General Welding Procedures {0679, 7000} Caterpillar


General Welding Procedures {0679, 7000}

Usage:

MT700 018


Caterpillar Products
All

Introduction

This Special Instruction provides the necessary information on all welding procedures.

Note: For welding procedures on 794 AC Off-Highway Trucks refer to BI618167 , "General Service Information" on Caterpillar Service Information System (SIS).

Proper Cleaning for Inspection

------ WARNING! ------

When it is necessary to work under the machine with the body (bed) raised, attach the body (bed) retaining cables to the rear tow points. Install the rear tow point pins through the ends of the retaining cables.

Failure to properly secure the body (bed) may result in personal injury or death.


------ WARNING! ------

Personal injury can result from working with cleaning solvent.

Because of the volatile nature of many cleaning solvents, extreme caution must be exercised when using them. If unsure about a particular cleaning fluid, refer to the manufacturer's instructions and directions.

Always wear protective clothing and eye protection when working with cleaning solvents.



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.


Before you inspect the area, clean the area with an appropriate high-pressure washer. Be careful not to damage wires or other components. Use an appropriate de-greaser to remove any oil or grease from the frame assembly. A wire brush or a scraper to remove excessive dirt and grease may also be needed. Make sure that the substances that follow are removed from the area that will be inspected.

  • Oil

  • Grease

  • Dirt

Preparing the Area for Welding

Clean the area that will be welded. Make sure that the substances that follow are removed from the area that will be welded.

  • Oil

  • Grease

  • Paint

  • Dirt

If the temperature of the base metal is below 0 °C (32 °F), heat the base metal to a temperature of at least 21 °C (70 °F). Maintain the temperature of the base metal at 21 °C (70 °F) during the welding process.

Note: Heat distortion of the base metal is possible when you weld. Avoid excessive heating of the base metal.

Attach the welding ground cable directly to the base metal. Protect machined surfaces from sparks. Protect the machined surfaces from the weld splatter.

Weld Specifications and Qualifications

------ WARNING! ------

Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can kill.

Read and understand the manufacturer's instruction and your employer's safety practices. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area. Wear correct eye, ear and body protection. Do not touch live electric parts.

Refer to the American National Standard Z49.1, "Safety in Welding and Cutting" published by the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125: OSHA Safety and Health Standards, 29 CFR 1910, available from U.S. Dept. of Labor, Washington D.C. 20210.


Note: Personal breathing protection should be worn by the personnel that are welding. Personal breathing protection will prevent fumes from entering the lungs of the person that is welding. Use a 237-5181 RESPIRATOR for breathing protection.

Qualifications

Welders must be qualified for fillet welding and groove welding. The welders should be qualified in the use of the welding processes that follow: Shielded Metal Arc Welding (SMAW), Flux Cored Arc Welding (FCAW) and Gas Metal Arc Welding (GMAW). Refer to "American National Standards Institute (ANSI)/American Welding Society (AWS) Specification D1.1, or Specification D14.3" for information that regards the qualifications for the processes that follow: SMAW process, FCAW process, and GMAW process. The welders must have used the process at some time within the last 6 months. The welders must complete the process of certification if the welders have not used the welding processes for 6 months.

Proper Welding Procedure on Machines and Engines with Electronic Controls

Proper precautions are necessary to prevent damage to electronic controls. When you weld on a machine with electronic controls, use the steps that follow:

  1. Turn off the engine. Put the key start switch in the OFF position.

  2. If the machine has a battery disconnect switch, open the switch. If the machine does not have a battery disconnect switch, disconnect the negative battery cable at the battery.

  3. Connect the ground cable for the welder directly to the actual machine component that will be welded. Attach the clamp for the ground cable as close as possible to the area that is being welded. The ground cable will reduce the chance of damage from welding current to the components that follow: bearings, hydraulic components, and electrical components.

    Note: Do NOT use electrical components as a ground point for the welder. Do NOT use ground points for electronic components as a ground point for the welder.

  4. Protect the wiring harnesses from the weld splatter.

Specifications

Low Hydrogen Electrodes for the SMAW Process

The tables that follow list the mechanical properties of welds that are deposited by low hydrogen electrodes.

Table 1
Mechanical Properties of Welds from Low Hydrogen Electrodes That Are Classified as "ANSI/AWS A5.5 E10018-D2" 
Tensile Strength  690 MPa (100076 psi) 
Yield Strength  600 MPa (87000 psi) 
Elongation  16% 
Impact Toughness  27 J @ -50 °C (20 ft lb @ -60 °F) 

Table 2
Mechanical Properties of Welds from Low Hydrogen Electrodes That Are Classified as "ANSI/AWS A5.1 E7018" 
Tensile Strength  480 MPa (69618 psi) 
Yield Strength  400 MPa (58015 psi) 
Elongation  22% 
Impact Toughness  27 J @ -18 °C (20 ft lb @ -20 °F) 

Low hydrogen electrodes must be stored in an electrode oven at 120 °C (248 °F). If low hydrogen electrodes get damp, scrap the low hydrogen electrodes or recondition the low hydrogen electrodes to the specifications from the manufacturer.

The table that follows shows setting for the welding current for the electrode diameter.

Table 3
Welding Current for Low Hydrogen Electrodes 
Diameter  Amperage Rating 
3.2 mm (0.125 inch)  70-140 
4.0 mm (0.157 inch)  110-180 
4.8 mm (0.189 inch)  190-270 

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The width of the weld should not exceed two times the electrode diameter.

Flux Cored Welding Electrode for the FCAW Process

As an alternative process, use the Flux Cored Arc Welding (FCAW) with E71T-1 H8 (ANSI/A5.20) welding electrode and the manufacturer's shielding gases that are specified for inside welding. The H8 implies that the electrode is designed to provide less than 8 ml/100 g of diffusible hydrogen in the weld deposit. The weld that is deposited by the flux cored welding electrode will have the following minimum mechanical properties:

The table that follows lists the mechanical properties of welds that are deposited by the flux cored welding electrode.

Table 4
Mechanical Properties from Flux Cored Welding Electrode That Is Classified as "ANSI/AWS A5.20 E71T-1"(1) 
Tensile Strength  480 MPa (69618 psi) 
Yield Strength  400 MPa (58015 psi) 
Elongation  22% 
Impact Toughness  27 J @ -18 °C (20 ft lb @ -20 °F) 
(1) The properties that are listed are for three passes of the welding electrode.

The table that follows shows setting for the welding current for the flux cored welding electrode that has a diameter of 1.3 mm (.051 inch).

Table 5
Welding Current for Flux Cored Welding Electrode That Is Classified as "ANSI/AWS A5.20 E71T-1" 
Wire Feed Rate  Voltage  Amperage 
Minimum 5080 mm (200 inch) Per Minute  24  210 
Optimum 6985 mm (275 inch) Per Minute  28  250 
Maximum 8255 mm (325 inch) Per Minute  29  300 

Note: The settings for the welding current can vary due to the position of the weld. Also, the settings for the welding current can vary with the manufacturer of the welding electrode.

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The fast freezing characteristics of flux cored welding electrode increases the possibility of evolving gas that is trapped in the weld. Control the size of the weld to reduce the possibility of evolving gas that is trapped in the weld. The volume of the fillet weld should not exceed 8.0 mm (.315 inch).

Arc Welding Electrodes for the GMAW Process

The table that follows lists the mechanical properties of welds that are deposited by the GMAW Process.

Table 6
Mechanical Properties of Welds from Arc Welding Electrodes That Are Classified as "ANSI/AWS A5.28 ER100S-2" 
Tensile Strength  690 MPa (100076 psi) 
Yield Strength  610 MPa (88473 psi) 
Elongation  16% 
Impact Toughness  68 J @ -51 °C (50 ft lb @ -60 °F) 

The welding parameters will vary with the position of the weld and with different electrode manufacturers.

Weld Inspection

The weld should not have any of the conditions that follow:

  • Cracks

  • Porosity

  • Undercut

  • Incomplete Fusion

To verify the quality of the weld, refer to"American National Standards Institute (ANSI)/American Welding Society (AWS) Specification D14.3".

General Repair for Cracked Welds

  1. Remove any components that prevent access to the cracked weld.

  2. Clean the weld of the substances that follow: oil, grease, and dirt.

  3. Use the dye penetrant to inspect the entire area for possible cracks.

  4. Protect machined surfaces from sparks and weld deposits.

  5. Use an air carbon arc torch or use a grinder to remove cracks. Use a grinder to remove cracks that extend through the castings. Remove at least 50.8 mm (2.0 inch) of material past each end of the crack. When the crack is removed, the bottom of the groove should have an angle of 90 degrees to ensure sufficient penetration. The side walls of the groove should extend upward at an angle of 45 degrees.

  6. Use the dye penetrant to inspect the gouged area to ensure that the crack has been removed. Be sure to clean the prepared groove before welding.

  7. Use Welding to repair the prepared groove by using passes that do not exceed two times the electrode diameter. If the alternate welding process is selected, the size of the weld pass should not exceed 7.88 mm (0.31 inch) by volume. Do not allow any slag inclusion when multiple pass welding is used.

  8. Clean the weld and inspect the weld. The weld must be free from the following: cracks, porosity, undercut and incomplete fusion. All quality of the weld must conform to ANSI/AWS standard 14.3.

Welding Instructions for Certain Truck Bodies

The following materials are used to fabricate the MSD II truck body:

  • 400 Brinell Hardness Material

  • 450 Brinell Hardness Material

Before welding on the MSD II truck body, verify the materials that are used to fabricate your MSD II truck body. There are specific welding procedures for each material. Refer to the following procedures to weld the materials during the assembly of the truck body.

Note: When two or more different materials need to be welded together, use the procedure for the material that has the more stringent requirements.

400 Brinell and 450 Brinell Hardness Material

The following procedure covers the requirements for welding the assembly of the MSD II truck bodies that are fabricated with 400 Brinell or 450 Brinell Hardness Material. Refer to "Cleaning Methods" for qualifications, safety, and welding electrode parameters. Attach the welding ground cable directly to the body assembly. Protect all the machined areas from sparks and spatter that are produced by welding, chipping, and grinding operations.

Proper preparation of the welding area must be conducted prior to welding. All weld joints and welding areas must be exceptionally clean. Clean the welding area with a grinder. Completely remove all paint, rust, scale, slag, dirt, moisture, grease, and so on, before welding.


NOTICE

400 Brinell and 450 Brinell Hardness Material are both sensitive to hydrogen induced cracking. Cleanliness of the weld joints and of the consumables is of utmost importance.


Tight fitup of the body assemblies is important. Ensure that every effort is made to minimize the gap spacing. Minimizing the gap spacing reduces the residual stresses.

To minimize the possibility of cracking, use large tack welds. The tack welds should have a maximum width of 8 mm (0.32 inch) and a length of 75 mm (3 inch).



Illustration 1g01286162
View of a TigerTorch

A TigerTorch can be used to preheat the material that is welded. Preheating is most critical during the tack welding procedure and during the welding of the root pass. Refer to Table 7 for the required preheat temperature of the weld area:

Table 7
Preheat Temperatures 
Combined Thickness of Material  Welding Preheat 
0 mm (0 inch) to 65 mm (2.6 inch)  100 °C (212 °F) 
66 mm (2.6 inch) to 100 mm (3.9 inch)  125 °C (250 °F) 
greater than 100 mm (3.9 inch)  175 °C (350 °F) 


Illustration 2g01125276
Calculations for Combined Thickness
(A) Combined thickness = t1 + t2
(B) Combined thickness = 2 * t1 + t2
(C) Combined thickness = 2 * t1 + t2
(D) Combined thickness = t1 + t2
(E) Combined thickness = t1 + t2
(F) Combined thickness = 2 * t1 + t2

Note: Use a backup strip were applicable.

Ensure that the weld groove and 76 mm (3 inch) in each direction from the weld groove is preheated to the specified temperature. Verify the preheat temperature with a 164-3310 Infrared Thermometer or with a temperature stick.

The minimum interpass temperature should equal the preheat temperature. The maximum interpass temperature should not exceed 250 °C (480 °F).

Note: When the ambient temperature is below 0 °C (32 °F), the initial preheat temperature should be taken to 121 °C (250 °F) 76 mm (3.0 inch) in each direction from the weld joint to avoid the heat sink effect of the floorplates.

Note: The above preheat and interpass temperatures are for mild restraint to moderate restraint. If clamping devices are utilized to reduce the gap spacing to less than 3 mm (0.12 inch), use the next higher preheat temperature, when possible. Additional stresses are offset by using the next higher preheat temperature.

All welded areas must be inspected. Hydrogen induced cracking normally occurs within 72 hours of welding. Allow the welded areas to cool for 48 hours to 72 hours prior to performing a visual inspection. If any welding areas are suspected of being cracked during the visual inspection, then use the dye penetrant process or the magnetic particle inspection process to inspect the welding areas. The welds shall be free from the following defects: cracks, porosity, undercut and incomplete fusion. All weld quality shall conform to American National Standards Institute (ANSI)/American Welding Society (AWS) D14.3.

Repair Procedure for Cracks in Truck Bodies

The following procedure covers the requirements for repairing the body assembly by welding. Refer to "Cleaning Methods" for qualifications, safety, and welding electrode parameters. Attach the welding ground cable directly to the body assembly. Protect all the machined areas from sparks and spatter that are produced by welding, chipping, and grinding operations.

Reference: Refer to the "Welding on Engines and Machines with Electronic Controls" section.

Crack Repair

  1. Through a visual inspection, locate all structural cracks and mark all structural cracks.

  2. Use an air carbon arc torch or use a grinder to remove the crack completely. Use the dye penetrant to inspect the gouged area to ensure that the crack has been removed.

  3. Preheat the welding area to 150 °C (300 °F). Do not exceed 250 °C (450 °F).

  4. Complete the repair weld by using one of the two repair options that are described below.

  5. Prepare the weld area for a thermal soak, and slow cooling. Allow at least an hour to cool.

  6. Perform any grinding or dress grinding of welds.

  7. Use the dye penetrant or the magnetic inspection process to check and make sure that the crack is removed.

Note: This sequence of repair weld is explained below.

Crack Repair Options

There are two repair options for removing a crack. The first option is the dye penetrant or the magnetic particle inspection process.

  1. Use the dye penetrant or the magnetic particle inspection process to locate the ends of the crack.

  2. Remove the crack by grinding.

  3. Use the dye penetrant or the magnetic particle inspection process to check and make sure that the crack is removed.

    Note: Clean the weld area to ensure that all dye penetrant is removed.

There are two repair options for removal of cracks. The second option is air arc gouging.

  1. The gouged area must be cleaned by grinding to remove both the carbon deposits and slag.

  2. Inspect the area of the crack to ensure that the crack is removed.

Groove Preparation

After the crack is removed, prepare a single V-groove by grinding or a U-groove by grinding. The groove should be at least 45 degrees. The groove can be a maximum of 90 degrees. If the crack is completely through the material and both sides are accessible, prepare a double V-groove or prepare a U-groove. Use a balanced approach to grinding.



Illustration 3g01620662
View of a typical V-groove that is used to remove a crack
(1) 67.5 degrees ± 22.5 degrees


Illustration 4g01620646
View of a typical U-groove that is used to remove a crack
(1) 67.5 degrees ± 22.5 degrees

Welding Electrodes

Proper preparation of the weld area must be completed prior to any repair welds. Clean the weld area with a grinder. All paint, rust, oil, scale, slag, dirt, moisture, and so on, must be removed. Any dye penetrant must also be removed with the appropriate cleaner.

Option 1

Preheat the weld groove and 76.2 mm (3.0 inch) in each direction from the center of the weld to 150 °C (300 °F). The maximum interpass temperature should not exceed 250 °C (450 °F).

Characteristic

The SMAW process may be used with E7018 (ANSI/A5.1) welding electrode. The weld that is deposited by these electrodes will have the following minimum mechanical properties.

Table 8
Mechanical Properties of Welds from Low Hydrogen Electrodes That Are Classified as "E7018 (ANSI/AWS A5.1)" 
Tensile Strength  480 MPa (69618 psi) 
Yield Strength  400 MPa (58015 psi) 
Elongation  22% 
Impact Toughness  27 J @ -18 °C (20 ft lb @ -20 °F) 

Note: The low hydrogen electrodes must be stored in an electrode oven at 120 °C (250 °F). The electrodes must be reconditioned to the manufacturer's specifications if the electrodes get damp.

The following table relates to the electrode diameter and approximate current settings for welding.

Table 9
Welding Current for Low Hydrogen Electrodes 
Diameter  Amperage Rating 
3.2 mm (0.125 inch)  70-140 
4.0 mm (0.157 inch)  110-180 
4.8 mm (0.189 inch)  190-270 

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The width of the weld should not exceed two times the electrode diameter.

Option 2

Preheat the weld groove and 76.2 mm (3.0 inch) in each direction from the center of the weld to 150 °C (300 °F). The maximum interpass temperature should not exceed 250 °C (450 °F).

As an alternative process, the FCAW process may be used with E71T-1 H8 (ANSI/AWS A5.20) welding electrode and the manufacturers specified shielding gas. The weld that is deposited by these electrodes will have the following mechanical properties.

Table 10
Mechanical Properties of Welds from Low Hydrogen Electrodes That Are Classified as "E71T-1 H8 (ANSI/AWS A5.20)" 
Tensile Strength  480 MPa (69618 psi) 
Yield Strength  400 MPa (58015 psi) 
Elongation  22% 
Impact Toughness  27 J @ -18 °C (20 ft lb @ -20 °F) 

Table 11
Welding Current for Flux Cored Welding Electrode That Is Classified as "ANSI/AWS A5.20 E71T-1" 
Wire Feed Rate  Voltage  Amperage 
Minimum 5080 mm (200 inch) Per Minute  24  210 
Optimum 6985 mm (275 inch) Per Minute  28  250 
Maximum 8255 mm (325 inch) Per Minute  29  300 

Note: The settings for the welding current can vary due to the position of the weld. Also, the settings for the welding current can vary with the manufacturer of the welding electrode.

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The width of the weld should not exceed two times the electrode diameter.

Note: Heat the repair weld to 150 °C (300 °F) for at least 30 minutes. Heat for 1 hour per 25 mm (1.0 inch) of the base material thickness. Cover the repair weld with a thermal blanket. The blanket will slow the cooling. The blanket will help in the release of hydrogen.

Finish Weld Inspection

Use the dye penetrant or the magnetic particle inspection process to inspect the repair weld. The repair weld should be allowed to cool for 48 hours to 72 hours. The weld shall be free from cracks, porosity, undercut, and incomplete fusion. All weld quality shall conform to (ANSI/AWS 14.3).

Welding on Engines and Machines with Electronic Controls


NOTICE

Because the strength of the frame may decrease, some manufacturers do not recommend welding onto a chassis frame or rail. Consult the OEM of the equipment or your Cat dealer regarding welding on a chassis frame or rail.


Proper welding procedures are necessary to avoid damage to the electronic controls and to the bearings. The following steps should be followed to weld on a machine or an engine with electronic controls.


NOTICE

Do not ground the welder to electrical components such as the ECM or sensors. Improper grounding can cause damage to the drive train bearings, hydraulic components, electrical components, and other components.

Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld. This will help reduce the possibility of damage.


  1. Turn off the engine. Place the engine start switch in the OFF position.

  2. If equipped, turn the battery disconnect switch to the OFF position. If there is no battery disconnect switch, remove the negative battery cable at the battery.

  3. Disconnect the J1/P1 and J2/P2 connectors from the ECM. Move the harness to a position that will not allow the harness to move back and contact any of the ECM pins.


    Illustration 5g01075639
    Use the example above. The current flow from the welder to the ground clamp of the welder will not damage any associated components.
    (1) Engine
    (2) Welding rod
    (3) Keyswitch in the OFF position
    (4) Battery disconnect switch in the open position
    (5) Disconnected battery cables
    (6) Battery
    (7) Electrical/Electronic component
    (8) Maximum distance between the component that is being welded and any electrical/electronic component
    (9) The component that is being welded
    (10) Current path of the welder
    (11) Ground clamp for the welder

  4. Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld. Make sure that the electrical path from the ground cable to the component does not go through any bearing. Use this procedure to reduce the possibility of damage to the following components:

    • Bearings of the drive train

    • Hydraulic components

    • Electrical components

    • Other components of the machine


    NOTICE

    Do not ground the welder to electrical components such as the ECM or sensors. Improper grounding can cause damage to the drive train bearings, hydraulic components, electrical components, and other components.

    Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld. This will help reduce the possibility of damage.


  5. Protect any wiring harnesses from the debris which is created from welding. Protect any wiring harnesses from the splatter which is created from welding.

  6. Use standard welding procedures to weld the materials together.

Welding on Machines Equipped with LiDAR


NOTICE

The varying current flow in welding operations results in electromagnetic radiation. The EMI radiation will be transmitted to any conductors that are positioned as antenna in the radiation field. This or any activity that can induce current will damage the sensor.


  1. Remove the electrical connections to the LiDAR sensor.

  2. Disconnect the M12 and Deutsch connector.

  3. Remove the ground straps that connect sensor to the machine ground.

  4. Keep sensor a minimum of 3.05 m (10 ft) away from the welding area and ground the sensor case to an earth ground that is not connected to the welder return.

    Note: Caterpillar recommends that the machine chassis is grounded, before the cables and ground straps are connected to the sensor.

Welding on Fuel Tanks and Hydraulic Tanks

The following information is not intended to replace any regulatory standards or practices of industries that have expert knowledge of handling hazardous substances.

Reference: National Fire Protection Association (NFPA), NFPA 326 "Standard for the Safeguarding of Tanks and Containers for Entry, Cleaning, or Repair"

Reference: American Welding Society (AWS), AWS F4.1:2007 "Safe Practices for the Preparation of Containers and Piping for Welding and Cutting"

------ WARNING! ------

Applying heat to a tank which has held flammable liquids, even when empty, can result in residual flammable liquid or vapor igniting with explosive force.

Personal injury or death can result from an explosion.

Do not weld or flame cut on any tank that has held flammable liquid without taking the proper precautions such as filling the tank with either inert gas or water.



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.



NOTICE

The fuel tank and/or hydraulic tank must be drained of all fuel and/or oil so that there is no residual fuel and/or oil left in the tank.



NOTICE

Do not put water in a hydraulic tank. Water can damage the valves in the hydraulic system.


Required Tooling

Table 12
Required Tooling 
Item  Part Number  Description 
Oxygen Indicator 
Combustible Gas Indicator 
1U-5490  Cleaner (de-greaser) 

The equipment is to be calibrated with a calibration gas that is appropriate to the potential hazard.

Calibrate the equipment prior to first use.

The adjustment of the equipment is to be checked daily before use.

The equipment is to be maintained in accordance to the manufacturer's recommendations.

Definitions

Hot Work: any work that is a source of ignition including open flames, cutting, and welding, sparking of electrical equipment, grinding, buffing, drilling, chipping, sawing, or other operation that create hot metal sparks or surfaces from friction or impact.

Inert Gas: any of the chemically inert gaseous elements of the helium group in the periodic table.

For purpose of tank cleaning, or repair, a gas that is nonflammable, chemically inactive, non-contaminating for the use intended, and oxygen-deficient to the extent required.

Inerting: a technique by which the atmosphere in a tank or container is rendered non-ignitable or non-reactive by the addition of an inert gas.

Qualified Person: a person designated by the employer or contractor, in writing, as capable by education or specialized training, or both, of anticipating, recognizing, and evaluating employee exposer to hazardous substances or other unsafe conditions. This person shall be capable of specifying the necessary control and protective action for worker safety.

Basic Precautions


NOTICE

The fuel tank and/or hydraulic tank must be drained of all fuel and/or oil so that there is no residual fuel and/or oil left in the tank.


Extreme caution shall be used when work is performed on a tank or a container that holds or has held flammable, combustible, or other hazardous substances.

Extreme caution shall be used when work is performed on a tank or a container that contains vapors related to the substances that are stored or were previously stored therein.

Before any work is performed on a tank or container that has held flammable, combustible, or other hazardous substances, the tank, or container shall be made safe.

The person conducting the work shall have a thorough understanding of the following:

  • The characteristics of the substance that is or was previously stored in the tank or container.

  • The potential health and safety risks associated with the work to be conducted.

  • The procedures for safeguarding the tank or container prior to conducting the work.

Preparing the Tank for Cleaning

Determination of hazardous characteristics of contents.

Before any tank or container is cleaned, the hazardous characteristics of the substance previously help by the tank or container shall be determined by a qualified person.

Unknown substances.

If the source and identity of the material in the container cannot be determined, and if chemical analysis cannot be performed, the tank or container shall be disposed of according to local, state, and federal regulations.

Designation of cleaning procedure.

A qualified person shall designate the cleaning procedure to assure that the cleaning can be performed safely in an environmentally responsible manner and can render the container free of all hazardous concentration of materials.

Tank or container location.

The tank or container shall be moved outdoors, if practical. If the tank or container is cleaned indoors, the room shall be well vented so that hazardous vapors will not accumulate and will be carried away from the worker's breathing zone quickly and safely.

Tank or container contents.

The tank or container shall be emptied and drained thoroughly, including all internal piping, traps, and standpipes. Sludge and sediment shall be removed. All residue and used cleaning agents shall be disposed of in an environmentally safe manner according to local, state, and federal regulations.

Cleaning Methods

Water cleaning.

Note: Water method for use on fuel tanks only.

Where the substance is known to be safely and readily soluble in water, the residue can be removed by completely filling the container with water and draining several times.

Hot chemical solution cleaning.

This method generally uses trisodium phosphate or a commercial caustic cleaning compound dissolved in hot water. Care must be taken to guard against injury from vapors, gases, or contact with the cleaning compounds. Suitable personal protective equipment (PPE) shall be used and adequate ventilation shall be provided.

Steam cleaning.

This method generally uses low-pressure steam and a hot soda or soda ash solution. Solution agitation is used to flush the inside surfaces, and steam is used to promote a good cleaning action. Care must be taken to avoid injury from vapors, steam, and cleaning solution. Suitable personal protective equipment (PPE) shall be used and adequate ventilation shall be provided.

Note: The tank and nozzle shall be grounded during steam cleaning to minimize the possibility of static charge buildup and spark discharge.

Chemical cleaning.

Use tooling (C) cleaner (de-greaser) to clean the tank or container.

When the tank or container holds deposits insoluble in water. Care shall be used in selecting a chemical solvent, some solvents may be hazardous as the deposits the solvents are intended to remove.

Note: If chlorinated solvents are used, all residue must be removed before welding or cutting begins.

Note: When selecting chemical solvents, consult the manufacturer of the material being removed. Chemical manufacturers may recommend a solvent to use and a detailed cleaning procedure.

Combination of methods.

Occasionally, combinations of the cleaning methods must be used. Care must be exercised when combining some of the cleaning methods to protect personnel and prevent hazardous reactions.

Preparing for Welding

The following guidelines ensure that the tank or container and the work area are safe for welding and cutting. The guidelines are intended to protect personnel and equipment by ensuring that the hazards are understood and adequate precautions are taken. The qualified person responsible for the work being performed on the tank or container shall ensure that the guidelines are followed.

Do Not Weld an Empty Fuel Tank.

Do Not Weld on a Closed Hydraulic Tank.

An empty fuel tank or hydraulic tank cannot be cleaned sufficiently to ensure that all the flammable vapors have been removed. Vapors remain even after cleaning with steam or washing with a caustic solution. Also, when caustic solutions are heated, caustic solutions can also be explosive. To prepare a fuel tank for welding, use one of the following procedures:

Safe Practices

The following steps must be taken to ensure that the work area and the tank or container are maintained safe for welding.

  1. The immediate area outside and inside the tank or container shall be cleared of all obstacles and hazardous materials.

  2. Personal protective equipment (PPE) and fire protection equipment shall be available, serviceable, and in position for immediate use.

  3. Ventilation shall be adequate for providing a safe work atmosphere prior to and during welding. Testing may be necessary to test for toxic or flammable vapors and to verify that the oxygen content of the atmosphere in the work area is maintained within acceptable limits.

    Where adequate ventilation is not available, an independent source of breathing air shall be provided.

  4. A qualified person shall inspect the tank or container to verify that the cleaning is adequate. All test equipment is to be suitable for the intended measurement. Prior to welding ensure that the atmosphere inside the tank or container is safe for welding.

  5. Use a calibrated and adjusted combustible gas indicator and test the tank or container for flammable vapors.

  6. Prevent pressure buildup in the tank or container during welding. Exhaust gases and other gases produced during welding shall be discharged in a safe and environmentally acceptable manner.

  7. Test the container for hazardous gases, fumes, and vapors periodically to ensure that the tank or container and the work area are safe during welding.

  8. Inert the tank or container. Maintaining the tank or container in a welding condition, free from flammable or explosive hazards by filling the tank or container with an inert medium such as water or inert gas.

  9. Inert gas method.

    Fill the tank or container with inert gas. When this method is used, the qualified person shall be informed of the percentage of inert gas that must be present and how to produce and maintain this percentage safely during welding, as well as be alert for suffocation hazards.

    These inerting guidelines are suitable for use with metal lined jacketed containers that might be difficult to clean thoroughly.

  10. Carbon dioxide method.

    Note: Portable carbon dioxide fire extinguishers cannot be used as a source of inert gas.

    When solid carbon dioxide is used, the solid carbon dioxide must be crushed and distributed evenly over the greatest area possible for rapid sublimation.

    Use a carbon dioxide indicator to measure the permitted oxygen percentage calculated from the percentage of carbon dioxide in the tank.

    Note: Use proper safety equipment and safe handling procedures when working with solid carbon dioxide.


    NOTICE

    Do not put water in a hydraulic tank. Water can damage the valves in the hydraulic system.


  11. Water Method.

    Note: Water method for use on fuel tanks only.

    Place the tank or container so that the tank or container can be kept filled with water within a few inches ( 25 mm (1.00 inch) to 75 mm (3.00 inch)) of the point where the welding is to be performed. Vent the space above the water level so the heated air can escape from the tank or container.

    Note: After welding on the fuel tank, the fuel tank must be drained and cleaned. Refer to the "Cleaning Methods" section for acceptable cleaning methods.

    Note: To remove the water from the tank perform the following Steps:

  1. Empty the water from the tank.

  2. Install the tank onto the machine.

  3. Fill the tank with fuel and let the machine stand without disruption for a minimum of 12 hours.


    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.


  4. After a minimum of 12 hours open the purge screw on the fuel tank, to drain any residual water and sediment that has settled in the bottom of the fuel tank. Close the purge screw when clean fuel begins to exit from the fuel tank.

  5. Drain the Fuel System Primary Filter (Water Separator) - Drain. Refer to Operation and Maintenance Manual.

  6. Continue to monitor and drain the Fuel System Primary Filter (Water Separator) - Drain as needed.

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