04-2429H- Coolant System Guidelines

GE Energy

Waukesha gas engines

ALL

SERVICE BULLETIN TOPIC: IDENT NO: DATE: SUPERSEDES:

Cooling System 4-2429H February 2012 4-2429G

SUBJECT: Cooling System Guidelines and Water Treatment Recommendations MODELS AFFECTED: All Models This bulletin, based on engineering documents S-06699-7 and S-07610-3, provides general information related to coolant and coolant system requirements for Waukesha gas engines. The many changes to this bulletin revision require the user to read and understand all the content prior to servicing the cooling system. Special note should be taken to information related to amine usage (see page 6).

WATER TREATMENT FOR ENGINE COOLING SYSTEMS The primary purpose of any water treatment program is to protect the surfaces of all water passages from corrosion and any scaling or sludge deposits which will impede the transfer of heat to or from the water. If the system is exposed to low ambient temperatures antifreeze protection is needed. In addition, cavitation erosion protection is a consideration for engine cooling systems. GENERAL COMMENTS Cooling water quality is one of the most often overlooked factors in an engine installation. Poor water quality and lack of coolant maintenance contribute to scaling, corrosion and sediment buildup within the entire cooling system. It leads to heat transfer problems which can result in failed parts and downtime. This is especially critical in low pressure steam systems with ebullient cooled engines.

To get the most benefit from any water treatment program, it is essential to apply the chemicals properly and maintain close control over the process. Briefly, inhibitors should be selected only after a thorough study of the entire system and the specific water to be used. It may be necessary to preclean or pretreat the system before it is put into operation. Higher treatment levels may be recommended during start-up to protect the system quickly. Later, after protection is established, treatment levels can be reduced to a maintenance value. In all cases, it is essential to monitor the water condition carefully and continuously. Corrosion, scale, fouling, cavitation and microbiological growth are the major problems in all types of cooling systems. Of these corrosion is the most important. PRETREATMENT Pretreatment is preparation of the water system to ensure that the treatment program itself can work effectively from start-up. New systems, or existing ones being returned to service, can contain contaminants. These include films of oil, grease or other protective coatings, biological contamination, rust spots, dirt, casting sand and welding slag. These materials are an unavoidable result of the system’s construction, transport and storage. If these materials are not removed by suitable pretreatment, the subsequent treatment program may not be effective. Common pretreatments are water flushing and acid cleaning. Water flushing may reduce solid contaminants, but may not be very effective on films. Untreated flushing water may react with unprotected metal surfaces to form corrosion.

* Trademark of General Electric Company

Service Bulletin 4-2429H © 2/22/2012

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Service Bulletin No. 4-2429H Acid cleaning removes corrosion products and some mineral scale but has little effect on organic material. Improper cleaning may lead to severe metal attack. Improper neutralization may leave metal surfaces in a highly reactive state and vulnerable to rapid corrosion. Like the treatment program itself, a system pretreatment must be based on the advice of a knowledgeable consultant. CORROSION The actual corrosion process is electrochemical. Refined metals in the cooling system are returned to a more basic metallic oxide state when they combine with oxygen carried by the coolant flow. These chemical reactions usually cause a low-voltage electric current. Where corrosion will occur in a water system and to what degree it will progress depends on a number of factors: quality of water, type of treatment, metals in the system, surface temperatures and mechanical conditions (vibration, stress, relative motion of two adjacent parts, etc.).

Figure 1

Several types of corrosion can be found in engine cooling water systems: 1. Crevice 2. Cavitation-related 3. Fretting 4. Selective leaching 5. Galvanic

The primary effect of hard scale is to reduce heat transfer efficiency. A scale layer only 0.025 in. (0.64 mm) (business-card thick) can reduce heat flow by 25 – 30%. The composition of the scale will determine the actual efficiency loss. This reduced heat flow increases operating temperatures and can end in parts cracking. Sludge tends to accumulate in low spots and where water velocity is low. Buildup can restrict or stop water flow, resulting, as with scaling, in parts cracking. Any new water brought into the system by a coolant change or as make-up will add new scale and sludge forming material to the system. CAVITATION Cavitation is a localized pitting which usually occurs on cylinder liners, pump impellers and certain crankcase surfaces. It is caused by a combination of mechanical erosion and corrosion. In severe cases, cavitation pits can be numerous and deep.

Figure 2

MICROBIOLOGICAL GROWTH The uncontrolled growth of microorganisms in a cooling system can lead to deposit formations which contribute to fouling. Microbial slimes are masses of microscopic organisms and their waste products and are usually gooey. This problem is usually associated with cooling towers or other open cooling systems. Removal of airborne debris is also of concern with a cooling tower or other open cooling system.

MINERAL SCALES AND FOULING Compounds and minerals dissolved in water tend to come out of solution when the water is heated. They form either a scale on the metal surfaces or a fouling precipitate (sludge) in the water system.


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Service Bulletin No. 4-2429H COOLING SYSTEM GUIDELINES FOR WAUKESHA ENGINES 1. The radiator or heat exchanger must be sized to maintain normal jacket water temperature out of the engine under all site conditions. Normal jacket water outlet temperature is: 180°F (82°C) for non-heat recovery applications 220°F (105°C) for alternate fuel applications 210° – 235°F (99° – 113°C) for heat-recovery applications Consult the Engine Specification sheet in the Technical Data Manual for operating temperatures of specific engine models. The engine power rating of intercooled engines is based on the maximum water inlet temperature to the intercooler (auxiliary) water pump. Consult the Power Rating Chart or Technical Data Manual for power ratings at various intercooler inlet water temperatures. The radiator or heat exchanger must be sized for the site conditions. Remember that special consideration must be given to altitude, high or low ambient temperature, and extremely dirty applications. Consult the Technical Data Manual – Heat Balance subsection of the specific model for engine, intercooler and oil cooler heat rejection. 2. The suggested minimum jacket water circuit return temperature into a warm engine is 30°F (16.6°C) less than the designed jacket water outlet temperature with a maximum return temperature change of 18°F (10°C) per minute while between the minimum and maximum operating temperatures. See latest edition of Form 1091, Installation Manual, for more information.

5. Heat rejection data are average values at standard conditions and will vary for individual engines and with site operating and ambient conditions and with timing or air/fuel ratio change. An adequate reserve for this variation and normal design fouling factors should be used when sizing the cooling system. Waukesha suggests a 15% reserve. 6. Use antifreeze protection for applications where the engine or cooling system can be exposed to ambient temperatures below 32°F (0°C) or boiling conditions are expected at the outlet. An adequate mixture of ethylene glycol and water or propylene glycol and water is recommended. 7. If antifreeze or significant levels of other water treatments are used, the cooling system heat rejection capacity must be increased. Antifreeze solutions reduce the heat transfer capability of the cooling system by approximately 3% for each 10% by volume addition of antifreeze. As an example, if a 50/50 solution of ethylene glycol and water is used instead of 100% water, the heat transfer capability of the radiator must be increased by about 15%. For this example, if the capability of the radiator system is not increased, there will be an approximate 10°F (5.5°C) decrease in the allowable ambient temperature. 8. Initial add and make-up water must be treated before use in a solid water system.

3. If a unit-mounted radiator with a pusher fan is used, reduce the allowable ambient or increase the design temperature by approximately 10°F (5.5°C). This is necessary because of the increase in air temperature as it flows across the engine. If the driven equipment, such as a generator, radiates significant heat, then a further temperature allowance must be made. 4. Coolant flow and allowable system resistance are based on the pump flow curves for the specific configuration to which the engine is built. Consult the Technical Data Manual – Cooling Systems subsection for the specific model.


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Service Bulletin No. 4-2429H 9. The cooling system must be designed to properly pressurize the system and remove entrained air from the coolant. This can be accomplished by proper use of vent lines, a static line and an expansion tank. Figure 3 illustrates this:

3 2

Table 1: Recommended System Pressure Cap Setting JACKET WATER TEMPERATURE

RECOMMENDED SYSTEM PRESSURE CAP SETTING

Up to 210°F (99°C)

7 psig (48 kPa)

210 – 235°F (99° – 113°C)

8 psig (55 kPa)

The pressure cap must have a vacuum relief function to prevent a vacuum from forming in the tank during load reduction or cool-down operation. Only a single pressure cap can be used in a cooling system and must be at the highest point on the expansion tank.

1 4

6

5 Figure 3 1 - Trapped Air 2 - Vent Line 3 - Expansion Tank

A pressure cap is required to prevent coolant evaporation losses and to prevent boiling in the system.

4 - Static Line 5 - Cooling Component 6 - Engine Component

Vent lines should be 1/4 in. (6.5 mm) diameter on systems with vent lines less than 10 ft (3 m) long, or 1/2 in. (13 mm) diameter with a 1/4 in. (6.5 mm) orifice on systems with vent lines more than 10 ft (3 m) long. These vent lines are piped from high points in the cooling system to the expansion tank below the coolant level but away from the static line connection. The expansion tank must be the highest component in the cooling system. Trapped air can then flow to the expansion tank. This system also bleeds air out of the system during filling. It must bleed air with the thermostat fully opened or fully bypassing. The static line is sized much larger than the vent lines to minimize flow velocity and pressure drop. The static line is typically 1 in. (25 mm) diameter or larger for greater than 400 GPM (1,500 l/min) systems, and 3/4 in. (19 mm) diameter or larger for less than 400 GPM (1,500 l/min) systems. This static line provides a static head pressure to the inlet of the water pump equal to the height of the expansion tank plus the pressure of the expansion tank. Do not assume that a pressure cap will pressurize the tank to the cap’s rating.

10. The expansion tank must be sized for 6% expansion of the coolant. An additional 5% is recommended for coolant make-up. With these volumes, an expansion tank should be sized to contain 11% of the total cooling system volume. Separate expansion tanks must be used for separate auxiliary and jacket cooling circuits. A sight glass is recommended for monitoring expansion tank level. 11. The expansion tank height and pressure must be sufficient to provide pressure at the water pump inlet to meet the requirements in latest edition of S-09068 for ATGL engines and S-07424-1 for all other Waukesha engines. Do not assume that a pressure cap will pressurize the tank to the cap’s rating. 12. As an alternative, pressurized expansion tanks can be used for systems that require high pressure levels. These are closed systems that do not allow air to enter the cooling system when the engine is cold and the coolant is at the lowest volume. A pressurized expansion tank has a bladder and uses compressed air or nitrogen to maintain the required pressure. This means that the pressure in the cooling system is not in the bladder. Air and other gases are removed by a degassing tank with an automatic degasser. A pressurized expansion tank requires a relief valve to prevent excessive pressures in case the system is overfilled with coolant.


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Service Bulletin No. 4-2429H

1

3

2

4

HT LT

HT

7

LT

5

HT

6

Figure 4 Bladder-Style Pressurization System with Degassing Tank 1 - Degassing Tank 2 - LT Pump 3 - Expansion Tank with Compressor 4 - Pressure Relief Valve

5 - Balance Line (see Note 17) 6 - HT Pump 7 - Engine

See latest edition of S-07424-1 for more information regarding minimum water pump pressure requirements. To safety and continuously meet this requirement, a bladder-style pressurization system with degassing tank and relief valve is strongly recommended. Waukesha offers such a system, which includes an air compressor for the pressure in the bladder, optionally for 220GL. The pressurization tank is to be connected near the inlet of the engine circuits. The degassing tank is to be connected, as mentioned above for the expansion tank and pressure cap system, to the highest points of the engine and its cooling system. 13. Bypass water filtration can remove debris from the cooling systems on any engine. Bypass water filtration sized to remove 15 – 25 micron particles from 2% of the water flow is recommended for Waukesha engines. Adding a coolant filter to your engine remains one of the most cost-effective means of keeping the cooling system clean. Every cooling circuit on every Waukesha engine should have a filter. This, in turn, extends the life of water pump seals and cylinder liner packing rings. The filter is designed to trap particles larger than 25 microns (0.001 in.) in size. Isolation valves should be adjusted to limit flow to 2% of the total circuit flow. Waukesha offers an optional glycol filter assembly with stand. These are 25-micron, stainless-steel mesh filters which can be cleaned and reused. Unlike what is common in the on-highway trucking industry, these elements do not contain a precharge.

Figure 5 Table 2: Optional Glycol Filter Assembly P/N* 489501

DESCRIPTION Coolant Filter Assembly

489508

Replacement Element

489528

Std. Temperature (200°F, 93°C) Flow Indicator

489648

High Temperature Flow (350°F, 177°C) Indicator

489527

Seal Kit

* Available 1/2012

Care must also be taken when welding external cooling system pipes together or when drilling and tapping a hole anywhere in the water system. Ensure that the weld slag and chips are totally cleaned from the cooling system before the engine is operated. Debris in the cooling system will cause erosion of water passages and water pump seals. 14. Jacket water and auxiliary water pump static inlet pressure must not exceed pressures published in the specifications section of the Technical Data Manual for the specific engine model.


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Service Bulletin No. 4-2429H 15. For information on ebullient cooled systems, see latest edition of Form 7030, Waukesha Cogeneration Handbook, and system manufacturers. 16. Consider thermosiphoning prevention in cooling system design. Thermal shock from thermosiphoning is often a problem in engines subjected to frequent shutdowns (several times a week or daily) and engines with coolers mounted above them. A shutoff valve in the return leg from the cooler will prevent thermosiphoning. 17. Because of the unique twin-circuit water pump on the 220GL product line, it is necessary to install a balance line between the LT (auxiliary) and HT (jacket) water circuits to avoid a pressure differential between the inlets of both sides of the pump. The LT and HT inlet pressures should balance to within less than 4.4 psi (0.3 bar). This balance line should be installed preferably within 6.6 ft (2 m) of the inlet locations to the engine and be a minimum DN25 (1 in.) pipe. Failure to apply these guidelines could result in premature water pump failure and/or poor engine cooling system performance. NOTE: This requirement for a balance line between the LT and HT circuits only applies to 220GL engines delivered with the gear-driven water pump. For engines shipped after January 2011 with the Auxiliary Module option code, this balance line is included. If separate electric pumps are used for each circuit, a pressure balance between the circuits is not necessary.

COOLING WATER TREATMENT RECOMMENDATIONS SOLID HOT WATER COOLING Solid hot water cooling is the common, closed loop radiator-type cooling system where steam is not allowed to form. These systems generally operate between 170° – 200°F (77° – 93°C), but maximum system temperatures up to 265°F (129°C) are possible. Being a closed system, very little make-up water is required so proper treatment of the original cooling water will ensure trouble-free service for longer periods than ebullient systems where make-up water may be constantly added. This doesn’t mean that closed systems should be ignored; water samples should be drawn periodically, daily in some cases, to ensure that additives are at the correct levels.

The following points should be kept in mind for a closed, solid water cooling system: 1. Sodium nitrite additive is recommended as a corrosion inhibitor to protect iron and steel components. Waukesha recommends 800 – 2,500 ppm nitrites. In addition to sodium nitrite, molybdate is added to prevent bacterial growth. 2. A common corrosion inhibitor used by automotive antifreeze suppliers is silicate. Silicates have the disadvantage of building up an insulating layer on components. Silicates more readily drop out of solution and become “used up.” Industrial-quality fluids combining corrosion inhibitors and glycol for freeze protection are the most commonly used coolants for closed systems. Silicates are not recommended for industrial engines and therefore should not exceed 25 ppm. 3. A copper corrosion inhibitor is recommended. Tolyltriazole (TT) is a good protector of copper components. 4. A synthetic polymer is suggested which assists in preventing scale buildup. Polymers coagulate the solids in the water, causing them to drop out of suspension. This action prevents calcium carbonate from forming hard scale on hot engine surfaces. 5. A borax buffer should be used as required to raise the pH of the coolant to between 8.5 and 9.2.

NOTICE Avoid AMINE solutions since high concentrations of these will attack critical O-rings in the engine. An engine that has had amine solutions in it must be flushed with fresh water or non-amine containing coolant prior to long-term dry storage. Steam condensate returning to the feedwater reservoir may be acidic and contain iron if corrosion has occurred. This condensate must be monitored to determine necessary treatment. 6. Softened or demineralized water should be used for any cooling system fill and make-up. Hard chemicals (calcium and magnesium) form a lime scale which insulates hot engine parts from the cooling water. Cooling water must meet the following specification: Calcium (Ca)

Less than 1 ppm

Magnesium (Mg)

Less than 1 ppm

Total Hardness (CaCO3)

Less than 1 ppm

Chloride

Less than 25 ppm

Sulfate

Less than 25 ppm


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Service Bulletin No. 4-2429H 7. A water sampling program will verify that coolant meets the requirements outlined here and determine when it needs changing. If a cooling system analysis program is not used, the cooling system should be cleaned and flushed annually. EBULLIENT SYSTEMS Ebullient, or controlled boiling water, cooled engines and equipment are extremely sensitive to water quality. Since water is essentially boiled off during the ebullient process, hard chemicals are left behind as scale deposits. If the low pressure steam is used in an external process, and not condensed for return to the engine, make-up water is always being added. On the other hand, closed steam loops which return condensate to be used again are susceptible to higher corrosion rates due to chemical changes in the water as it cycles through the system. The type of water treatment required depends upon the design of the steam system and the quality of the water used. Ebullient cooling systems require the following attention: 1. Hardness Removal Ebullient systems (engines and heat-recovery equipment) cannot tolerate high levels of hard chemicals – calcium and magnesium. It is recommended to maintain 0 ppm hardness by one or a combination of the following methods: a. Water softening, sodium zeolite type, similar to common home water softeners, but sized for the application. Sodium zeolite (salt brine) causes a reaction that attracts hard chemicals which congregate on resin beads within the softener. These chemicals are then periodically flushed away. Softeners can greatly reduce water hardness but not totally eliminate it. Levels of 0.5 to 1 ppm hardness may remain, which should be further reduced by phosphate treatment. b. Phosphates can be used which causes a precipitative reaction when in contact with calcium. This means that calcium phosphate is formed which drops out of suspension as a soft sludge at the lowest points of the system. Bottom blowdown ports are required to periodically rid the system of accumulated sludge. As phosphate will not react with magnesium salts, silicates are added to precipitate the magnesium. Again, blowdown is required. For silicates to work, pH of the engine water must be 10.5 minimum.

c. Chelants and polymers, chemical additives which prevent scale, do not precipitate the hard chemicals. Instead, the hard chemicals are kept in suspension until reaching the surface of the steam separator where continuous surface blowdown will purge them from the system. d. Deionization or demineralization is a process similar to sodium zeolite softening. The end result, however, is completely mineral-free water. Although mineral-free, demineralized water is corrosive and must be treated accordingly. 2. Blowdown of Ebullient Systems There are two types of blowdown: surface and bottom. Continuous surface blowdown in the heatrecovery unit will reduce the total dissolved solids (TDS) which increase through addition of make-up water or condensate return. TDS includes hardness ions, alkalines, silicates and iron. Total alkalinity, also called “M” alkalinity, is that portion of TDS composed of carbonate, bicarbonate and hydroxide alkalinity. A conductivity meter and probes mounted near the surface level of the steam separator will monitor the TDS level to indicate when a blowdown is required. The probes measure electrical conductivity of the coolant which increase as TDS increase. Too high a level of TDS can cause foaming with carryover of liquid through the steam system. This produces undesirable wet steam. Bottom blowdowns are required, especially when precipitative chemicals such as phosphates and silicates are added to reduce scaling. These chemicals produce a soft sludge which must be removed at the lowest areas of the engine and steam separator through blow ports. Blowdown frequency should be twice per shift for 15 seconds or as recommended by a local water treatment specialist. See Figure 6 for recommended chemical feed and blowdown locations. 3. Oxygen Scavengers Water can contain dissolved oxygen and carbon dioxide. These gases can lead to corrosion of metal parts. An oxygen scavenger eliminates oxygen and reduces the likelihood of corrosion. Sodium sulfite is a typical chemical oxygen scavenger. This chemical reacts with oxygen to form sodium sulfate which stays in suspension until surface blowdown eliminates it from the system.


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Service Bulletin No. 4-2429H Other scavengers are available but they are not as safe to handle as sodium sulfite. 4. pH pH is a measure of alkalinity or acidity of water. As mentioned, pH of the engine jacket water should be maintained at 10.5 to 11.5 to allow certain hardness removal chemicals to work. In the steam separator, H2O and CO2 combine to form carbonic acid, H2CO3. This acid is corrosive to downstream pipework and equipment. The pH after the steam separator will drop in conjunction with H2CO3 production. pH should be kept at 7.5 to 8.5 in the steam loop to prevent corrosion. Neutralizing chemicals may be added to improve pH. WATER QUALITY AND TESTING Water treatment products vary in the chemicals used in their makeup. All are proprietary to the water treatment specialist who markets them and he knows how they will perform with a given quality of water in a particular cooling system. Most products will do a good job with a good quality distilled or deionized water but may not perform well with a poor quality water, which may be hard with chlorides and/or sulfates. Some products may perform well with a poorer quality water but may require an increased treatment level.

Their recommendations should include the following: a. Any required cleaning of the system and how it should be done b. Any pretreatment required if the quality of the water is questionable c. Type of water treatment to be used and the level at which it is to be maintained d. Control limits, if required, for pH, hardness, total dissolved solids, alkalinity, chlorides, sulfates, silica, etc. that must be held in the treated water e. Frequency of tests for level of treatment and/or when water samples should be taken and analyzed f. Corrective actions to be taken when control limits are exceeded g. Amount and frequency of blowdown (ebullient cooled systems) Once the treatment program is in place, frequent testing of the engine jacket water, make-up water and any condensate returned must be performed to ensure that the required water quality is being maintained. Table 3 lists recommended tests and acceptable limits for ebullient cooling systems. Some of these tests may be applicable to solid water systems. Consult your water treatment specialist.

It is absolutely essential that a competent water treatment specialist be consulted to prepare a good water treatment program. Mogul Division of Dexter Corp., Calgon Corp. and other knowledgeable companies are available. Review with the chosen representative the details of the engine water system to be treated. The following should be covered at a minimum: a. Metals in the system contacted by the coolant b. Operating temperatures c. Source and quality of water (if known) d. Type of system: solid water or ebullient (steam) e. Amount of make-up water required f. Age of installation g. Previous water treatments used and any history of corrosion or scaling problems h. Engine model, speed and type of operation (standby, loading, etc.)


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Service Bulletin No. 4-2429H Table 3: Recommended Testing for Ebullient Cooling Systems WATER CIRCUIT

TEST TYPE

Feed Water Make-up Water

ACCEPTABLE LIMITS

Total Hardness

0 ppm

Water softening/phosphates

Total Hardness

0 ppm

Water softening/phosphates

Chlorides

Should equal untreated water

Check softener rinse cycle

10.5 – 11.5

Adjust blowdown frequency

2,500 – 3,000 MMHO

Adjust blowdown frequency

pH Conductivity Engine Jacket Water

Condensate

CONTROL

O2 Scavenger

30 – 50 ppm sulfites

Total alkalinity

200 – 600 ppm

Scale Inhibitor

Varies

pH

7.5 – 8.5

Adjust treatment level Adjust blowdown frequency Adjust treatment level Adjust neutralizing chemical level (see NOTICE below)

NOTICE: Avoid AMINE solutions since high concentrations of these will attack critical O-rings in the engine. An engine that has had amine solutions in it must be flushed with fresh water or non-amine containing coolant prior to long-term dry storage. Steam condensate returning to the feedwater reservoir may be acidic and contain iron if corrosion has occurred. This condensate must be monitored to determine necessary treatment.

RECOMMENDED FEEDING AND BLOWDOWN CONTROL (SCHEMATIC REPRESENTATION ONLY) EXHAUST OUTLET STEAM TO PLANT USER

EXHAUST NEUTRALIZING CHEMICAL

WAUKESHA DIESEL OR GAS ENGINE INTERNAL JACKET AND MANIFOLD

HEAT RECOVERY BOILER

1 SOFT MAKE UP H20

HOT WATER EBULLIENT CONDENSATE RETURN FEED WATER RESERVOIR 3

4

5

6

FEED WATER PUMP 2

FRONT AND REAR CORNERS

CHEMICAL PUMP

O2 SCAVENGER AND CHEMICAL INHIBITORS

Figure 6


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Service Bulletin No. 4-2429H BLOWDOWN PROCEDURES 1

Continuous surface blowdown controlled at recovery boiler.

2

Bottom blowdown for recovery boiler – Frequency should be twice/shift for 15 seconds each or as recommended by local water treatment company.

3, 4, 5, 6

Bottom blowdowns for ebullient engine – Frequency: Before start-up and after shutdown (to prevent starving engine or circulating water) or as recommended by local water treatment company.

CHEMICAL FEED • The O2 scavenger may be fed mechanically to the feed water section or to the hot water ebullient section based on feed water pump impulse – consult local water treatment company. • Neutralizing chemical fed continuously to steam header with pump.

GLOSSARY OF WATER TREATMENT TERMS Alkalinity

A measurement of the acid-neutralizing capacity of a water or coolant. It is usually expressed as “M” alkalinity (methyl orange indicator) or “P” alkalinity (Phenolphthalein indicator). These values are also used in boiler water and cooling tower water as controls to predict the tendency for a water to precipitate calcium and form scale. Reserve “alkalinity” is a term used by antifreeze manufacturers to indicate the level of inhibitors in solution. “Total” alkalinity is another name for “M” alkalinity.

Blowdown

The process of removing total dissolved solids or precipitated sludge from a cooling water system.

Cavitation

A type of localized pitting occurring on cylinder liners and other surfaces, usually perpendicular to the axis of the crankshaft. The mechanical vibrations of the liner cause dissolved gas and vapor bubbles to form collapse on the surface. As the bubbles collapse, the shock forces remove the protective films or coatings and erode the surface. If the inhibitors of the water treatment cannot keep up with this erosion, rapid localized corrosion also occurs. These actions combine to form deep pits on the liner surface. This type of damage is also found on water pump impellers if the net positive suction head (NPSH) requirement of the pump is not maintained.

Chelates

Chemical compounds used in cooling system cleaners to remove oil contamination, scale and deposits from a cooling system. System must be flushed with water before filling with treated water.

Chloride

A dissolved salt in water which forms ions that increase the conductivity of water and interfere with the protective films formed on the surfaces of metals. It increases the corrosion tendency of water.

Chromates

A common corrosion inhibitor. Chromate treatments are usually used in a pH range of 7.0 – 9.5. A typical dosage is 600 – 1,500 ppm CrO4. Since chromate is an anodic inhibitor, it is essential that a continuous chromate film be maintained. At chromate levels less than 200 ppm, the inhibiting film can become spotty. Corrosion will then become concentrated at individual points causing rapid, severe pitting. Chromates cannot be used with ethylene glycol antifreeze because of chemical reactions which will occur. Chromates can also be altered chemically to a non-inhibiting, sludging form by reaction with hydrogen sulfide (H2S), stack gases, nitrites, ammonia and certain organic chemicals.


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Service Bulletin No. 4-2429H Crevice Corrosion

A type of localized pitting occurring in or at the edges of close-fitting areas such as the liner flange to the crankcase. The stagnant conditions of the coolant in the fit area make it difficult to establish films or coatings for corrosion protection.

Deaeration

All water contains some dissolved gases. Increased pressure of the gas and any splashing at the water surface will increase the amount of dissolved gas in the water. Deaeration removes these gases by steam scrubbing, heating or by the addition of chemicals. Dissolved oxygen and carbon dioxide increase corrosion in water systems.

Deionization

Or demineralization is a process in which all dissolved mineral salts and ions are removed from water, resulting in almost chemically pure water. This purity makes the water very corrosive, so it must be treated with inhibitors before use in an engine water system.

Fretting Corrosion

Occurs when two highly loaded surfaces rub rapidly together, causing mechanical removal of metal and the protective films or coatings. The localized frictional heat accelerates corrosion. This type of corrosion can occur in fit areas of liner to crankcase.

Galvanic Corrosion

When dissimilar metals are coupled in an electrolyte such as an engine coolant, they tend to cause an electronic current to flow through the metal. Metals high on the galvanic series chart (anodic) tend to go into solution leaving electrons behind to flow to the metals low on this chart (cathodic). Corrosion tends to concentrate on the metals high on the galvanic series chart, particularly if the relative area is small compared to the cathodic parts. This type of corrosion may occur in aluminum parts such as valves, fittings, heaters, etc. when used in a water system and requires special attention when selecting a water treatment.

Hardness

Calcium and magnesium salts in water cause hardness. It is usually measured and reported as “total hardness as CaCO3 in PPM.” If not removed from the water or treated chemically, these salts will break down with heat to form sludge, carbon dioxide and scale on the hot surfaces in the engine. The carbon dioxide recombines with the water to form carbonic acid and accelerates corrosion. Temporary or carbonate hardness will “drop out” (form scale or precipitate to form sludge) with increased temperatures; permanent or non-carbonate hardness will not.

Inhibitor

A chemical part of a water treatment which reduces or stops corrosion by interfering with the corrosion mechanism. They function by forming a protective film on the metallic surfaces of the cooling system. The inhibitors are known as “anodic” or “cathodic” depending on what part of the corrosion cell the films are formed on. Those that form films on all metal surfaces are called “general corrosion inhibitors.”

Ions

When any substance dissolves in water, it breaks down into electrically charged atoms called “ions.” Some are (+) charged (cations); others are (-) charged (anions).

pH

A measurement of hydrogen ion concentration which indicates the acidity of alkalinity of the water. The pH scale is from 0 (highly acidic) to 14 (highly alkaline), with a 7.0 reading neutral.

PPM

A ratio calculated on the basis of the whole being divided into 1 million equal parts. The value may be calculated on a volume (ppmv) or weight (ppmw) basis. For example, if 1 pound of chemicals is mixed with 9,999 pounds of water, there is 100 ppmw of chemicals in the mixture. Note that 10,000 ppm equals 1%.

Pretreatment

Any preliminary cleaning or preparation of the water system to ensure that the treatment program works effectively right from the start.


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Service Bulletin No. 4-2429H Rainwater

A natural deionized water. Rainwater contains large amounts of dissolved oxygen (O2) and carbon dioxide (CO2), however, which makes it unsuitable for cooling systems without treatment.

Selective Leaching

Or de-alloying is a type of corrosion of alloyed metals. In brass it is called dezincification and involves the process of zinc dissolving into the water, leaving a weak porous copper structure in place of the original brass alloy. This type of corrosion is sometimes found in heat exchangers and radiators if a poor quality water and/or marginal water treatment is used.

Silica

A dissolved mineral in water which combines with calcium and magnesium to form a dense scale.

Softening

A pretreatment given to water before it is treated with inhibitors and used in an engine. Several different softening processes are used to reduce the hardness and scale forming tendency of water. In some processes, the calcium and magnesium in the hardness salts are replaced with sodium resulting in no reduction in the total dissolved solids in the water. In other processes the chemical reactions actually remove these dissolved salts and result in a large reduction in total solids. None of the softening processes will remove chlorides, sulfates or silica from water if they are present.

Solder Bloom

A type of lead/tin corrosion found in solder-type radiators if poor quality water and/or marginal water treatment is used. Corrosion is concentrated at the solder joint because of galvanic action and the relatively small area of lead/tin to copper in the radiator. The “bloom” or corrosion deposit formed is relatively weak and rapidly disintegrates the solder joint to cause leakage.

Solids

“Suspended solids” are those that can be removed by settling or filtration. “Dissolved solids” are impurities and organic matter in solution. “Total solids” are the sum of suspended and dissolved solids. Higher levels of total solids increases the conductivity of water, tending to increase corrosion.

Sulfate

A dissolved salt in water which forms ions that will combine with calcium and magnesium to form sulfate scale. These compounds can also combine with hydrogen to form acids which make water corrosive.


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04-2429H- Coolant System Guidelines

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