PDS: 10, 30, 40, 50
Preliminary remarks
The engine cooling water, like the fuel and lubri-cating oil, is a medium which must be carefully selected, treated and controlled. Otherwise, corrosion, erosion and cavitation may occur on the walls of the cooling system in contact with water and deposits may form. Deposits impair the heat transfer and may result in thermal over-load on the components to be cooled. The treat-ment with an anti-corrosion agent has to be effected before the first commissioning of the plant. During subsequent operations the con-centration specified by the engine manufacturer must always be ensured. In particular, this ap-plies if a chemical additive is used.
Requirements
Limiting values
The characteristics of the untreated cooling wa-ter must be within the following limits:
1) 1°dH (German hardness):
10mg CaO/litre 17.9mg CaCO3/litre 0.357mval/litre 0.179mmol/litre
2) 1 mg/l 1 ppm
Test device
The MAN B&W Diesel water test kit includes de-vices permitting, i.a., to determine the above-mentioned water characteristics in a simple manner. Moreover, the manufacturer of anti-corrosion agents are offering test devices that are easy to operate. As to checking the cooling water condition, see Chapter 3.4 "Checking cooling water", Page 3-19.
Supplementary information
Distillate
If a distillate (from the freshwater generator for instance) or fully desalinated water (ion ex-changer) is available, this should preferably be used as engine cooling water. These waters are free from lime and metal salts, i.e. major depos-its affecting the heat transfer to the cooling wa-ter and worsening the cooling effect cannot form. These waters, however, are more corro-sive than normal hard water since they do not form a thin film of lime on the walls which pro-vides a temporary protection against corrosion.
This is the reason why water distillates must be treated with special care and the concentration of the additive is to be periodically checked.
Hardness
The total hardness of the water is composed of temporary and permanent hardness. It is largely determined by calcium and magnesium salts.
The temporary hardness is determined by the hydrogen carbon content of the calcium and magnesium salts. The permanent hardness can be determined from the remaining calcium and magnesium salts (sulphates). The decisive fac-tor for the formation of calcareous deposits in the cooling system is the temporary (carbonate) hardness.
Water with more than 10°dH (German total hardness) must be mixed with distillate or be softened. A rehardening of excessively soft
wa-Property/
feature Characteristics Unit
Type of water
Distillate or freshwater, free from foreign matter.
Not to be used: Sea water, brackish water, river water, brines, industrial waste water and rain water
-Total hardness max. 10 °dH 1)
pH-value 6.5 - 8
-Chloride ion
content max.50 mg/l 2)
Table 3-8 Cooling water - characteristics to be adhered to
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ter is only necessary to suppress foaming if an emulsifiable anti-corrosion oil is used.
Damage in the cooling water system
Corrosion
Corrosion is an electro-chemical process which can largely be avoided if the correct water qual-ity is selected and the water in the engine cool-ing system is treated carefully.
Flow cavitation
Flow cavitation may occur in regions of high flow velocity and turbulence. If the evaporation pres-sure is fallen below, steam bubbles will form which then collapse in regions of high pressure, thus producing material destruction in closely limited regions.
Erosion
Erosion is a mechanical process involving mate-rial abrasion and destruction of protective films by entrapped solids, especially in regions of ex-cessive flow velocities or pronounced turbu-lences.
Corrosion fatigue
Corrosion fatigue is a damage caused by simul-taneous dynamic and corrosive stresses. It may induce crack formation and fast crack propaga-tion in water-cooled, mechanically stressed components if the cooling water is not treated correctly.
Treatment of the engine cooling water
The purpose of engine cooling water treatment is to produce a coherent protective film on the walls of the cooling spaces by the use of anti-corrosion agents so as to prevent the above-mentioned damage. A significant prerequisite for the anti-corrosion agent to develop its full ef-fectively is that the untreated water which is used satisfies the demands mentioned under
"Requirements", Page 3-11.
Protecting films can be produced by treating the cooling water with a chemical anti-corrosion agent or emulsifiable anti-corrosion oil.
Emulsifiable anti-corrosion oils fall more and more out of use since, on the one hand, their use is heavily restricted by environmental protection legislation and, on the other hand, the suppliers have, for these and other reasons, commenced to take these products out of the market.
Treatment before operating the engine for the first time
Treatment with an anti-corrosion agent should be done before the engine is operated for the first time so as to prevent irreparable initial dam-age.
Attention!
It is not allowed to operate the engine without cooling water treatment.
Cooling water additives
No other additives than those approved by MAN B&W Diesel and listed in Table 3-9, Page 3-16 up to Table 3-12, Page 3-17.
Permission required
A cooling water additive can be approved for use if it has been tested according to the latest rules of the Forschungsvereinigung Verbren-nungskraftmaschinen (FVV), ”Testing the suita-bility of coolant additives for cooling liquids of internal combustion engines” (FVV publication R 443/1986). The test report is to be presented if required. The necessary testing is carried out by Staatliche Materialprüfanstalt, Department Oberflächentechnik, Grafenstraße 2, 64283 Darmstadt on request.
To be used only in closed circuits
Additives can only be used in closed circuits where no appreciable consumption occurs ex-cept leakage and evaporation losses.
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• Chemical additives
Additives based on sodium nitrite and sodi-um borate, etc. have given good results. Gal-vanised iron pipes or zinc anodes providing cathodic protection in the cooling systems must not be used. Please note that this kind of corrosion protection, on the one hand, is not required since cooling water treatment is specified and, on the other hand, considering the cooling water temperatures commonly practised nowadays, it may lead to potential inversion. If necessary, the pipes must be dezinced.
• Anti-corrosion oil
This additive is an emulsifiable mineral oil mixed with corrosion inhibitors. A thin protec-tive oil film which prevents corrosion without obstructing the transfer of heat and yet pre-venting calcareous deposits forms on the walls of the cooling system.
Emulsifiable anti-corrosion oils have nowa-days lost importance. For reasons of environ-mental protection legislation and because of occasionally occurring emulsion stability problems, they are hardly used any more.
The manufacturer must guarantee the stabil-ity of the emulsion with the water available or has to prove this stability by presenting em-pirical values from practical operation. If a completely softened water is used, the possi-bility of preparing a stable, non-foaming emulsion must be checked in cooperation with the supplier of the anti-corrosion oil or by the engine user himself. Where required, adding an anti-foam agent or hardening (see Chapter 3.4 "Checking cooling water", Page 3-19) is recommended. Anti-corrosion oil is not suitable if the cooling water may reach temperatures below 0°C or above 90°C. If so, an anti-freeze or chemical additive is to be used.
• Anti-freeze agent
If temperatures below the freezing point of water may be reached in the engine, in the cooling system or in parts of it, an anti-freeze
agent simultaneously acting as a corrosion inhibitor must be added to the cooling water.
Otherwise the entire system must be heated.
(Designation for armed forces of Germany:
Sy-7025).
Sufficient corrosion protection will be achieved by admixing the products listed in Table 3-12, Page 3-17 taking care that the specified concentration is observed. This concentration will prevent freezing down to a temperature of about -22°C. The quantity of anti-freeze actually required, however, also depends on the lowest temperatures expect-ed at the site.
Anti-freeze agents are generally based on ethylene glycol. A suitable chemical additive must be admixed if the concentration of the anti-freeze specified by the manufacturer for a certain application does not suffice to af-ford adequate corrosion protection or if, due to less stringent requirementswith redard to protection from freezing, a lower concentra-tion of anti-freeze agent is used than would be required to achieve sufficient corrosion protection. The manufacturer must be con-tacted for information on the compatibility of the agent with the anti-freeze and the con-centration required. The compatibility of the chemical additives stated in Table 3-9, Page 3-16 with anti-freeze agents based on ethyl-ene glycol is confirmed. Anti-freeze agents may only be mixed with each other with the supplier’s or manufacturer’s consent, even if the composition of these agents is the same.
Prior to the use of an anti-freeze agent, the cooling system is to be cleaned thoroughly.
If the cooling water is treated with an emulsi-fiable anti-corrosion oil, no anti-freeze may be admixed, as otherwise the emulsion is broken and oil sludge is formed in the cooling system.
For the disposal of cooling water treated with additives, observe the environmental protec-tion legislaprotec-tion. For informaprotec-tion, contact the suppliers of the additives.
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• Biocides
If the use of a biocide is inevitable because the cooling water has been contaminated by bacteria, the following has to be observed:
- It has to be ensured that the biocide suita-ble for the particular application is used.
- The biocide must be compatible with the sealing materials used in the cooling water system; it must not attack them.
- Neither the biocide nor its decomposition products contain corrosion-stimulated constituents. Biocides whose decomposi-tion results in chloride or sulphate ions are not permissible.
- Biocides due to the use of which the cool-ing water tends to foam are not permissi-ble.
Prerequisites for efficient use of an anti-corro-sion agent
Clean cooling system
Before starting the engine for the first time and after repairs to the piping system, it must be en-sured that the pipes, tanks, coolers and other equipment outside the engine are free from rust and other deposits because dirt will considera-bly reduce the efficiency of the additive. The en-tire system has therefore to be cleaned using an appropriate cleaning agent with the engine shut down (see MAN B&W Diesel Work Card 000.03 and Chapter 3.5 "Cleaning cooling water", Page 3-23).
Loose solid particles, in particular, have to be re-moved from the system by intense flushing be-cause otherwise erosion may occur at points of high flow velocities.
The agent used for cleaning must not attack the materials and the sealants in the cooling system.
This work is in most cases done by the supplier of the cooling water additive, at least the suppli-er can make available the suitable products for
this purpose. If this work is done by the engine user it is advisable to make use of the services of an expert of the cleaning agent supplier. The cooling system is to be flushed thoroughly after cleaning. The engine cooling water is to be treat-ed with an anti-corrosion agent immtreat-ediately af-terwards. After restarting the engine, the cleaned system has to be checked for any leak-ages.
Periodical checks of the condition of the cooling water and cooling system
Treated cooling water may become contaminat-ed in service and the additive will loose some of its effectively as a result. It is therefore neces-sary to check the cooling system and the condi-tion of the cooling water at regular intervals.
The additive concentration is to be checked at least once a week, using the test kit prescribed by the supplier. The results are to be recorded.
Important!
The concentrations of chemical additives must not be less than the minimum concentrations stated in Table 3-9, Page 3-16.
Concentrations that are too low may promote corrosive effects and have therefore to be avoid-ed. Concentrations that are too high do not cause damages. However, concentrations more than double as high should be avoided for eco-nomical reasons.
A cooling water sample is to be sent to an inde-pendent laboratory or to the engine supplier for making a complete analysis every 3 – 6 months.
For emulsifiable anti-freeze agents , the supplier generally prescribes renewal of the water after approx. 12 months. On such renewal, the entire cooling system is to be flushed, or if required to be cleaned (also see Chapter 3.5 "Cleaning cooling water", Page 3-23). The fresh charge of water is to be submitted to treatment immedi-ately.
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If chemical additives or anti-freeze agents are used, the water should be changed after three years at the latest.
If excessive concentrations of solids (rust) are found, the water charge has to be renewed completely, and the entire system has to be thoroughly cleaned.
The causes of deposits in the cooling system may be leakages entering the cooling water, breaking of the emulsion, corrosion in the sys-tem and calcareous deposits due to excessive water hardness. An increase in the chloride ion content generally indicates sea water leakage.
The specified maximum of 50mg/kg of chloride ions must not be exceeded, since otherwise the danger of corrosion will increase. Exhaust gas leakage into the cooling water may account for a sudden drop in the pH value or an increase of the sulphate content.
Water losses are to be made up for by adding untreated water which meets the quality de-mands according to "Requirements", Page 3-11. The concentration of the anti-corrosion agent has subsequently to be checked and cor-rected if necessary.
Checks of the cooling water are especially nec-essary whenever repair and servicing work has been done in connection with which the cooling water was drained.
Protective measures
Anti-corrosion agents contain chemical com-pounds which may cause health injuries if wrongly handled. The indications in the safety data sheets of the manufacturers are to be ob-served.
Prolonged, direct contact with the skin should be avoided. Thoroughly wash your hands after use. Also, if a larger amount has been splashed onto the clothing and / or wetted it, the clothing should be changed and washed before being worn again.
If chemicals have splashed into the eyes, imme-diately wash with plenty of water and consult a doctor.
Anti-corrosion agents are a contaminating load for the water in general. Cooling water must therefore not be disposed off by pouring it into the sewage system without prior consultation with the competent local authorities. The re-spective legal regulations have to be observed.
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Permissible cooling water additives
Chemical additives (Chemicals) - containing nitrite
1) The values in the marked areas can be determined with the test kit of the chemical manufacturer.
Chemical additives (Chemicals) - free from nitrite
Manufacturer Product designation
CWT Diesel/QC-2 16l 16,000 4,000 6,000
Nalfleet Marine Chemicals P.O. Box 11 Northwich
Cheshire CW8DX, UK
Nalfleet EWT Liq (9-108) Nalfleet EWT 9–131 C Nalfleet EWT 9–111
Marisol CW 12 l 12,000 2,000 3,000
Uniservice
Via al Santuario di N.S.
della Guardia 58/A Table 3-9 Chemical additives - containing nitrite
Manufacturer Product designation Initial dose
per 1,000 l
Table 3-10 Chemical additives - free from nitrite
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Emulsifiable anti-corrosion oils
Anti-freeze agents with corrosion inhibiting effect
Manufacturer Product
(Designation) BP Marine
Breakspear Way Hemel Hempstead Herts HP2 4UL, UK
Diatsol M Fedaro M
Castrol Int.
Pipers Way
Swindon SN3 1RE, UK
Solvex WT 3
DEA Mineralöl AG Überseering 40
22297 Hamburg, Germany Targon D
Deutsche Shell AG Überseering 35
22284 Hamburg, Germany
Oil 9156
Table 3-11 Emulsifiable anti-corrosion oils
Manufacturer Product
(Designation) Minimum concentration BASF
Carl-Bosch-Str.
67063 Ludwigshafen, Rhein, Germany
Glysantin G 48
Swindon SN3 1RE, UK
Antifreeze NF,SF
BP, Britannic Tower, Moor Lane,
London EC2Y 9B, UK Antifrost X 2270A
DEA Mineralöl AG Überseering 40
22297 Hamburg, Germany Kühlerfrostschutz Deutsche Shell AG
Überseering 35
22284 Hamburg, Germany
Glycoshell
Höchst AG, Werk Gendorf 84508 Burgkirchen, Germany
Genatin extra (8021 S) Mobil Oil AG
Steinstraße 5
20095 Hamburg, Germany Frostschutz 500 Arteco/Technologiepark, Zwijnaarde 2,
B-9052 Gent, Belgium Havoline XLC
Total Lubricants 50 %
Paris, France Glacelf Auto Supra
Total Organifreeze Table 3-12 Anti-freeze agents with corrosion inhibiting effect
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