JO Tankers Tank Cleaning Guide

8/16/2019 JO Tankers Tank Cleaning Guide

1/48

PDF By MKP JO TANKERS CLEANING GUIDE Pages 1 of 48

JO TANKERS

GENERAL CARGO CLEANING GUIDE

SEPTEMBER 1999

Distribution : All vessels (including Time Chartered Vessels)Owners/Managers of the vessels.

Prepared by: CPZJ’TMD


2/48


INDEX

CHAPTER CONTENTS

1. INTRODUCTION.

2. AGGRESSIVE CARGOES (MISCELLANEOUS)

IN EPOXY COATED CARGO TANKS.

3. ABSORPTION AND DESORPTION OF EPOXY COATING

AFTER AN AGGRESSIVE TYPE OF CARGO.

4. TANK CLEANING.

5. CLEANING AFTER A CARGO OF ANIMAL AND

VEGETABLE OIL.

6. TANK CLEANING PROCEDURES.

7. SPECIAL TANK CLEANING PROCEDURES.

8. TANK CLEANING CHEMICALS.

9. JO TANKERS STANDARD WALL WASH TESTS

10. WALLWASH TESTS

11. ACID PICKLING AND PASSIVATION OF STAINLESS STEEL.


3/48


SEPT 1999 99.09.01

1. INTRODUCTION

The cleaning instructions in this manual are meant to be guidelines.

Theses guidelines will be updated based on future experience.

The cleaning suggestions given herein are generally accepted tank cleaning procedures, which assume among others a

reasonable coating condition.

The cleaning methods in this manual are to be used for cleaning to water white standards.

The cleaning methods mentioned in this manual are after the mandatory pre-wash, if any.

Ventilation: - Time may vary depending on atmospheric conditions and available ventilation equipment.

Tank entry procedures - Safe tank entry procedures in accordance with company instructions should be followed at all

times.

Tank cleaning has to be performed after every discharge, irrespective of next carg6 to be loaded. Quality programs

developed by shippers require ever-higher standards of tank cleanliness. Analytical methods have improved

(Gascomatograph / Photospectrometer / Infrared).

Surveyors will perform more and more wall washes.

Not only are chlorides and water miscibility (Hydrocarbons) tested, but more and more the

Permanganate Fading Time (PTT) will be performed, especially after a vegetable or a mineral oil and

prior to many sensitive cargo’s. Also wall washes are being tested for Non Volatile Matter, (NYM)

Effective tank cleaning can prevent contamination by previous cargoes


4/48


Sept 1999 09 01

AGGRESSIVE CARGOES (MISCELLANEOUS) IN EPOXY COATED CARGO TANKS

Epoxy coated cargo tanks and the influence of aggressive cargo on the epoxy tank lining in general.

The epoxy coating film will be influenced by all type of liquid cargoes, but aggressive cargoes are those with greatest

influence.

Miscellaneous Aggressive Cargoes.

Such commodities must only be carried in fully cured epoxy coated tanks.

The rule for all types of epoxy coated tanks, is that no aggressive types of cargoes should be carried vithin the first three- (3)

months following coating application.

Most of the aggressive cargoes are mentioned in the cargo resistance list with a note, but it lust be remembered that some

aggressive cargoes are not mentioned with a note in the resistance list, but cleaning/ventilation etc. must be done as for

aggressive cargoes.

The question will be in case of no note: “what is an aggressive Cargo?” In this cases we have to rely on experience and

common sense.

Even if the epoxy coating is fully cured, it must be restored after the carriage of an aggressive type of argo. Some aggressive

cargoes will be absorbed more than others will.

These cargoes must be carried in clean, dry tanks.Condensation within the ullage space must be avoided and the moisture content of the cargo must be below 0.0 1% (100

PPM).

These products must be completely removed from the tank and the epoxy coating must be RESTORED before any tank

cleaning operations, involving the use of water or steam.

t his is strongly recommended that the remains of such cargoes are removed by ventilation.

THE TANK MUST BE VENTILATED UNTIL GAS FREE”.

The serious risk of damage to the tank lining is encountered in the case of sequences containing aqueous products and water

miscible chemicals.

Most aggressive cargoes will soften the epoxy coating to a certain extent and if the coating is not restored/re-cured

(conditioned) by ventilation, the absorbed cargo will not be removed and the storing/recurring of the coating will not take

place.

This will result in deep blistering, which will expand and break open, which will then be visible as a lot of small half round

rust striped (hair look alike ) so called ‘Horse shoes blistering”.


5/48


SEPT 1999 99.09.01

Restoring/recurring/conditionins of an epoxy coated tank after discharge of an afgressive cargo.

After an aggressive type of cargo, the epoxy coating must be restored.

Restoring of aggressive cargo in an epoxy coated tank can only be done by ventilation until “GASFREE” and not by washing with water or cleaning with detergent or other cleaning fluid.

To avoid damage to the epoxy coating an aggressive cargo should never be followed by an aggressive cargo.

The cargo after an aggressive cargo should be a fully approved non-aggressive cargo without any remark in the cargo

resistant list.

The time required for restoring an epoxy coating after an aggressive cargo depends on the:

a) Type of cargo, volatile properties of the cargo.

b) Film thickness. (High film thickness requires longer ventilation than a low film thickness.c) The air temperature in the tank (20-30C) is the most suitable for restoring of an epoxy coating.

d) The number of air changes used for ventilation.

If the absorption is water or another less volatile cargo, removal of absorption by ventilation must be done by ventilation

with dry air with a relative humidity below 40%.

A too high a temperature does not speed up the restoring process. The epoxy has become soft due to the aggressive cargo and

with a too high temperature the epoxy film will remain soft even after the absorbed cargo is ventilated out of the coating.

The best circumstances for restoring of epoxy coating is as many air changes as possible and with an air temperature of 25-

30C.Approximate times required for restoring of an epoxy lining after an aggressive cargo. (This is only a guidance and exact

time depends on type of cargo and the volatile properties of the cargo and temperature and number of air changes).

STEEL TEMP. IN CELSIUS

4

Rel. humidity 100C. 15

0C. 20

0C. 25

0C. 30

0C.

20% or less 17 days 13 days 9 days 6 days 4 days

20-30% 17 days 9 days 6 days 4 days

30-40% 17 days 12 days 8 days


6/48


Sept 1999 99.09.01

The coating film thickness in relation to the absorDtion of aggressive cargo.

The thickness of an epoxy coating is usually specified to be between 280 and 300 microns dry film in a 3-coat system.

Due to circumstances such as accessibility etc., the coating thickness will vary, usually between 290 and 500 microns.In certain areas with overlap, small areas may be above 500 microns.

Damage to an epoxy coating by absorption is usually occurs in overlap areas and in areas where a stripe coat was applied.

During re-coating, extremely high film thickness should not be accepted and small areas will be repaired by sand papering

and larger areas by re-blasting.

Practically, it is not possible to avoid having a film thickness over 500 microns on stripe coated areas and areas of overlap.

High thickness coating is more absorbent and will take much longer to restore to a condition suitable for loading the next

cargo.


7/48


Sept 1999 99.09.01

3. ABSORPTION AND DESORPTION OF EPOXY COATING AFTER AN AGGRESSIVE TYPE

OF CARGO

Phenolic epoxy is resistant to solvents, such as Ketones, low molecular weight alcohol’s, Ethers and

Esters.

However, caution must still be used when cleaning the tanks and selecting the next cargo.

After containing these types of solvents, the tank should be well ventilated to remove all traces of the:

chemical prior to cleaning.

The next cargo should not be any water ballast or diluted aqueous solutions such as liquid fertilizer solution or latex

emulsions.

Reference notes:

a) ESTERS. PHTHALATES. ETC.

Certain products such as esters (acetates, phthalates etc.) and chlorinated or brorninated materials can react with water to

form acidic compounds.

These products are suitable for storage in PHENOLIC EPOXY 373 coated tanks, but the presence of any moisture will

make them aggressive and unacceptable. Such products must therefore be dry, free from acidity and carried in completely

dry tanks. Water contamination must be avoided and water content of the cargo should not exceed

0.02% (200 PPM).

b) KETONE. ALCOHOL’S. NITRITES AND ESTERS.

These aggressive cargoes can only be carried when the coating is fully cured and this will be obtained after a service period

of 3 months with non-aggressive cargoes (without notes).

After transportation of cargoes marked with a note, the coating has to be restored to its original condition.

This will be obtained by ventilating the tank thoroughly until the tank is in a gas-free condition, followed by carriage of

non-aggressive cargoes without a note (in the resistance list) for a period of at’ least 10 days.

c) AGGRESSIVE WATER MISCIBLE CARGOES.

Before loading these aggressive, water miscible cargoes, it is essential to remove all traces of water from the tanks.

After carriage of these cargoes, no steam, ballast water, wash water, slops or aqueous cargoes must come into contact with

the coating before its original coating condition is restored.


8/48


SEPT I999 99.09.01

The coating will be restored by thorough ventilation until the tank is gas-free, followed by the carriage of non-aggressive

cargoes (without a note) for a period of at least 10 days.

Ventilation of the tank must be carried out after an aggressive/water miscible cargo has been discharged.

This is to ensure the removal of any cargo which may have been absorbed into the coating.

THIS MUST BE DONE PRIOR TO ANY TANK CLEANING PROCEDURES BEING CARRIED OUT.

Any residue left in the tank after cleaning must be removed immediately and drying completed by venting.

Cargo residues or absorbed cargoes in the coating, is a potential source of contamination of subsequent cargoes.

Cargo residue and absorbed cargo in the coating film may cause a chemical reaction, and produce products, which could

cause breakdown of the coating system.

There is also a category of aggressive cargoes, which can only be stowed in epoxy coated tanks for a limited number of days.

This number of days must not be exceeded, as the coating will be softened and the absorption of chemicals will increase,

which will obviously damage the tank coating.

The limitation of days is mentioned in the cargo resistance list for the cargo in question. Explanation of absorption.

When a liquid cargo is loaded into a tank coated with an organic coating (Phenolic epoxy), part of the liquid will be absorbed by the binder phase of the coating through a diffusion process. Absorption will continue until the binder phase is saturated

with the liquid.

When the cargo is later discharged from the tank, desorption will take place, again by diffusion process and will ideally

continue until all absorbed liquid has been removed from the coating.


9/48


SEPT 1999 99.09.01

Factors affecting drying of EPOXV coatin2.

Reiterating that drying is to be understood as the removal of absorbed chemicals, it will first take place after a visible

dry state of tank surface has been reached.The dry film thickness is very important, especially during drying.

Doubling the film thickness means drying times four (4) times longer in order to obtain the same degree of drying.

The drying time in a given tank, (desorption time) is governed by the largest thickness. This could be one of the

reasons for the premature damage of coatings on the tank top and the lower part of a tank, as the higher film thickness

is usually found here.

Also lower temperature and less ventilation for desorption could be the reason for premature damages to the coating in

the lower areas of the tank.

During the coating of new tanks and application during re-coating, extra attention should be given to the control of the

coating thickness.

Coating of a traditional constructed cargo tank with specified minimum thickness of 240 microns dry film for three

coats, will often result in an average thickness of approximately 350 microns with peaks up to 500 microns which is

40-50% more than specified.

In some overlap zones and on flat bar faces, a film thickness of more than 500-600 microns may be found.

The amount of absorbed cargo into the coating film finally depends on the coating film thickness and especially areas

of extreme thickness as mentioned above of 500-600 microns will absorb noticeable more chemicals than the minimum

thickness of 240 microns.

Cargoes such as methanol, benzene, methyl acetate are absorbed into the coating film to a higher degree than other

chemicals.

Among the various chemical families, glycol ethers represented by diethylene glycol monomethyl ether is absorbed

most.

Followed by the esters, nitriles, aromatic hydrocarbons and alcohols.

The selected families are aggressive to epoxy coating due to their solvency power and water miscibility.


10/48


Sept 1999 99.09.01

2 ND CONCLUSION

~fter the carriage of an aggressive cargo it is essential that the tank be ventilated to a gas free condition

nor to washing.

Vashing will stop or delay the desorption of previous cargoes from an epoxy coating and ~ese absorbed

cargoes will cause small blistering and cracked blistering in the coating. mbedded, absorbed cargoesmay also cause contamination to subsequent cargoes as traces C these may be desorbed by certain

cargoes.

.bsorption of cargo by the epoxy coating may occur and subsequent desorption purely spends on

ventilation and tank cleaning procedures.

isufficient ventilation may lead to cargo entrapment in the coating, which could damage the coating id

contaminate subsequent cargoes.


11/48


SEPT 1999

99.09.01

4. TANK CLEANING

Tank cleaning can be done in two ways:

- Evaporation of the residue in the tank

- Washing of the tank with water or an other suitable liquid using tank cleaning machines.

Water is the main washing liquid, however some substances can react vigorously ~vith water, resulting

in a dangerous reaction.

Also, the formation of insoluble hard to remove material etc.

Some examples of these reactive substances are isocyanates and sulphuric acid.

After the discharge isocyanates, the tanks must be washed with a non-reactive solvent.

After washing the tanks have to be cleaned by another means to remove any small amounts of product left in the tank in so

called shadow areas (areas not reached by the jet of the tank cleaning machines).

This mostly involves re-washing and rigging extra machines to reach the shadow areas. Additional spot cleaning, steamingand ventilation is required.

4.1 WHAT TO CLEAN.

Not only the cargo tanks have to be cleaned, also lines and pumps.

Special attention has to be paid to vent-lines, stripping lines and sampling and drain cocks. These small diameter lines, drain

cocks and blind sections can contain sufficient previous cargo to contaminate subsequent cargo. There it is imperative that

they are not forgotten and are thoroughly cleaned and drained.

Volatile substances with a melting point above ambient temperature often solidify in these areas. When not properly cleaned

and with a rising temperature the substance may contaminate the next cargo.

It is also imperative that the cargo pump manufactures purging routines and cleaning instructions are followed.

~ 4.2 SELECTION OF THE PROPER CLEANING METHOD.

The planning of the tank cleaning procedure is very important.

Starting with the correct initial procedure is of utmost importance it is very difficult to obtain a good

result after an initial failure.

If in doubt ask your operator.

Jo Tankers standard is to clean to water white standard.


12/48


SEPT 1999 99.09.01

In general tank-cleaning procedures are based on chemistry and earlier experiences with the product

which is being cleaned.

The choice of a procedure must be based on:

- Properties of the substance to clean from.

Vapor pressure

Solubility in water

Melting point

Viscosity

Reactivity

- Materials of construction I tank coating.

- Tank coating manufacturer’s instructions.

- Absorption.

- Specification and purity of the substance to be loaded.

4.3 PROPERTIES OF THE SUBSTANCE TO BE CLEANED FROM.

4.3.1 VAPOUR PRESSURE.

Substances with a vapor pressure higher than 50 mbar at 200C may be removed from the tank by ventilation/evaporation.

(Care must be taken with noxious vapors).

Tank cleaning by ventilation/evaporation is restricted to substances, which will leave no residue. The non-volatile matter

(NVM) content, indicated in the specification of the substance can be used to evaluate the possibility residues remaining.Substances which contain polymerization inhibitors, (although the quantities are low), the tanks must be washed thoroughly.

It is not recommended to clean these tanks ventilation/evaporation. The inhibitor is difficult to remove and has often a bad

influence on the wall wash and quality of the next product to be loaded.

4.3.2 SOLUBILITY IN WATER.

Water miscible substances are easy to remove with water and also substances with a reasonable solubility (down to 0.1 %)

will be removed with water.

A factor often forgotten, is the fact that the solubility of some substances increase as the temperature rises.


13/48


Sept 1999 99.09.01

4.3.3 MELTI1~G POINT.

When substances are solid at ambient temperatures, the wash water has to be heated to a temperature well above the melting

point of the substance.

The wash water should be at least 200C higher than the melting point. The solidified material will melted and be washed

away. Washing as soon as possible after discharge will prevent some solidification.

Also the stowage of solidifying materials in tanks which are not adjacent to cold (loaded) tanks or in tanks adjacent to the

sea, will help to prevent any build up of solid materials on the tank walls. (Especially valid for substances with a melting

point above 50-600C).

4.3.4 VISCOSITY.

Substances with a high viscosity also require a higher temperature wash water.If possible the temperature of the wash water should be such that the viscosity of the pure substance is low, at least below 20

to 60 mPas (cp.) at that temperature.

4.4 REACTIVITY.

For the cleaning procedure relevant reactions of the substance are:

- Self reaction

- Reactions with water

- Reactions with oxygen- Inhibited cargo’s

- Smell producing cargo’s

4.4.1 SELF-REACTION.

Examples of a self-reaction is the polymerization of monomer substances i.e. styrene and acrylic acid. Higher temperatures

increase the reaction speed of this type of reaction, washing with hot water may result in polymerized material being left in

the tank, which is very difficult to remQve. Polymerization may also take place when a tank is not cleaned and left dirty for

a few days. Because the inhibitor is not as volatile as the monomer substances , condensation of the vapor will allow

inhibitor free liquid to be formed.Cleaning of these cargoes should always start with a cold wash.


14/48


SEPT 1999 990901

REACTIONS WITH WATER.

igraph 4 the reaction of water with isocyanates was mentioned.

~action will produce two products, a urethane, which is insoluble and difficult to remove and ‘dioxide gas, which is

dangerous when, formed in large quantities (depending on the amount of nate available for the reaction).

cannot be used to clean tanks from this group of substances.

oncentrated sulphuric acid reacts vigorously with water setting free large amounts of heat, ermic).

the water contains chlorides (seawater) hydrochloric acid vapors may also be formed. chioric acid is very corrosive to

stainless steels.

lie warm diluted sulphuric acid is corrosive to stainless steel.

the tank is rapidly washed with large amounts of cold water, the water will absorb the heat. and chlorinated products are

slowly hydrolyzed to acids, normally this is no problem except ank cleaning is stopped in an early stage.

animal oils, vegetable oils and fats are transported in a zinc silicate coated tank, the formation of nay be a danger to the

coating.

oating is not resistant to oils and fats with a free fatty acid content above 2.5%. ~e fatty acid content may increase rapidlywhen cleaning is stopped for longer few hours.

REACTIONS WITH OXYGEN.

‘and semi-drying vegetable and animal oils react with oxygen to form a varnish like polymeric ~hich is very difficult to

remove.

~creases the reaction speed, therefore the initial washing has to be done with cold water. also takes place when the empty

tank is left uncleaned., if this is case the air should be removed lie tank.

iay be done by filling up the tank with water, however, this should not be done with zinc coated (see the previous paragraph).

INHIBITED CARGO’S.

nhibitor is not properly removed , then this will have a negative effect on the PTT test. ‘mmon inhibitors are fully soluble in

water.

Libited cargoes must be thoroughly pre-washed with cold Fresh or Seawater, followed by warm (Use an alkaline I caustic

solution)

water wash alone is not sufficient.


15/48


SEPT 1999 99.09.01

4.4.5 SMELL PRODUCING CARGOtS.

To neutralize the smell of some chemicals (Acrylates, Crude ‘Turpentine), the use of a •smell killer is recommended.

Special seals of Tank- and Butterworth hatches.

The use of smell killers like P3/NA Henkel(CP), Airfresh (Vecom), Nilodor (Int.Medical Zutphen) o an alcohol will help

neutralize the smell.

After the carriage of a product with a strong odor and prior to loading a sensitive cargoes the seals of tank and butterworth

hatches maybe have to be renewed / exchanged.

4.5 MATERIALS OF CONSTRUCTION / TANK COATINGS.

The material used to construct the tank determines also the duration of the cleaning process. The surface of stainless steel

tanks and lines is only slightly absorbent, but the surface of coated tanks is more absorbent.

The degree of absorption is dependent on the type of coating and on the substance carried. This absorption process softens

organic type coatings (epoxy, phenolic epoxy and polyurethane).

Absorbed substances are difficult to remove, time (for washing and venting) is an important factor in this respect.

4.6 TANK COATING MANUFACTURERS INSTRUCTIONS.

When an organic coating which is saturated with a water soluble solvent like methanol or ethanol is washed with water,

severe blistering of the coating may take place. Tank coating manufacturers give instructions in their product lists how to

deal with this problem. Long term ventilation is always required before water is introduced into the tank. It is doubtful if a

water wash is still necessary after a prolonged ventilation period (except in cases where the product leaves a non-volatile

residue).


16/48


Sept 1999 99.09.01

4.7 SPECIFICATIONS OF THE SUBSTANCE TO BE LOADED.

The specification of the substance to be loaded has also influence on the required cleanliness of the cargo tank.

Jo Tankers is transporting:

Very pure substances (purity ranging from 99.5 to 99.99% by weight).

Solutions (in water)

Mixtures of homologous series

Animal and vegetable oils and fats

Mineral oil products and feedstock’s

7he required degree of cleanliness for the first group is without any doubt higher than for most ~roducts from the last

group.

Vhen tanks are inspected before the loading of pure substances, tanks are tested for cleanliness by wall iashing and

analysis.

efore loading substances and products of the other groups, the tanks will most likely be inspected isually.

ut more and more inspection companies are convincing charterers that wall wasWs are required for tore and more cargo’s.


17/48


Sept 1999 99.09.01

5.CLEANING PROCEDURE AFTER A CARGO OF ANIMAL AND VEGETABLE OILS

STAINLESS STEEL TANKS AND EPOXY COATED CARGO TANKS.

Pre-cleaning, is the removal of oil and residue before the full cleaning operation starts.

The purpose of pre-cleaning tanks with butterworth machines using either salt or fresh water, is to remove oil and its residue

from bulkheads, tank bottom and under deck.

The sooner the pre-cleaning is carried out after discharge, the easier oils and residues will be removed and the better the final

result will be.

Pre-cleaning is highly important since large deposits of oil andlor other residue in the tank must be removed to ensure an

effective cleaning operation.

Adding POTASSIUM HYDROXIDE will assist in the pre-cleaning of stainless steel tanks (KOH). This will saponify the oilresidue and create a soft soap, which is water-soluble.

Be careful with CAUSTIC SODA, as this will saponify the oil residue, but leave a hard soap particle which is, not or almost

not water-soluble (insoluble).

Caustic Soda can only be used in stainless steel or epoxy coated cargo tanks.

After cleaning with an alkali, the residue has to be removed with warm water.

To overcome white colored deposit, which may occur after cleaning with alkali’s by a forming of insoluble magnesium and

calcium salts, pre-cleaning may be carried out by adding a detergent instead of an alkaline cleaning agent.

Alkaline agents like water based alkaline HD cleaners, emulsifiers, detergents and synthetic soap are generally used.

If an alkaline cleaner is not allowed, water based neutral cleaner can be used, followed by a hydrocarbon free cleaner.

At all times drying vegetable oils must be pre-washed with cold water first.

ZINC SILICATE COATED CARGO TANKS.

Adding Potassium Hydroxide or other alkali’s for saponification in zinc silicate coated cargo tanks must NEVER be done.

For zinc silicate coated tanks, pre-cleaning to be carried out by use of cold water or water with the same temperature as the

residue i~ the tanks.

~Never use hot water for pre-cleaning.


18/48


Sept 1999 99.09.01

Explanation:

Vegetable oil and Animal oils have a FREE FATTY ACID content (FFA).

By using water with a temperature above the temperature of the residue the FFA will increase rapidly to a level, which will

create coagulation of the albumen in the Vegetable/Animal oil.

This increase of the FFA will have a negative influence on the surface of the zinc silicatc film and part of the film will be

damaged.

The extent of the damage depends on the FFA content.

It is not possible to remove this white/grayish layer on the zinc silicate surface without damaging part of the coating.

The manufactures of Zinc silicate coating describe a maximum FFA content of 2.5% as maximum, which in practice is far

too high.

During the voyage it is possible that the FFA of certain cargoes will increase, this is due to the heating. If the moisture

content of the oil is above normal, the increase of the FFA content will be faster and reach a level which will have a negative

effect on the zinc coating and even damage the coating entirely.

Vegetable oil and Animal oil are cargoes, which may have a difference specific gravity in one and the same tank.

This will be the case after a few days of transportation.

When heating a cargo to the required carriage/discharge temperature, more heat is transferred to the product closest to the

coils. This will result in the EFA of the cargo closest to the coils increasing faster than the rest of cargo, which then cause

more damage to the lower part of the tank. Pre-cleaning of zinc coated cargo tanks after Vegetable or Animal oils to be

carried out by

BUTTER WORTHING.

The time necessary for pre-cleaning depends on the extent of oil and residue

Butterworthing to be carried out for a certain time and then inspect the tank.

If there is still oil and residue on the bulkheads, deckheads and bottom, pre~-cleaning to be continued.


19/48


Sept 1999 99.09.01

After a thorough pre-cleaning, the standard cleaning of vegetable oil or Animal oil to be continued.

1. Pre-cleaning as mentioned above.2. Butterworthing with seawater (80 C.) for about 1 hour.

3. Butterworthing with hot water and 0.05% liquid detergent for about 1,5 hrs at each drop.

4. Butterworthing with fresh water for about 0.5 hour.

5. Draining of tank, lines and pump.

6. Drying.

(The detergent is breaking down the water tension and is making the water soft, making cleaning easier).

During pre-cleaning, cleaning and rinsing the by pass valves of the cargo pump and the stripping lines should be

opened and closed several times with the cargo pump working.

This to clean the pump and stripping lines as well.

Drop lines should also be cleaned by connecting a flexible hose from butterworth line top line and allow occasional

flush through the drop line during the cleaning operation.

A forced circulation of the cargo during transportation prevents sedimentation in the tanks and a minimum of sludge

is therefore left after discharging the tanks.

Circulation of Vegetable oil and Animal oil in coated cargo tanks is in fact a must to prevent not only sedimentation

but also avoid creating a difference in the FFA content between the lower and upper pai of the tanks.

The heating instructions are to be followed and too high temperature of Vegetable oil and Animal oils should be

avoided.

A too high moister content will cause extensive increase of the FFA during transportation.


20/48


Sept 1999 99.09.01

6. TANK CLEANING PROCEDURES

In general tank cleaning operations must be carried out in accordance with the 1SGOTT. manual chapter 9.2.4. Cleaning in

undefined atmosphere.

The procedure for tank cleaning may include the following stages:

- Pre-cleaning (washing with water)

- Cleaning (washing with water or water and detergents)

- Rinsing (washing with water)

- Flushing (with fresh water)- Steaming

- Draining

- Drying

6.1 PRE-CLEANING.

The purpose of pre-cleaning tanks with tank cleaning machines using either salt or fresh water, is to remove residues from

bulkheads, tank bottom and underdeck,(Bulk cleaning)

The sooner the pre-cleaning is carried out after the discharge, the easier residues will be removed. During pre-cleaning thetank cleaning machines should be moved frequently, in order to cover the entire surface.

After pre-cleaning the tank should be inspected and, if residues are found, the tank cleaning machines should be centered

over the areas for further cleaning.

6.2 CLEANING.

Cleaning is carried out with the aid of water or water and cleaning chemicals. In most cases we recommend 0,05% of the

detergent.

The cleaning solution can be applied cold or hot, using tank cleaning machines.

When applying a solvent cleaner by spraying it will be obvious that after the reaction time (mm 30 minutes) the residues

have to be washed away.

~ Tank cleaning machines with cold or warm water should be used for this, not too hot, otherwise the applied solvent will

evaporate.

The machines must be lowered down into the tank at recurring intervals in order to obtain an effective cleaning throughout

the tank.

Throughout the cleaning operation the tank bottom has to be kept as dry as possible by constantly pumping out the water.

When using recirculation, the cleaning solution can be used two or three times iE light petrodiemical products are to be

removed.

However, precautions have to be taken in order to prevent build up of static electric charges.


21/48


Sept 1999 99.09.01

When plain water is used as the cleaning agent, the cleaning operation is based on solubility of the substance in water,

recirculation is not recommended (static electricity) when cleaning from substances with a low solubility in water.

During the washing operation the washing water is pumped out through the discharge lines, this should

clean the line and pump sufficiently, the stripping lines have to be flushed also.

The cleaning of vent lines is best done by steaming with live steam.

Cleaning procedures should be continued for several hours depending on the product.

After the tank has cooled down, inspection can take place.

If traces of residues are found, cleaning has to be prolonged.

We may sub-divide the cleaning procedure after the nature of the general category of cargoes. There are three categories:

- Animal and vegetable fats and oils

- Mineral oils

- Petrochemicals and solvents

General cleaning outlines for these groups are:

Animal and vegetable oils: use water and detergent, avoid alkaline cleaners when seawater is used.

When cleaning from drying or semi drying oils cold water during the pre-cleaning has to be used.

An effective pre-cleaning method for non-drying fats is to steam the tanks during a short time prior to

pre-cleaning with hot water.

Cleaning of Mineral Oils can be carried out with water and detergents or water and a solvent cleaner. Petrochemicals and

Solvents are removed by one of the following (general) procedures:

Substances with a low boiling point and a high vapor-pressure (50 mbar or more) at ambient temperature can be removed

by evaporation or a light cleaning. In case of evaporation the pre-cleaning step may be omitted, however evaporation of

substances from lines and pump is difficult. Flushing with fresh water of the lines is recommended.

Substances with a lower vapor-pressure are removed by water washing and steaming.

~ In the first stage cold water is recommended; volatile substances show a higher solubility in cold water.


22/48


SEPT 1999

99.09.01

6.3 RINSING.

Directly after the cleaning operations the tanks should be rinsed with warm or cold water by means of tank cleaning

machines.

It is most important that the cleaning solution should not allowed to dry as this will effect the outcome of the tank cleaning.

Rinsing should nonnally continue until no residue can be found in the tank.

6.4. FLUSHING.

The tank has to be flushed thoroughly with fresh water to remove salts from seawater.

6.5 STEAMING.

Steaming is an important step in removing traces of volatile substances by evaporation,

Also traces of less volatile material are often successfully removed by steaming.

During steaming condense water has to be continuously pumped out from the tank.’

Steaming should be performed in a gas free tank.

6.6 DRAINING.

Tank line, venting system, stripping line and pump must be well drained.

All plugs etc. should be removed.

6.7 DRYING.

After the cleaning procedure the wet surfaces of tank, lines and pump have to be dried by ventilation. During this stage of the

cleaning procedure absorbed volatile substances will evaporate from the coating of coated tanks.

CONCLUSION.

Tank cleaning effective solutions?

From the previous pages we have seen that a lot of factors influence the tank cleaning process.

Only when sufficient information is available of the substance to clean from, can one develop a correct

tank Cleaning procedure.


23/48


SEPT 1999 99.09.01

CLEANING PROCEDURE 1

Substances with a vapor pressure higher than 50 mbar at 200C.

The non -volatile matter content indicated in the Cargo specification can be used to evaluate the

possibility to perform only ventilation.Inhibited cargoes are excluded.

HRS.

Gas-free I Drain lines! Eject tank 4.0

Fresh water rinse. 0.5

Steaming if necessary. 1.0

Mop! dry! inspect. 1.0

8.0

An extra freshwater flush of the cargo line to remove remaining liquid in pockets is advisable.


B/W with cold to warm (30 deg C) seawater 1.5 (Max Cargo Temp.).

Freshwater rinse 0.5

Steaming 1.0

Gas-free tank and Ventilate 2.0

Visual inspection tank 0.5

Mop and dry 1.0

6.5


B/W with warm and ending with hot 2.0

Bw hot water with detergent / degreaser 2.0

1-lot fresh water rinse 0.5

Steaming 2.0

Gas-free and ventilate 2.0

Visual inspect tank 0.5

Mop and dry 1.0

10.0

Before starting BW seawater some Lube. Additive requires roundwash with MDO or light mi peral oil

- direct after discharge. Do not use hot-water firstIf next cargo is sensitive to Hydrocarbons use HCF cleaner.

If ijecessary a final spray tank with an Ethanol / Methanol / Ketones.


24/48


Sept 1999 99.09.01


BWcold. 2.0

BW warm I hot seawater with detergent I degreaser 4.0

Fresh water rinse 0.5

Steaming 2.0

Gas-free / ventilate 0.5

Mop and Dry 2.0

11.0

In case of cleaning from an edible oil, first ascertain if the oil is drying or non drying.

Start to preach at discharge temperature.Another option after the preach is to spray tank with a degreaser.


B/W with warm freshwater 1.0

Steam 1.0Gas-free and ventilate tank 2.0

Mop and Dry 1.0

5.0


B/W with warm to hot seawater 2.0

Freshwater rinse 0.5

Gas-free and ventilate tank 2.0

Mop and dry 1.0

5.5


I

131W with cold seawater 1.5

13/W with warm to hot with detergent or degreaser 2.5

B/W warm seawater 0.5


Gas-free and ventilate 2.0

Mop and dry 1.0

8.0


25/48


Sept 1999 99.09.01


B/W with cold seawater 1.5

B/W hot freshwater with smell killer 1.5

Steam with smell killer if needed. 2.0

If ok fresh water rinse tank 0.5

Gas-free /ventilate tank 3.0

Mop and dry 1.0

------

9.5

If odor, continue steaming with smell killer.


Substances with a vapor pressure higher than 50 mbar at 200C.

The non -volatile matter content indicated in the Cargo specification can be used to

evaluate the possibility to perform only ventilation.

Inhibited cargoes are excluded.

B/W with cold I ambient seawater 1.0

B/W with warm / hot seawater 1.0

Fresh water rinse tank 0.5

Gas-free / ventilate tank 2.0

Mop and dry 1.0

5.5


B/W with hot seawater 2.0

B/W with hot fresh / seawater with

Detergent or degreaser 2.0

Freshwater rinse tank 0.5


Mopanddry 1.0

7.5


26/48


SEPT 1999 99.09.01


B/W with cold / warm seawater 2.0


Freshwater rinse tank 0.5


Mop and dry 1.0

6.5


B/W with lukewarm seawater 1.0



Gas-free I ventilate tank 2.0Mop and dry 1.0

6.5


27/48


Sept 1999 99.09.01

7. SPECIAL TANK CLEANING PROCEDURES

PHOSPHORIC ACID

First a cold butterworth wash for 2 - 3 hours.

Use extra tank cleaning machines to increase the water flow.

Take care of clogged lines.

If sediments remain, hand hose to pumpwell as soon as possible using fresh water.

Note the “TANK ENTRy” procedures.

F~fW cold water. If seawater has been used, rinse directly after with fresh water.

Passivate whenever possible. Never leave slops and water in the tanks, this will become concrete.

Tampa Phosphoric Acid. After the usual washing, hard concrete like layers remain on bulkheads, ladders, stiffeners etc.

Even high pressure wash does not work.

A recirculation with Phosphoric Acid will work (COW procedure).

Based on a tip from captain Hoogerbeets, Jo Brevik, tried following procedure:Mix 500 It. phosphoric acid and 5/6 Mt. Freshwater, recirculate this solution around for 2/3 hrs. Result was very gQod,

everything removed and tank very shiny/smooth.

500 liters phosphoric acid seems to be on the high side, may be 200 liters will work as well.

SULPHURIC ACID

Preferably fresh water to be used. If not possible then seawater.

A~ much as water as possible should be pumped into the tank (via cargo lines and butterworth

machines), which should be pumped out immediately as well.

If not possible to pump wash water away immediately tank should be left untouched and

Completely closed avoiding entry of moisture.

This situation however should be as short as possible.

Followed by direct B/W with freshwater.

Gas-free / Ventilate.

Mop and dry.

Passivating providing time available.

MDI AND TDI

Pre-washing with preferably METHYLENE CHLORIDE (max 50 PPM water)

Monochlorobenzene as second choice (max 50 PPM water)MDI and IDI are completely soluble in Normal Propanol as well.

Load first batch (quantity depending ott pump suction), then recirculate, via B/W machines cow-head two cycles and pump

slop back to shore facility.

Load second batch and repeat earlier procedure. After completion clean tank for MEC.

Avoid at all times moisture/air entering the tank(s).


28/48


SEPT 1999 99.09.01

VEGETABLE OILS

Instead of a solution of 0,05% Teepol, Grato 14, GratoSO (suitable in Stainless Steel and Epoxy ) or a Caustic solution

can be used, however bear in mind that often a white layer on the stainless steel bulkheads will remain.

Also all kinds of LIQUID ALKALINE CLEANERS may be used in a solution mentioned in the data sheet.More and

more so called “soft cleaners” are used to prevent the white layers. If lines still feeling greasy, steam with Metal

brightner.(5 - 10 Ltrs).

FISH OIL

B/W with Cold seawater.

B/W with hot sea or freshwater. (Solution 0.5% Teepol or Caustic/detergent mix).

Good result with Lead Clean CP with extra Citronella (inject or recirculate).

Rinse with fresh water.

Vent and dry tank.

Inspect, if still fish oil remains, than spray lead clean and hot Bw.

Rinse with fresh water.

Vent, mop and dry.

CLEANING FROM FISH OIL USING CTC-CLEANER-VLC.

B/W with cold to warm (max 300C) seawater two hours.

Flush tank with freshwater.

Fill 5 - 10 cbm. fresh water into tank ,heat till 400C and add 1 - 2 buckets of the CTC cleaner and 50 to

100 kg. Caustic soda.

Recirculate solution for 4 - 6 hours.

B/W Sea water for one hour.

Freshwater rinse, ventilate mop and dry.

Fatty Acid Oils.

Cleaning media for Acid oils, Grato 50 (not suitable in zinc coated tanks)•.

Cleaning after Fatty Acid Oils is never easy, especially if the are not heated properly.

d These particular grades mixed with seawater has at times, upon drying, produced a white powder that stubbornly

adheres to bulkheads after cleaning.

To prevent creation of this, the acid oil and seawater can be neutralized with a generous dose of freshwater to minimize

the white layer.

Start cleaning the acid oils at discharge temperature (4 - 6 hours).

Cleaning options to remove the white powder (if coating permits).

Circulate a 20 - 25% nitric acid solution in freshwater.

Circulate a 3 - 5% Phosphoric acid solution in freshwater.

Fresh water solution add 1 till 2% Bufferelean Ph.5.5 heat till 600C.


29/48


SEPT 1999 99.09.01

PHENOL

Note that direct after discharge some hot fresh water must be put trough lines into the tank and circulated in order to bring

the freezing point down prior to the prescribed tank cleaning procedure.

SPI~AYING WITH METHANOL OR ACETONE:

Bear in mind that the bulkheads must be completely dry before one starts spraying.

SMELL KILLERS

Especially after cleaning of acrylates etc. HENKEL P3/NA, VECOM AIR FRESH and NILODOR may be used.

Cleaning cq washing with f.e. Methanol of tank hatch and BIW hatch gaskets may be required as these usually accumulate

strong odors.

HEAVILY LEADED AND/OR DYED GASOLINES.

1.

Thoroughly Bw cold freshwater first!!!!.

Measure chlorides and Ph value. If tank chloride free passivate tank.

Mix 25% Nitric Acid water solution by volume in tank. (Add Acid to water!!!!)

Good suction by pump to provide recirculation.

First drop one hour second drop 30 mm. 15” from bottom.

Thoroughly freshwater rinse.(measure PH).

2.

Thoroughly Bw cold freshwater first! !!!.Recirculate with 3,5% solution Chlorax.Rinse with fresh water.

Steaming to get rid of possible chlorides.

3.

Preach cold seawater 2 hours, followed by a 4 hours hot seawater wash.

Recirculate 3 - 4 hours a solution of 200 ltr bleach (Sodiunt hypochlorite) and I cbm freshwater, heatsolution up to 70

0C.

Cold seawater wash 2 hours followed by a freshwater rinse.

Lead is completely soluble in Nitric Acid, passivating after leaded products is the best option.

Other suitable chemicals are: Leadclean CP (spraying method).

Bufferclean Ph 5.5 Vecom.(Recirculation method).Aromatic solvents like toluene and Xylene are good solvents of lead as well.


30/48


SEPT 1999 99.09.01

CRUDE TALL OIL

1)

Direct after hot pre-wash for 2 hours.

Recirculate with a solution of 2,5 cbm. fresh water and 3 bags of caustic soda flakes

(or pro rata), add 5-10 liters Metal Brightner, heat the solution up to

50-60C recirculate the solution for about 4 hours.

Fresh water rinse.

Ventilate, suck and dry.

Other cleaning media: Coaltar cleaner - Grato 14 - Grato 50 - CTC Cleaner in combination with

Caustic soda.

Myrcene - (Di) Pentene - Nonene.

2)

Hot pre-wash for 3 hours.

Recirculate 2 hours with a solution of 2,0 cbm freshwater and 100 kg caustic soda, 150 ltrs myrcene,

start washing at 500C and increase slowly to 80

0C Fresh water rinse.

Ventilate, suck and dry, result ok.

3)

Hot 800C pre-wash for 2 hours, followed by freshwater rinse.

Recirculate 2 hours with a solution of 3,0 cbm freshwater and 50 kg. caustic soda, 1 can of CTC

cleaner, start washing at 500C and increase slowly to 80

0C recirculate solution for about 3 hours.

Fresh water rinse.

Ventilate, suck and dry, tank ok.

PITCH CRUDE TALL OIL

1) Cleaning with 50% water and 50% myrcene.

,,ife steam for 1 hr.

3utterworth 3 hours hot 800C.

Dirculate 3 hours with myrcene/water solution at 600

C. ~utterworth 3 hours hot 800

C. Tank nearly clean. ;pot cleaning bottonilbulkheads by spraying Grato 14. ~reshwater rinse, vent suck mop and dry. Tank ok.


31/48


SEPT 1999 99.09.01

2) Cleaning with 80% water and 20% Coaltar cleaner.

Life steam for 1 hr.Butterworth 3 hours hot 80

0C.

Circulate 3 hours with coaltar/ water solution at 600C.

Butterworth 3 hours hot 800C. Tank nearly clean.

Final freshwater rinse.

Tank ok except tank used as sloptank this tank circulated with mixture of CTC / Caustic / Freshwater.

CLEANING FROM (Light) LUBRICATING OILS USING CTC-CLEANER-VLC.

B/W with hot seawater two hours.

Freshwater rinse 15 mm.

Fill 5 - 10 cbm. Freshwater or seawater into tank and add I - 2 buckets of the CTC cleaner.

B/W tank by means of circulation (method 1) 60 to 700C.

B/W tank with hot fresh / seawater.

Freshwater rinse, gas free / ventilate / mop and dry.

LUBE ADDITIVES.

Products with high viscosity should be discharged at the highest permissible temperature.

Pre-wash the heavy additives with a light Base Oil, SN 100, White Oil or MDO.

Parabars 9344 / ECA 11190 polymerizes in water, don’t use it in first cleaning step.

Hot (900C) spindle oil is used to clean shore tanks.

Lube additives are soluble in hydrocarbon solvents and insoluble in water.

After pre-wash clean tank with a heavy duty degreaser by circulation method for 4 hours, and spot clean

with Shellsol A or similar product.

Cleaning of Clay-slurry with freshwater only.

Don’t mix different grades of slurry (reaction between different ionic types).

Commence cleaning as soon as possible after discharge, preferable to clean thoroughly with

freshwater.

HAnd hose with freshwater until tank is free of residues, only a film of slurry left. Butterworth

freshwater 2 - 4 hours (tank size) warm 35- 400C or recirculate a solution of 250 litres of nitric acid into

1000 litres of freshwater.

Refill 50 litres off acid into the mixture for each tank to be used. Circulate 2 hours at 80 - 100 bars pump pressure.

To clean cargo lines fill 10 - 20 cbm. freshwater in tank and pump out to both ends of manifold xyith

max pressure.

Drain tank and remove water residues.


32/48


SEPT 1999 99.09.01

Cleaning of Clay-slurry using Nitric Acid and CTC cleaner.

Through reaction with Co2 in atmosphere the product dries and hardens!!! .void higher temperatures and heatedcargo in adjacent tanks.

Do not mix different grades of slurry (reaction between different ionic type). refer to clean direct overboard.

Clean as soon as possible after discharge, preferable to clean thoroughly with seawater. and hose with seawater

until tank is free of residues, only a film of slurry left. Butterworth with seawater 2 - 4 hours (tank size) warm

35- 400C.

To clean cargo lines fill 10 - 20 cbm. seawater in tank and pump out to both ends of manifold with max pressure.

Drain tank and remove seawater residues by a freshwater flush.

Fill 3 to 5 cbm. cold freshwater into tank and add following amount of Acid and CTC.

3-cbm freshwater 16 cans of Nitric Acid 63% one bucket CTC-cleaner. 5 cbm freshwater 26 cans of Nitric Acid

63% one bucket CTC-cleaner. Recirculate solution 2- 4 hours. (Transfer solution to next tank). Freshwater flush,

vent and dry tank.

Cleaning from Coaltar.

After Pre-wash.

Prepare 2 cbm FW. and add one drum of coaltar cleaner. ,circulate solution 3 / 4 drops,.each drop one hour.

After recirculation immediately start washing hot seawater 800C, 3 drops one hour. During hot seawater wash

steam vent line 15 - 20 minutes.

During hot seawater cleaning, flush through drop line 5 times, don’t forget the stripping line.Finally connect freshwater pump to clean back through lines and tank with a thoroughly FW rinse.

Steam cargo lines with Metal brightner if necessary.

Creosote.

After Pre-wash

Prepare 2 cbm FW. and add one drum of coaltar cleaner. circulate solution 3 / 4 drops, each drop one hour.

After recirculation start washing at discharge temperature increase to hot seawater 800C, 3 drops one hour.

During hot seawater wash steam vapor line, steam PV, flush drop line, clean through stripping line. Lally

connect freshwater pump to clean back through lines and tank witha thoroughly FW rinse. Steam cargo lines with Metal brightner if necessary.


33/48


SEPT 1999 99.09.01

Slack Wax.

Adjacent tanks should be empty in order to have the temperature of the bulkheads abowe the melting point.

Preheat washing water to 800C !!! direct after discharge flush cargo lines from both sides of manifold back into tank for

about 10 minutes.

Clean with SW for 30 minutes hot, leave water in tank and keep heating on. Untill discharging of the wash water keep live

steam slowly into tank. than BW.SW. 3 drops of 45 min. 800C, freshwater rinse, ventilate suck and dry. Do not clean with

toluene.

In case cargo in adjacent tanks, a recirculation with Gas oil could be another option. Injection 10% solution in hot water of

CTC - VLC cleaner during hot wash.


34/48


Sept 1999 99.09.01

8. TANK CLEANING CHEMICALS

Tank cleaning chemicals are used to improve the cleaning effect, they may help to reduce the amount of

time and the quantity of water to be used.

Not in all cases the addition of chemicals improves the cleaning effect, the addition of the wrong type of

chemicals may leave the tank in such a condition that the tank may only be cleaned with

a lot of effort.

In general the use of cleaning chemicals is restricted to the final washing stage, after the bulk of the

substance has been removed from the tank by washing with water.

Addition of tank cleaning chemicals is often not accepted when discharging slop water to reception

facilities.

8.1 DETERGENTS.

The surface tension of water is lowered by the addition of detergents.

As a result water insoluble substances are washed away more easily from the tank walls.

An emulsion of the substance and water is formed, depending on the nature of the detergent. the emulsion

is more or less stable.

Some manufacturers of detergents have developed emulsion breakers, which may be added to the slop

water to separate the emulsion.

Detergents can be used for cleaning of water insoluble substances.

Pure detergents are used in concentrations of 0.05%, commercial preparations may require higher

concentrations.

Solutions of detergents may foam very strongly, addition of a small amount of a higher alcohol (i.e.

bu~anol) breaks down the foam.

8.1 SOLVENT CLEANERS.

Solvent cleaners are a mixture of solvent(s) and detergents.

They are used to clean from highly viscous water insoluble substances.

This type of chemicals are mixed with the washing water in concentrations of a few percent or are

sprayed on the tank walls without dilution.

In which case the mixture of substance and solvent cleaner is washed away with water after a soaking

period of 30 to 60 minutes.When it is decided to use a solvent cleaner, one has to be certain that the substance to clean from is

absolutely soluble in the solvent cleaner.

If the substance is a complex mixture of components such as found in heavy mineral oil products and

coaltar the substance may separate into a soluble and insoluble part when using an improper solvent. To

find a suitable solvent to remove the insoluble part is most difficult.’

A small scale test is recommended, if there is any doubt do not use the solvent cleaner, try water and

detergent instead.


35/48


SEPT 1999 99.09.01

8.2.1 SOLVENT CLEANERS WITH HYDROCARBON TYPE SOLVENTS

The solvents in this type of cleaners are mineral oil based with a flash point of approximately 600C, two main types are

used:

- with a high aromatics content

- with a low aromatics content

The best solvents are the high aromatic type hydrocarbon solvents, which unfortunately have a disdgreeable smell.

The solvents, which are very low in aromatic compounds often, are designated as “odor free When mixed with water this

type of solvent cleaners will form a milk like emulsion because the solvent is not soluble in water.

They are best suited to clean from heavy mineral oils, especially the high aromatic type. Their purpose is to dilute the

substance to clean from and lowering the viscosity. Occasionally the hydrocarbons are of vegetable origin i.e. orange oil.

The transport of methanol and other substances requires hydrocarbon free tanks, after washing with a solvent cleaner traces

of hydrocarbons may be left in the tank, for that reason hydrocarbon free solvent cleaners were developed.

8.2.2. SOLVENT CLEANERS WITH GLYCOLETHER TYPE SOLVENTS (HYDROCARBON FREE)

The glycol ether type solvents are water miscible at ambient temperatures, when mixed with water they will form clear

solutions.

The purpose of this cleaner is also to lower the viscosity of the substance to clean from by dilution, when the solvent cleaner

is sprayed in its pure form this works fine, but what happens when the cleaner is diluted with water?

A diluted solvent does not work very well as we all know, here the decrease of solubility of the glycol ether at higher

temperature helps us.

At high temperatures glycol ether is much less soluble in water the solvent separates from the solution and does the required

job.

In short this type of cleaner works well at higher temperatures, above 500C when 2- butoxy ethanol is used as the solvent.

a


36/48


SEPT 1999 99.09.01

8.3. ALKALINE CLEANERS

Alkaline cleaners are historically used to clean from fats and oils, good results are obtainable but a word of

caution is important.

When these cleaners are used with seawater a white solid material (magnesium and calcium carbonate) will

be formed, only a diluted acid removes this. material.

Strong alkaline cleaners may be used in steel, epoxy coated and stainless steel tanks. Strong alkaline

cleaners will dissolve zinc coating.

To avoid attack of zinc coatings buffered alkaline cleaners are used, the PH. value is about 10, on mbst zinc

coatings his type of alkaline cleaners can be used.

The oils and fats are partly saponified by the alkaline cleaners.

Fats with a high melting point will form hard soaps when caustic soda is used in the cleaner, when

potassium hydroxide is used softer soaps are formed.


37/48


SEPT 1999 99.09.01

Preferred supplier CP Manufacturing.

StockDoints:

- Rotterdam — Amsterdam - Antwerp — Hamburg - Algeciras

- Los Angeles - Houston- Dubai - Singapore.

- Durban

Produc’ts also can be obtained in other ports than the agreed at additional costs with sufficient notice.

Products with main purpose:

P3 Grato 14 Marine

Product can be used for cleaning after vegetable oils as well as mineral oil

Product can be used very well as hydro carbon remover

Suitable for stainless steel, epoxies and zinc coating.

P3 Grato 50 Marine

Product can be used for cleaning high melting point vegetable oils

Suitable for stainless steel and epoxy coating

CP Leadelean

Product can be used for cleaning light mineral oils and fish oil

Suitable for stainless steel, epoxy and zinc coating

CP Super degreaser

Product can be used for cleaning after mineral oilsSuitable for stainless steel, epoxy and zinc coating

CP Hydrocarbon remover

Product can be used as hydrocarbon remover

Suitable for stainless steel, epoxy and zinc coating

P3 NA Marine

Smell ~mover after products like: Cresols, Acrylates, Phenols

Suitable for stainless steel and restricted for coating

P3 Ti 166 Marine (Metal brightner, Rust remover)Suitable for stainless steel.

All type of raw materials can be ordered with CP Manufacturing for which prices are subject to daily, fluctuations.

SEPT 1999 99.09.01


38/48


39/48


SEPT 1999 99.09.01

9. JO TANKERS STANDARD WALL WASH TESTS

Acid wash colour test.

Chloride test.

Water miscibility also known as hydrocarbon test. (Including Tindle Test see drawing)

Permanganate time test.

Jo Tankers Standard Equipment to perform a wall wash.

Material and liquids to Derform the Acid wash color test.

Funnel.

Test tube lower mark at 7 ml. and upper mark 28 ml.

High purity Toluene — Benzene — or Xylene.

Sulphuric Acid (concentrated).

Colour Standards.

Material and liquids to perform the chloride test.

Funnel.

Nessler tubes lOOmi. short form lower mark at 25 ml. upper mark 100 ml.Pipette 2m1.Dropping bottle.

Distilled water Chloride free.

Silver nitrate

Standard Chloride solution.

Material and liquids to perform the water miscibility or hydrocarbon test.Funnel.

Nessler tubes lOOmI. short form lower mark at 33 ml. upper mark 100 ml.


High purity Lab approved METHANOL.

Material and liquids to perform the Permanganate Time Test.Funnel.

Measunng cylinder 50 ml. long form.

Pipette 2m1.

Stopwatch.

Temperature Bath.


40/48


SEPT 1999 99.09.01

Colour standard.


Distilled

KMNO4 crystals in brown bottles (30 ml. or 100 ml).Hydrochloric Acid (as cleaning agent).

Additional material.

Safety labelled (Methanol) Wash Bottle 1000 ml

Safety labelled (Distilled — water) Wash Bottle 1000 ml.

Safety labelled (Hydrochloric Acid) Wash Bottle 500 mL

Safety labelled (Toluene) Wash Bottle 500 ml.

Measuring cylinder 50 ml. long form with stopper.(4x)

Bath / Cooling container.

Approved clean chemical gloves.

Paper filters.

Jo Tankers Standard procedure to perform a wall wash.

Method:

Flush the testing liquid as far as reachable against the tank wall and collect same at approximately 2

meter from starting point directly by means of a funnel into a clean sample bottle.

Filter liquid from sample bottle into a Nessler test tube, quantity pending test to perform.

Places I spots.

I .Top of tank: First reachable highest point in tank. (Fe. top bulkhead first bordes)

2.Middle of tank, nearest reachable bulkhead from staircase.

3.Down in tank, all four tank walls and frames if applicable.

5. Bottom in case of loading (Hexene -1)

6 Heatingcoils?

7 .Pump?

Note!

Spots Heating coils and Pump (in case visual clean and free of greasy spots) calculated in PPM,

negligiblA in relation to their surface and total cubic meter to load.

In case of extreme sensitive cargoes recommend to take these spots as well.


41/48


SEPT 1999 99.09.01

10. WALLWASH TESTS

ACID WASH COLOUR TEST OF

Industrial Aromatic Hydrocarbons

(Benzene-Toluene-Xylene) Astm D848 method

This method is generally used for aromatics.

Product is shaken with concentrated sulphuric acid and discoloration is observed.

All carbohisable substances will discolour the sulphuric acid layer due to the combustion of especially oils and fat.

APPARATUS

Nessler tubes short form.

Colour Standards

REAGENTS

Sulphuric Acid (concentrated)

PROCEDURE

Transfer 7 ml’s sulphuric acid(concentrated) in a glass tube and add 21 ml’s of

aromatic(benzene-toluene-xylene)on top of it.

shake thoroughly at least 150 strokes and store for 15 minutes in the dark. Fill a second tube with

7 ml’s sulphuric acid(concentrated) and add 21 ml’s of the wall wash(taken with benzene,

toluene, xylene) and compare with the standard.

NOTE Take care for concentrated sulphuric acid.

All safety precautions must be taken.

Use clean equipment to perform the wall wash.


42/48


SEPT 1999 99.09.01

STANDARD TEST METHOD FOR DETERMINATION OF

TRACES INORGANIC CHLORIDES

IN WATER MISCIBLE SOLVENTS

APPARATUS

Nessler tubes I OOml. short form.

Pipette 2m1.

Dropping bottle.

REAGENTS


Silvernitrate.

Standard Chloride solution (1 ml 0.025 mg CL).

PROCEDURE

Transfer 25 ml’s DI — water from wall wash sample into one of the Nessler tubes and fill to the

upper mark, with distilled water.

Fill a second tube to the upper mark with distilled water, and add 1 ml. standard chloride

solution.

Mix both tubes and add abt. 5 drops Silvemitrate.

Compare the cloudiness of the standard against the sample tube by viewing downward through

the tubes toward a dark background.

Add as much ml’s Chloride standard as necessary to the second tube to compare the cloudiness

of the sample.

CALCULATION

ML’S STANDARD X 0,025

X 1000 = PPM CHLORIDE

ML’S SAMPLE X DENSITY

NOTE: Use clean equipment to perform the wall wash.


43/48


SEPT 1999 99.09.01

ORGANIC CHLORIDES ARE PRESENT IN:

CHLORINATED HYDROCARBONS CHLORINATED AROMATICS

Methylene Chloride Monochlorobenzene

Carbon Terachloride Orthonitrochlorobenzene

Ethylene Dichloride Orthonitrotoluene

‘Perchloroethylene Paradichlorobenzene

Trichioroethylene Paranitrotoluene

Trichioroethane

Chloroform

Organic Chlorides (chlorine) = Total Chlorides - Inorganic Chlorides (salt). Chlorides by

Conductivity Meter

The inorganic chlorides are complete soluble in water and in most of the chemicals.

Chlorides (salt) are then in ionic form ,which can be measured by conductivity.

Distilled water is never complete non-ionic and measure its conductivity as a blank.

Use the correct scale on the apparatus: /umho.

Choose the correct range (0-2000 x l0~).

The read out is shown for 2 minutes,and switch off automatically.

The cell can be tested by recheck on a standard chloride solution.

A Chloride standard solution of 100 ppm cI. can be controlled and shows approx. 330/umho.

Clean the cell after each use with distilled water.

Examole:Concentration as cI. Measured conductivity. Conductivityafter blank correction.

Distilled water 2 2

• 0.5 ppm 4 2

1.Oppm j 6 42.0 ppm 9 7

5.0 ppm 21 19

10.0 ppm 39 37

100.0 ppm 324 322

Plot on a curve the measured conductivity against the standard chlorides solution.

The conductivity indicates the maximum possible chlorides content.

Also traces of acids and alkalines (cleaners and chemicals) are indicated.


44/48


Sept 1999 99.09.01

STANDARD TEST METHOD WATER MISCIBILITY

All organic chemicals are hydrocarbons (hydrogen - carbon in the bruto structure), not all of the organic chemicals show a

failure on “watermiscibility”.

Therefore the test must be called “watermiscibility” instead of “Hydrocarbon test.

According to the fact that the surface of a tank or container for the shipping of Methanol must be free of any hydrocarbons, a

test was performed , starting from the principle that hydrocarbons together with water gives a milky cloudy solution.

APPARATUS : Funnel.

Nessler tubes lOOmI. short form.

REAGENTS : Distilled water Chloride free.

Test Methanol.

PROCEDURE :

Transfer 33 ml’s Methanol (used for Wallwash) into one of the Nessler tubes and fill to the

upper mark, with distilled water. The mixture is shaken and must stand for 20 minutes. Fill

a second tube to the upper mark with distilled water. Examine vertically against a black

ground ,a difference will indicate the presence of hydrocarbons.(cloudy)

REMARKS : When performing the test use clean plastic throw-away gloves, and clean

apparatus before use.

A visual check can be made in the tank by means of a penlight.(Tindle

test). The light beam will deviate by contamination.

Tindle Test. (Test in a dark area )

Light bean and look direction.

OK

Bottom will work as a miror .

Wrong

NOTE: use clean equipment to perform the test.


45/48


46/48


47/48


SEPT 1999 99.09.01

11. ACID PICKLING AND PASSIVATION OF STAINLESS STEEL

The reason for acid pickling is to achieve a clean steel surface that has the corrosion resistant one may expect from the steel

grade in question.

The attainment of surface that are free from iron, metallic deposits and other contamination depends on combination of proper design, fabrication methods, cleaning and descaling and protection, preventing the recontamination of clean surface.

Note: Oxidizing agent (air) must be present and replenished regularly to maintain passivity. Passivating

is not a constant state, it only exists in certain environments or under certain conditions. In circumstances

favorable to passivity, Stainless steel has a solution potential approaching that of noble metals. If

Dassivity is destroyed, the Dotential aDDroximates that or ordinary iron. Most corrosion problems can

be traced back to this fact.

Before stainless steel is subjected to acid pickling, it is important to know the composition of the alloy. On Jo Tankers’

vessels we are only using two (2) standard compositions. One composition is to a standard (acid resistant stainless steel)

AISI 316 LN and the other standard type of acid resi~tant steel is Duplex Steel 2205.

The acids most commonly used for scale removal are nitric acid, hydrofluoric acid and sulphuric acid. But there exist no

single acid solution or process that is equally effective for removing oxide scale form all grades of stainless steel.

Acid picking is usually carried out in a mixture of acids containing hydrofluoric. It is in particular the best process for

Stainless Steel. Mixtures of nitric acid and hydrofluoric acids have the advantage of being only mildly corrosive to the

majority of stainless steel. The attack is uniform and the corrosion rate can be predicted easily.

Acid Pickling

All repair jobs such as welding, grinding etc., shall be pickled. All welding of pipes should be pickled and the most practical

execution of pickling a piping system is to circulate the pickling media via a tank or container. Fluid velocity must not be too

slow. Low ambient temperatures may be a problem, partic~ilarly winters in northern countries.

Never pickle more than 20-30 minutes without inspection.

Passiviation

In principle passivation of stainless steel surface helps build up the natural oxide layer. A passivation with nitric acid will,

on a clear surface, rapidly build up a sound oxide layer.

The same oxide layer will also form in air but this takes somewhat longer and it will not be as thick.


48/48

SEPT 1999 99.09.01

Cleaning with acid

Surface treatment of stainless steel involving acid pickling and washing is necessary and this is referred to as “passivation”implying that a protective film is developed on the steel surface.

In fact this acid cleaning removes contamination which would interfere with the passive oxide film of stainless steel. This

treatment should also be carried out in case of completely ground surface. The pickling ensures the highest resistance

against pitting corrosion.

Pickling with Pastes

Pickling with pastes is a methods often applied to areas where surface contamination is evident, for example colored oxide

films near welds etc. Pastes based in nitric acid or mixture of nitric acid and hydrofluoric acid should be used. It is well

known that pastes containing ferric chlorides have been marketed for this purpose. These should be avoided as traces of

ferric chloride left on the stainless steel surface are likely to cause pitting.

Pickling with nitric acid solutions

The best method is to wash down the tank surface with a nitric solution and hydrofluoric acid in a mixture of about 20-30%

nitric acid and 3-5% Hydrofluoric acid.

The nitric acid/hydrofluoric acid solutionis the most effective comparing with nitric acid alone. However, care must be

taken that the steel surface is not over-etched. Over-etching of stainless steel may produces coarse surfaces. Guidelines for

this Drocedure are alven in A.S.T.M. Standard A.380.

To achieve the best results of passivating/pickling is when the temperature of the mixture can be between 25 and 450C.

NOTE: In view of the unpleasant nature of the operation of pickling/passivation there is scope for use of tank washing

machines or especially spraying nozzle for application of the mixture.

It must be made very clear that pickling pastes and nitric acids give off nitrous fumes, which are strongly toxic.

The toxic effect of nitrous fumes shows up much later.

I

END OF TANK CLEANING GUIDE

Documents

JO Tankers Tank Cleaning Guide