Tank Cleaning Procedure « Knowledgebase

Use of this Section

These guidelines have been made up using the USCG Compatibility Guide to assign cargoes to different groups. There are certain groups example: 20 – Alcohols, Glycols that, on the basis of compatibility, encompass a range of cargoes, from those with high vapor pressures to those with low vapor pressures and from completely water soluble products to totally insoluble products. As such, it is very important to take examine those basic characteristics – solubility, vapor pressure, melting point, and flash point – when planning the cleaning method.

The guidelines do not account for the degree of solubility, treating completely soluble products and those that are partly or even just slightly soluble all in the same way. The only distinction made is between soluble and non-soluble products, but this factor should also be taken into consideration when planning the cleaning method.

The recommended cleaning times are only a guide and may need to be adjusted up or down for differences in tank structures, coating conditions, coating types fixed or portable butter worth machines, or machine coverage (shadow areas) etc.

In many cases, the guidelines make reference to a number of machine cycles. For ships equipped with fixed butter worth machines that have good coverage (no need to supplement with portable machines) this is fairly straightforward. For ships that use fixed butter worth machines supplemented by portable, or all portable machines and depending upon the solubility of the product, the cycles may need to be repeated at more than one drop.

Acids

Phosphoric- See Special Cargoes Handling Manual

Sulfuric, Spent Sulphuric- See Special Cargoes Handling Manual

Acrylic- See Special Cargoes Handling Manual

Formic – See Special Cargoes Handling Manual

Water Soluble Acids

Acids that are water-soluble can usually be cleaned only using ambient temperature salt and/or fresh water. With all water-soluble acids, it is important that initial cleaning is done with copious amounts of fresh or salt water being introduced into the tank at the beginning. The violent chemical reaction between the acid and the water is thus rapidly and progressively reduced. It is important that portable machines supplement fixed machines where necessary to introduce the necessary volume. As with any cleaning, ensure the melting point of the acid is less than that of the water used for cleaning. It is very important that all areas of the tanks, lines, drains, dead ends, valve plugs, etc. are completely flushed with an adequate amount of water so as not to allow any acid to remain. Any mixture of acid and water left in any part of the cargo system can result in serious pitting problems and in many cases, cause the specification failure of first-foots or even full tanks of subsequent cargo.

Non Water Soluble Acids

Acids that are not water-soluble are generally those which derive their acid content from processes, during which they are progressively refined. The percentage of acid is generally quite small, so other factors, such as Melting point, Odor, solubility in solvents, alcohols, surfactants, acids, alkalyenes etc, are more important in determining the best cleaning.

Cleaning of non water soluble acids in stainless steel

If cleaning cannot start immediately, or shortly after completion of discharge, it is important that the tank atmosphere is kept both moist (not allowed to dry) and warmer than the melting point of the product discharged. Moisture can be added by means of a quick fresh water rinse down or, where local regulations prohibit this, the additional of a small amount of low-pressure steam, being careful not to apply too much heat to the tank.

Once machine washing can be performed, start cleaning with ambient temperature water or, in cases where the product was heated for discharge, at water equal to discharge temperature. Wash for 1 hour, followed by hot water for a minimum of 2 hours. Inspect the tank and, if more than hand cleaning is needed, utilize one of the following, depending upon the amount of residue remaining and the time available.

Light residues

The tank can be sprayed with RXSOL-20-1011-MB, left to stand for ½ to 1 hour and then washed. It may also be beneficial to spray with RXSOL-20-2002-PLUS immediately after applying the RXSOL-20-1011-MB, as it gels and holds onto larger or problem areas of the tank surfaces for a longer period.

Heavier residues

The tank can be recirculated with a 15-20% Caustic flake / fresh water solution, mixed with 105 – 210 liters of Teepol, heated to 40°C for 2-3 hours. At no time should the solution be allowed to be greater than 50°C, otherwise this will leave Caustic residues (white powder) on the surfaces. Following the recirculation period, the tank has to be further butter worthed with sea water 60 – 70°C for 3 hours and then fresh water rinsed; alternatively, this process can be carried out using fresh water only if the quantity is available. As normal during any tank cleaning, the pump stack drain outlet water should be checked to see that it is clear.

Making caustic / Teepol solutions

Accurately measuring the components of a solution is not difficult. The required amount of chemical can be based on the known volumes of a standard drum (210 liters) or smaller containers as supplied, usually of 20, 30 or 50 liters capacity. To determine the amount of water to fill into the tank, take an empty 210 liter drum, fill it with water from the supply hose, noting the time it takes to fill and then multiply this as required to match the full amount.

The water should be heated to the required 40°C before the Caustic flakes are added. Those handling the Caustic should wear the appropriate personal protective safety equipment, including goggles and rubber gloves. Great care must be taken not to allow the internal plastic membrane of the bag to fall into the tank, as it can foul the cargo pump impeller. Once the Caustic and Teepol have been introduced and all the tank hatches covered with plastic sheeting, recirculation of the mixture can commence.

If portable machines are being used, recirculation should be stopped whenever lowering to the next drop, in order to avoid a jet of the solution possibly striking the seaman maneuvering the hose.

100 kgs caustic flake added to 1000 ltrs fresh water will equal 10% solution

For each 5,000 liters of fresh water, add 105 liters of Teepol.

See separate solution mix guidelines sheet.

Alternative to caustic / Teepol re-circulation

Recirculate the tanks with 3 – 5 % solution of RXSOL-20-1011-MB.

Fill the tank with desired amount of fresh water, heat to 45-50°C and then add the measured quantity of RXSOL-20-1011-MB to obtain the desired 3-5% solution. The solution should be circulated for a minimum of 2 hours, followed by seawater BW and then rinsed out with fresh water. The whole process can be carried out with fresh water if a sufficient quantity is available. The outlet water from the stack drain must be checked to ensure that there are no traces of acid or foam. Testing for acid content should be done with litmus paper (PH neutral 7.0) for use mainly in stainless tanks.

Cleaning of non water-soluble acids in epoxy lined tanks

As with Stainless Steel linings, it is important to keep the atmosphere warm and moist if cleaning cannot take place immediately upon completion of discharge.

If more than water cleaning is required, then the Caustic / Teepol / fresh water solution should be made up as described for Stainless Steel and recirculated for at least 3 hours. More time will be required in tanks under certain ambient conditions (single skin cold water), or in those tanks with many frames and internal structures, or those with poor coverage by the fixed or portable BW machines etc.

Caustics

Products from this Compatibility Group routinely carried include:

Caustic Soda

Caustic Potash

Potassium Hydroxide

Sodium Hydorsulfide

The Caustic solutions we carry are all completely water-soluble, making them fairly straightforward to clean.

Cleaning in Stainless Steel

Initial wash water temperature should be at least 10°C above the melting point, but never above 50°C. Temperatures above 50°C may result in white powder (Caustic salts) remaining on the tank surfaces. Should this happen, these residues can be removed by spraying a 2-3% solution of RXSOL-20-1011-MB, followed by washing with fresh water or with salt water followed by fresh water. Normally 2-3 machine cycles is sufficient for cleaning after Caustics.

Cleaning in Epoxy

The same procedure as described for Stainless Steel should be followed. However, if any white powder remains after cleaning, try to avoid the use of RXSOL-20-1011-MB. Odorless Mineral Spirits can be a useful alternative in hand cleaning spots or even larger areas. If all tank surfaces have residues, recirculation of a Caustic solution should be considered.

Ammonia Solutions

There are only a few cargoes which we carry that fall into this group. All are water-soluble, making them fairly straightforward to clean. Depending upon the exact Ammonia content, Urea Ammonium Nitrate solution may be assigned to this group. With the exception of residual odor, this is a relatively easy product to clean. However; it is common practice to apply a blanket of black oil in the shore tanks, to minimize evaporation of the product. Occasionally, the shore tanks at the load port may be emptied and part of this oil blanket may be pumped to the ship as well. When this happens, the oil will float to the surface in the ship’s tank. During transit and discharge, it will effectively coat all surfaces with an oily residue. It is important to not only ask at the load port if any shore tanks will be emptied but also to sample/check the ship’s tanks after loading and before discharge. In cases where the black oil is present, then the tanks will need to be cleaned in a similar manner as after Lube oils/additives. To rid the tanks of odor after the initial wash with warm (45-50°C) water, the temperature should be increased to hot 80°C or above and washing continued for a minimum of 4 hours.

• When cleaning is carried out on tanks that have last contained these solutions, there is initially an in-rush of air to the space followed by an escape of vapors as the wash water is first introduced. To avoid damages to the tank (s) first from over pressure followed by a vacuum sufficient hatches should be opened. Also, to ensure that any escaping hazardous vapors do not approach to the accommodation block, the course should preferably be such that the prevailing wind is blowing across the ship.

Aromatic Amines

These products vary from completely soluble to slightly soluble in water. However, any residues from those that are only slightly soluble can be removed during normal water washing. Most all of these products have an odor that will need to be removed. If there is residual odor, spraying with Butyl Cello solve, followed by a hot wash, or spraying with 1-2% bleach solution, washed off immediately and completely with fresh water, will assist in removing the odor.

Cleaning in Stainless Steel tanks

For products that do not require any heating during voyage and/or discharge, commence washing with ambient temperature water. For products that require heating for voyage and/or discharge, the initial wash water should be similar to discharge temperature of the product. Initial washing should be done for 2 machine cycles and the temperature should then be increased to 60-70°C for non heated cargoes and 80°C for those which required heating for discharge and washed for a minimum 2 hours. If odor is still present after washing, it can be removed from Stainless Steel tanks by spraying down with bleach, followed by a fresh water rinse.

Cleaning in Epoxy Tanks

Similar to Stainless Steel, but hot wash should continue for minimum of 3 hours.

As some products in these groups may soften certain tank linings, the odor may be persistent, making it necessary to extend or even repeat cleaning processes. If odor is still present after washing in Epoxy tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach leave for two or three days. Then ballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit such a lengthy procedure, then spraying with 1-2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Recirculation with Butyl Cello solve will also assist in odor removal.

Cleaning in Zinc Tanks

Similar to Stainless Steel, but hot wash should continue for a minimum of 4 hours.

As some products in these groups may similarly soften certain tank linings, the odor may again be persistent, likewise necessitating repeating or extending cleaning processes. If odor is still present after washing in Zinc tanks and there is time available, it can also be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit this lengthy option, spraying with 1-2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Steaming with Methanol or recirculation with Butyl Cello solve will also assist in odor removal.

Amides

Dimethyl Formamide (DMF) is the only product in this Compatibility Group that we normally carry. As the product is soluble in water, cleaning is fairly straightforward. If any other Compatibility Group #10 cargo is scheduled for carriage, contact the Ship Operator for cleaning guidelines.

Cleaning in Stainless Steel Tanks

Organic Anhydrides

Acetic Anhydride is the only product in this Compatibility Group that we normally carry. As the product is water-soluble, cleaning is fairly straightforward. If any other Compatibility Group #11 cargo is scheduled for carriage, contact the Ship Operator for cleaning guidelines.

Cleaning in Stainless Steel Tanks

Commence cleaning with ambient temperature water for 2 machine cycles, followed by hot water for 2 hours. Do not start with hot water as product can decompose and form Acetic Acid. If odor is still present after washing, Stainless Steel tanks may be sprayed with a 1 – 2% Bleach solution, washed off immediately and completely with fresh water.

Epoxy and Zinc linings currently used on board ships we operate at the present time are not suitable for carriage. Should the cargo be carried in coated space the cleaning procedure for Stainless Steel should be used.

Commence washing with ambient temperature water for 2 machine cycles, followed by hot 80°C for a minimum of 2 hours. If odor is still present after washing for Stainless Steel tanks, spraying down with Bleach follow by a fresh water rinse should prove adequate.

Cleaning in Epoxy Tanks

Similar to the procedure for Stainless Steel tanks, but hot wash should continue for a minimum of 3 hours.

As some products in these groups may soften certain tank linings, the odor may be persistent, making it necessary to extend or even repeat cleaning processes. If odor is still present after washing in Epoxy tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit such a lengthy procedure, then spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Recirculation with Butyl Cello solve will also assist in odor removal.

Cleaning in Zinc Tanks

Similar to Stainless Steel, but hot wash should continue for a minimum of 4 hours.

As some products in these groups may similarly soften certain tank linings, the odor may again be persistent, likewise necessitating repeating or extending cleaning processes. If odor is still present after washing in Zinc tanks and there is time available, it can also be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit this lengthy option, spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Steaming with Methanol or recirculation with Butyl Cello solve will also assist in odor removal.

Isocyanates

Refer to Special Cargo Handling Manual

Vinyl Acetate

Products from this Compatibility Group routinely carried include:

Vinyl Acetate Monomer (VAM)

Vinyl Neodecanoate

Veova 10

Vinyl Acetate Monomer is inhibited and is soluble in water, whereas Vinyl Neodecanoate and Veova are neither inhibited, nor water-soluble. Although inhibited products are generally quite easy to clean to Water White standard, they can cause problems with Permanganate Time, when cleaning to Wall Wash standard. Indeed, this may involve products back as far as the 5th previous cargo.

Cleaning in Stainless Steel Tanks

Initial washing with ambient water for 3 machine cycles followed by warm water 50-60°C for 2 hours.

Cleaning in Epoxy Tanks

These products are likely to soften epoxy-lined tanks and reference should always be made to the Manufacturer’s Coating Resistancy Guidelines. This softening can further complicate the process when cleaning to a standard higher than Water White.

Tanks should be well emptied of product and, where possible, ventilated prior to washing. The Acetate and water form Acid, which can damage the coating. Initial washing should be with ambient water for 3 machine cycles, followed by warm water 50-60°C for 3 hours. Inspect the tank and if the coating is softened, further forced ventilation for 24 hours or a mild 5% Caustic recirculation for 2-3 hours will help to cure the coating.

Cleaning in Zinc Tanks

These products are likely to soften zinc-lined tanks and reference should always be made to the Manufacturer’s Coating Guidelines. This softening can further complicate the process when cleaning to a standard higher than Water White.

Tanks should be well emptied of product and, where possible, ventilated prior to washing. Acetate and water form Acid, which can damage the coating. Initial washing should be with ambient water for 3 machine cycles, followed by warm water 50-60°C for 3 hours. Inspect the tank and if the coating is softened, further forced ventilation for 24 hours will help to cure the coating.

Acrylates

We carry many Acrylates and the solubility ranges from those that are completely soluble to others that are not soluble at all in water. However, the main difficulties in cleaning Acrylates involve the removal of odor and problems with low Permanganate Time when cleaning to a Wall Wash standard.

Cleaning in Stainless Steel Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot for 2 hours. If odor is still present after washing, Stainless Steel tanks may be sprayed with a 1 – 2% Bleach solution, washed off immediately and completely with fresh water. The application of a 1 – 2% Bleach ( or other Oxidizer) solution will also assist when problems are experienced with Permanganate Time, in preparation for a subsequent Wall Wash standard cargo.

Cleaning in Epoxy Tanks

Reference to the Manufacturer’s Coating Resistancy Guidelines will indicate if there is a likelihood of softening of the coating. Wash with ambient water for 3 machine cycles, followed by hot water for 3 hours.

If odor is still present after washing in Epoxy tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit such a lengthy procedure, then spraying with Butyl Cello solve, followed by a hot wash, or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, are both alternative procedures that will assist in odor removal.

Cleaning in Zinc Tanks

If odor is still present after washing in Zinc tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit this lengthy option, spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Steaming with Methanol or spraying with Butyl Cello solve, followed by a hot temperature wash, will also assist in odor removal.

Substituted Allyls

Products from this Compatibility Group routinely carried include:

Acrylonitrile (See also Special Cargo Handling Manual – inclusion at specific Customer’s requirement)

Methacrylonitrile

Allyl Alcohol

Dichlorpropene

Note – Check the Inhibitor Certificate for the Acrylonitrile as supplied at the load port. Most often the product is inhibited to 150°F (65°C). Experience suggests that washing immediately after discharge with hot water (80°C+) assists in increasing the Permanganate Time when preparing for a subsequent cargo with a Wall Wash requirement.

Cleaning in Stainless Steel Tanks

Except for Acrylonitrile as per the note above, wash with ambient temperature water for 2 machine cycles, followed by hot water (80°C) for 2 hours.

Cleaning in Epoxy Tanks

Wash with ambient temperature water for 2 machine cycles, followed by hot water (80°C) for 3 hours. When stowed in Epoxy tanks, cargoes of this category may soften the coating, making it necessary to ventilate the tanks for 24 hours or more after discharge. Alternatively, recirculation with a 5% mild Caustic solution will help cure the coating.

Cleaning in Zinc Tanks

Wash with ambient temperature water for 2 machine cycles, followed by hot water (80°C) for 3 hours. Cargoes in this category may soften the coating making it necessary to ventilate the tank for 24 or more hours to help cure the coating.

Alkylene Oxides

See Special Cargo Handling Manual

The only Compatibility Group No. 16 cargo that we carry is Propylene Oxide. Refer to Special Cargo Handling Manual.

Epichlorohydrin

Cleaning in Stainless Steel Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot water for 3 hours. If odor is still present after washing, Stainless Steel tanks may be sprayed with a 1 – 2% Bleach solution, washed off immediately and completely with fresh water.

Cleaning in Epoxy Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot water for 4 hours. If odor is still present after washing in Epoxy tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit such a lengthy procedure, then spraying with Butyl Cello solve, followed by a hot water wash (80°C), or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, are both alternative procedures that will assist in odor removal.

Ketones

Depending on odor, next cargo and vapor pressure, some cargoes from this group can be cleaned by ventilation alone. Whenever cleaning by ventilation, it is very important that the pump and line systems are completely flushed out with fresh water. This includes removal of all valve drain plugs, flushing of drain-cocks, draining of the vent line and trap, stripping lines, etc.

However, the above procedure does not apply to all cargoes in this group and a full machine wash may be required. For those products with a persistent odor, an initial ambient temperature water wash, followed by hot water should prove sufficient. For products with a solubility or vapor pressure problem, machine-washing with ambient temperature water for 2 hours should be adequate in all linings.

As some of these products may soften the tank coating, ventilation prior to any water washing will help to restore the hardness of the coating. Attention is drawn to the notes against such cargoes in the Manufacturer’s Coating Resistancy Guides and in the STOW program.

Aldehydes

The majority of products in this Compatibility Group are not water-soluble and have strong odors.

Cleaning in Stainless Steel Tanks

Wash with ambient temperature water for 2 machine cycles, followed by hot (80°C or higher) for 3 hours. If there is persistent residual odor, then spraying with Butyl Cello solve, followed by a hot water wash, or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard.

Alcohols, Glycols

Depending on odor, next cargo and vapor pressure, some cargoes from this Compatibility Group can be cleaned by ventilation alone. Whenever cleaning by ventilation, it is very important that the pump and line systems are completely flushed out with fresh water. This includes removal of all valve drain plugs, flushing of drain-cocks, draining of the vent line and trap, stripping lines, etc.

Glycol cargoes, being completely water-soluble and with low melting points, will generally require an ambient temperature wash. If residual odors are persistent, this should be followed with a hot water wash.

Fatty Alcohol cargoes are not water-soluble and often have a melting point above that of ambient temperature seawater. These generally require an initial ambient temperature wash for 3 machine cycles, followed by a hot water wash for 4 hours.

Cleaning in Epoxy Tanks

Wash with ambient temperature water for 2 machine cycles, followed by hot (80°C or higher) for 3 hours. If there is persistent residual odor, then spraying with Butyl Cello solve, followed by a hot wash, or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard.

Cleaning in Zinc Tanks

Wash with ambient temperature water for 2 machine cycles, followed by hot (80°C or higher) for 3 hours. If there is persistent residual odor, then spraying with Butyl Cello solve, followed by a hot water wash, or steaming with Methanol, will assist in preparing the tank to the required standard.

Phenols Cresols

Cargoes in this Compatibility Group are either soluble or slightly soluble. However, they can have rather strong odors.

Cleaning in Stainless Steel Tanks

The initial wash should be at the discharge temperature of the product for 3 machine cycles, followed by hot water 85°C wash for 4 hours. If there is persistent residual odor, then spraying with Butyl Cello solve, followed by a hot water wash for 1 hour, or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard.

Cleaning in Epoxy Tanks

Cleaning in Zinc Tanks

The initial was should be at the discharge temperature of the product for 3 machine cycles, followed by hot water 85°C was for 4 hours. If there is persistent residual odor, then spraying with Butyl Cello solve, followed by a hot water wash for 1 hour, or spraying with 1 -2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard. Steaming with Methanol is an additional process that may be considered.

Caprolactam Solution

Cargoes in this Compatibility Group have a strong odor and, depending upon the solution, may have a high melting point.

Cleaning in Stainless Steel Tanks

Determine the melting point of the product and wash for 3 machine cycles at 10°C above that melting point, followed by hot water 85°C for 4 hours. If there is a strong and persistent residual odor, further hot water washing should be applied. When the odor has been reduced to a moderate level, spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard. Steaming with Methanol is an additional process that may be considered.

Cleaning in Epoxy Tanks

The initial wash should be at the discharge temperature of the product for 3 machine cycles, followed by hot water 85°C wash for 4 hours. If there is persistent residual odor, then spraying with Butyl Cello solve, followed by hot water wash for 1 hour, or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard.

Cleaning in Zinc Tanks

Olefins

There are a number of products we carry that are assigned to this Compatibility Group. Generally they are Not water-soluble. The inhibitor in Styrene Monomer will affect Permanganate in preparation for a subsequent Wall Wash standard cargo.

The various Olefins, such as Propylene Tetramer and Nonene, can all exhibit problems with Hydrocarbons, in preparation for a subsequent Wall Wash standard cargo. Products such as Dipentene and Dicyclopentadiene have odors, which can be difficult to remove.

Regardless of type of tank lining, the initial wash should be carried out with ambient temperature water and for a duration long enough to displace the remaining product.

Styrene Monomer

For Styrene Monomer follow guidelines as per Acrylates

All others

Cleaning in Stainless Steel Tanks

Initial wash with ambient temperature water for 3 machine cycles followed by hot water at 85°C for 4 hours. If the subsequent cargo requires a Wall Wash check tank for Hydrocarbons. For light Hydrocarbons, Methanol or MEK spray may be all that is required. For heavier Hydrocarbons recirculation of a RXSOL-20-2002-PLUS solution or Butyl Cello solve followed by hot wash may be required. If odor persists recirculation of Butyl Cello solve, spraying with Bleach, which is immediately and thoroughly, rinsed/washed off or steaming with Methanol should help.

Cleaning in Epoxy Tanks

Wash with ambient temperature water for 3 machine cycles followed by hot water 85°C for 4 hours. Check particularly for Hydrocarbons in preparation for a subsequent Wall Wash standard cargo. For light Hydrocarbon residues, an MEK spray may prove adequate. For heavier Hydrocarbon residues, recirculation of a RXSOL-20-2002-PLUS solution or Butyl Cello solve, followed by hot water wash may be required. If there is a persist residual odor, then recirculating Butyl Cello solve, followed by hot water wash for 1 hour, or spaying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard.

Cleaning in Zinc Tanks

Paraffins

Cargoes we carry covered by this Compatibility Group are generally not water-soluble. With the exception of waxes, ambient water should be used for initial cleaning.

Wash with ambient temperature water for 3 machine cycles, followed by hot water 85°C for 4 hours. Check particularly for Hydrocarbons, in preparation for a subsequent Wall Wash standard cargo. For light Hydrocarbon residues, an MEK spray may prove adequate. For heavier Hydrocarbon residues, recirculation of a RXSOL-20-2002-PLUS solution or Butyl Cello solve, followed by a hot water wash for 1 hour, or spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water, will assist in preparing the tank to the required standard. Steaming with Methanol is an additional process that may be considered.

Waxes

At the completion of discharge the tanks must be confirmed well stripped/empty. This should normally be accomplished by checking the shore quantity received against the ship’s arrival figure. In cases where the shore figure cannot be obtained, the ship’s officers should use all possible means to determine that there is not a large amount of “clingage”. An experienced officer should perform an efficient stripping procedure as tank (s) are emptied, dipping the tank(s) and visual confirmation should be obtained whenever possible.

If the amount of “clingage” is determined to be excessive, rough washing of the tanks to appropriate slop reception facilities must be carried out.

Any solids collected from the tank(s) during any part of the cleaning process should be disposed of ashore.

Any cleaning at sea, irrespective of whether it is the initial wash or after the rough wash ashore, should be carried out at not less than 30 miles from shore, in at least 25 meters of water, with a speed not less than 7 knots and with the discharge below the water line.

We carry numerous grades of waxes and the ones with high melting points may require special cleaning procedures and the application of chemicals to reach the required standards. In cases where the melting point is higher than 65°C; the Ship Operator should be consulted to as to best method to utilize.

In all tank linings, the initial wash should be at the discharge temperature of the wax for 3 cycles, followed by hot water (as hot as possible) for at least 4 hours. Final rinsing should be carried out with fresh water.

Cargoes other than waxes

Cleaning in Stainless Steel Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot water wash for 2 hours. If there is persistent residual odor, then spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water or recirculation with Butyl Cellosolve, followed by a hot water wash for 1 hour, will assist in preparing the tank to the required standard. Steaming with Methanol is an additional process that may be considered.

Cleaning in Epoxy Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot water wash 85°C for 2 hours. If there is persistent residual odor, then spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water or recirculation with Butyl Cello solve, followed by a hot water wash for 1 hour, will assist in preparing the tank to the required standard.

Cleaning in Zinc Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot water wash for 2 hours. If there is persistent residual odor, then spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water or recirculation with Butyl Cello solve, followed by a hot water wash for 1 hour, will assist in preparing the tank to the required standard.

Aromatic Hydrocarbon Mixtures

Cargoes in this Compatibility Group can generally be cleaned quite easily. Depending upon the requirements of the subsequent cargo however, additional cleaning may be required as follows:

Tank Cleaning After Last Cargoes “ENES” – Toluene, Benzene, Xylene, Pygas, CPP

There is a relatively high and hidden risk of contamination, detectable only by Gas Chromatograph analysis, when the previous cargo was an “ENE”. Although these products are generally considered as easy cargoes to clean, tests show that the complete removal of residues from tank linings and even Stainless Steel surfaces requires a considerable amount of heat (hot water).

To minimize liabilities, the following should be considered:

If possible, the following cargoes should not be loaded in tanks that last contained Benzene, Toluene, Xylene, Pygas or CPP:

Light Alcohols (Ethanol, Isopropyl Alcohol, Normal Propyl Alcohol)

Glycols (Ethyl, Propyl, Diethyl, Voranols and Polyols)

Mineral Oils (Medicinal Oils, White Oils, Whiter exes, Arco Primes, Baby Oils)

Glycerine (especially USP grade)

Paraffins (Hexane, Isopars, Expars, Paraffin Waxes (especially food grades)

Membrane caustic

Close dialogue must be maintained with the Ship Operator to fully explore alternative stowages.

If alternative stowage is not possible, the following wash times should be used:

Zinc lined tanks – minimum 6 hours, very hot 85°C wash
Stainless Steel lined tanks – minimum 4 hours, very hot 85°C wash
Epoxy Lined tanks – should be avoided, but if needed then a procedure should be discussed and

agreed between the ship and the Ship Operator on a case-by-case basis.

If the next cargo does not merit these special procedures, the following should be employed for all tank linings: Wash with ambient temperature water (but minimum 5°C above the melting point of the cargo – for example, the melting point of ParaXylene is 12°C, so the initial wash water temperature should be at least 17°C) for 3 machine cycles, followed by a warm water wash (55 – 60°C) for 1 hour should be sufficient to prepare the tank to the required standard. Ventilation alone should not be considered, as the presence of some gases/vapors can result in health risks to personnel in the vicinity, eg. with Benzene.

Miscellaneous Hydrocarbon Mixtures

If the product being cleaned is Gasoline, Jet Fuel, CPP (Clean Petroleum Product) or similar and the subsequent cargo requires further cleaning, the methods to be employed are as per those indicated for Group 32.

The products in this group are generally not water-soluble. Check particularly for Hydrocarbons, in preparation for a subsequent Wall Wash standard cargo.

Although some require quite high discharge temperatures, unless knowledge of the particular product dictates otherwise, initial washing should be done with ambient water.

Cleaning in Stainless Steel Tanks

If the product is a Lube Oil or Lube Additive and the subsequent cargo requires a Wall Wash test, spraying with RXSOL-20-2002-PLUS or an alternative degreaser before commencing the initial washing should be considered. Wash with ambient temperature water for 3 machine cycles, followed by hot water 85°C wash for 4 hours. Inspect the tanks and if more than hand cleaning is necessary, either recirculation with a Caustic Soap (Teepol or RXSOL-20-2002-PLUS) solution or recirculate with Butyl Celloslove, followed with a hot water wash for 1 hour.

Cleaning in Epoxy Tanks

Cleaning in Zinc Tanks

Esters

We regularly carry a number of products normally assigned the Compatibility Group number 34 . However, for the purposes of this manual, we need to further sub-divide this allocation:

For those group 34 products which are Vegetable or Animal Oils, the following procedures apply:

Cleaning Guidelines for Non-Drying Vegetable Oils.

Non-drying vegetable oils that we regularly carry are the Palm and Coconut Oil grades, such as:

Cargo	Wash Temperature
Palm Oil	Hot
RBD Palm Oil	Hot
Palm Kernal Oil	Ambient followed by hot (80°C)
RBD Palm Kernal Oil	Ambient followed by hot (80°C)
Palm Stearine	Ambient followed by hot (80°C)
RBD Palm Stearine	Ambient followed by hot (80°C)
Coconut Oil	Hot (80°C)
Refined Coconut Oil (Cochin)	Hot (80°C)
Palm Mid Fraction	Ambient followed by hot (80°C)
RBD Palm Olein	Warm (10°C degrees above melting point) followed by hot (80°C)

It is very important that the tanks are cleaned Soonest upon completion of discharge. If full cleaning is not possible at this stage, then the tanks should be given a quick wash to ensure the atmosphere in the tank remains moist. If port and / or berth regulations prohibit any machine washing, then an alternative means of ensuring the atmosphere remains moist should be employed, such as the injection of low pressure steam. Assuming all applicable safety precautions are taken, limited hand-hosing is a further possible alternative. If there are no options available to ensure that the atmosphere remains moist, then consult with the Ship Operator, as soon as this becomes apparent. Wash as per the temperatures indicated in the table above, with ambient/warm being for 3 cycles and hot being for 6 hours.

RXSOL-20-2015-LAC or other Veg Oil cleaner may be injected into the wash water during the first cycle of hot washing in all linings.

Depending upon the outcome of the tank and line inspection, further chemical cleaning may be necessary. In such cases, Zinc and Epoxy tanks are treated differently and the following guidelines should be followed:

Cleaning in Epoxy Tanks

A Caustic / Soap solution consisting of:

10-30 m³ of fresh water depending upon number and size of tank(s)
10% Caustic Soda (100 kilos Caustic Soda flake per cubic meter of water)
1 drum of RXSOL-20-2015-LAC for each 10 m³ of water or 0.5 drum of Teepol per 10 m³ of water

Those involved in making up the solution should wear appropriate personal protective equipment, including goggles and rubber gloves.

The solution should be made up in a tank and heated to (40º-45º C). Do not allow the solution to get warmer than this, as the Caustic may leave white powder-like residues on the tank surfaces at temperatures above 50ºC.

This solution should be re-circulated for 6 hours and transferred to the next tank to be cleaned. After transfer, wash the tank with warm (40º-45ºC) water for 1 hour, followed by hot water at 85°C for 3 hours or until all soap is removed. Inspect the tank, if further cleaning is necessary, then discuss further cleaning method(s) with the Ship Operator.

Cleaning in Zinc Tanks

A Soap / Bleach solution consisting of:

10-30 m³ of fresh water depending upon number and size of tank(s)
2 drums of RXSOL-20-2015-LAC or 1 drum of Teepol for each 10 m³ of water
1 drum of bleach (Sodium Hypochlorite) per each 10 m³ of water

The solution should be made up in a tank and heated to (40°C). The solution should be recirculated for 6 hours and transferred to the next tank to be cleaned. After transfer, wash the tank with warm (40° – 45°C) water for 1 hour, followed by hot 85°C seawater until all soap is removed. This is important, otherwise soap will show up the test tube whenever performing a Wall Wash analysis. Inspect the tank to determine if further cleaning is required. If the inspection reveals the tank is clean then carry out fresh water washing / rinsing the tank.

If further cleaning is necessary, then discuss further cleaning method(s) with the Ship Operator.

Cleaning Guidelines for Drying and Semi-Drying Oils.
Drying and Semi-Drying oils that we regularly carry include:

Soyabean Oil
Rape seed oil
Fish Oil
Cotton Seed Oil
Linseed Oil
Olive Oil
Peanut Oil

It is very important that the tanks are cleaned immediately upon completion of discharge. Most receiving terminals understand this operational requirement and, provided it is fully discussed at the pre-cargo conference, they are cooperative. However, if full cleaning is not possible at this stage for whatever reason, then the tanks should be given a quick wash to ensure the atmosphere in the tank remains moist. If port and / or berth regulations prohibit any machine washing, then an alternative means of ensuring the atmosphere remains moist should be employed, such as the injection of low pressure steam. Assuming all applicable safety precautions are taken, limited hand-hosing is a further possible alternative. If there are no options available to ensure that the atmosphere remains moist, then consult with the Ship Operator, as soon as this becomes apparent. Initial washing must be done using ambient fresh or salt water. Basic cleaning should be done for 3 hours followed by 3 hours hot washing (80°C). If further cleaning is necessary, follow the guidelines for non drying oils above.

Acetates

It is important to note that Acetates can soften tank linings. Whenever possible, coated tanks should be dried / thoroughly ventilated prior to introducing any water. Sumps should be ejected / blown dry where accessible. Acetates are generally somewhat soluble in water.

Cleaning in Stainless Steel Tanks

Cleaning should be carried out using ambient temperature water wash for 3 cycles, followed by warm water (40° – 45°C) wash for 2 hours.

Cleaning in Epoxy Tanks

Cleaning should be carried out using ambient temperature water wash for 3 cycles, followed by warm water (40° – 45°C) wash for 2 hours.

Cleaning in Zinc Tanks

Cleaning should be carried out using ambient temperature water wash for 3 cycles, followed by warm water (40° – 45°C) wash for 2 hours.

Pthalates

These are not water soluble and require cleaning to be started with ambient temperature wash water. This should be for at least 3 cycles, followed by hot water (80°C) for 3 hours, in all linings.

Vinyl Halides

At present, we carry no cargoes assigned to this Compatibility Group. If one is to be loaded, contact the Ship Operator for cleaning guidelines.

Halogenated Hydrocarbons

This Compatibility Group is predominately made up of Chlorinated Solvents, many of which we regularly carry. Such products are either slightly soluble or not soluble in water. The mixture of Chlorinated Solvent and water can damage coatings and cleaning must therefore be such as to ensure that all residues are completely removed.

Cleaning in Stainless Steel Tanks

The residues of many Chlorinated Solvents may be removed by ventilation, due to the high vapor pressure of these products. Such ventilation should continue until no freestanding solvent remains in any part of the tank. After ventilation, the tank should be washed with hot water (80° – 85°C) for a minimum of 3 hours.

Cleaning in Epoxy Tanks

Cleaning in Zinc Tanks

Nitriles

Generally, the only cargo we carry from this Compatibility Group is Adiponitrile. If any other Compatibility Group No. 37 cargo is scheduled for carriage, contact the Ship Operator for cleaning guidelines.

Cleaning in Stainless Steel Tanks

Wash with ambient temperature water for 3 machine cycles, followed by hot (80°C or higher) for 2 hours. If there is persistent residual odor, then spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water will assist in preparing the tank to the required standard. Spraying with Bleach, or other Oxidizer will also help in increasing the Permanganate Time when preparing for a subsequent cargo with a Wall Wash requirement.

Cleaning in Epoxy Tanks

Reference to the Manufacturer’s Coating Resistancy Guidelines will indicate if there is a likelihood of softening of the coating. Wash with ambient temperature water for 3 machine cycles, followed by hot water for 3 hours.

If odor is still present after washing in Epoxy tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit this lengthy option, spraying with 1 -2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Spraying with Butyl Celo solve, followed by a hot water wash, will also assist in odor removal.

Cleaning in Zinc Tanks

If odor is still present after washing in Epoxy tanks and there is time available, it can be removed by ballasting. Fill the tank with sea water, add 2 x 210 liter drums of Bleach and leave for two or three days. Then deballast the tank, washing the tank as you do so, using hot water, followed by a good fresh water rinse. If time does not permit this lengthy option, spraying with 1 – 2% Bleach solution, washed off immediately and completely with fresh water is an alternative. Steaming with Methanol or spraying with Butyl Cello solve, followed by a hot water wash, will also assist in odor removal.

Carbon Disulphide

At present, we carry no cargoes assigned to this Compatibility Group. If any other Compatibility Group No. 38 cargo is scheduled for carriage, contact the Ship Operator for cleaning guidelines.

Sulpholane

At present, we carry no cargoes assigned to this Compatibility Group. If any other Compatibility Group No. 39 cargo is scheduled for carriage, contact the Ship Operator for cleaning guidelines.

Glycol Ethers

Cargoes carried under this group are generally slightly or moderately water soluble and fairly easy to clean.

Cleaning in Stainless Steel Tanks

For those cargoes, which require heat for discharge, start washing with water which is 10° – 15?°C above the melting point for 3 cycles, followed by hot water for 2 hours. For those that do not require heat for discharge, start with ambient temperature water for 3 cycles, followed by hot water for 2 hours.

Cleaning in Zinc Tanks

Cleaning in Epoxy Tanks

Ethers

There are two cargoes from this Compatibility Group that we regularly carry: MTBE (Methyl Tertiary Butyl Ether) and Diphenyl Ether /Diphenyl Oxide. MTBE is completely water soluble and can generally be cleaned with ambient water wash. If odor remains, additional hot washing should remove it.

Diphenyl Ethers/Diphenyl Oxide – requires a mandatory MARPOL prewash and is not water-soluble. After the prewash, washing with hot water for a minimum of three hours should bring the tank to a water white standard.

Nitrocompouds

Nitrochloro benzene is the only cargo we normally carried which is covered under this group. Depending upon melting point, viscosity and discharge temperature may require a prewash. The cargo is not water soluble but should be able to remove/clean using hot water for at least 3 hours in all linings.

Generally, the only cargo we carry from this Compatibility Group is Nitrochloro benzene. If any other Compatibility Group No. 42 cargo is scheduled for carriage, contact the Ship Operator for cleaning guidelines.

Miscellaneous Water Solutions

With the exception of Latex (for which cleaning procedures are detailed in the Special Cargo Handling Manual), as the name implies the cargoes in Compatibility Group No. 43 are all, to one degree or another, water soluble and almost all these cargoes should clean with just ambient to warm water.

One cargo under this Compatibility Group that may be more difficult to clean is Urea Ammonium Nitrate (UAN), especially in cases where one or more shore tanks were emptied at the load port. It is common to place a fuel oil blanket on top of the product in the shore tanks. When these tanks are emptied, the fuel oil will also be transferred into the ship’s tanks, which can complicate the cleaning. Whenever loading UAN, the surveyors should be asked if any shore tanks will be emptied and, if so, whether or not there is oil on top of the UAN. In cases where oil is present, the cleaning procedure will often be the same as after a lube oil/lube additive.


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