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Saber TyT Maquinaria practice questions

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Question 1Machine assembly, metrology, bearings and power transmission

In a SENA taller in Soacha, a técnico reads an esquema eléctrico of a conveyor starter. A circle containing the letter M appears on the power diagram next to three-phase lines. What does that symbol represent in the assembly documentation?

  1. A mechanical flexible coupling on the gearbox shaft
  2. A three-phase electric motor Correct answer.
  3. A hydraulic motor on the power unit
  4. A pressure switch on the pneumatic line

Explanation

In industrial electrical esquemas, a circle marked M denotes an electric motor. The técnico uses that symbol to locate the motor, its terminals, and the associated protection on the plano before landing cables.

Question 2Machine assembly, metrology, bearings and power transmission

An exploded plano of a two-stage gearbox for an IES lab bench shows, in order away from the housing, the input shaft, keys, bearings, gears, then the housing cover and fasteners. Which assembly sequence follows the plano?

  1. Fit keys and bearings on the shaft, seat the shaft assembly in the housing, then close the cover with the specified fasteners Correct answer.
  2. Bolt the cover on first so the housing is rigid, then drive the shaft through the closed cover
  3. Drop the gears into the housing last after the cover is sealed, so they can be changed without opening the unit
  4. Weld the housing joint closed before inserting bearings so oil cannot leak at the split

Explanation

An exploded plano encodes build order from the inside out. Shafts, keys, and bearings must be assembled before the cover closes the housing. Fasteners are last so the unit can still be aligned and inspected.

Question 3Machine assembly, metrology, bearings and power transmission

A bracket plano for a Bucaramanga workshop is drawn at escala 1:2. A linear dimension printed on the drawing reads 80 mm. What length should the finished part have?

  1. 80 mm, because the written dimension is the real size; the escala only sets how large the view is drawn Correct answer.
  2. 40 mm, because escala 1:2 means every printed number must be halved
  3. 160 mm, because escala 1:2 means the part is twice the drawing number
  4. 800 mm, converting centimetres on the title block into millimetres on the shop floor

Explanation

On a manufacturing plano, the numerical dimension is the actual size of the feature. Escala 1:2 means the graphical view is drawn half size so it fits the sheet; it does not rescale the 80 mm callout.

Question 4Machine assembly, metrology, bearings and power transmission

A detalle plano for a pump bracket specifies a locating hole Ø20 H7. The machinist has drilled Ø19.5 mm. What finishing action matches the plano before ensamblaje of the locating pin?

  1. Tap the hole M20 so the pin can be locked with a thread-locking compound
  2. Ream or bore the hole to the H7 tolerance band specified on the plano Correct answer.
  3. Leave the drilled hole; H7 only names the pin material, not the hole size
  4. Knurl the hole wall so the pin is held by friction regardless of diameter

Explanation

H7 is an ISO hole-basis tolerance class. Drilling undersize is only the roughing step. Reaming or boring brings the hole into the H7 size band so the specified fit with the pin can be achieved.

Question 5Machine assembly, metrology, bearings and power transmission

A pump skid in Cartagena uses a flexible coupling between an induction motor and a centrifugal pump. What is the primary mechanical function of that coupling?

  1. It increases the gear ratio so the pump always runs faster than the motor
  2. It is a brake that stops the shaft whenever the relief valve opens
  3. It replaces the need for a foundation because it absorbs 100 percent of misalignment
  4. It transmits torque and accommodates small residual misalignment and thermal growth Correct answer.

Explanation

A flexible coupling transmits rotary power while allowing a limited amount of angular, parallel, or axial mismatch that remains after alignment. It is not a speed increaser and it does not remove the duty to align the machines.

Question 6Machine assembly, metrology, bearings and power transmission

A técnico is coupling a 15 kW motor to a fan in a cement plant in Boyacá. Which procedure is consistent with sound montaje practice?

  1. Tighten the coupling bolts to the maximum possible torque first, then check alignment if the set has time
  2. Grout the motor in place before any alignment because grout cannot be adjusted later
  3. Align the shafts to the coupling manufacturer’s limits, then torque the coupling fasteners to specification Correct answer.
  4. Run the set at full load immediately so thermal growth will finish the alignment

Explanation

The set receives preliminary alignment before grouting and a final alignment check after the base is secured and grout has cured. Coupling fastener torque comes from the manufacturer, and any specified thermal-growth offset belongs in the cold-alignment target.

Question 7Machine assembly, metrology, bearings and power transmission

A technician is landing hydraulic hoses on a new power unit in Manizales. Which practice matches technical norms for ensamble of fluid-power lines?

  1. Keep plugs in ports until the moment of connection, avoid twisting the hose, and tighten fittings without using the hose as a lever Correct answer.
  2. Blow shop air through open ports toward the valves to confirm that passages are free
  3. Pre-fill every hose with water so the first start cannot run the pump dry
  4. Route hoses in the tightest possible bend against hot manifolds to shorten the bill of materials

Explanation

Cleanliness and hose geometry dominate hydraulic assembly quality. Caps stay on until connection, hoses are not used as wrenches, and bend radius follows the hose specification so the reinforcement is not kinked.

Question 8Machine assembly, metrology, bearings and power transmission

A pump casing flange with eight bolts is being closed after gasket replacement in a Cartagena terminal. Which tightening procedure is technically appropriate?

  1. Tighten bolts in clockwise order around the flange, finishing each bolt to final torque on the first pass
  2. Tighten only the two bolts nearest the suction so the gasket pinches where leakage was seen
  3. Use an impact wrench on every bolt until it stops turning, regardless of the specified torque
  4. Snug in a star or crisscross pattern, then apply specified torque in several passes around the pattern Correct answer.

Explanation

Flange load must be even so the gasket compresses uniformly. A star pattern and multiple passes prevent cocking the flange. Final torque comes from the joint specification, not from sequential one-pass tightening.

Question 9Machine assembly, metrology, bearings and power transmission

During montaje of a pump-motor skid, a feeler gauge shows one motor foot lifting when its bolt is tightened. What is the technically correct response before grouting?

  1. Torque that foot extra hard so the frame yields and sits down
  2. Ignore it if the coupling still looks centered by eye
  3. Correct the soft foot with cleaning and shims so all feet share load, then complete alignment Correct answer.
  4. Cut a slot in the baseplate so the foot can slide when the pump heats

Explanation

Soft foot is a foot that is not coplanar with the others. Tightening it twists the motor frame, misaligns the air gap and shaft, and makes coupling readings unstable. The fix is contact, shim, and then alignment-not more bolt load.

Question 10Machine assembly, metrology, bearings and power transmission

A técnico must install a ball bearing on a gearbox input shaft in an IES lab. The inner ring is a tight fit on the shaft. Which method is consistent with bearing-mounting practice?

  1. Heat the bearing with a temperature-controlled induction heater within the manufacturer's limit and slide it to the shoulder Correct answer.
  2. Hammer on the outer ring so the blows transmit through the balls to seat the inner ring
  3. Press on the cage with a screwdriver because the cage is the strongest part
  4. Hold a direct flame on the seals until the grease smokes and the ring drops on

Explanation

For the stated interference fit, an approved temperature-controlled induction-heating method can permit mounting without forcing damaging loads through the rolling elements. The actual bearing, seals, lubricant and manufacturer limits determine permissible conditions. This is conceptual method selection, not a universal heating temperature or authorization to mount equipment.

Question 11Machine assembly, metrology, bearings and power transmission

A técnico is installing a V-belt drive between a motor and a fan in an Ibagué textile mill. After pulley alignment with a straightedge, the belts are tensioned. Which criterion is technically sound?

  1. Tension until the motor feet lift, because extra tension prevents all slip forever
  2. Set belt deflection or force to the belt manufacturer’s tension value; over-tension overloads bearings and shafts Correct answer.
  3. Leave belts slack so bearings last longer, and accept continuous squeal as normal
  4. Mix old and new belts on the same set so stock is used evenly

Explanation

Correct tension is a specified deflection or frequency for that belt profile and span. Too little tension slips and burns belts; too much tension is a static radial load that shortens bearing life. Alignment is a separate, prior step.

Question 12Machine assembly, metrology, bearings and power transmission

In a SENA metrology corner, a técnico must verify a 25 mm ground bearing seat to hundredths of a millimetre before fitting the bearing. Which instrument is the appropriate first choice?

  1. An outside micrometer with a suitable range and resolution Correct answer.
  2. A vernier caliper used only once across the diameter
  3. A dial bore gauge set to the nominal shaft diameter
  4. A feeler gauge inserted between the bearing and shaft

Explanation

A ground bearing seat normally needs repeatable external-diameter measurements at several axial and angular positions. An outside micrometer of the correct range resolves hundredths of a millimetre and helps reveal taper or out-of-round before assembly.

Question 13Machine assembly, metrology, bearings and power transmission

A metric pie de rey with 0.02 mm least count is used on a bushing. The main scale reads 18 mm before the zero of the vernier, and the 12th vernier division coincides with a main-scale line. What is the reading?

  1. 18.12 mm
  2. 18.24 mm Correct answer.
  3. 12.18 mm
  4. 18.02 mm

Explanation

Reading = main scale + (coincident division × least count) = 18 mm + (12 × 0.02 mm) = 18 + 0.24 = 18.24 mm. The 0.02 mm least count is the usual 50-division metric vernier.

Question 14Machine assembly, metrology, bearings and power transmission

A cylinder bore is dimensioned 80 mm on the plano. The técnico must enter the diameter in metres in a force spreadsheet that uses SI units. Which value is correct?

  1. 0.080 m Correct answer.
  2. 0.80 m
  3. 80 m
  4. 0.008 m

Explanation

1 m = 1000 mm, so 80 mm = 80/1000 = 0.080 m. Using 80 m or 0.80 m would throw hydraulic force calculations off by orders of magnitude.

Question 15Machine assembly, metrology, bearings and power transmission

A metric outside micrometer (0.01 mm thimble, 0.5 mm sleeve half-line) is used on a shaft. The sleeve shows 8 mm past the index, the 0.5 mm line is visible, and the thimble coincides at 23. What is the reading?

  1. 8.23 mm
  2. 8.53 mm
  3. 23.80 mm
  4. 8.73 mm Correct answer.

Explanation

A standard metric micrometer adds sleeve millimetres, a 0.5 mm half-revolution if that line is exposed, and thimble hundredths: 8 + 0.5 + (23 × 0.01) = 8.73 mm. Missing the half-millimetre line is the usual shop error.

Question 16Measurement, feedback, PLC and automation

On a ladder esquema for a 24 VDC start-stop station in a Tocancipá auto-parts cell, the start pushbutton is drawn as a normally open contact in series with the contactor coil, and the stop pushbutton as a normally closed contact in the same series string. What does that symbology require during wiring?

  1. Wire both buttons as normally open so the coil is de-energized until either button is pressed
  2. Wire the stop button as normally open held closed by a jumper so a broken wire still allows starting
  3. Omit the stop contact because the thermal overload already opens the circuit on every stop command
  4. Wire start so it closes only when pressed, and wire stop so it is closed at rest and opens when pressed Correct answer.

Explanation

A normally open start contact closes only while pressed (or is sealed by an auxiliary). A normally closed stop contact is closed at rest so the coil can energize, and it opens the circuit when the operator hits stop. That fail-safe stop wiring is what the esquema specifies.

Question 17Measurement, feedback, PLC and automation

A plano de conjunto for a packaging machine in Cali shows a protective-earth symbol at the motor terminal box and at the machine frame. During ensamblaje, what does that symbology require?

  1. Bond only the control-panel DIN rail and leave the motor housing floating to avoid ground loops
  2. Install a continuous protective-earth conductor to the motor frame and other marked metallic parts so exposed metal is referenced to earth Correct answer.
  3. Connect earth only to the pneumatic FRL body because compressed air is the higher energy source
  4. Paint over the earth bosses so corrosion cannot start at the bonding points

Explanation

Earth symbols on the plano identify mandatory protective bonding points. Colombian electrical practice under RETIE, the technical regulation for electrical installations (MinEnergía), requires exposed conductive parts of equipment to be earthed so a fault clears instead of leaving the frame live.

Question 18Measurement, feedback, PLC and automation

A 24 VDC solenoid coil on a pneumatic electroválvula has a flyback diode drawn across it on the electronic esquema. What is the diode doing in that circuit?

  1. It provides a path for the coil’s inductive current when the transistor or PLC output turns off, limiting voltage spikes Correct answer.
  2. It converts the 24 VDC supply into 220 VAC so the solenoid can share the motor feeder
  3. It stores hydraulic energy the way an accumulator stores pressure
  4. It measures coil resistance for the GMAO and replaces the need for a multimeter

Explanation

A solenoid is an inductor. When current is interrupted, the collapsing field would produce a high voltage. The diode is oriented to be reverse-biased in normal excitation and forward-biased for the decaying current, protecting the switching device.

Question 19Measurement, feedback, PLC and automation

A 220 V resistive heater on a shrink tunnel in a Cali plant draws 5 A in steady operation. What electrical power is the heater converting?

  1. 44 W
  2. 225 W
  3. 1100 W Correct answer.
  4. 1100 kW

Explanation

For a DC or purely resistive AC load, P = V × I. Substituting the measured values gives P = 220 V × 5 A = 1100 W. That is the heat the element delivers if voltage and current are true RMS and in phase.

Question 20Measurement, feedback, PLC and automation

A braking resistor on a small VFD in an IES lab has 8 Ω and carries 5 A during a deceleration pulse. How much instantaneous electrical power is dissipated in that resistor?

  1. 40 W
  2. 3.1 W
  3. 320 W
  4. 200 W Correct answer.

Explanation

Joule heating follows P = I²R. Here I² = 25 A² and 25 × 8 Ω = 200 W. Equivalently, voltage across the resistor is V = IR = 40 V and P = VI = 200 W. The 40 V figure is voltage, not power.

Question 21Measurement, feedback, PLC and automation

A single-phase control transformer on a Barranquilla panel is rated 440 V primary and 110 V secondary. The primary has 800 turns. Assuming an ideal transformer, how many secondary turns are required?

  1. 3200 turns
  2. 200 turns Correct answer.
  3. 690 turns
  4. 110 turns

Explanation

The turns ratio equals the voltage ratio: Np/Ns = Vp/Vs. Then Ns = Np × Vs/Vp = 800 × 110/440 = 800 × 0.25 = 200 turns. The secondary has fewer turns because it is the lower voltage winding.

Question 22Measurement, feedback, PLC and automation

During installation checks, a 24 VDC control circuit feeds a solenoid whose measured resistance is 48 Ω. What current should a healthy coil draw from 24 V?

  1. 0.5 A Correct answer.
  2. 2 A
  3. 1152 A
  4. 24 A

Explanation

Ohm’s law is I = V/R. I = 24 V / 48 Ω = 0.5 A. A clamp meter or series milliammeter should be in that order of magnitude at room temperature; a much higher current suggests a shorted coil.

Question 23Measurement, feedback, PLC and automation

Three heaters in a panel are wired in series for a laboratory oven: 12 Ω, 18 Ω, and 10 Ω. What resistance should the técnico read across the string with the supply isolated?

  1. 4.2 Ω
  2. 13.3 Ω
  3. 216 Ω
  4. 40 Ω Correct answer.

Explanation

Series resistances add: R = 12 + 18 + 10 = 40 Ω. A much smaller reading would suggest a parallel connection or a shorted element; a much larger reading would suggest an open.

Question 24Measurement, feedback, PLC and automation

Two 80 Ω drain resistors are connected in parallel across a DC bus discharge point. What equivalent resistance should the técnico expect?

  1. 160 Ω
  2. 80 Ω
  3. 40 Ω Correct answer.
  4. 0 Ω

Explanation

For two equal resistors in parallel, Req = R/2. Here 80/2 = 40 Ω. From reciprocals: 1/Req = 1/80 + 1/80 = 2/80, so Req = 40 Ω.

Question 25Measurement, feedback, PLC and automation

A motor-starter control esquema shows the normally closed auxiliary contact of the thermal overload relay in series with the contactor coil. What function must that contact provide after an overload trip?

  1. Keep the contactor energised while the overload relay cools
  2. Open the coil circuit so the contactor drops out and the motor stops Correct answer.
  3. Reverse two motor phases so the shaft unloads
  4. Short the start pushbutton so the motor automatically restarts

Explanation

The overload relay senses sustained overcurrent through its power path, while its normally closed auxiliary contact belongs in the control circuit. A trip opens that contact, de-energises the contactor coil, and disconnects the motor until the fault is addressed and the relay is reset.

Question 26Measurement, feedback, PLC and automation

Before connecting a newly installed 440 V motor, a técnico must assess insulation between each winding and the frame with the motor isolated. Which instrument and method fit that task?

  1. Use a clamp meter around all three disconnected leads and read leakage current
  2. Use the continuity buzzer of a multimeter while the motor remains connected to the VFD
  3. Use an insulation-resistance tester at the manufacturer-approved test voltage, with sensitive electronics disconnected Correct answer.
  4. Use a phase-sequence indicator across a winding and the motor frame

Explanation

A suitable insulation-resistance tester and manufacturer-approved conditions address winding-to-frame insulation in the stated isolated motor. Relevant sensitive electronics must be protected or disconnected according to the actual procedure. No universal voltage, acceptance threshold or live-work permission is established by this instrument-choice question.

Question 27Pneumatic and hydraulic model reasoning

A pneumatic esquema for a clamp on a Medellín IES bench shows a five-port, two-position valve feeding a double-acting cylinder. Which statement correctly interprets that symbology for ensamblaje?

  1. The valve is a 3/2 unit, so one cylinder port must be plugged and the rod will only extend
  2. The valve is a 2/2 unit that only dumps the system to atmosphere when de-energized
  3. The valve is a 5/2 directional valve that alternately pressurizes one cylinder port while exhausting the other Correct answer.
  4. The five ports are all pressure inlets, so the cylinder extends and retracts at the same time

Explanation

A 5/2 valve has five ports and two positions. In each position it sends air to one side of a double-acting cylinder and opens the opposite side to exhaust. That is the standard actuator interface shown on the esquema.

Question 28Pneumatic and hydraulic model reasoning

A hydraulic esquema for a forming press shows a one-way flow-control valve in the rod-end line of a double-acting cylinder. Its check valve allows free flow toward the rod end but forces return flow through the adjustable restriction. Which operating behaviour does that arrangement specify?

  1. Meter-in speed control while retracting, with the rod end blocked in both directions
  2. Regeneration of rod oil into the cap end on every stroke, independent of the directional valve
  3. Unrestricted flow in both directions so the press speed is set only by pump displacement
  4. Meter-out speed control while extending, with free flow into the rod end during retract Correct answer.

Explanation

During extension, oil leaving the rod end must pass the restriction, so the flow control meters out and controls speed under load. The bypass check opens for the reverse direction, so retract filling of the rod end is essentially free. That is the procedure encoded in the esquema.

Question 29Pneumatic and hydraulic model reasoning

On a hydraulic power unit in a Bogotá zona franca, the relief valve is piped from the pump outlet to tank. What is the functional role of that element in the system?

  1. It increases pump displacement whenever actuator speed is too low
  2. It filters solid particles before oil reaches the directional valves
  3. It limits maximum system pressure by dumping excess flow to tank Correct answer.
  4. It converts hydraulic pressure into rotary mechanical power

Explanation

A relief valve is a pressure-limiting device. When load or a blocked actuator would otherwise stall the pump against a closed volume, the valve opens to tank and caps the pressure at its setting.

Question 30Pneumatic and hydraulic model reasoning

A hydraulic press accumulator is precharged with nitrogen and teed into the pressure line. What function should the técnico expect from that element during cycling?

  1. It chemically dries the oil so water cannot enter the cylinder
  2. It stores hydraulic energy and helps absorb pressure peaks, supplying extra flow for short high-demand strokes Correct answer.
  3. It is a mechanical flywheel that must be clutched to the electric motor
  4. It raises the relief-valve cracking pressure automatically as oil temperature falls

Explanation

A bladder or piston accumulator stores pressurized fluid against a gas precharge. During a fast press stroke it can add flow; when the directional valve centers it can also damp shocks. Nitrogen is used because it is relatively inert compared with air.

Question 31Pneumatic and hydraulic model reasoning

A hydraulic directional valve on a press is specified as 4/3 with a closed center. What does that tell the técnico about functioning when the spool is centered?

  1. P, T, A, and B are blocked in center; actuator movement is resisted but a loaded cylinder may still need a dedicated load-holding valve Correct answer.
  2. The cylinder rod always floats in center because A and B are joined to tank
  3. The pump is regeneratively connected to the rod side only
  4. The valve becomes a 5/2 pneumatic unit whenever the solenoid drops out

Explanation

4/3 means four flow ports and three spool positions. Closed center blocks P, T, A, and B in the middle position, but spool leakage means it must not be treated as a certified load-holding device. Pump protection depends on a relief or unloading arrangement shown elsewhere on the esquema.

Question 32Pneumatic and hydraulic model reasoning

A new hydraulic power unit will feed a servo-valve manifold on a press. Which montaje sequence best protects the valves and matches technical practice?

  1. Connect the servo valves first, then start the pump so the valves flush themselves with dirty assembly oil
  2. Fill the reservoir with any leftover engine oil from the transport truck to save stock
  3. Skip flushing if the pipes look shiny, because new steel pipe is already clean enough for servo valves
  4. Assemble and flush the circuit with filters in place and the servo valves bypassed or replaced by flushing plates, then install the servo valves Correct answer.

Explanation

Sensitive servo components should be protected from assembly contamination under the actual manufacturer-approved flushing plan. Appropriate flushing plates or bypass arrangements can keep debris out before those components are installed. The selected sequence is a conceptual contamination-control comparison, not a complete generic commissioning or pressure-test instruction.

Question 33Pneumatic and hydraulic model reasoning

A hydraulic test stand holds a 12000 N load on a jack with an effective piston area of 0.004 m². What pressure should the manómetro indicate, neglecting friction?

  1. 48 Pa
  2. 3 MPa Correct answer.
  3. 3 kPa
  4. 0.333 MPa

Explanation

Pressure is P = F/A. P = 12000 N / 0.004 m² = 3000000 Pa = 3 MPa (which is 30 bar). Friction would raise the required pressure slightly, but it does not change the order of the ideal calculation.

Question 34Maintenance diagnosis, condition evidence and controlled restoration

A GMAO in a Cali bottling plant lists an oil change on a gearbox every 2000 operating hours, regardless of a current vibration alarm. Which maintenance type is that scheduled oil change?

  1. Correctivo, because oil is only changed after the gearbox has already seized
  2. Predictivo, because 2000 hours is a measured vibration symptom
  3. Preventivo, because the task is time- or hour-based before a functional failure is required Correct answer.
  4. Redesign, because the interval changes the gearbox geometry

Explanation

Preventivo work is planned on calendar time, running hours, or a fixed cycle to reduce the chance of failure. An oil change at 2000 h is classic preventivo even if other predictivo tools exist on the same machine.

Question 35Maintenance diagnosis, condition evidence and controlled restoration

A technician in a Medellín plant walks a monthly route with a vibration collector on critical fans and compares spectra with a baseline. Which maintenance approach is being applied?

  1. Predictivo, because decisions use condition measurements before catastrophic failure Correct answer.
  2. Correctivo, because any spectrum means the fan has already failed
  3. Preventivo only, because walking a route is the same as changing parts on a calendar
  4. Run-to-failure by policy, because no parts are replaced during the walk

Explanation

Vibration analysis is a standard predictivo technique. The route itself is only the data-gathering method; the maintenance type is defined by acting on condition, not on a fixed replacement date.

Question 36Maintenance diagnosis, condition evidence and controlled restoration

A hydraulic pump seizes on Saturday night and is replaced so the line can run on Monday. No condition monitoring had been used on that pump. Which classification fits the work that was done?

  1. Preventivo lubrication, because a pump was involved
  2. Predictivo oil analysis, because the failed pump contained oil
  3. Mejorativo redesign, because a like-for-like pump was bolted in
  4. Correctivo, because the intervention restores function after a failure Correct answer.

Explanation

Correctivo maintenance is performed after a functional failure to restore the required function. A like-for-like emergency replacement without prior condition tasks is correctivo, not preventivo or predictivo.

Question 37Maintenance diagnosis, condition evidence and controlled restoration

A hydraulic return-filter housing has a differential-pressure indicator that has reached the change zone. The calendar still says the element is due in six weeks. What should the preventivo/predictivo plan do?

  1. Reset the indicator and wait for the calendar date so the warehouse min-max is not disturbed
  2. Leave the element installed but raise the bypass-valve setting so the indicator returns below the change zone
  3. Change the element now; the delta-P indicator is a condition trigger that overrides a later calendar date Correct answer.
  4. Change the oil but retain the loaded element until the original calendar date

Explanation

The specified condition indicator is a reason to assess the filter under the equipment’s actual criteria rather than blindly wait for a later calendar date. Temperature, flow, bypass configuration and safe replacement conditions also matter. The reading is not a universal instruction to open a pressurized housing.

Question 38Maintenance diagnosis, condition evidence and controlled restoration

A lubrication route specifies grease type, quantity, and 250 h interval on conveyor pillow blocks, taken from the bearing manufacturer. Which maintenance procedure is being executed?

  1. Correctivo, because the route responds to a bearing that has already lost function
  2. Predictivo, because any specified quantity is a measurement of current bearing condition
  3. Condition-based replacement, because 250 operating hours is an alarm threshold
  4. Preventivo lubrication according to a programmed plan Correct answer.

Explanation

A planned lubrication route with specified interval and quantity is preventivo. It aims to delay wear before functional failure. Grease quantity still must stay within the manufacturer’s guidance to avoid blowing seals.

Question 39Maintenance diagnosis, condition evidence and controlled restoration

An infrared camera survey of an MCC in a Cartagena plant shows one contactor lug much hotter than the parallel phases under similar load. Which maintenance action does that predictivo finding support?

  1. Tighten the live lug immediately while watching the thermal image, without isolating the MCC
  2. Plan an isolated re-termination or repair of that connection before it becomes an open-circuit or fire source Correct answer.
  3. Replace the motor bearings because every electrical hot spot originates at the driven load
  4. Accept the lug because its absolute temperature is below the camera range, despite the phase-to-phase anomaly

Explanation

A localized abnormal temperature under comparable load supports investigation of a connection or other relevant fault. It does not uniquely establish one cause. Appropriate authorized personnel should assess the evidence and plan any correction under actual isolation and safety procedures rather than tighten an energized terminal.

Question 40Maintenance diagnosis, condition evidence and controlled restoration

A critical air compressor has only correctivo history: several unplanned seizures, long downtime, and no lubrication records. Management asks for a better plan. Which package best matches preventivo plus predictivo practice?

  1. Keep the correctivo policy but reserve more weekend labour so seizures are repaired faster
  2. Add only fixed annual replacement of every bearing, regardless of condition or failure history
  3. Add a lubrication and inspection preventivo route, plus vibration and temperature monitoring to catch incipient faults, and keep correctivo as backup Correct answer.
  4. Add vibration monitoring but leave lubrication, filters, and cooling out of the planned route

Explanation

Critical assets need planned preventivo tasks that are known to affect failure modes (lubrication, filters, cooling) and predictivo measurements that give warning. Correctivo remains for residual failures. The mix is chosen by criticality, not by hoping operators remember.

Question 41Maintenance diagnosis, condition evidence and controlled restoration

Two gearbox events are logged. Event A: vibration amplitude at bearing frequency has doubled over six weeks, oil still looks clean, and the mill still runs. Event B: the output shaft snaps and the mill stops. How should those events be classified?

  1. Both are incipient because each event began with material deterioration
  2. A is incipient (a developing fault with remaining function); B is catastrophic (sudden loss of required function) Correct answer.
  3. A is catastrophic because its amplitude changed; B is incipient because the fracture face is fresh
  4. Both are catastrophic because the same gearbox family is involved

Explanation

The supplied developing bearing-frequency trend is an incipient condition concern while function remains; the snapped shaft is a sudden loss of required function in the scenario. The labels describe the supplied observations, not proof that every precursor has one cause or that a developing fault is safe to ignore.

Question 42Maintenance diagnosis, condition evidence and controlled restoration

A hydraulic press cylinder extends much more slowly than before, but the electric motor sounds normal. Which analysis path is the most disciplined first isolation?

  1. Replace the pump immediately because slow speed uniquely proves lost displacement
  2. Adjust the flow-control valve fully open before recording any pressure or temperature data
  3. Check oil level and temperature, pump outlet pressure, filter delta-P, and internal leakage (cylinder or valve) before swapping random parts Correct answer.
  4. Replace the cylinder seals first because normal motor sound rules out every other cause

Explanation

Slow extension with a healthy-sounding drive points to hydraulic flow not reaching the cap end: low level, aeration, a worn pump, a clogged filter in bypass, a mis-set flow control, or leakage across the piston or valve. Measuring pressure and restriction isolates the layer before parts changing.

Question 43Maintenance diagnosis, condition evidence and controlled restoration

A bearing on a fan is replaced, and three weeks later the new bearing shows the same spalling. The GMAO lists the cause as bearing failed. What is the methodological problem?

  1. The second bearing should be replaced with the same part again because the component name is already a sufficient cause code
  2. The repeat should be classified only as a supplier-quality problem before inspecting lubrication or alignment
  3. The replacement interval should be shortened below three weeks without examining installation conditions
  4. The stated cause is only the failed part; analysis must continue to lubrication, alignment, imbalance, or overload that killed both bearings Correct answer.

Explanation

Naming the component that broke is not root-cause analysis. Repeat spalling on a new bearing points to a remaining condition: misalignment, unbalance, contamination, or lubrication. Tools such as 5 Why or Ishikawa are meant to push past the part name.

Question 44Maintenance diagnosis, condition evidence and controlled restoration

After a sudden jam, a gearbox is opened. Several teeth are broken with fresh, shiny fracture faces and little prior polishing. A second gearbox from the same line, opened during a planned inspection, shows grey pitting on the pitch line of still-complete teeth. How should the analysis treat those morphologies?

  1. Both cases are identical lubrication failures, so both get the same oil change and no further study
  2. The broken teeth after a jam point to overload/shock; the pitting on intact teeth points to contact-fatigue or lubrication film problems developing over time Correct answer.
  3. The broken teeth indicate progressive contact fatigue, while pitch-line pitting proves a single shock overload
  4. Both morphologies prove misalignment and exclude lubrication or shock loading

Explanation

The supplied fresh fracture after a jam supports an overload/shock hypothesis, while progressive pitch-line pitting supports contact-fatigue or lubrication-related investigation. Surface appearance alone is not conclusive root-cause proof. Review actual loading, materials, lubrication and operating history before a repair decision.

Question 45Maintenance diagnosis, condition evidence and controlled restoration

For an authorized diagnostic plan with safe test conditions and no protective-function bypass, which listed sequence best uses the reported intermittent stop and available PLC evidence?

  1. Replace the guard switch immediately from the first HMI message without capturing PLC input history
  2. Restore an older PLC program before reproducing the stop, then compare whether the fault disappears
  3. Reproduce the stop, note the PLC diagnostic and input states (guards, E-stop, pressure switch, solenoid outputs), then test the implicated field device before changing uninvolved hardware Correct answer.
  4. Trend only plant air pressure and disregard the intermittent guard indication until a pressure alarm appears

Explanation

Intermittent mechatronic faults need reproduction and layer isolation: what the PLC saw, whether the input really opened, and whether the output drove the valve. Field devices and wiring fail more often than an entire program. Safety inputs must stay in the analysis, not be jumped.

Question 46Maintenance diagnosis, condition evidence and controlled restoration

An orden de trabajo (OT) for a mixer gearbox in a lácteos plant says only Fix it. Which documentation improvement is required for maintenance management?

  1. Leave the OT vague so technicians can be creative on the floor
  2. Replace the OT with a verbal WhatsApp message so nothing is auditable
  3. State the asset, the observed symptom, the required task, isolation/bloqueo y etiquetado needs, and parts or references Correct answer.
  4. Copy a turbine overhaul procedure into the OT even though the asset is a small mixer

Explanation

An OT is a control document. It must identify the machine, the problem or task, safety isolation, and resources. Vague orders produce incomplete work, missed lockout, and useless history.

Question 47Maintenance diagnosis, condition evidence and controlled restoration

A mill motor has failed three times in a year, but the historial de equipo only shows the last rewind invoice. Why does that documentation gap hurt management?

  1. Without dates, hours, failure modes, and actions, repeat failures cannot be seen or used to change the preventivo/predictivo plan Correct answer.
  2. Invoices are the only legal maintenance document required, so history is optional
  3. Three failures in a year prove the motor should be deleted from the asset list
  4. Rewind invoices automatically generate vibration baselines

Explanation

Equipment history is the memory of the plan. Dates, running hours, symptoms, and what was actually done allow trend analysis and criticality decisions. A single invoice is a cost record, not a technical historial.

Question 48Maintenance diagnosis, condition evidence and controlled restoration

A coupling bolt torque is not listed on the local OT. The manufacturer’s installation manual on the machine folder specifies a torque and a tightening sequence. What should the técnico follow?

  1. The largest torque the impact wrench can deliver, because extra clamp load is always safer
  2. The manufacturer’s specified torque and sequence, recorded on the closed OT Correct answer.
  3. A torque copied from a different coupling size used last month
  4. Hand-tight plus a quarter turn, which is a universal hydraulic standard

Explanation

Manufacturer documentation is part of the maintenance information system. When the OT is silent, the manual is the technical source. The closed OT should then capture the torque actually used so the historial is complete.

Question 49Measurement, feedback, PLC and automation

A three-phase motor on a mill trips on thermal overload after an hour of work. The mechanic’s first idea is to fit a larger overload relay. What is the sounder failure-analysis first step?

  1. Verify load, ventilation, ambient temperature, voltage balance, and that the overload is set to the motor nameplate before raising the protection Correct answer.
  2. Increase the relay setting one step first, then investigate only if the larger setting also trips
  3. Replace the overload relay with a larger frame while preserving its highest available setting
  4. Reduce cooling-air inspection frequency because the trip occurs only after the motor warms

Explanation

An overload trip is a symptom. Root-cause thinking checks whether the motor is truly overloaded, poorly cooled, or seeing voltage problems, and whether the relay matches the nameplate. Enlarging protection without that check hides a real failure in progress.

Question 50Measurement, feedback, PLC and automation

A motor trips instantly at start, before it can turn. A second identical motor runs normally on the same starter. Which checks best separate a phase-to-frame or phase-to-phase motor fault from a mechanical seizure?

  1. Insulation-resistance and winding-resistance checks on the suspect motor, plus a free-rotation check of the uncoupled shaft Correct answer.
  2. A phase-sequence check at the starter, with no measurements on the suspect motor
  3. A running vibration route attempted while the shaft remains unable to turn
  4. A higher breaker or overload setting followed by another coupled start

Explanation

Appropriate isolated winding and insulation tests, together with a safe mechanically assessed free-rotation check, can help distinguish electrical and mechanical hypotheses. Use authorized equipment-specific procedures and protect connected electronics. A trip alone does not uniquely diagnose a winding short, and these written choices do not authorize live work.