Red Seal Heavy Duty Equipment Technician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Zero energy verification

After isolating and locking out all energy sources, the technician confirms no stored energy remains by relieving pressure, blocking suspended parts, and attempting a start to prove the machine cannot move.

Confined space atmospheric limits

Entry testing requires oxygen between 19.5 and 23.5 percent, flammable gas below 10 percent of the lower explosive limit, and toxic gases such as hydrogen sulfide and carbon monoxide within regulated exposure limits.

Micrometer thimble resolution

On a metric micrometer, each thimble division represents 0.01 mm, so the reading is the barrel value plus the thimble number multiplied by 0.01, giving two-decimal precision.

Torque wrench usable range

Accuracy is normally specified over the upper 20 to 100 percent of scale, so a wrench should not be used below one-fifth of its capacity and is stored at its lowest setting.

Leak-down test interpretation

Pressurizing a cylinder at top dead center and listening at the intake, exhaust, and crankcase breather locates leakage past intake valves, exhaust valves, or piston rings respectively.

Diesel cranking speed requirement

Compression ignition needs sufficient cranking speed, typically 150 to 250 rpm, to create ignition heat, so a slow-turning starter can mimic a fuel or injection fault.

Torque converter stall speed

Stall speed is the engine speed reached with the output held stationary at full throttle; a reading above or below specification indicates an engine power, converter, or driveline fault.

Final drive ratio calculation

The final drive ratio equals the number of ring gear teeth divided by the number of pinion teeth; it determines the trade-off between machine travel speed and tractive effort.

Hydraulic horsepower formula

Hydraulic horsepower equals flow in gallons per minute multiplied by pressure in psi, divided by 1714; in metric units, kilowatts equal liters per minute times bar divided by 600.

Cylinder retraction force

Retraction force equals pressure times the annulus area, which is the bore area minus the rod area, so a cylinder pulls less force and retracts faster than it extends.

Battery open circuit voltage

A rested 12 volt lead-acid battery reads about 12.6 volts at full charge and roughly 12.2 volts at half charge; a 24 volt series pair reads about 25.2 volts when full.

Cranking voltage drop test

While cranking, measure voltage drop across each cable from battery positive to the starter and from the starter case to battery negative; each should stay below about 0.5 volts.

Air brake leak-down limit

With the engine off, brakes released, and system at governed pressure, leakage should not exceed about 3 psi per minute, which is roughly 20 kPa per minute.

Spring brake caging

Spring brakes are applied by a heavy spring and released by air pressure, so the spring must be mechanically caged with the proper tool before a chamber is removed.

Coolant pressure and boiling point

Raising cooling system pressure raises the boiling point by roughly 3 degrees Celsius for every 10 kPa of cap rating, so a 100 kPa cap adds about 30 degrees.

Exhaust backpressure diagnosis

Excessive backpressure measured upstream of the turbocharger or aftertreatment reduces power, raises exhaust temperature, and often indicates a restricted diesel particulate filter or catalyst.

Track chain pitch wear

Chain wear is measured as increased pitch, the distance between pin centers over several links, and a stretched chain requires new pins and bushings or complete chain replacement.

Multi-piece rim safety

Multi-piece rims are serviced only with the tire fully deflated and a restraining device in place, because a partially inflated assembly can separate explosively and cause fatal injury.

Severe duty service interval

Operation in dust, extreme cold, or continuous heavy load shortens service intervals, so the interval is set by hours, calendar time, or fuel used, whichever occurs first.

Fluid sample procedure

Samples are drawn at operating temperature from a running stream after the system is cycled, using a clean container, because cold or dirty samples give misleading wear metal results.

Plastigauge bearing clearance

A strip of plastic gauge is placed across the bearing journal, the cap is torqued, and the compressed strip width is compared to a printed scale to read oil clearance.

SAE and metric bolt grades

SAE bolt heads carry radial lines, with three lines for grade 5 and six for grade 8; metric bolts are stamped with property classes such as 8.8, 10.9, and 12.9.

Wet versus dry compression test

Adding oil to a cylinder and repeating the compression test raises pressure if rings or cylinder walls leak, but leaves pressure unchanged if valves or the head gasket leak.

Planetary gear ratio rule

With the ring gear held and the sun gear driving the planet carrier, the reduction equals one plus ring teeth divided by sun teeth; locking any two members gives direct drive.

Hydraulic cavitation versus aeration

Cavitation is vapor collapse from a restricted pump inlet or low oil level and causes noise and damage; aeration is entrained air from suction leaks and causes spongy, erratic operation.

ISO cleanliness code

The ISO code reports particle counts per size class, such as 18/16/13, and most mobile hydraulic systems are specified at that level or cleaner to protect pumps and valves.

CAN bus termination check

The CAN bus is a twisted differential pair terminated by two resistors of about 120 ohms each, so resistance measured across the bus with the key off should read about 60 ohms.

Alternator charging voltage

A healthy 12 volt system charges at about 13.8 to 14.4 volts and a 24 volt system at about 27.6 to 28.8 volts, measured at the battery with the engine running.

Slack adjuster pushrod stroke

With the brake fully applied, pushrod travel is measured and compared to the chamber stroke limit; excessive stroke reduces braking force and indicates worn shoes or misadjustment.

Aftertreatment DEF derate

Selective catalytic reduction injects diesel exhaust fluid to reduce nitrogen oxides, and an empty, frozen, or contaminated DEF tank triggers a power derate that limits machine operation.

Attachment pin clearance

Excessive clearance between attachment pins and bushings allows bucket or boom movement, reduces breakout force, and is corrected by measuring and replacing pins and bushings as a set.

Daily walk-around inspection

Before operation, the operator checks fluid levels, leaks, tire or track condition, guards, lights, horn, backup alarm, seat belt, and extinguisher, recording defects that must be corrected.