Oxidation Catalyst Converter for Stationary Engines and Non-Road Mobile Engines {1091} Caterpillar

Electric Power Generation

3516B GEN SET (S/N: ZAP1-UP)

Engine

3412 (S/N: 81Z1-UP)

3412C (S/N: 81Z1-UP)

3508 (S/N: 8TL1-UP; 3LS1-UP; 23Z1-UP; 70Z1-UP)

3508B (S/N: 4GM1-UP; 6PN1-UP; 2HW1-UP)

3512 (S/N: 3MS1-UP; 24Z1-UP; 67Z1-UP)

3512B (S/N: CTB1-UP; FFG1-UP; 6WN1-UP; 4DR1-UP; 4AW1-UP; 5AW1-UP; 1GZ1-UP)

3512C (S/N: WF31-UP; WF51-UP; LLA1-UP; R2A1-UP; LLD1-UP)

3516 (S/N: 7KM1-UP; 2TS1-UP; 3JS1-UP; 3NS1-UP; 25Z1-UP; 73Z1-UP)

3516B (S/N: DD31-UP; DDJ1-UP; TAK1-UP; 6HN1-UP; 7RN1-UP; YAT1-UP; 1NW1-UP; 2JW1-UP; CCX1-UP)

3606 (S/N: 8RB1-UP)

3608 (S/N: 6MC1-UP)

3612 (S/N: 9RC1-UP)

3616 (S/N: 1PD1-UP)

G3412C (S/N: 6ZM1-UP; 5KR1-UP)

G3516B (S/N: CEY1-UP; 7EZ1-UP)

G3606 (S/N: 4ZS1-UP)

G3608 (S/N: BEN1-UP)

G3612 (S/N: BKE1-UP)

G3616 (S/N: BLB1-UP)

Generator Set

3456 GEN SET (S/N: BGA1-UP; 9BZ1-UP)

Industrial Engine

3406 IND (S/N: 90U1-UP)

Petroleum Engine

3512C PETROLEUM (S/N: R1A1-UP; R1S1-UP)

Pumper

SPF343C (S/N: RTX1-UP)

SPF743 (S/N: MLX1-UP)

Introduction

Do not perform any procedure in this Special Instruction until you read this information and you understand this information.

The Caterpillar catalytic converter is designed to convert carbon monoxide, hydrocarbons, and aldehydes into carbon dioxide and water. The equations in Table 1 are the unbalanced chemical reactions.

Table 1

Unbalanced Chemical Reactions
Carbon Monoxide	CO + O2 ⇒ CO2
Hydrocarbons	CxHy + O2 ⇒ CO2 + H2O
Aldehydes	CxHyO + O2 ⇒ CO2 + H2O

Substrate - A layer that lies underneath another layer

Conversion efficiency - The ratio of a systems output that is compared to the systems input

Catalyst - A catalyst is a substance that accelerates a chemical reaction without being affected by the reaction.

The conversion is accomplished by a process that is called oxidation. Oxidation of CO does not occur spontaneously at ambient conditions. Therefore, a catalyst is added to the substrate in order to cause the chemical reactions to occur at lower temperatures. The catalyst is designed to have a conversion efficiency for one or more specific pollutants within a specific operating range. The catalyst is designed to have a 93 percent carbon monoxide conversion efficiency in natural gas engines and a 70 percent carbon monoxide conversion efficiency in diesel engines.

Illustration 1	g01046023

The efficiency of a catalyst is dependent upon the amount of the catalyst that is used, the properties of the catalyst, and the temperature of the exhaust gas. This catalyst is designed for use in stationary applications with the following characteristics:

• Diesel and gas engines

• Engines with 372 kW (500 hp) and higher power ratings

• A temperature range of 315 °C (600 °F) to 705 °C (1300 °F)

Conversion of CO starts around 121 °C (250 °F). As temperature increases, the conversion efficiency of the catalyst increases. Refer to Illustration 1.

Description

The catalytic converter has two basic profiles: rectangular and cylindrical.

The rectangular profile is used with larger engines. Refer to Illustration 2.

Illustration 2	g01043701
Rectangular profile

The cylindrical profile is used with smaller engines. Refer to Illustration 3. The cylindrical profile is available with one or two-element blocks. Refer to Illustration 4.

Illustration 3	g01043654
Cylindrical profile

Illustration 4	g01067281

The rectangular profile and the cylindrical profile are available in various sizes. The variations are dependent upon the volume of catalyst that is needed for the application. Refer to Table 8 for part numbers for the catalysts.

The substrate of the catalyst element includes a stainless steel foil that is contained by a stainless steel frame. The foil surface is coated with catalyst material. The materials are usually metals of the platinum group. These metals are selected due to the high levels of activity and durability. As exhaust gas flows through the catalyst, the thin foil walls provide a large surface area that allows the chemical reactions to take place.

The cylindrical substrate is 88.90 mm (3.5 inch) thick with a diameter that is determined by the type of engine, the type of fuel, and the horsepower rating.

The rectangular substrate is manufactured as a block. Each block measures 590.55 mm (23.25 inch) by 565.15 mm (22.25 inch) by 88.90 mm (3.5 inch).

Shipping and Handling

Use care when you handle the catalysts and the converter assemblies. If the catalysts are handled improperly, the thin metal foils may be damaged or nested. This will result in plugged channels. Also, bending or striking of the metal or excessive shock will cause the catalyst to flake off resulting in lower efficiency of conversion.

Installation

The converter resembles the size and shape of a muffler. The assembly is normally installed in the same manner as a muffler. The assembly must be isolated from engine vibration and from external loading due to thermal expansion. The assembly is not designed to be a structural member. Avoid excess stresses on the assembly.

Installation Procedure for the Converter Assembly

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Illustration 5	g01044819
Example of the converter that is installed upstream of the muffler (A) Converter (B) Muffler

1. Install the converter assembly in a location that is easily accessible for loading and for unloading of the catalysts during service and inspections.

   The assembly can be installed upstream of the muffler or downstream of the muffler.

   If the diameter of the muffler inlet is smaller than the diameter of the assembly inlet, mount the muffler upstream of the assembly. This will minimize the pressure drop in the system. Refer to Illustration 5.

   Ensure that the muffler, exhaust piping, and the assembly are insulated when the assembly is mounted downstream of the muffler.

2. To prevent excess stress on the assembly, place an expansion joint between the engine and the beginning of the exhaust piping. This will isolate the assembly from engine vibration. Use an expansion joint whenever the assembly is installed between two fixed points.

3. Place an expansion joint prior to the assembly. This prevents the catalyst from being damaged due to thermal expansion.

4. Avoid long piping runs prior to the assembly.

   Long piping runs can cause a loss of temperature that will decrease the CO conversion efficiency of the catalysts.

   Install the assembly 1 m (3 ft) to 3 m (12 ft) downstream of the engine and/or of the turbocharger.

5. Provide even exhaust gas flow across the face of the catalyst by eliminating elbows immediately prior to the assembly. Allow a minimum of six widths of pipe between an elbow and the inlet of the assembly.
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   Illustration 6	g01046048

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   Illustration 7	g01051700
   Example of a suspended mounting bracket

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   Illustration 8	g01052346
   Example of a base mounting bracket Refer to Table 2.

6. The cylindrical assembly may be mounted horizontally or the assembly may be mounted vertically. Horizontal mounting is preferred. Mount the assembly with structural steel supports that are designed to accommodate thermal expansion. The mounting brackets must be designed to compensate for thermal expansion. Do not mount the assembly at flanges.

   Mounting brackets can be supported from structural supports that are under the assembly or from the structural supports that are above the assembly. Refer to Illustration 6.

   Refer to Illustrations 7 and 8 for examples of the mounting brackets. For reference dimensions for the mounting brackets, refer to Table 2.

7. If the assembly is mounted in a vertical application, the assembly must be mounted so that the assembly does not support the weight of the exhaust piping. This includes the exhaust stack above the assembly in vertical applications. In vertical applications, ensure that the supports are sufficient for the weight of the assembly plus the force of pressure drop across the catalyst. Do not mount the assembly at flanges.

8. The rectangular assembly must be mounted horizontally and the rectangular assembly must be supported from the bottom. Mount the assembly with structural steel supports. Four mounting holes are located on the bottom of the assembly. Do not mount the assembly at flanges.

9. Ensure that the assembly is installed in the correct direction of flow. Note the arrow that is on the housing of the assembly for the correct direction of flow.

10. For the cylindrical assembly, use lifting straps in two locations to lift the assembly into position. For the rectangular assembly, two holes for lifting eyes are provided on the top of the assembly. Do not support the assembly by the flanges.

11. Do not weld to the body of the muffler. Mounting brackets for the muffler may be designed for use.

12. Align the inlet and the outlet with the connecting flanges. Insert the gasket and loosely tighten several bolts in each flange connection.

13. Make any necessary adjustments to the position of the assembly.

14. Complete the flange connections and check for leaks.

    The system must be checked for leaks whenever the cover plate is removed or whenever the access door is opened. The system must not leak more than 0.10 percent of the total volume of exhaust gases.

15. The assembly must be insulated in order to retain heat for maximum efficiency. Insulation is provided with the assembly. Ensure that the mounting bracket and structural steel supports are lined up with openings in the insulation.

16. Exhaust piping prior to the assembly must be insulated in order to prevent excessive heat loss.

Table 2

Example of Dimensions for Mounting the Assembly (1) (2)
Part Number	Diameter of Housing	A	B	C	D
249-0412	444.5 mm (17.5 inch)	457.2 mm (18 inch)	138.2 mm (5.4375 inch)	555.7 mm (21.875 inch)	22.25 mm (0.875 inch)
249-0413	609.6 mm (24 inch)	609.6 mm (24 inch)	182.5 mm (7.1825 inch)	728.4 mm (28.675 inch)	25.4 mm (1 inch)
249-0414	685.8 mm (27 inch)	762 mm (30 inch)	227.1 mm (8.9375 inch)	901.7 mm (35.5 inch)	31.75 mm (1.25 inch)
249-0415	774.7 mm (30.5 inch)	762 mm (30 inch)	227.1 mm (8.9375 inch)	901.7 mm (35.5 inch)	31.75 mm (1.25 inch)
249-0416	774.7 mm (30.5 inch)	762 mm (30 inch)	227.1 mm (8.9375 inch)	901.7 mm (35.5 inch)	31.75 mm (1.25 inch)
249-0417	870 mm (34.25 inch)	762 mm (30 inch)	227.1 mm (8.9375 inch)	901.7 mm (35.5 inch)	31.75 mm (1.25 inch)
249-0418	870 mm (34.25 inch)	762 mm (30 inch)	227.1 mm (8.9375 inch)	901.7 mm (35.5 inch)	31.75 mm (1.25 inch)

(1)	Refer to Illustrations 7 and 8.
(2)	All dimensions are only for reference.

Operation

Installation and Removal Procedure for the Catalyst

Use Caution. All work must be performed in a safe manner, and in accordance with all OSHA guidelines or with other applicable guidelines.

Installation of Cylindrical Catalyst

Illustration 9	g01043648
(1) Inlet flange (2) Retainer (lock ring) (3) Catalyst (4) Housing (5) Wraparound cover (6) Clamp (7) Outlet flange (8) Opening (9) Clamping brackets (retainer) (10) Retaining bolts

Note: The catalyst must be removed from the housing prior to starting the engine for the first time. Verify that the catalyst is not installed. Refer to the section on "Removal of Cylindrical Catalyst".

1. Start the engine and run the engine under load for 40 hours prior to the installation of the catalyst. Ensure that the exhaust piping is free from debris before installing the catalyst . This protects the catalyst against damage or from contamination during initial setup.

2. The catalyst may be serviced without removing the housing from the exhaust system.
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   Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

3. The engine and the auxiliary equipment must be safely locked out. Ensure that the engine is cool.

4. Before the cover plate on the housing is removed, ensure that there are no compressive forces on the converter .

5. Loosen clamp (6) on cover (5). Open the cover and slide the cover along the assembly in order to expose the interior.

6. Remove catalyst (3) from the shipping container. Position the catalyst over opening (8), and slide the catalyst into position.

7. Tighten the three retaining bolts (10) on housing (4) in order to secure retainer (2) against catalyst (3).

   The retainer is normally already installed in the converter assembly when the assembly is shipped. If the retainer is shipped separately, the retainer must be installed prior to installing the catalyst. For an installed view, refer to Illustration 10.

   To install the retainer, position the retainer over the opening and slide the retainer toward the retaining bolts. Align clamping brackets (9) with the three retaining bolts.

8. Install the second catalyst in the same manner as the first element, if you are installing a converter with dual catalysts. Refer to Illustration 4.

9. Repeat the tightening sequence for the retaining bolts until all the retaining bolts are tight.

10. Position the wraparound cover between the guides for the cover so that the clamps are 180 degrees from the center of the opening in the housing that is used to access the catalyst. Engage the clamp.

    This will center the retainer bars on the cover over the opening in the housing.

11. Start the engine and check for leakage at the seam in the cover. Make any necessary adjustments to the position of the cover and/or to the tightness of the clamp nut.

Illustration 10	g01067295
(A) Retainer (lock ring) (B) Catalyst (C) Test tap

Removal of Cylindrical Catalyst

Illustration 11	g01067301
(D) Housing (E) Catalyst (F) Loading strap

1. The engine and auxiliary equipment must be securely locked out.
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   Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

2. Before the cover plate on the housing is removed, ensure that there are no compressive forces on the converter. Ensure that the engine is cool.

3. Loosen the clamp on the wraparound cover. Open the cover and slide the cover along the housing in order to expose the interior.

4. Loosen the three adjustable retainer bolts, but do not remove the bolts.
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   Moving heavy parts must be done safely and with adequate lifting capacity. Failure to do so can result in injury or death. Use caution and adequate lifting capacity when moving heavy parts.

5. Pull loading strap (F) toward you in order to slide catalyst (E) halfway out of housing (D). Complete the removal of the catalyst by hand. Refer to Illustration 11.

Installation of Rectangular Catalyst

Illustration 12	g01043686
(1) Inlet flange (2) Housing (3) Catalysts (4) Access door (5) Outlet flange

Note: The blocks of catalyst must be removed prior to starting the engine for the first time. Verify that the blocks are not installed. Refer to the section on "Removal of the Rectangular Catalyst".

1. Start the engine and run the engine under load for 40 hours prior to the installation of the catalyst. Ensure that the exhaust piping is free from debris before installing the catalyst. This protects the catalyst against damage or from contamination during initial setup.

2. The catalyst may be serviced without removing the housing from the exhaust system.
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   Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

3. The engine and the auxiliary equipment must be safely locked out. Ensure that the engine is cool.

4. Before the access door on the housing is opened, ensure that there are no compressive forces on the converter.

5. Unbolt access door (4). Open the access door.

6. Place each catalyst (3) onto the supporting tracks. Slide the catalyst into housing (2). Close the access door. Bolt the access door.

Removal of the Rectangular Catalyst

1. The engine and the auxiliary equipment must be securely locked out.
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   Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

2. Before the access door on the housing is opened, ensure that there are no compressive forces on the converter. Ensure that the engine is cool.
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   Moving heavy parts must be done safely and with adequate lifting capacity. Failure to do so can result in injury or death. Use caution and adequate lifting capacity when moving heavy parts.

3. Unbolt the access door and open the access door. Slide the catalysts out of the housing.

Maintenance

A catalyst is a substance that accelerates a chemical reaction without being affected by the reaction. Certain factors affect the performance of a catalyst and the need for maintenance.

Factors that Affect the Performance of the Catalyst

Temperature

The operating temperature that is necessary to efficiently convert hydrocarbons to carbon dioxide and water are dependent upon the hydrocarbon species that is contained in the exhaust and on the hydrocarbon concentration. The performance of the catalyst is highly dependent upon the active surface area of the platinum group metals (PGM). The PGM on the catalyst are evenly spread across the substrate. This creates a large surface area of active catalyst on the substrate.

At temperatures above 732 °C (1350 °F), the particles of PGM begin to move. As the particles move, the particles come into contact with each other. This creates larger particles. This also reduces the PGM surface area. This change is called sintering. Sintering is not reversible. Extreme temperatures will destroy the thin metal foils. To avoid thermal damage, exhaust temperatures must not exceed 705 °C (1300 °F).

Contamination can occur more easily at lower temperatures. Operating temperatures below 300 °C (572 °F) may result in plugging of the catalyst.

Contamination

Contamination occurs when materials chemically combine with the catalyst. This forms compounds that arenot ableto be converted. Contamination is usually permanent and the catalyst must be replaced after the source of the contamination is identified and eliminated.

Typically, the consumption of lube oil is the primary source of contamination. Many additives to lube oil contain measurable amounts of phosphorous. When the lube oil is burnt, the phosphorous is deposited on the catalyst. Other contaminants may be found in applications that use landfill gas or in applications that use imported fuels. Do not use this converter in applications that use landfill gas. Caterpillar's recommended fuels and oils meet the guidelines for contamination. The rate of deactivation of the catalyst is roughly proportional to the concentration of the contaminant in the exhaust stream.

The following elements are known contaminants: antimony, arsenic, barium, bismuth, calcium, chromium, copper, iron, lead, magnesium, mercury, nickel, phosphorus, potassium, sodium, tin and zinc.

Catalyst Inhibition

Inhibition occurs when materials chemically adhere to the catalyst. Inhibitors are large molecules. The inhibitors keep the pollutants from reaching the catalyst and from being converted. The performance of the catalyst is restored when the inhibitors are removed.

The following compounds are examples of inhibitors: sulfur dioxide, fluorohydrocarbons, chlorohydrocarbons and bromine hydrocarbons.

The operation of the catalyst is affected once the levels of sulfur dioxide in the exhaust reach 20 ppm for a natural gas engine.

The operation of the catalyst is affected once the levels of sulfur dioxide in the exhaust reach 50 ppm for a diesel engine.

The combustion of chlorinated hydrocarbons produces hydrochloric acid (HCI) that can have a detrimental effect on the system. Refer to the section on "Corrosion" for details.

Plugging, Fouling, and Masking of the Catalyst

All of the above conditions prevent pollutants from reaching the catalyst and from being converted. In many cases, performance can be regained by cleaning the catalyst. The exact cleaning procedure is dependent upon the type of materials in the engine exhaust. The cleaning procedure is also dependent upon the normal operating conditions, and on maintenance intervals.

Plugging occurs when deposits on the face of the catalyst prevent exhaust gas flow through the catalyst. Plugging is caused by high oil consumption and/or by high levels of soot. Soot is a by-product of combustion. The following conditions can cause plugging.

• A plugged air filter or filters

• Improper carburetor adjustment

• Too high of a fuel air mixture

• Worn injectors

• Low cylinder compression

• Operating temperature too low

Fouling occurs when deposits in the internal channels of the catalyst prevent exhaust gas flow through the catalyst. This can be caused by large particulate material in the engine exhaust. Fouling is also caused by deposits of silica, ash, or carbon as a by-product of combustion.

Although the efficiency of converting CO may not be affected, fouling causes the internal passages to become blocked. The narrowing or plugging of channels will cause high back pressure in the engine. This will affect engine performance. High back pressure can cause the following problems:

• Loss of power

• High exhaust temperature

• Shortened valve life

• High fuel consumption

Masking occurs when a film of materials physically covers the catalyst coating. This prevents the exhaust from contacting the catalyst and from being converted. Even though the flow of exhaust is unrestricted, the catalyst cannot promote conversion. This affects the conversion efficiency. Masking can be caused by zinc phosphate from the burning of antiwear oil additives. Caterpillar recommends the use of lube oils and fuels with a low content of ash and regular engine maintenance.

Corrosion

The catalyst substrate is composed of stainless steel that is highly resistant to corrosion and to corrosive gases. The following substances will corrode stainless steel:

• Condensed hydrochloric acid (HCl)

• Condensed sulfur dioxide (SO₂)

• Condensed sulfur trioxide (SO₃)

If operating temperatures are kept above the dew point of the acids, the acids cannot condense.

If the acids are allowed to condense within the catalyst, the acids can corrode the substrate for the catalyst. This will permanently lower the performance of the catalyst. Also if any chlorohydrocarbons or hydrogen sulfides (H₂S) will be burned in the engine, the downstream equipment may need to be designed with corrosion protection.

Maintenance Schedule

The service intervals for the catalyst and the catalytic converter are dependent upon the concentration of contaminants in the exhaust. The frequency of inspections and of maintenance will vary. The intervals are dependent upon the operating conditions of the different applications.

An annual inspection is sufficient for a natural gas engine if the exhaust is free from particulate contamination, and when oil consumption is low.

A monthly inspection is required when the exhaust contains high levels of particulate contamination and of fouling agents. A monthly inspection is also necessary if the engine consumes high amounts of lube oil.

The optimum service interval is based upon the conditions of the installation. An average maintenance schedule is given in Table 4. Consult your environmental operating permit in order to determine if additional monitoring is necessary. Record all measurements under typical operating conditions. Record all measurements at the same operating conditions. A well maintained maintenance log is highly recommended. Table 5 is an example of a maintenance log.

Inspect the catalyst under the following conditions:

• Abnormal system operation

• Loss of conversion efficiency

• Change in monitored parameters

In order to inspect the catalyst, the catalyst must be removed. This will allow the catalyst to be visually examined. A visual inspection will identify any physical damage or blocked passages. Pay particular attention to the inlet side of the catalyst during the visual inspection. Any blockage of the channels in the catalyst must be cleared by using a vacuum or by chemically cleaning the catalyst. Always use the vacuum on the inlet side of the catalyst.

Table 3

Maximum Allowable Pressure Drop
Engine Model	Part Number of the Catalytic Converter	Pressure Drop (Inches of Water)
3606	249-0473	1.2 kPa (4.8 inch of H2O)
3608	249-0474	1.2 kPa (4.8 inch of H2O)
3612	249-0476	1.2 kPa (4.8 inch of H2O)
3616	249-0477	1.15 kPa (4.6 inch of H2O)
G3606	249-0473	1.07 kPa (4.3 inch of H2O)
G3608	249-0474	0.40 kPa (1.6 inch of H2O)
G3612	249-0476	1.22 kPa (4.9 inch of H2O)
G3616	249-0477	1.32 kPa (5.3 inch of H2O)
3516	249-0472	0.72 kPa (2.9 inch of H2O)
3512	249-0470	0.6 kPa (2.4 inch of H2O)
3508	249-0468	0.67 kPa (2.7 inch of H2O)
3516B	249-0473	1.7 kPa (6.8 inch of H2O)
3512B	249-0470	0.92 kPa (3.7 inch of H2O)
3508B	249-0469	0.85 kPa (3.4 inch of H2O)
G3516B	249-0473	1.0 kPa (4.4 inch of H2O)
G3520C	249-0475	1.15 kPa (4.6 inch of H2O)
G3516C	249-0473	1.15 kPa (4.6 inch of H2O)
G3512C	249-0471	1.05 kPa (4.2 inch of H2O)
3412	249-0468	0.62 kPa (2.5 inch of H2O)
3456	249-0467	0.67 kPa (2.7 inch of H2O)
3406	249-0467	0.6 kPa (2.4 inch of H2O)
G3412	249-0468	0.9 kPa (3.5 inch of H2O)

Table 4

Recommended Maintenance
Description	More than 4000 Hours of Operation Per Year	500 to 4000 Hours of Operation Per Year	Less Than 500 Hours of Operation Per Year
Visual Inspection	Every Year or Every 5000 Hours whichever comes first.	Every Year	Every 2 Years
Temperature Reading	Continuous monitoring is required.
Back Pressure Check	Monthly (1)
Chemical Cleaning of the Catalyst	Every 8,000 to 10,000 hours of operation	Every 8,000 to 10,000 hours of operation	Every 8,000 to 10,000 hours of operation
Check for Leaks (2)	Every 3 Months	Every 6 Months	Every Year
Emissions	Check your license for the inspection interval.

(1)	Continuous monitoring with an in-line pressure gauge is also acceptable.
(2)	The assembly must be checked for leaks whenever the cover plate is reinstalled.

Table 5

Sample of a Maintenance Log
Date	Hours Of Operation	Engine Speed and Load	Inlet Temperature and Outlet Temperature	Pressure Drop After the Catalyst	Emission Levels Before the Catalyst Emission Levels After the Catalyst	Notes

Troubleshooting

Normal engine operation may cause the catalyst to exhibit a light to dark brown appearance. If the exhaust back pressure, the exhaust temperature and emission levels are normal, a small amount of ash is normal.

Table 6

Troubleshooting
Condition	Appearance of the Catalyst	Performance	Cause of the Condition	Required Action
Plugging	Deposits on the face of the catalyst that prevent exhaust flow through the channels.	Increased back pressure which leads to decreased CO conversion	High oil consumption, plugged air cleaner, improper carburetor adjustment, too rich fuel air mixture, weak ignition voltage discharge, or low cylinder compression	Vacuum clean the inlet face of the catalyst. If the problem persists, chemically wash the catalyst.
Fouling	Deposits that are plugging the internal channels of the catalyst	Increased back pressure which leads to decreased CO conversion	High oil consumption, high ash content in the engine oil, and/or lean fuel air mixture	Vacuum clean the inlet face of the catalyst. If the problem persists, chemically wash the catalyst.
Catalyst Masking (1)	A film of material that covers the catalyst coating This prevents exhaust gases from contacting the active catalyst and being converted.	Decreasing temperature difference across the assembly and lower CO conversion efficiency	High oil consumption and use of oils that are not recommended by Caterpillar.	Chemically wash the catalyst.
Overheating	Clean appearance white powder is present.	Decreasing temperature difference across the assembly, lower CO conversion and sintering of the catalyst coating	Advanced ignition timing, low engine cooling, low engine efficiency, lean fuel air mixture, leaking intake manifold, low fuel pressure, improper crankcase ventilation	Replace the catalyst.

(1)	Misfiring may result in burning of deposits and of the surface of the catalyst.

The following engine-related problems also affect the catalyst. The catalyst must be inspected and possibly replaced if the following conditions exist.

• Excess vibration or an engine backfire may cause physical damage to the catalyst. Inspect and possibly replace the catalyst. Perform a complete recalibration of all engine parameters in order to ensure correct engine operation before installing the new catalyst.

• Detonation can produce very high temperatures, which can cause permanent damage to the catalyst. The operating temperature of the catalyst must not exceed 705 °C (1300 °F). Inspect and possibly replace the catalyst.

• An engine misfire allows unburned air and fuel to enter the exhaust. When the unburned air/fuel mixture contacts the catalyst, the mixture starts to burn. This raises the operating temperature in the catalyst to damaging levels. The operating temperature of the catalyst must not exceed 705 °C (1300 °F). The effects of prolonged operation at high temperatures are sintering and/or melting of the catalyst. Inspect and possibly replace the catalyst.

Test Procedures

Performance Test

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Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

Measure the performance of the catalyst by taking a measurement of the exhaust gas concentration at the inlet of the converter and at the outlet of the converter. The measurement is taken by utilizing a portable analyzer that is designed to measure NO_x, CO and HC concentrations. The housing includes a test tap for the inlet and a test tap for the outlet. The reading from the test tap in the outlet is subtracted from the reading from the test tap in the inlet. This number is then divided by the reading from the test tap in the inlet. Multiply this number by 100. This is the conversion percentage.

Table 7

Conversion Percentage
Percent CO reduction =	(CO inlet − CO outlet)	× 100
	(CO inlet)

Wash Procedure

Note: The catalysts can be washed two times during the warranty period. If the catalysts are washed more than two times the warranty is voided.

Safety

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Personal injury can result from acid. Wear all necessary protective equipment, such as rubber gloves and goggles when working with acid. The bottle containing the etchant should be properly marked ACID and should be stored in a protective place.

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Personal injury can result from improper handling of chemicals. Make sure you use all the necessary protective equipment required to do the job. Make sure that you read and understand all directions and hazards described on the labels and material safety data sheet of any chemical that is used. Observe all safety precautions recommended by the chemical manufacturer for handling, storage, and disposal of chemicals.

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Moving heavy parts must be done safely and with adequate lifting capacity. Failure to do so can result in injury or death. Use caution and adequate lifting capacity when moving heavy parts.

Ensure that all work is performed in a safe manner in accordance with all OSHA and with other applicable guidelines. Request Material Safety Data Sheets (MSDS) from chemical suppliers. The following examples are areas of concern:

• Removal of the catalyst element from the housing and from the exhaust pipe

• Handling of oxalic acid and of acetic acid

• Disposal of used cleaning solutions

The following safety equipment is required:

• Proper ventilation

• Use of chemical resistant gloves

• A face shield

• Safety glasses

• Coveralls

• Shoes

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NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates.

Materials

• Technical grade oxalic acid

• Technical grade acetic acid

• Deionized water

• Tank or tanks for holding chemical solutions used for washing the catalysts

• Spacers for separating catalysts (four per each catalyst)

• Chemical resistant electric pump for 55 gal drums

Preparation

Acid Solution for Washing the Catalysts

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Add acid to the water at normal room temperature. Do not add water to the acid. Add neutralizing agents to the water. Do not add water to the neutralizing agents. There are many safety precautions when handling acid. Therefore, this should only be done by qualified personnel.

The acid solution must be a solution of 5 percent by weight oxalic acid, 5 percent by weight acetic acid, and 90 percent deionized water by weight. The acids must be fresh chloride free technical grade. Concentrated acid solutions, anhydrous powders or anhydrous pellets must be diluted with deionized water. Always add the acid or anhydrous powder to the water. Heat can be generated if the solution must be diluted. The acid solution can only be used if the solution is between the temperatures of 16 °C (60 °F) and 32 °C (90 °F).

Each cubic foot of catalyst requires 15 gal of the acid solution. The acid solution cannot be reused under any circumstances. Preparation of the acid solution must be finished before placing the catalysts into the tank.

Deionized Water

The system for deionizing water must be large enough to produce at least 130 gal of deionized water per cubic foot of catalyst. This amount should cover the steps for washing with deionized water, dilution of concentrated acids, and cleaning the wash tank. Use only deionized water. No substitutes are allowed. Canisters that convert tap water into deionized water are available.

Tank(s) for Holding Chemical Solutions and Catalysts

One or more tanks can be used to hold the acid solution and catalysts. The tank or tanks must be clean. The tank or tanks must be able to withstand the acid solution. The tank or tanks must be large enough and correctly sized in order to completely submerge the catalysts in the acid solution. This includes accounting for the volume of the catalysts. Also, enough room for lifting the catalysts in and out of the tank is needed.

Spacers for Separating the Catalysts

Spacers are needed to separate the catalysts when more than one element is placed in the tank for washing. Use four spacers per element. Place the spacers near the corners of the catalysts. The spacers must be resistant to the acid solution. The spacers can be made from 50.80 mm (2 inch) stainless steel pipe cut to a length of 19 mm (0.75 inch).

Procedure

1. Fill the tank with the premixed acid solution. Use 15 gal of acid solution for each cubic foot of catalyst. Preparation of the acid solution must be done before the catalysts are added to the solution.

   Note: The catalysts must be added to the acid solution. Do not add the acid solution to the catalysts in the tank. This will result in a poorly cleaned catalyst. This can allow air to be trapped in the cells of the catalyst which will prevent the solution from contacting the catalyst.

2. Place 19 mm (0.75 inch) spacers on the bottom of the tank. Submerge the catalysts horizontally in the acid solution. Place 19 mm (0.75 inch) spacers between the catalysts. Lower the catalysts slowly into the solution so that all the cells are wetted by the solution. Lowering the catalysts horizontally into the solution will remove air from the cells of the catalyst. This will also help to wet the catalyst. Cover the tank and allow catalysts to soak for four hours. The color of the acid solution will be a light brown to a dark brown after the catalyst is added.

3. After the catalyst soaks for four hours in the acid solution, use an electric pump to transfer the acid solution from the tank to a 55 gal drum that is used for waste. Do not pour the used acid solution directly down the drain. Refer to the section "Disposal of Used Cleaning Solutions". Run deionized water over the catalysts. This will dilute any of the acid solution that remains on the elements. Remove the catalysts from the tank and allow the catalysts to drain. Do not shake the catalysts. Not all the solution will come off. The wet catalysts will be heavy because the catalyst acts as a sponge. Clean any sediment from the tank with deionized water and drain the tank.

4. Place 19 mm (0.75 inch) spacers on the bottom of the tank. Fill the tank with clean deionized water at 15 gal per cubic foot of catalyst. Submerge the catalysts horizontally in the deionized water. Place 19 mm (0.75 inch) spacers between the catalysts. Allow the catalysts to soak in the deionized water for 30 minutes.

5. After the catalyst soaks for 30 minutes, use an electric pump to transfer the deionized water from the tank to a 55 gallon drum that is used for waste. Do not pour the used solution directly down the drain. Refer to the section on "Disposal of Used Cleaning Solutions". Remove the catalysts from the tank and allow the catalysts to drain. Do not shake the catalysts. Clean any sediment from the tank with deionized water and drain the tank.

6. Repeat Steps 4 and 5 again.

7. Measure the pH level of the deionized water in the third cycle. The level of pH must be from 6 to 9. Repeat Steps 4 and 5 until the level of pH is correct. The level of pH must be correct before proceeding to the next step.

8. The catalyst can be partially dried with clean compressed air or with nitrogen. Ensure that the compressed air or nitrogen is free from oil. The maximum air pressure for cleaning purposes must be below 205 kPa (30 psi). Sweep the air gun slowly across the face of the catalyst so that airflow is directed through each cell. Adjust the pressure in order to provide cleaning of fluid from the cells. Excessive pressure can damage the catalyst coating. Do not touch the face of the catalyst with the tip of the air gun while the air gun is moving. This may distort the metal foil.

9. Dry the catalyst in an oven for one hour at 121 °C (250 °F) to 149 °C (300 °F) if the catalyst is installed immediately after washing. If the catalyst is not installed in the housing within two days of being washed residual moisture must be removed before storage. Residual moisture is removed by drying the catalyst in an oven for four hours at 121 °C (250 °F) to 149 °C (300 °F).

   Drying procedures will help extend the life of the catalyst.

10. Reinstall the catalyst in the housing.

11. Check the system for leaks and resume normal engine operation.

Disposal of Used Cleaning Solutions

All used solutions must be considered hazardous. Dispose of fluids according to local regulations.

The used acid solution can be neutralized to a pH of 6 to 7 with caustic soda. Caustic soda can be purchased from the company that supplies the acids.

Serviceable Parts

Refer to Illustration 9 for an expanded view of the cylindrical assembly. Refer to Illustration 12 for an expanded view of the rectangular assembly. Refer to Table 8 for information on ordering an assembly.

Table 8

Information for Ordering the Housing and Catalyst
Engine Model	Part Number for the Converter	Total Weight	Part Number for the Housing	Weight of the Housing	Part Number for the Catalyst	Quantity of Catalysts	Weight of the Catalysts
3606, G3606	249-0473	272 kg (600 lb)	249-0418	212 kg (467 lb)	249-0380	2	30 kg (66 lb)
3608, G3608	249-0474	653 kg (1440 lb)	249-0419	544 kg (1200 lb)	249-0377	4	26 kg (58 lb)
3612, G3612	249-0476	762 kg (1680 lb)	249-0421	544 kg (1200 lb)	249-0377	8	26 kg (58 lb)
3616, G3616	249-0477	975 kg (2150 lb)	249-0422	705 kg (1550 lb)	249-0375	4	16 kg (36 lb)
					249-0377	8	26 kg (58 lb)
3516	249-0472	229 kg (505 lb)	249-0417	198 kg (437 lb)	249-0380	1	30 kg (66 lb)
3512	249-0470	202 kg (445 lb)	249-0415	176 kg (389 lb)	249-0379	1	25 kg (54.2 lb)
3508	249-0468	145 kg (320 lb)	249-0413	129 kg (285 lb)	249-0376	1	15 kg (33.2 lb)
3516B	249-0473	272 kg (600 lb)	249-0418	212 kg (467 lb)	249-0380	2	30 kg (66 lb)
3512B	249-0470	202 kg (445 lb)	249-0415	176 kg (389 lb)	249-0379	1	25 kg (54.2 lb)
3508B	249-0469	181.5 kg (400 lb)	249-0414	161 kg (355 lb)	249-0378	1	23 kg (50 lb)
G3516B	249-0473	272 kg (600 lb)	249-0418	211 kg (467 lb)	249-0380	2	30 kg (66 lb)
G3520C	249-0475	599 kg (1320 lb)	249-0420	435 kg (960 lb)	249-0377	4	26 kg (58 lb)
					249-0375	4	16 kg (36 lb)
G3516C	249-0473	272 kg (600 lb)	249-0418	211 kg (467 lb)	249-0380	2	30 kg (66 lb)
G3512C	249-0471	240 kg (530 lb)	249-0416	190 kg (419 lb)	249-0379	2	25 kg (54.2 lb)
3412	249-0468	145 kg (320 lb)	249-0413	129 kg (285 lb)	249-0376	1	15 kg (33.2 lb)
3456	249-0467	93 kg (205 lb)	249-0412	85 kg (187 lb)	249-0374	1	8 kg (18 lb)
3406	249-0467	93 kg (205 lb)	249-0412	85 kg (187 lb)	249-0374	1	8 kg (18 lb)
G3412	249-0468	145 kg (320 lb)	249-0413	129 kg (285 lb)	249-0376	1	15 kg (33.2 lb)

Table 9

Parts Ordering Information
Engine Model	Part Number for the Converter	Part Number of the Clamps	Quantity of Clamps	Part Number for the Center Body	Part Number for the End Plates	Part Number for the Insulation
3606, G3606	249-0473	249-0427	2	249-0461	249-0466	249-0439
3608, G3608	249-0474	NA	NA	NA	NA	NA
3612, G3612	249-0476	NA	NA	NA	NA	NA
3616, G3616	249-0477	NA	NA	NA	NA	NA
3516	249-0472	249-0427	2	249-0460	249-0466	249-0438
3512	249-0470	249-0426	2	249-0458	249-0465	249-0438
3508	249-0468	249-0424	2	249-0456	249-0463	249-0434
3516B	249-0473	249-0427	2	249-0461	249-0466	249-0439
3512B	249-0470	249-0426	2	249-0458	249-0465	249-0436
3508B	249-0469	249-0424	2	249-0457	249-0464	249-0435
G3516B	249-0473	249-0427	2	249-0461	249-0466	249-0439
G3520C	249-0475	NA	NA	NA	NA	249-0441
G3516C	249-0473	249-0427	2	249-0461	249-0466	249-0439
G3512C	249-0471	249-0426	2	249-0459	249-0465	249-0437
3412	249-0468	249-0424	2	249-0456	249-0463	249-0434
3456	249-0467	249-0423	2	249-0455	249-0462	249-0433
3406	249-0467	249-0423	2	249-0455	249-0462	249-0433
G3412	249-0468	249-0424	2	249-0456	249-0463	249-0434

Reference Dimensions

Catalytic Converter with Single Catalyst

Illustration 13	g01048434
Refer to Table 10 and Table 11.

Table 10

Housing Dimensions
Part Number for the Housing	A	B	C	D	E	F	G	H
249-0412	914 ± 6 mm (36 ± .25 inch)	464 mm (18.25 inch)	311 mm (12.25 inch)	146 mm (5.75 inch)	457 mm (18 inch)	95 mm (3.75 inch)	165 mm (6.5 inch)	9.5 mm (0.375 inch)
249-0413	914 ± 6 mm (36 ± .25 inch)	629 mm (24.75 inch)	311 mm (12.25 inch)	146 mm (5.75 inch)	457 mm (18 inch)	95 mm (3.75 inch)	165 mm (6.5 inch)	9.5 mm (0.375 inch)
249-0414	914 ± 6 mm (36 ± .25 inch)	705 mm (27.75 inch)	311 mm (12.25 inch)	146 mm (5.75 inch)	457 mm (18 inch)	95 mm (3.75 inch)	165 mm (6.5 inch)	9.5 mm (0.375 inch)
249-0415	914 ± 6 mm (36 ± .25 inch)	800 mm (31.5 inch)	311 mm (12.25 inch)	146 mm (5.75 inch)	457 mm (18 inch)	95 mm (3.75 inch)	165 mm (6.5 inch)	9.5 mm (0.375 inch)
249-0417	914 ± 6 mm (36 ± .25 inch)	882 mm (34.75 inch)	311 mm (12.25 inch)	146 mm (5.75 inch)	457 mm (18 inch)	95 mm (3.75 inch)	165 mm (6.5 inch)	9.5 mm (0.375 inch)

Table 11

Dimensions of the Flange
Part Number for the Housing	1	2	3	4
249-0412	254 mm (10 inch)	406.4 mm (16 inch)	25.4 mm (1 inch)	361.95 mm (14.25 inch)
249-0413	304.8 mm (12 inch)	482.6 mm (19 inch)	25.4 mm (1 inch)	431.8 mm (17 inch)
249-0414 249-0415 249-0417	457.2 mm (18 inch)	635 mm (25 inch)	31.75 mm (1.25 inch) (1)	577.85 mm (22.75 inch)

(1)	There are 18 bolt holes.

Catalytic Converter with Dual Catalysts

Illustration 14	g01048442
Refer to Table 12 and Table 13.

Table 12

Part Number for the Housing
Housing Dimensions	249-0416	249-0418
A	914 ± 6 mm (36 ± .25 inch)	914 ± 6 mm (36 ± .25 inch)
B	800 mm (31.5 inch)	882 mm (34.75 inch)
C	489 mm (19.25 inch)	489 mm (19.25 inch)
D	146 mm (5.75 inch)	146 mm (5.75 inch)
E	457 mm (18 inch)	457 mm (18 inch)
F	95.25 mm (3.75 inch)	95.25 mm (3.75 inch)
G	165 mm (6.5 inch)	165 mm (6.5 inch)
H	114 mm (4.5 inch)	114 mm (4.5 inch)
I	9.5 mm (0.375 inch)	9.5 mm (0.375 inch)

Table 13

Dimensions of the Flange
Part Number for the Housing	1	2	3	4
249-0416 249-0418	457.2 mm (18 inch)	635 mm (25 inch)	31.75 mm (1.25 inch) (1)	577.85 mm (22.75 inch)

(1)	There are 18 bolt holes.

Rectangular Catalytic Converter

Illustration 15	g01059060
Refer to Table 14 and 15. 254-9219 Exhaust Flange Gp

Table 14

Part Number for the Housing
Housing Dimensions	249-0419	249-0420	249-0421	249-0422
A	1981 mm (78 inch)	1568 mm (61.75 inch)	1727 mm (68 inch)	2134 mm (84 inch)
B	489 mm (19.25 inch)	489 mm (19.25 inch)	489 mm (19.25 inch)	489 mm (19.25 inch)
C	9.5 mm (0.375 inch)	9.5 mm (0.375 inch)	9.5 mm (0.375 inch)	9.5 mm (0.375 inch)
D	686 mm (27 inch)	686 mm (27 inch)	686 mm (27 inch)	686 mm (27 inch)
E	1354 mm (53.312 inch)	1354 mm (53.29 inch)	1354 mm (53.312 inch)	1354 mm (53.312 inch)
F	1317 mm (51.875 inch)	1034 mm (40.72 inch)	1318 mm (51.875 inch)	1612 mm (63.47 inch)
G	1067 mm (42 inch)	1067 mm (42 inch)	1067 mm (42 inch)	1067 mm (42 inch)
H	8 mm (0.3125 inch)	8 mm (0.3125 inch)	8 mm (0.3125 inch)	8 mm (0.3125 inch)
I	101 mm (4 inch)	101 mm (4 inch)	101 mm (4 inch)	101 mm (4 inch)
J	147 mm (5.79 inch)	147 mm (5.79 inch)	147 mm (5.79 inch)	147 mm (5.79 inch)

Table 15

Dimensions of the Flange
Part Number for the Housing	1	2	3	4
249-0419	457.2 mm (18 inch)	635 mm (25 inch)	31.75 mm (1.25 inch) (1)	577.85 mm (22.75 inch)
249-0420	508 mm (20 inch)	698.5 mm (27.5 inch)	31.75 mm (1.25 inch) (2)	635 mm (25 inch)
249-0421 249-0422	609.6 mm (24 inch)	812.8 mm (32 inch)	34.93 mm (1.375 inch) (3)	749.3 mm (29.5 inch)

(1)	There are 18 bolt holes.
(2)	There are 20 bolt holes.
(3)	There are 24 bolt holes.

Illustration 16	g01062335
Typical example of a flange adapter

Table 16

Flange Adapters
Part Number for the Converter	Part Number for the Adapter	Flange (1)	Flange (2)
249-0467	250-8524	10 ANSI	8 ASA
	250-8525		6 ASA
249-0468	250-8523	10 ANSI	12 ANSI
249-0469 249-0470 249-0471 249-0472 249-0473 249-0474	250-8521	16 ANSI	18 ANSI
249-0475	250-8522	16 ANSI	20 ANSI
249-0468	255-2835	12 ANSI	8 ANSI
	255-2836	16 ANSI	12 ANSI
249-0469 249-0470 249-0471 249-0472 249-0473 249-0474	255-2837	18 ANSI	14 ANSI

Table 17

Adapter Group Parts
Flange Size	Adapter Group Part Number	Adapter Part Number	Gasket Part Number	Bolt Part Number	Quantity Required	Washer Part Number	Quantity Required	Nut Part Number	Quantity Required
6 ANSI	254-9219	250-8520	255-0886	9X-8887	8	5P-8248	16	2J-3506	8
8 ANSI	254-9220	250-8519	255-0887
10 ANSI(1)	254-9221	250-8515	255-0888	1D-4627	12	5P-8249	24	2J-3505	12
12 ANSI(1)	254-9222	255-0838	255-0889
14 ANSI	255-1276	255-1275	255-1274	1D-4709		5P-8250		2J-3507
16 ANSI	254-9223	255-0839	255-0890		16		32		16
18 ANSI(1)	254-9224	255-0840	255-0891	1J-2814		3S-1349		4J-5977
20 ANSI	254-9225	255-0841	255-0892		20		40		20
24 ANSI(1)	255-0895	255-0894	255-0893

(1)	Needed for bolting directly to the housing.