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HEAVY MECHANICAL TRADESFOUNDATION / LEVEL 1

Line J: Structural Components and Accessories Competencies J-1 and J-2

© 2016 by Industry Training Authority

This publication may not be reproduced in any form without permission by the Industry Training Authority.

Version 1, November 2016

ISBN 978-0-7726-6671-0

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Every effort has been made to secure copyright permission for the images used in this document.

AcknowledgmentsHeavy Mechanical Trades Project Working Group Writer: Mark ScorahReviewers: Lloyd Babcock, Rick Cyr, Bob Glover, Brian Haugen, Terry Lockhart, Paul Mottershead, Dave Wharf

Open School BCChristina Teskey, project managementDennis Evans, photography, illustrationBeverly Carstensen, print layoutJanet Bartz, art coordinationShannon Sangster, copyright managementMax Licht, illustrationOdette Hidalgo, illustrationGreg Aleknevicus, editingKeith Learmonth, editing

DisclaimerThe materials in these booklets are for use by students and instructional staff and have been compiled from sources believed to be reliable and to represent best current opinions on these subjects. These manuals are intended to serve as a starting point for good practices and may not specify all minimum legal standards. No warranty, guarantee, or representation is made by the Heavy Mechanical Articulation Committee of BC, the British Columbia Industry Training Authority or the Queen’s Printer of British Columbia as to the accuracy or sufficiency of the information contained in these publications. These manuals are intended to provide basic guidelines for heavy mechanical trades practices. Do not assume, therefore, that all necessary warnings and safety precautionary measures are contained in this booklet and that other or additional measures may not be required.

Please note that it is always the responsibility of any person using these materials to inform him/herself about the Occupational Health and Safety Regulation pertaining to his/her work. The references to WorkSafeBC safety regulations contained within these materials do not / may not reflect the most recent Occupational Health and Safety Regulation (the current Standards and Regulation in BC can be obtained on the following website: http://www.worksafebc.com).

We want your feedback! Please go to the BC Trades Modules website (www.bctradesmodules.ca) to enter comments about specific sections that require correction or modification. All submissions will be reviewed and considered for inclusion in the next revision.

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HEAVY MECHANICAL TRADES — FOUNDATION / LEVEL 1 3

Line J: Structural Components and AccessoriesCompetencies J-1 and J-2

Table of Contents

Competency J-1: Identify Protective Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Goals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Learning Task 1: Describe the Design and Function of Operator Protective Structures . . . . . . . . . 9

Competency J-2: Service Cab Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Goals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Learning Task 1: Cabs, Bodies, and Cab Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Learning Task 2: Repair Cabs, Bodies, and Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Self-Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Answer Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4 HEAVY MECHANICAL TRADES — FOUNDATION / LEVEL 1

J-1 PROTECTIVE STRUCTURES

COMPETENCY J-1IDENTIFY PROTECTIVE STRUCTURES

HEAVY MECHANICAL TRADES:LINE J—STRUCTURAL COMPONENTS AND ACCESSORIES

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1 7

Goals When you have completed the Learning Tasks in this Competency, you will be able to:

• identify cab protective structures on heavy equipment, trucks and transport vehicles• describe the regulations related to cab protective structures and their repair or modification• inspect cab protective structures

8 HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1


Notes

J-1 PROTECTIVE STRUCTURES LEARNINg TASk 1

LEARNING TASK 1

Describe the Design and Function of Operator Protective Structures

Machines, equipment and vehicles require structures that protect the operator from falling objects or rollovers. These structures must comply with standards outlined by WorkSafeBC and the BC Motor Vehicle Act.

Function of Protective Structures Protective structures may be identified by their function:

• falling object protective structures (FOPS)• rollover protective structures (ROPS)

Falling Object Protective Structures Machines and equipment may be outfitted with protective structures that provide protection from falling objects. Falling object protective structures (FOPS) are designed to deflect falling material. FOPS canopies deflect rocks and dirt from cabs on dump trucks and haul trucks. A FOPS canopy encloses the operator compartment on a forklift. FOPS canopies similar to those shown in Figure 1 and Figure 2 provide falling object protection and some protection should the machine tip on its side.

Figure 1 – FOPS Canopy

Notes


LEARNINg TASk 1 J-1 PROTECTIVE STRUCTURES

Figure 2 – FOPS Canopy

Rollover Protective Structure Heavy machinery is widely used in logging, mining, road-building and construction. Heavy-duty machines often operate on uneven ground and steep slopes. Soft, unstable ground can break away under the weight of a machine. These conditions present the danger of a machine rollover. In these work environments, machines are often equipped with rollover protection. The primary function of a rollover protective structure (ROPS) is to protect the operator if the machine should tip over. However, a rollover protective structure cannot provide protection if the operator falls out of the machine—for this reason a seatbelt should always be worn.

The machine shown in Figure 3 has a very simple rollover protective structure with minimal protection from falling objects.

Figure 3 – Simple ROPS


Notes


In more dangerous work environments, greater protection is required. For example, operating a machine on steep slopes in a forested area requires protection from tree branches and falling debris, rocks and soil. Steel mesh screens are used to surround the ROPS canopy and provide protection from these hazards (Figure 4).

Figure 4 – Rollover and Falling Object Protective Structures

Steel mesh on the rear of the canopy also protects the operator from injury if a wire rope on the winch breaks.

Protective Structures for Truck Cabs There are two basic types of protective structures for truck cabs:

• overhead cab guard• rear cab guard

Overhead Cab Guard In dump truck applications, falling object protection is designed as part of the dump box structure. This structure is primarily used to prevent material from falling on the operator’s cab while the truck is being loaded. The FOPS canopy shown in Figure 5 is an overhead cab guard designed as an integral part of the dump box.

Notes



Figure 5 – Dump Box FOPS Canopy

Rear Cab Guard In logging truck and semi-truck applications, operator protection is achieved with a rear cab guard. This type of structure is designed to protect the driver from loads that shift forward during accidents or sudden stops. The structure is mounted to the truck frame just behind the cab. This structure is also called a headache rack or chain rack. Mount locations for truck rear cab guards are shown in Figure 6 and Figure 7. If a rear cab guard can’t be mounted to the truck frame, a cab guard may be attached to the front of a flat deck trailer as a bulkhead.

Figure 6 – Cab Guard


Notes


Figure 7 – Cab Guard

Cab Protective Structure Mounting The vertical structural members of the ROPS canopy in Figure 8 are positioned closely around the operator compartment. The entire structure is moved to the machine to provide full operator protection in a rollover.

Figure 8 – ROPS Canopy with Side Guards

The protective structures used to mount FOPS and ROPS to machines are engineered to meet strict requirements. The safety standards are established by agencies such as the Society of Automotive Engineers (SAE) as mandated by WorkSafeBC. The mounting systems are designed to withstand considerable

Notes



impact forces and have the ability to transfer those forces to the main frame of the machine without collapsing. These structures are designed to provide a good field of vision for the machine operator and not interfere with working attachments.

FOPS and ROPS components are designed and engineered to meet strict safety standards. Damaged components must be replaced with parts supplied by companies that have the engineering skills to meet the required safety standards. Mounting components for ROPS and FOPS systems cannot be modified or altered in any manner.

Truck Cab Protective Structure Mounting The headache rack mounting structure rests on the top flange of the truck frame close to the rear of the cab. The mounting structure is usually held in place by the clamping force of large U-bolts that extend below the lower flange of the frame. Angle brackets that bolt through the web of the frame are also sometimes used.

Truck cab protective structures are engineered to withstand severe impacts in the event of an accident and should not be modified without approval from the manufacturer. Care must be taken to avoid drilling or welding heat-treated truck frame flanges. Drilling or welding on truck frame flanges will weaken the frame and increase the possibility of frame rail breakage.

Some off-road haul trucks and construction site dump trucks have the FOPS canopy attached as part of the dump box structure (Figure 9).

Figure 9 – Haul Truck FOPS Structure


Notes


Installing Lights and Accessories on Cab Protective Structures The metal frame of a cab protective structure is a tempting place to attach machine accessories or lighting. All modifications to a cab protective structure can only be made with approval from the structure’s manufacturer. Light and accessory brackets are often added to a protective structure during the manufacturing process to avoid the need for work site modification. In some cases, light brackets can be attached to the front of a canopy without affecting its strength. Do not weld or drill the main upright support members of a cab protective structure—heat from a weld or removing material with a drill will affect its structural strength.

Cab protective structures may surround an enclosed cab that has a heater or air-conditioning unit. For these machines, a roof-mounted condenser may be attached to the canopy. Air-conditioning components should only be attached to brackets provided by the manufacturer. Care should be taken to avoid damage to air-conditioning components while performing service work on the canopy.

Cab Protective Structure Inspection and Repair Cab protective structures should be inspected whenever the equipment is scheduled for major service or maintenance. Small dents and scratches may be cleaned up and painted, but structural supports with major damage should be replaced. All repair and replacement must be performed to meet the manufacturer’s standards. Labels may be found on protective structures to indicate repair recommendations (Figure 10).

Figure 10 – Forklift FOPS Canopy with Warning Label for Repair Standards

Notes



Operator protective structures should be inspected for cracks, impact damage and improper mounting of lighting and accessories. Mounting a fire extinguisher on a main support member of a canopy will weaken the structure (note the location of the fire extinguisher in Figure 11).

Figure 11 – Fire Extinguisher on Forklift

Welding repairs to protective structures should only be performed by a qualified welder (with approval of a qualified engineer) and should meet the manufacturer’s load test standards. If load test standards can’t be met, the canopy should be replaced.

Glass enclosures such as the one shown in Figure 12 offer additional protection from workplace hazards and provide a comfortable environment for the machine operator. Safety windows must meet ANSI standard Z26.1-1990 according to WorkSafeBC regulations.

Figure 12 – Enclosed Cab with Safety Glass


J-1 PROTECTIVE STRUCTURES SELF-TEST 1

SELF-TEST 1

1. What type of protection does a FOPS canopy provide?

2. What type of protection does a ROPS provide?

3. What extra precaution must an operator take to fully benefit from the protection offered by FOPS and ROPS?

4. What additional guard can be added to the ROPS canopy to protect the operator from side hazards such as tree branches or debris?

5. List the two types of cab protective structures found on heavy trucks.

6. From what hazard does a rear cab guard protect the operator?

7. If a ROPS or FOPS canopy has major structural damage, what is the recommended repair procedure?

J-2 SERVICE CABS

COMPETENCY J-2SERVICE CAB STRUCTURES

HEAVY MECHANICAL TRADES:LINE J—STRUCTURAL COMPONENTS AND ACCESSORIES


Goals When you have completed the Learning Tasks in this Competency, you will be able to:

• identify cab types on trucks and heavy equipment• identify cab components• operate cab components for testing and repair• service cabs, bodies and components• inspect cab components on trucks and heavy equipment• repair and replace cab components• adjust and lubricate cab components• describe lockout procedures for trucks and heavy equipment


Notes

J-2 SERVICE CAbS LEARNINg TASk 1

LEARNING TASK 1

Cabs, Bodies and Cab Components

Trucks and machinery work in a wide variety of conditions. Cab design is usually suited to the work environment and is engineered to make the operator comfortable and efficient.

To service cabs, knowledge of the following areas is required:

• cab and body types for heavy machinery• cab and body types for heavy trucks• cab components• operation of equipment and cab controls

Cab and Body Types for Heavy Machinery Heavy machinery cabs may be either fully enclosed or open. Both must provide falling object protective structures (FOPS) and rollover protective structures (ROPS).

The severe working environment of most heavy machinery requires that equipment cabs be designed to protect the operator from hazards as well as provide good all-round visibility. The backhoe shown in Figure 1 is an example of these features—large safety glass windows provide excellent visibility with the protection of a ROPS canopy.

Figure 1 – Backhoe with Enclosed Cab

Notes


LEARNINg TASk 1 J-2 SERVICE CAbS

A complete cab enclosure provides a comfortable, dust-free environment for the operator. Equipment cabs are often supplied with heating and air-conditioning units. Due to the large glass areas, heat from the sun can raise the cab temperature to an uncomfortable level. Air conditioning provides relief from this heat. Air filters installed in HVAC units remove dust from the air.

The seat shown in Figure 2 swivels to the rear for rear-facing backhoe operation. The rear-facing window and side windows latch in the open position if the operator chooses to be exposed to outside air.

Figure 2 – Swivel Seat for Rear-facing Operation

Where the operator is exposed to hazards from the side and rear of the machine, protective screens are installed over the windows (Figure 3).

Figure 3 – Enclosed Cab with Additional Wire Mesh Hazard Protection


Notes


All glass used in mobile equipment cabs must meet WorkSafeBC requirements as outlined in Section 16.11 regarding mobile equipment glazing. Windows on mobile equipment must be safety glazing meeting ANSI standard Z26.1-1990. Tempered glass meeting ANSI/SAE Z26.1-1990 may be used as a windshield.

When the expense of an enclosed operator compartment is not considered necessary, the minimum requirement of a FOPS or ROPS canopy must be met (Figure 4). This option does not provide much in the way of operator comfort, but minimum safety requirements are maintained.

Figure 4 – Compactor with Minimum Cab Enclosure

Cab and Body Types for Heavy Trucks Trucks and equipment used on roads and highways have their own visibility and safety requirements. Truck drivers often work very long days—comfortable cabs help maintain driver alertness. Comfortable seating is required for the driver and sometimes a co-driver.

When team drivers share a truck, having a sleeper unit mounted behind the cab allows one driver to sleep while the other drives the truck. The lengths of driver work days are regulated by provincial legislation. Individual drivers are required by law to rest after reaching their allowed number of work hours each day. For individual drivers, a sleeper unit is mounted behind the cab so rest breaks can be taken.

Notes



Figure 5 – Tractor with Sleeper Unit

A tractor equipped with a sleeper unit can consume a lot of electrical energy during an operator’s rest break. To avoid running the large diesel engine for power, this type of rig is often equipped with an isolated battery or an independent frame-mounted generator to supply power for interior lights, refrigerators, microwave ovens and other amenities.

A more basic type of tractor is equipped with a day cab only. This type of tractor is used only for short hauls and is sometimes referred to as a town tractor (Figure 6).

Figure 6 – Town Tractor with Day Cab


Notes


Cab Components Cab components are designed to help the operator work safely and efficiently during a shift. An examination of these components will help you understand how each one affects the operation of the vehicle:

• cab shell ▸ heavy machinery cabs ▸ truck cabs with sleeper compartments

• cab mounts ▸ fixed ▸ air ride

• doors• windows• ventilation systems• hood, cowl, engine compartment• seats

▸ seatbelts ▸ supplemental restraint systems

Cab Shell Cab design varies with the different jobs each machine is required to do, and the cab components are designed specifically for each particular work environment:

• heavy machinery cab• truck cabs with sleeper compartment

Heavy Machinery Cabs The metal frame of a heavy machine cab is a structure that encloses and protects the operator. It’s also the structure that provides a mounting surface for most cab components. Correct alignment of the cab frame is important for structural integrity, proper operation of doors and windows and proper operation of the machinery itself. Repairs to the cab framework must meet the manufacturer’s specifications. The cab of a heavy machine may appear to be mostly made of glass, but the glass will be supported by a strong steel ROPS framework.

The cabs of highway tractors, logging trucks and construction trucks are generally fabricated with panels of formed steel to which doors and windows are attached. Logging trucks, dump trucks and other construction trucks have additional reinforcement in the cab framework to withstand the shock loads of off-road operation. Windshields in many current highway and off-road trucks contribute to the structural strength of the cab. Particular care should be taken during windshield installation. Most windshields are now installed using high-strength urethane glues. Due to the importance of the windshield for operator safety, windshield installation should only be performed by properly trained persons. Windshields should be safety glass meeting the ANSI/SAE Z26.1-1996 standard.

Notes



Truck Cabs with Sleeper Compartments The sleeper compartment on highway tractors makes the driver feel more at home on the road and contributes to aerodynamic efficiency of a tractor semi-trailer. The sleeper compartment has a bed so that the driver can pull over at rest areas to sleep. The sleeper unit often has other amenities such as a refrigerator, microwave oven and small television. The cab and sleeper may be a single integral unit, or they may be mounted to the truck frame independently. When mounted individually, the sleeper and cab are connected with a flexible rubber tube or bellows. (This style of sleeper mount is now uncommon and most often found on older-style tractors.)

The demand for improved fuel economy has resulted in more streamlined cab and sleeper units. On new highway tractors, the sleeper and cab are fastened together as one integral unit with a shared mounting system attached to the truck frame. This improves airflow around the outside of the cab, lowers wind resistance and improves fuel economy. To further improve fuel economy, fairings are often attached to the rear sides of the sleeper to close the side gap between tractor and trailer. Fairings may also cover side-mount fuel tanks and extend around and below the front bumper. Even the tractor itself will have a more aerodynamic and streamlined hood (as opposed to the classic square-nosed hood of traditional tractors) in an effort to further improve fuel efficiency (Figure 7).

Figure 7 – Aerodynamic Cab and Sleeper

Cab Mounts Cab mounts are the components that secure the cab body to the truck frame. There are two types of cab mount:

• fixed cab mount• air ride cab mount


Notes


Fixed Cab Mount Fixed cab mounts are used on most heavy machinery cabs and less-expensive truck cabs. Fixed mounts generally consist of a metal bracket mounted on the truck frame and a bracket on the cab (Figure 8). The two brackets are cushioned with a round rubber isolator. The rubber isolator is sandwiched between the metal mount brackets with a single large bolt. Solid mounts require little maintenance and are easily replaced when they wear out.

Figure 8 – Fixed Cab Mount

Air Ride Cab Mount Air ride cab mount systems are used on most modern semi-tractors and most construction and logging trucks. Flexible rubber cushions filled with compressed air support the weight of the cab. The cushion effect of the air spring provides a softer and smoother ride. The height of the cab air suspension is controlled by an air ride height control valve. The air springs and height control valve are mounted to the truck frame under the cab or sleeper (Figure 9).

Figure 9 – Air Ride Cab Mount



Doors Doors are a major part of the cab structure. Doors contribute greatly to operator safety and must always be properly adjusted and maintained. Due to visibility requirements, heavy equipment cab doors are designed quite differently from truck doors. The major component of the equipment cab doors shown in Figure 10 is glass.

Figure 10 – Large Glass Component of Heavy Equipment Cab Doors

Heavy equipment moves at slower speeds, and it’s important that the operator have a clear view of the ground so that ground-engaging tools can be observed.

Latches are used to hold doors firmly in place while the equipment is operated. Proper adjustment of latches is very important for sealing the cab and maintaining door security. Latches can also secure the door in the open position if desired (Figure 11).

Figure 11 – External Door Latch Used to Hold Door Open

The external door latch shown at the left in Figure 11 latches to the loop shown at the right of Figure 11 to hold the door securely open. A release mechanism is usually located in the cab or door to release this external latch.


Notes


Cab doors usually swing on a pair of pin-style hinges or a single long piano-style hinge. Both types are adjustable and will be examined more closely in Learning Task 2 when dealing with door adjustment.

Trucks doors are constructed from formed steel panels. They have tempered glass windows that open and close by moving up and down in a window track. This type of door window may be serviced and adjusted by a heavy truck repair technician. Proper door adjustment ensures a good airtight seal when the door is closed. (A tight seal around the door frame is important for driver comfort and efficient operation of the cab ventilation system.)

Windows All glass used in heavy equipment cabs must meet strict SAE and ANSI standards. WorkSafeBC regulations govern the glass standard for use in mobile equipment. WorkSafeBC OHS Regulation 16.11 states that safety glass meeting the ANSI Z26.1-1990 standard must be used on heavy equipment. Tempered glass meeting the ANSI Z26.1-1990 standard may be used on equipment windshields. Polycarbonate windows meeting ANSI Z26.1-1990 may also be used. All windows must be tagged to indicate that safety standards have been met.

Windshields are installed using high-strength urethane glue. Special tools are required and windshields should only be installed by properly trained technicians. Door windows are usually made of tempered glass and may be replaced by a truck repair technician.

Ventilation Systems When a machine is operating with the doors closed and securely sealed, proper operation of the ventilation system is very important. A modern cab ventilation system usually draws fresh air in through an air filtration system to remove dust and moisture before the air is passed through the cab’s HVAC unit. In addition to maintaining a comfortable temperature and clean air, the ventilation system also defrosts and defogs the cab windows on cold, moist days.

Although the ventilation systems for both heavy equipment and heavy trucks perform similar functions, with trucks a large volume of air may be moved by the ventilation system (particularly on highway tractors with a sleeper unit).

Notes



Hood, Cowl, Engine Compartment To complete the truck body, a front hood with integral side fenders is used to cover the engine and steering axle wheels. The hood is usually made of fibreglass. The front of the hood pivots on hinges mounted to the truck frame just behind the front bumper. The front bumper of the truck is also mounted to brackets on the front of the frame. Alignment of the hood and bumper can be achieved by moving an adjustable hood hinge (Figure 12).

Figure 12 – Adjustable Hood Hinge and Bumper Mount Bracket

The hood and front fender assembly is hinged at the front and drapes over the front cowl of the cab. Hood latches attached to the rear of the hood hold it firmly to the front of the cab. The alignment of the hood and bumper is important because they’re used to attach lighting and other accessories. Mud flaps are usually mounted to the rear of the front fender to prevent road gravel from damaging the fuel tanks mounted on the frame below the cab.

A grill mounted to the front of the hood allows air to flow through the radiator and protects it from gravel and road hazards. During summer, a bug screen (sometimes referred to as a summer front) is placed over the grill—this prevents the radiator fins from being plugged with dead insects. During winter, a grill cover called a winter front is sometimes used to help maintain the proper operating temperature in the engine. Winter fronts are less common than they once were—blocking airflow through the grill reduces the efficiency of the air cooler and reduces available engine horsepower.

The design of truck and equipment hoods is a key contributer to engine performance. Efficient airflow under the hood is very important for maintaining proper engine coolant temperatures. Care must be taken when making repairs to fan shrouds and hood recirculation shields. Note the air vents in the front and rear of the engine compartment hood on the tele-handler in Figure 13.


Notes


Figure 13 – Engine Hood on Tele-handler

Seats The operator’s seat in a heavy machine or heavy-duty truck is one of the most important components in the cab. The operator must be comfortable sitting in the seat for extended periods. Most seats have some sort of suspension system to cushion the operator from shock loads while operating the machine on a rough road or work site. On machines and trucks with a compressor and air system, the seat suspension system will have an inflatable air spring that allows the driver to adjust the desired level of cushioning. On machines not equipped with an air compressor, the seat is generally equipped with a spring suspension.

Seats have a wide range of adjustments to maintain operator comfort. If operator comfort cannot be achieved, use caution when relocating or replacing a seat. Operator seats are stress- and crash-tested to withstand the forces encountered in a collision. Cab floors are reinforced in the seat mounting area. Changing the location or mounting fasteners may not meet crash test standards. Seatbelts must be anchored so that they’re not affected by the seat suspension system. On equipment where the operator must face the rear of the machine during stationary operation (e.g., a backhoe), the operator seat may swivel 180 degrees.

Seatbelts Safety components such as seatbelts and supplemental safety restraints are often overlooked since they don’t affect performance and don’t prevent a machine from doing the job it’s designed to do. Furthermore, seatbelts provide years of service without failure. However, repairs to safety components are required to comply with WorkSafeBC rules. When repairs are needed, very strict safety protocols must be followed. Seatbelts and seatbelt anchors go through stringent engineering tests to comply with safety standards. When seatbelts are removed for replacement or to access another part of the cab, consult a

Notes



service manual. If seatbelt anchor bolts have to be replaced, do so only with bolts specified by the equipment manufacturer and tighten them to the torque specified in the service manual.

Supplemental Restraint Systems Supplemental restraint systems (SRS) such as airbags are becoming more widely used in heavy trucks. Although not yet mandatory in trucks, they’ve been proven to significantly reduce injury in the event of a serious crash. Airbags are most effective when a seatbelt is used at the same time. Airbags may be mounted in the steering column to protect the driver or in the right dash panel to protect the passenger. Airbags may also be deployed from the side of the seat to protect from rollover and side impact. Airbag deployment is controlled by the airbag control unit (ACU).

The ACU receives input from two sensors:

• crash sensor – senses the rate of deceleration• safing sensor – senses only deceleration

The two sensors are connected in series. Both sensors must send a signal to the ACU to trigger deployment of the airbag. When crash conditions for deployment have been met, the ACU sends a signal to an igniter or heating unit called a squib. The heating element ignites sodium azide pellets, causing a chemical reaction that produces a large volume of nitrogen gas and instantly inflates the airbag. The entire sequence from crash to inflation takes about 100 milliseconds (0.1 seconds). After inflation, the airbag deflates in about 0.5 seconds.

Certain steering column repair procedures require airbag removal; consult a service manual before proceeding with the repair.

Accidental discharge of the airbag may occur if proper repair procedures are not followed.

Airbag igniters get their ignition signal from a charged capacitor. Time is required for capacitors to discharge before removing an airbag module from the steering column. Allow 30 minutes after the power has been disconnected from the module for the capacitors to discharge.


Notes


Operation of Equipment and Cab Controls It’s important that you be able operate a machine and cab controls in order to diagnose equipment problems. Operating a machine in working conditions is sometimes required to confirm a system failure or to confirm the machine operates properly once the repair has been completed. Service manuals and operator’s manuals are a recommended source of information for safe equipment operation and testing procedures.

With the complexity of today’s electronically controlled trucks and equipment, a good understanding of how machines and controls operate is essential. Injury may result and damage may occur if safe operating procedures are not followed when testing equipment during the repair process.

There is no Self-Test for this Learning Task.


Notes


LEARNING TASK 2

Repair Cabs, Bodies and Components

As with other components on trucks and heavy equipment, it’s common for cab and body components to wear out over time. When this happens, these components must be repaired or replaced. Routine maintenance and adjustment will increase the operating life of the machine.

A normal maintenance plan should involve the following procedures:

• inspection• adjustment• lubrication• replacement and installation

Inspection Part of a vehicle maintenance plan is a regular inspection of components that wear or require adjustment. The machine operator is often the best source of information regarding what to check during an inspection—the operator spends more time in the machine than anyone else. Much information can be learned by reading pre-trip reports or listening to comments on the vehicle’s condition at the end of a shift.

For example, the operator may complain of a drafty cab or a door that does not close properly. Use that information and proceed to check for a cause. If the door does not appear to close, check the adjustment of latches and hinges. Missing or torn weather-seal may result in a leak and cause the door to feel loose when in the closed position replacing the seals will make the door tight and secure. With repeated use, door latches (Figure 1) and striker pins may come out of adjustment. Loosening and moving the striker pin will allow the door to close more securely.

Notes



Figure 1 – Door Latch

Inspection of components under the hood of a truck or piece of equipment is very important, but hood attachments are often ignored. One example is to look behind the grill to see if leaves or debris are trapped there and preventing clean airflow through the radiator. Are recirculation shields tight and in the proper position (Figure 2)? (Recirculation shields direct airflow through the radiator—they must be in place for efficient engine cooling.) Are hood mounts tight and secure? Alignment of the hood, fan shrouds and recirculation shields is an important factor contributing to efficient engine cooling.

Figure 2 – Fan Shroud and Recirculation Shields


Notes


Adjustment There are many adjustments necessary on cab components, but one of the most common is to doors and their latches.

The door latch mechanism is usually mounted on slotted holes to allow minor adjustments (Figure 3). The striker pin may also be loosened and moved slightly. If a cab door does not seal properly, the fault could be in way the door hinges are mounted in the door frame. When a cab door is closed, there should be an even gap around the door between its frame and the cab. The profile of the door should match the contour of the cab. If not, the door hinges may require adjustment.

Figure 3 – Adjustable Door Hinge

Lubrication Most cab components are designed to operate with minimal lubrication—excess lubrication has a tendency make a mess in the cab and stain the operator’s clothing. If lubrication is required in or on a cab assembly, it should be applied sparingly. Always check the service manual for recommended lubrication procedures.

Cab door hinges are a component that does require periodic lubrication, particularly piano-style hinges (Figure 4).

Notes



Figure 4 – Piano-style Door Hinge

Piano-style door hinges are less common than they once were. The outside of the hinge is exposed to the weather and has a tendency to rust. Without frequent lubrication, it’s noisy and has a tendency to seize up. Most new vehicles use a pair of pin-style hinges that are better protected from the weather.

Replacement and Installation Replacement of cab components requires greater attention to detail and cleanliness than repair work performed on other parts of the machine.

Most modern vehicles and equipment have electronic dash controls—wear a ground strap when working on these components to avoid static discharge.

A commonly replaced item on trucks and heavy equipment is the windshield and other glass panels. Glass replacement requires special training and special tools. Damage to the cab or cab interior may result if proper repair procedures are not followed. Most windows on newer vehicles are bonded in place with urethane glue, and the windshield contributes part of the structural strength of the cab.

Equipment owners may want to replace broken windows with Plexiglas or polycarbonate panels because they’re usually less expensive than safety glass. However, they may not meet WorkSafeBC regulations or required motor vehicle safety standards. Plastic windows must meet WorkSafeBC standards if they are to be used. Confirm that all glass panels meet the recommended ANSI/SAE Z26.1 standards before installing them on a vehicle. Any vehicle or machine manufactured after 2002, or any glass panels replaced after 2002, must have a sticker on the window to identify the certification level of the panel.


Notes


Installing accessories on a machine or truck requires some thought and care. Installing extra lighting or other accessories on the cab of a machine may affect the structural integrity of a ROPS or FOPS canopy; follow the manufacturer’s recommendations when adding accessories. Adding accessories to a truck is no less complicated. Highway tractor units with sleepers often have aftermarket accessories such as refrigerators and power inverters, and these require ventilation for cooling. Airflow around these devices is important and should be considered during the installation process.

Lockout Tags Workplace safety must be a primary concern throughout the entire workday. When service or repair work is being performed on a truck or piece of heavy equipment, lockout tags must be applied to that unit (Figure 5). Lockout tags are generally applied to key components in the cab to prevent accidental operation of the machine while repair work is being performed. Lockout tags should be applied by the technician performing the repair work and only be removed by that technician once repair work is completed. Only the person who applied the lockout tag should remove it. Do not work under the protection of another technician’s lockout tag—each technician must apply their own tag.

Figure 5 – Lockout Tag Placed on Battery Disconnect Switch


SELF-TEST 2 J-2 SERVICE CAbS

SELF-TEST 2

1. Where the operator is exposed to hazards from the side or rear of a machine, what is installed for protection?

2. What industry safety standards must the glass in enclosed cabs meet?

3. Why are fairings added to truck cabs with sleeper compartments?

4. What type of cab mount provides a softer, smoother ride?

5. What two safety features are found in truck cabs to protect a driver in the event of an accident?

6. If an operator reports drafts in the cab and a door that doesn’t close properly, what could be the cause?

7. What safety procedure is required while repair work is being done on trucks and heavy equipment?


Answer Key Line J: Structural Components and AccessoriesCompetencies J-1 to J-2Table of ContentsCompetency J-1: Identify Protective Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Self-Test 1 44

Competency J-2: Service Cab Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Self-Test 1 44Self-Test 2 44


ANSWER KEY COMpETENCY J-1: IDENTIFY pROTECTIVE STRUCTURES

Competency J-1: Identify Protective StructuresSelf-Test 11 falling objects

2 roll-over

3 wear a seatbelt

4 steel mesh screens

5 i overhead cab guard

ii rear cab guard

6 loads that shift forward during accidents or sudden stops

7 All structural supports with major damage should be replaced with a new part from the equipment manufacturer

Competency J-2: Service Cab StructuresSelf-Test 1There are no questions for this Learning Task

Self-Test 21 protective screens

2 WorkSafeBC standards and ANSI standard Z26 1-1990

3 to improve fuel economy

4 air ride cab mounts

5 i seatbelts

ii airbags

6 missing or torn seals or improperly adjusted door latches

7 lockout tags must be applied

Heavy Duty Mechanical Lines and CompetenciesLine A Common Occupational Skills Line F Trailer

A-1 Use Safe Work Practices F-1 Service Landing Gear and Trailer AccessoriesA-2 Apply Occupational Health and Safety F-2 Service and Repair Coupling SystemsA-3 Use Environmental Practices F-3 Service, Diagnose, and Repair Trailer Body ComponentsA-4 Use Hand Tools, Power Tools, and Shop Equipment F-4 Service, Diagnose, and Repair Trailer Heating andA-5 Use Fasteners and Fittings Refrigeration SystemsA-6 Lift and Support Loads A-7 Operate Equipment Line G Heating, Ventilation and AirA-8 Use Shop Resources and Record Keeping Practices G-1 Describe Heating and Air Conditioning FundamentalsA-9 Service Winch Wire Rope G-2 Diagnose and Repair Heating andA-10 Identify Lubricants Air Conditioning SystemsA-11 Service Bearings and Seals A-12 Apply Math and Science Line H Engines and Supporting SystemsA-13 Use Electronic Media H-1 Describe Engine FundamentalsA-14 Use Cutting and Welding Equipment H-2 Service Engine Support SystemsA-15 Prepare Job Action H-3 Diagnose and Repair Engine Support SystemsA-16 Describe Diagnostic Procedures H-4 Service Diesel Fuel Supply SystemsA-17 Prepare for Employment H-5 Diagnose and Repair Diesel Supply Systems H-6 Service Gasoline Fuel Systems

Line B Brakes H-7 Describe Alternative Fuel SystemsB-1 Service and Repair Hydraulic Brakes H-8 Diagnose Engines and ComponentsB-2 Service and Repair Hydraulic Power Brakes H-9 Remove and Install Diesel EnginesB-3 Service and Repair Air Brakes H-10 Repair Engines and Components H-11 Describe Diesel Fuel Injection Fundamentals H-12 Diagnose and Repair Mechanical Fuel

Line C Hydraulics Injection SystemsC-1 Describe Hydraulic Systems H-13 Diagnose and Repair Electronic Diesel Fuel SystemsC-2 Service Hydraulic Components H-14 Diagnose and Repair Diesel Emission SystemsC-3 Diagnose and Repair Advanced Hydraulic Systems H-15 Diagnose and Repair Engine Brakes H-16 Service, Diagnose, and Repair Electronic

Line D Electrical Ignition SystemsD-1 Describe Electricity D-2 Use Electrical Testing Instruments Line I PowertrainD-3 Service and Diagnose Batteries I-1 Describe Power Transfer SystemsD-4 Service Charging Systems I-2 Service ClutchesD-5 Diagnose and Repair Charging Systems I-3 Diagnose and Repair ClutchesD-6 Service Starting Systems I-4 Service Manual TransmissionsD-7 Diagnose and Repair Starting Systems I-5 Diagnose and Repair Manual TransmissionsD-8 Service Electrical and Electronic Circuits I-6 Diagnose and Repair Automated TransmissionsD-9 Diagnose and Repair Electrical Components I-7 Service Torque Converters and Dividers and Systems I-8 Service Powershift and Automatic TransmissionD-10 Diagrnose and Repair Electronic Compoments I-9 Diagnose and Repair Automatic Transmissions and and Systems Torque ConvertersD-11 Diagrnose and Repair Vehicle Management Systems I-10 Diagnose and Repair Powershift TransmissionsD-12 Service, Diagnose, and Repair Hybrid Systems I-11 Service DrivelinesD-13 Service, Diagnose, and Repair Electric Drive Systems I-12 Diagnose and Repair Drivelines I-13 Service Drive Axles

Line E Suspension and Steering I-14 Diagnose and Repair Drive AxlesE-1 Service and Diagnose Tires, Wheels, and Hubs I-15 Service Final DrivesE-2 Service Steering Systems I-16 Diagnose and Repair Final DrivesE-3 Diagnose and Repair Truck Hydraulic Assisted I-17 Diagnose and Repair Driveline Retarders Steering Systems I-18 Diagnose and Repair Winches E-4 Service, Diagnose, and Repair Machine I-19 Diagnose and Repair Power Takeoffs and Suspension Systems Transfer CasesE-5 Remove and Install Undercarriage I-20 Remove and Install TransmissionsE-6 Diagnose and Repair Frames I-21 Remove and Install Driveline and DifferentialsE-7 Align Vehicle I-22 Remove and Install Final DrivesE-8 Diagnose and Repair Wheeled Equipment Steering E-9 Diagnose and Repair Track Machine Steering Line J Structural Components and AccessoriesE-10 Diagnose and Repair Undercarriage J-1 Indentify Protective Structures J-2 Service Cab Structures J-3 Repair Advanced Cab and Body Structures J-4 Diagnose and Repair Working Attachments J-5 Diagnose and Repair Pnuematic System

heavy mechanical trades · heavy mechanical trades— foundation / level 1 15 ... the metal frame...

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