protein and moistures (normally < 0.5 percent for crude edible fats and oils and < 0.1 percent for refined edible fats and oils), microorganism contamination is not an issue.

Chemical substances causing microbial or pathogenic contamination are not known.

When lipids are removed from their natural protective environment (oleiferous cells for vegetable oils and adipocytes for animal fats) and stored or used, they undergo a reaction known as autoxidation.                       
Although oxidation is a spontaneous phenomenon, its kinetics can be accelerated or decelerated under the effects odifferent parameters .

Type of fat or oil, in particular the type of fatty acid. The more unsaturated the fat or oil, the greater its susceptibility to oxidative rancidity .

Old oils. Fresh oil should never be mixed with old, as the older oil catalyses oxidation in fresh oil extremely quickly. Pumps should therefore always be cleared of older oils, and the pipes should be inclined so that oil never remains in them .

      Temperature. Oxidation proceeds more rapidly as temperature increases, so each operation should be carried out at the lowest practicable temperature. The higher the temperature, the greater the extent of oxidation. A rule of thumb is that a temperature rise of 10°15°C reduces shelf-life by half. By the same token, shelf-life is doubled if the temperature is reduced by the same amount. An oil should never be stored at more than 10°–15°C above its melting point. Also, the external temperature of heating coils should never exceed 80°C, in order to prevent local overheating of the oil. By storing at the lowest possible temperature, taking into account the oil's setting pointoxidation can be kept to a minimum .

      Time. The greater the storage time, the greater the extent of oxidation. By minimizing the oil's storage time, oxidation can be kept to a minimum .

Light. Light, in particular UV, increases the rate of oxidation. Fats and oils should         therefore always be stored and handled protected from light transition metals. The rate of oxidation is greatly increased by the catalytic action of copper or copper alloys; such metals (exposed or plated copper alloys, brass, bronze, gun metal) must therefore be rigorously excluded from the systems. Other metals, such as iron, also have catalytic effects although less than copper. For this reason, pumps, tanks, pipes, valves, heating coils and other equipment coming into contact with the oil should never be made of or contain such metals


Hydrolysis

Hydrolysis is a reaction of oil with water to yield free fatty acids. Partial hydrolysis of triglycerides will yield mono- and diglycerides and free fatty acids. When hydrolysis is carried to completion with water in the presence of an acid catalyst, the mono-, di- and triglycerides will hydrolyse to yield glycerol and free fatty acids (acid hydrolysis). With aqueous sodium hydroxide, glycerol and the sodium salts of the component fatty acids (soaps) are obtained (alkaline hydrolysis). Hydrolysis does  no normally cause any  problems, as  long  as  the  products are  handled hygienically and have not come into contact with water . The hydrolysis of edible fats and oils is promoted by the presence of water, particularly at higher temperatures.
     
      Enzymes (lipases): lipases are often found in connection with contamination by organic material; they are present in the digestive tracts of humans and animals and in bacteria, and are also present in some edible oil sources (palm fruit, coconut); any residues of these lipolytic enzymes (present in some crude edible fats and oils) are deactivated by the elevated temperatures normally used in oil processing.
chemical catalysts (acids, bases, reactive metals).

Previous cargoes that might be able to induce/accelerate hydrolysis of edible fats and oils are:
acids and bases e.g. acetic acid, acetic anhydride, fatty acids, phosphoric acid, sulphuric acid, citric acid solution and sodium hydroxide solution.

       Previous cargoes containing water (> 5 percent water), e.g. fruit juices and potable water.
     
       Crude edible fats and oils containing lipases (palm fruit oil, coconut oil, animal fats); The first stage of producing palm oil is steaming to kill the lipases which are present in the fruit.

Hydrolysis reactions are not relevant in the context of the evaluation, because acids and/or bases are added to edible fats and oils during the refining process. Sodium hydroxide (basic) is added during saponification to remove the free fatty acids, while phosphoric and citric acids (acidic) are added during the degumming stage to remove phospholipids.

Deterioratioof edible fats and oils is dependent on the conditions during transport/storage (temperature), the materials of the tankers (possibility of leaching of tanker materials), the shape of the system itself (air/oil ratio and possibility of mixing with air) and the duration/residence time of edible fats and oils in the transport/storage system.

      Heating coils within tanks, tubes and the internal shell of heat exchangers are made of stainless steel. Valves and pipelines (supply lines) that come into contact with edible fats and oils are made of stainless steel or aluminium Aluminium may only be used when the acidity of the oil is low .

      The temperature during loading/discharge is 10°–70°C, depending on the fat or oil type. Heating should be applied such that average oil temperature increases at a rate of not more than 5°C in 24-hour period .  The  temperature during  storage/transport is  between  ambient  and  45°C, depending on the fat ooil type .
    
     
The  possibility  of  mixing  with  air  during  loading/unloading  and  during transport/storage or too much air contact in ullage space should be minimized. Nitrogen is used at sea to prevent air contact.

The general loss of quality due to oxidation (increase in peroxide values) or hydrolysis (increase in free fatty acid [FFA] content) during a voyage has always been present in the shipping of edible fats and oils in bulk by sea.

There are ways of reducing this as required  for example, nitrogen-blanketing the tank, if the cargo is refined oil to be used directly in the food-chain without re-refining.

Under FOSFA conditions, samples of a fat or oil are taken at three stages: pre- shipment, loading and discharge. At least five pre-shipment samples of the fat or oil loaded are taken at the ship’s rail or the nearest practical point prior to loading. At least five samples representative of the fat or oil are taken from each ship’s tank. At least five representative samples are taken during discharge at the ship’s rail or the nearest practicable point thereafter. Sampling is done in accordance with ISO 5555. In general, one of the samples taken at loading and one of the samples taken at discharge is analysed, and therefore data are available on the fat or oil contamination and quality change during transport

Oxidation affects the colour and flavour (taste, odour) of the oil, producing oxidative rancidity.

Hydrolysis affects the flavour (taste, odour) and acidity of the oil, producing hydrolytical rancidity.

Analytical methods for hydrolysis are based on determination of the hydrolysis products. Hydrolysis tests are based on the determination of the FFA content, humidity, acid value (or saponification value) or hydroxyl value. The acid value is the most widely used test method. Refined oils for domestic consumption are most susceptible to hydrolysis .

Normal values for refined oils in the Codex Standards indicative for oxidative or hydrolytic rancidity status are:
Peroxide value: up to 10 meq active oxygen/kg oil; and
Acid value/saponification value: up to 0.6 mg KOH/g oil.

Levels in cold pressed, virgin and crude edible oils and animal fats are higher. Previous cargoes with a colour, odour or strong taste might have an organoleptic effect on edible fats and oils (e.g. the odour of fish oil could affect the odour of other oils).

Chief officer must smell the tanks before they are loaded or unloaded and look into them during loading and unloading. Smell is a very sensitive sense.

Some  of  the  deterioration  of  oils  (e.g.  oxidation,  hydrolysis,  contamination by previous cargoes) can be cancelled by refining the oils.

There are few edible fats and oils, such as cocoa butter, olive oil and palm oil, which are not refined, because the organoleptic qualities would be lost after refining. Peanut oil and soybean oil are refined before transport to avoid allergenicity.

There are two main refining processes used on crude edible oils and fats: chemical/alkali refining and physical refining. They differ principally in the way free fatty acids are removed/

       Chemical refining consists  of degumming, neutralization, winterization, bleaching and deodorization.

       Physical refining consists of degumming, winterization, bleaching and deodorization.

Degumming
Crude edible fats and oils have relatively high levels of phosphatides (e.g. soybean oil) and may be degummed prior to refining. The purpose of degumming is to removseed particles,                                         impurities, phosphatides oholipids), pigments, carbohydrates, proteins and traces of metals.

Neutralization
Neutralization (sometimes referred to as refining or alkali refining) is generally performed on edible fats and oils to reduce the content of free fatty acids, oxidation products of free fatty acids,      residual  protein, mucilaginous substances, phosphatides (phospholipids), carbohydrates, sulphur compounds, traces of metals, pigments, oil-insolubles and water solubles.
Winterization is a process whereby edible fats and oils are subjected to controlled temperature decrease. During this process, waxes are crystallized and removed from the fat or oil by filtration to avoid clouding of the liquid fraction at cooler temperatures.– dewaxing – is utilized to clarify edible fats and oils containing trace amounts of clouding constituents

Bleaching
The purpose of bleaching (or decolorizing) is to reduce the levels of pigments, such as carotenoids and chlorophyll, but  it also further removes residues of phosphatides, traces of soap, traces of metals, oxidation products, sulphur compounds and proteins. The usual method of bleaching is by adsorption of these substances on an adsorbent material.

 Deodorization
The purpose of deodorization is to reduce the level of free fatty acids and to remove odours, off-flavours and other volatile components, such as pesticides and light polycyclic aromatic hydrocarbons. Further removal of the proteins is achieved at this step. The deodorization of edible fats and oils is accomplished by distillation.

SQUEEGEING AND PUDDLING
  

It may be necessary to “squeeze” (sweep) the cargo tanks, especially when carrying Vegetable and Animal Oils. This will involve personnel (either from the vessel or ashore) entering the cargo tanks to assist by manual means (squeegees etc) to maximize the outturn of cargo.

Most animal and vegetable oils undergo decomposition, this process, known as putrefaction, generates obnoxious and toxic vapours and deplete the oxygen in the tank. Tanks that have contained such product must be properly ventilated and the atmosphere tested prior to tank entry. This is especially important prior sending personnel into the tank for sweeping purposes.

In addition to putrefaction, certain oils like coconut coil can have hazards associated with the production of Carbon Monoxide (CO). These dangers are heightened during heating and the final stages of discharge when CO levels have been known to reach in excess of 3,000ppm. As a result, it is essential that before entering a tank for either “squeezing” the last remaining cargo or for tank cleaning that the following precautions are taken.

The atmosphere of the tanks is monitored regularly throughout discharge for the presence of CO. Temperatures should also be taken as excessive temperatures will assist in the production of CO.

The eight-hour safe exposure limit for CO is given as ,  30PPM  although short-term exposure (15 minutes) of up to 200ppm can be allowed under exceptional circumstances. CO is toxic by inhalation and can cause serious damage to heath. Accordingly, a meter, capable of measuring these limits, must be on board. Full enclosed space entry procedures as detailed in the SEM must also be followed with additional checks made for CO. Failure to follow these precautions may result in fatalities.

Use the 4 runner portable gas instrument to measure O2/ HC/ CO/ H2S with ventilation STOPPED.

In such cases, all Enclosed Space Entry Procedures and precautions must be adhered to. While squeegeing veg oils the vent fans must be run and steam coils put off. Oxidizing and putrifying veg/ animal oils are dangerous for the sweeper. For high MP cargoes in winter, the crew must do this job FAST, and in a intelligent manner ,or the cold vent air will cause clingage , and unpumpables, which will cause surveyor to demand fresh intake of hot cargo and redoing the whole job a second time.

For cargoes which require “squeezing” (sweeping), it is essential that correct voyage and discharge temperatures are maintained and that the tank bottoms are checked for hard factions in ample time before arrival at the discharge port.

Providing that the vessel arrives with the correct discharge temperature, heating should be gradually reduced when the discharge is commenced and finally shut off when the tank is approximately ¾ empty (this is important to prevent burning of the cargo as the heating coils become exposed).

At least one hour before the commencement of “squeezing” (sweeping) operations, the air blowers must be put on the tank to ensure a safe atmosphere during the operations. Special attention must be paid to the possibility of CO (Carbon Monoxide) being present in tanks which have contained Coconut Oils and the CO content of the tanks prior to and during “squeezing” (sweeping) operations must be monitored (this, in addition to LEL, O2, H2S) and mechanical ventilation of the tanks must be effective and in continuous operation throughout.

All Enclosed Space Entry precautions and procedures must be in place prior to personnel entering the tank(s).

A risk assessment form must be completed. 

USE A MATRIX OF 

SEVERITY-- VERSUS PERIOD OF IMPACT/ CERTAINTY 

-- your company RISK ASSESSMENT form may be a bullshit form 

with a capital B -- 

you as a responsible Captain or Chief officer or OOW need to 

protect your crew NOT keep an external auditor and your own 

company S&Q dept happy. 

Remember there might be Carbon Monoxide inside the tank, the 

tank can be slippery, fish oils and animal fats can have viruses 

which requires virus filters, you crew can get scalded badly 

without proper waders, while sweeping at the bellmouth sudden 

stop of Framo impeller can cause a vacuum in the stack due to 

falling column causing liquid flashing into hot vapour, too much

difference between temperatures inside and outside tanks can 

cause back ache and cramps , you can have a stupid and over 

zealous shore surveyor etc 

Personnel should wear all necessary PPE prior to entering the tank(s).

Personnel should enter the tank when the cargo level drops below the framing but above the heating coils (approximately 0.5m of cargo remaining).

Agitation and mixing of the cargo by personnel in the tanks should continue until the tank is pumped dry. If heavy clingage is apparent on the tank bulkheads and stringers, wash down this residue with cargo from the tank by re-circulating from the offshore manifold via a hand hose back into the tank.

During the “squeezing” (sweeping) operations a person must be standing by at the pump controls to adjust the discharge rate according to the progress of the operations.

Immediately on completion of the “squeezing” (sweeping) operations, all equipment used should be thoroughly cleaned. Footwear should be changed immediately on evacuating the tank in order to prevent the spread of residues overall.

Sweeping high MP palm oils heated to high dischg temperature requires close supervision . Sweeping equipment and waders must be kept in readiness and tank dry surveyor must be available to declare when enough is enough.  Remember once the cargo falls below the level of steam coils things must happen the way it is desired, before it solidifies.

FFA of certain heating cargoes cargoes will increase if the moisture content is too high. Veg and animal oils have different SG at different levels after long storage. FFA of the layer closest to the coils increases faster and cause damage to the bottom—so recirc  Vegetable oil and Animal oil in coated cargo tanks. Advantages are less manual labour for squeezing.

Before anybody enters an empty tank for squeezing , it must be ventilated and a gas measurement carried out. Oxidation processes may lead to a life-threatening shortage of O2. Contact of oils and fats with oxygen, present in the atmosphere, causes chemical changes in the product which downgrade the quality. Much can be gained by reducing the amount of air contact . Oxidation proceeds more rapidly as temperature increases, so each operation should be carried out at the lowest practicable temperature

If vsl is discharging high MP cargoes the surveyor must be present at stripping/ sweeping time.

If you do puddling after wearing approved heat resistant boots reaching above the knees, the squeegeing effort later,  becomes a lot easier.

                     FOSFA


FOSFA stands for ------Federation of oil seeds & fats association.

Internationally 85% of global trade in oils and fats is under FOSFA terms, as they claim in their web site. They have about 57 banned cargoes and 104 acceptable cargoes in their list.

NIOP stands for-------National institute of oil seeds production ( A&B)

Both these agencies have an acceptable and banned list of previous cargoes.

Edible oils can be booked only under one of the above 4. Find out which list is valid/ FOSFA acceptable or banned. Master to ensure in writing.

FOSFA and NIOP may not agree with each other. The list are revised regularly and make sure you have the latest if you cant find the chemical name.

Other lists are EU, Procter & Gamble and Kosher.

EU list is between members of the European union, and they like to keep things stricter than FOSFA.

For Procter and Gamble , zinc tanks are not accepted for fatty acids.

Kosher list is a small one for Jews . When you load acetic acid , crude Glycerine  etc you can have a couple Rabbis on deck to do some ceremony. After this ceremony the value of the cargo goes up multifold, hence ensure that the ship staff  co-operates and do not quote some safety/ security rule and drive the souls away. They will also need to watch the entire process of loading and seal the tank openings. For Kosher, the last 3 cannot be Tallow or Tallow derivative , Fish oil or Wine.

No closed blisters or loose splits shall be allowed in a coated cargo tank. Mild steel exposure in coated tanks shall be reduced to a minimum and in no case can have loose rust.

Tankcleaning solvents must be accepted as previous cargo. You will be required to give a written tankcleaning history. Nitric acid is a FOSFA banned chemical. BSolve is an NIOP banned chemical.

Styrene and EDC are banned as last 2 cargoes in epoxy tanks. Both are banned as last cargo in stainless steel and zinc tanks.

NIOP does not permit lead products like leaded gasoline as the last three. When you carry gasoline ensure you get the lead content in writing.

Proper sampling procedures incl foot sampling of cargo tansk is called for.

Last 3 should be atleast 60 percent by volume of the tank in case the fourth last  previous cargo is banned.

Recoated cargo tanks are considered as newbuildings.

A statement in the form of FOSFA ‘ international ship’s qualification combined  master’s certificate’ signed by master/ mate shall be provided for the shipper, certifying that the ship is qualified for the coming voyage with edible oil.

There is no difference between oils and fats---only that fats are solid at room temperatures.

Fatty acids and Carboxylic acids are present in animal and veg oils. Most veg oils are mixtures of several fatty acids.

FOSFA requires ships to follow IASC heating instructions, which means no use of thermal heating fluids other than water and steam.

TYPES OF VEGETABLE OILS

* DRYING OILS.
CHINA WOOD OIL POPPYSEED OIL PREWASH WITH
CANDLE NUT OIL RUBBERSEED OIL COLD SEA WATER
HEMPSEED OIL SAFFLOWER OIL THEN MAIN WASH
LINSEED OIL SOYA BEAN OIL WITH HOT SW AND
MENHADEN OIL TALL OIL INJECT CAUSTIC
MUSTARDSEED OIL TUNG OIL POTASH LIQUID
OTTICEA OIL WALNUT OIL ( LAC)
PERILLA OIL

* SEMI-DRYING OILS.
BABASSU OIL COD OIL PREWASH WITH
CODLIVER OIL COTTONSEED OIL COLD SEA WATER
CROTON OIL HERRING OIL THEN MAIN WASH
JAP FISH OIL MAIZE OIL WITH HOT SW AND
SARDINE OIL SESAME OIL INJECT CAUSTIC
SHARK OIL SUNFLOWERSEED OIL POTASH LIQUID.
WHALE OIL WHEAT OIL (LAC)

* NON-DRYING OILS.
ALMOND OIL ARACHIS OIL (GROUNDNUT)
CAMPHOR OIL CANADA OIL
CARAPA OIL CHASHEW NUT OIL
CASTOR OIL COCONUT OIL
COHUNE OIL CURI CURI OIL PREWASH WITH HOT
GERANIUM OIL LARD OIL (ANIMAL) SEA WATER THEN
NEATSFOOT OIL OLIVE OIL MAIN WASH WITH
PALM OIL PINE OIL HOT SW AND INJECT
RAPESEED OIL (COLZA) RICE OIL CAUSTIC POTASH
SEAL OIL SPERM OIL BASED LIQUID
TACUM OIL TALLOW OIL ( LAC )
TEA SEED OIL
* WATER SOLUBLE PRODUCTS.
MOLASSES


-------CAPT AJIT VADAKAYIL ( 28 YEARS IN COMMAND )

6 comments:

  1. Well done for all your hard work in providing this high quality blog.Thanks for great information you write it very clean.Tanker loading

    ReplyDelete
  2. Dear Capt. Ajit
    Please explain, in the last case, the last cargo is RBD Palm stearin in ship's tanks, then the next cargo to be loaded is Pyrolysis Gasoline (PYgas) how the ship tank cleaning methods. In the case of a vessel load for one foot, after unloading the sample is taken and then sent to a laboratory, the results of the
    analysis stated that Extinten Gum 'Off Specification (Spec. < 4 mg), the question, whether RBD Palm stearin contains a lot of Gum.

    ReplyDelete
    Replies
    1. hi ad,

      RBD Palm stearine is a very difficult last cargo to clean --as it has VERY HIGH melting point, requiring ballast and cold interface on all 5 sides to be removed before washing with water with temp as high as 80 deg c and then washed with caustic potash alkaline cleaner . additionally all the lines have to be flushed same way.

      i am 100% sure that the tank was NOT washed properly .

      PYgas dissolves the remanent stearine and show up in the first foot sample.

      capt ajit vadakayil
      ..

      Delete
  3. Dear Capt. Ajit,

    Myself Anisha, an interior designer. I'm here for my husband Abhimanue Ambatt, who's a chief officer and he's on board. Few days ago,he asked me to search for the tank cleaning procedure for loading vegetable oil and as a part of my search,I came across your blog. So here are the conditions on board.

    - last cargo was gasoline
    - next cargo would mostly be crude soya bean oil.

    The queries are if any particular chemical to be used for tank cleaning also there's this pungent smell of gasoline.

    Please advise on the doubts he has.

    Thank you in advance.

    Cheers!

    ReplyDelete
    Replies
    1. hi a,

      tanks must be cleaned with a detergent ( which includes a surfactant and an emuslifier ) to remove the traces of annex 1 gasolene. --inject it into the wash water .

      steam the tanks after wash to get rid of odour.

      if the tanks are epoxy-- before washing, the tanks have to be vented.

      capt ajit vadakayil
      ..



      Delete
  4. Sir,
    Is Kachi Ghani Mustard Oil good for health and body massage?

    ReplyDelete