Diesel Engine Cooling Water Treatment

7/29/2019 Diesel Engine Cooling Water Treatment

http://slidepdf.com/reader/full/diesel-engine-cooling-water-treatment 1/3Vecom Marine is a joint venture o Vecom Group & Unimarine Group - Version 3.1 - Chapter 11 - Page 46

Vecom Marine

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his inormation is not to be taken as a warrant or repre-entation or which we assume legal responsibilit, nor as

permission, inducement or recommendation to practice

n patented invention without a license. The inormation

s oered solel or our consideration, investigation and

erication.

CORROSION OF DIESEL ENGINE COOLING WATER SySTEM

Although VECOM Inhibitors or Cooling Water Sstem i used according the

instruction, provide excellent metal protection, other signicant problems

ma aect the Water Cooling Sstem.

OXyGEN CORROSION: The corrosion process in these sstems is normall due to the presence

o dissolved oxgen in the water. Air enters these “open” sstems and the

oxgen dissolves into the water and attacks errous and non-errous metals.

The presence o air should be kept to a minimum to avoid “air locks” which

can cause serious local overheating o the engine b interrupting heat trans-

er. This is normall controlled b the use o air vents tted to high points on

the clinder covers. These vents and atmospheric seals should be kept in

good working order.

ACIDIC CORROSION:

This is normall the result o acidic gases (i.e. combustion gases) entering

the sstem via poor seals, especiall around the clinder head area. These

gases lower the pH o the cooling water leading to attack o the metal. Acid-

it can also be caused b the leakage o sea water into the sstem, via leak-

ing coolers.

CAVITATION CORROSION / EROSION:

Cavitation is normall caused b vibration and/or turbulent water fow in

the sstem. The damage caused b these phenomena appears like deep pit-

ting corrosion. It is the result o high- and low-pressure waves in the sstem,

creating vapor bubbles on metal suraces. These bubbles expand and then

collapse at a ver ast rate with high impact pressure. This action removes

the protective laer o oxide and “eats” into the metal. Cavitation Corrosion /

Erosion is thereore both mechanical and chemical in nature. The mechani-

cal aspects are design oriented, but it has been ound that modern highleective “lming” corrosion inhibitors greatl reduce the loss o metal.

PRODUCTS OF CORROSION:

The various orms o corrosion described result in soluble and particulate

metal oxides in the cooling water. The are mainl iron oxides, but some

copper oxide is usuall present due to corrosion o heat exchanger tubes.

These oten orm a hard oxide scale, in the areas o greatest heat exchange.

NEW BUILDING PRE-COMMISSION CLEANING:

When an engine sstem is rst built it is inevitable that man o the com-

ponents become corroded beore completion. Man problems later in the

lie o the sstem are due to poor or no pre-commission cleaning. It is in theinterests o ship owners to speci this when building new vessels or carr-

ing out major overhauls.

HARDNESS SCALE:

The presence o calcium carbonate, sulate, silicate and a host o other salts

in shore water or through seawater contamination, are bound to result in

the build up o ‘scale, particularl in areas o high heat exchange. This can be

greatl reduced b using distilled water in the sstem. However, i scale has

built up or an reason, it must be removed beore overheating occurs and

to avoid “under deposit corrosion”.

See next page or recommended cleaning o cooling sstems.

DIESEL ENGINECOOLING WATER

TREATMENT

RECOMMENDED TREATMENT

COOLTREAT NCLT

(nitrite base)

COLORCOOLING

(nitrite base - color indicating)

NCLT AL / ALUMINUM

(nitrite base)

All products approved b major engine

manuacturers

Note: onl NCLT is kept in all major stock

ports

WATER TREATMENT



WATER TREATMENT DIESEL ENGINE COOLING WATER

CLEANING OF COOLING SySTEMS

BLEED OFF OF COOLING WATER SySTEMS

As in a boiler, solids tend to accumulate in low points o cooling water sstems. The must be periodicall “Bled-o”.

As a practical guideline, it is recommended that the sstem be bled whenever chlorides exceed 100 parts per million.

Consult the engine manuacturer’s instructions or urther recommendations according the VECOM Inhibitor used.

OIL

Oil ma be present rom leaking telescopic tubes o piston cooling water sstems or other sources. Also, when con-

verting rom a soluble oil tpe water treatment to a VECOM treatment, oil must be removed to avoid over heating

problems. DEGREASER GP or ALKACLEAN are added to the sstem being cleaned at the rate o 26 liters per ton (2

1/2 per cent b volume) and circulated through the sstem or 6 to 12 hours. Heat the solution to 60°-73°C. (140°-

160°F.) or best results. Dump the solution, then rell and dump again. Flush the sstem thoroughl, hosing through

access covers or other openings, as possible. An carbonized encrustation, which cannot be emulsied, should be

spot cleaned using carbon remover according to instructions on the package. Rell and add the initial dose o the

Vecom treatment selected. Consult engine manuacturer’s instructions or specic fushing and cleaning procedures

in addition to the above.

SCALE

Scale ma var considerabl in its composition. A sample should be presented to VECOM or analsis. In most o the

case that ma be accomplished b DESCALING LIQUID or SAFE DESCALER POWDER (Consult proper technical bro-

chure or instructions). In both cases, to neutralize an remaining traces o acid and to passivate the circuit, circulate a

1% to 2% o ALKALINITy CONTROL or 2 to 6 Hours.

OPERATIONAL DESCALING WITH SCALE SEQUESTRANT AND NCLT

VECOM oers a unique approach to both clean and protect a cooling water sstem without downtime. This treatment

was designed with the ollowing points in mind:

1. The sstem should be made clean and scale-ree.

2. No dangerous poisonous substances should be used.

3. The procedure should be simple.

4. No damage to packing or metals should occur.

SCALE SEQUESTRANT is used or chelation o metallic ions (calcium, magnesium, etc.). COOLTREAT NCLT is used to

inhibit and protect the sstem against corrosion. Both chemicals are used together or three months. Thereater,

COOLTREAT NCLT is used alone to protect the sstem.

SCALE SEQUESTRANT PROCEDURE

The sstem to be cleaned should be fushed to remove as much red-brown sludge as possible. I necessar remove

the cooling water inlet line. Note the amount o scale present beore treatment begins. Dose SCALE SEQUESTRANT at

the initial dosage, rate o 2 liters per ton o cooling water. Thereater dose dail at the rate o 1 liter per 10 tons cool-

ing water capacit. At the same time, add an initial dose o COOLTREAT NCLT at the rate o 4 to 8 liters per ton cooling

water. The sstem will take some time to build up the recommended concentration o 2300-4500 PPM Sodium Nitrite

(Nitrite 1500-2300). Thereater dose small maintenance amounts o COOLTREAT NCLT to maintain this concentration.

The sstem should be bled o weekl, or more requentl as the color o the cooling water becomes darker as theSCALE SEQUESTRANT removes the deposit rom the sstem.

Ater three to our months, the sstem should be Scale-ree and the SCALE SEQUESTRANT can be discontinued. Con-

tinue with COOLTREAT NCLT to maintain 1500-2000 PPM nitrite, correcting or evaporation, leaks, repairs, etc. b regu-

lar testing.

Note: While descaling the sstem pH should be checked and maintained at 7.5-9.5. I it is necessar to lower the pH,

add small amounts o SAFE DESCALER (POWDER). This sstem o descaling is intentionall a gradual process. Do not

overdose to speed up the process.



WATER TREATMENT DIESEL ENGINE COOLING WATER

REDUCTION OF NITRITE IN COOLING WATER SySTEMS

BACTERIA

The bacteriological contamination o diesel engine cooling circuits being treated with COOLTREAT NCLT or COLOR-

COOLING can cause a signicant reduction in nitrite concentration. In such cases, one must rst make sure that the

“disappearance” o the nitrite is not due to a loss o water resulting in intake o resh water. I there is no water loss

and despite the act the addition o COOLTREAT NCLT or COLORCOOLING, the Nitrite level continue to decrease, it isrecommended to add ECOSPERSE to the NCLT

treatment. The quantit o ECOSPERSE to be used is one liter per 10 tons o water, on a weekl basic. ECOSPERSE

protects the cooling water against growth or a wide spectrum o microorganism. The bacteria, which are mono-

cellular bodies, exempt rom chlorophll can be divided in several groups: STAPHILOCOCCUS, STREPTOCOCCUS, SAL-

MONELLA, PSEUDOMONAS AERUGINOSA, etc. Pseudomonas causes ormation o mud and algae and contaminates

the cooling circuits resulting in transormation o Nitrite into Nitrates.

IF THERE IS A CONTINUOUS REDUCTION IN NITRITE WITHOUT LOSS OF WATER IN THE CIRCUIT AND IF THE SITUATION

IS NOT IMPROVED By THE ADDITION OF ECOSPERSE, IT IS RECOMMENDED TO DECONTAMINATE THE CIRCUIT WITH

THE FOLLOWING SySTEM:

1. Flush completel the cooling circuit to be decontaminated and re-ll it with resh water. Add 5 lt. o CHLOR 12 or,

better, 2 tablets o CHLORINE TABLETS (20 gr.) or ever 5 tons o water. CHLORINE TABLETS dissolve ver

quickl and have the same eect as CHLOR 12.

2. Circulate the solution in the entire circuit or at least 6 to 12 hours and check that the level o active chlorine is at

least 2 to 5 PPM. I it is below that level, add CHLOR 12 or CHLORINE TABLETS until a concentration o 2 to 5 PPM

is achieved. That concentration must be maintained during the entire period o decontamination. The solution

must be circulated while the engine is at standstill, i.e. the engine is cold because i the temperature o the water

goes above 25° to 30°C., the chlorine evaporates rapidl.

3. Check the level o active chlorine ever hour to make sure its concentration remains above 2 PPM. I necessar,

keep adding CHLOR 12 or CHLORINE TABLETS.

4. Ater the above-mentioned circulation empt the circuit and fush it with resh water in order to eliminate all

traces o

5. chlorine. Re-ll with resh water and add IMMEDIATELy the initiall recommended dosage o COOLTREAT NCLT

or COLORCOOLING, which will protect the metal rom the corrosive action o chlorine.

Chlorine is highl corrosive i let in the circuit over a long period o time. One should make sure that the circuit is

fushed properl ree o all traces o chlorine. Check or residual chlorine with our test kit to make sure that TOTAL

ACTIVE CHLORINE = 0.

PSEUDOMONAS AERUGINOSA, even in colonies in excess o 50.000 SPP, can be easil eliminated with the decontami-

nation operation described above.

INFLUENCE OF OXyGEN AND TEMPERATURE

Oxgen excess in the water sstem ma be also one o the main reasons o the oxidation o NITRITE converting into

NITRATE. The reduction o NITRITE level or causes other than leaks o water in the sstem will result in a serious loss

o protection o the metal, thus starting corrosions and scale. In new building o ships o same class, same tpe o

Engine Manuacturer, same ard construction, same water cooling sstem (high-low temperature) one can be acedwith ew cases o unusual NITRITE reduction and suddenl, ater a certain period, this phenomenon disappear with

no apparent reason. Or in some rare other cases it continues or man ears. That act was brought to the attention o

a highl qualied Universit laborator that could not come up with a satisactor answer despite o deep research

and studies o this phenomenon. In one or two “chronic” cases VECOM has solved the problem b changing the tpe

o treatment rom the NITRITE based to PHOSPHONATE based anticorrosion product. In a ew other cases the problem

was solved b completel changing the water in the circuit without even decontaminating with Chlorine disinect-

ing operation as described above. The onl common events o this problem were the HIGH-LOW temperature tpe

o cooling sstems in new building vessels, which never happens in aged vessels. Temperature variation (high-low

temperature sstem) is also one o the reason o NITRITE reduction problem, but the real infuence o all parameter

is still uncertain. We suggest thereore to contact our VECOM technical oce i an o above problems aect our

cooling water sstem.

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Diesel Engine Cooling Water Treatment