Construction Plant Fitting flashcards

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

Relief valve function

It limits maximum system pressure by diverting flow to tank when the set pressure is reached, protecting components and setting the working pressure of the circuit.

Pump displacement vs flow

Displacement is the volume moved per revolution; flow equals displacement times speed, so a worn pump loses flow at pressure but may still show normal flow at no load.

Cylinder extend force formula

Force equals system pressure multiplied by full bore area. For a 100 mm bore at 200 bar this is roughly 157 kN, ignoring friction and back pressure.

Cylinder retract force

Retract force equals pressure times the annulus area, which is bore area minus rod area, so retract force is always lower than extend force for the same pressure.

Hydraulic hose pressure rating

Working pressure must be at least four times the maximum continuous system pressure in pulsating plant circuits; burst rating is not used for selection.

ISO 4406 cleanliness code

A three-number code counting particles above 4, 6 and 14 micrometres per millilitre; typical plant target is 18/16/13, tighter for proportional or servo systems.

Aerated hydraulic oil symptoms

Foamy oil, spongy or jerky cylinder motion, noisy pump and overheating; causes include low oil level, loose suction fittings and worn shaft seals admitting air.

Hydraulic accumulator isolation

Accumulators store pressure energy after the pump stops; bleed them to zero and verify at the gauge before opening any line or fitting on that circuit.

Torque wrench limitations

It measures applied torque, not bolt preload; friction from threads and under-head surfaces varies preload, so lubricant condition and the maker's table must be followed.

Torque-to-yield bolts

These bolts stretch plastically during tightening and must be replaced after removal; reusing them risks loss of clamp load and joint failure.

Diesel cranking voltage check

During cranking, battery voltage on a 12 V system should stay above about 9.6 V at the battery posts; lower values point to battery, cable or starter faults.

Air in diesel fuel lines

Symptoms are hard starting, misfire and white smoke; bleed the low-pressure side and injector lines per the maker's procedure after any filter or line work.

Cooling system pressure cap

The cap raises coolant boiling point by roughly 3 degrees C per 0.1 bar; a weak cap allows boiling under load while the engine is fine at idle.

Glycol coolant mix ratio

A 50/50 glycol-to-water mix gives freeze protection near minus 37 degrees C and raises boiling point; stronger mixes reduce heat transfer and are not automatically better.

Rated capacity chart basis

Charts assume level firm ground, correct tyre pressure or full outrigger extension and no wind load; capacity drops rapidly as load radius increases.

Load moment indicator role

It warns and cuts motion when load or radius approaches the chart limit, but it is an aid, not a substitute for reading the rated capacity chart.

Outrigger ground bearing

Outrigger pads spread load; soft or sloping ground reduces effective support and can cause overturning even when the chart load is respected.

Lockout tagout sequence

Isolate all energy sources, including hydraulic pressure, gravity loads and springs, then lock, tag and verify zero energy at the point of work before disassembly.

Blocking raised implements

Any raised loader arm, blade or mast must be mechanically blocked or lowered to the ground before work beneath it; hydraulics alone are not a support.

Roller chain wear check

Measure elongation over a set number of links against the maker's limit, usually around 1.5 to 2 percent; beyond that the chain and often sprockets are replaced.

Chain sag adjustment

Correct sag is set by the maker, commonly 2 to 4 percent of span; too tight loads bearings and too loose causes snatch and jumping on sprockets.

Sprocket wear pattern

Worn sprockets show hooked or sharpened teeth; fitting a new chain to worn sprockets accelerates chain wear, so both are usually replaced together.

Bearing interference fit rule

Rotating inner ring on a shaft needs an interference fit, typically a light press or shrink fit; a slip fit allows creep, fretting and shaft damage.

Bearing installation force path

Force must be applied to the ring being fitted, never transmitted through the rolling elements; press on the inner ring for shaft fits and outer ring for housing fits.

Alignment after coupling fit

Check angular and parallel alignment with dial gauges or laser tools; misalignment causes vibration, coupling wear and premature bearing failure.

V-belt tension rule

Set tension so deflection at mid-span matches the maker's figure, often about 10 to 16 mm per metre of span; recheck after the first running hours.

V-belt matched sets

Belts running in multiple grooves must be a matched set of the same length code; mixing worn and new belts overloads the tightest belt.

Weld defect: lack of fusion

Incomplete fusion between weld metal and parent metal, caused by low current, poor travel angle or contamination; it is a planar defect and is rejected under most plant repair standards.

Weld preheat purpose

Preheat slows cooling to reduce hardness and hydrogen cracking risk in thick or high-carbon steel; the required temperature comes from the procedure, not guesswork.

Structural crack stop drilling

Drilling a small hole at each end of a crack relieves the stress concentration and stops propagation temporarily; it is not a permanent repair.

Grease nipple function

It lets a grease gun force lubricant into a bearing or pin joint while sealing against dirt; a blocked nipple causes dry running and must be cleared or replaced.

Pin and bush wear check

Measure pin diameter and bush bore against the maker's limits; excessive clearance causes shock loading, so both parts are usually renewed as a pair.