Technical Skills & Application Flashcards

An apprentice millwright is installing a v-belt drive system. Belt tension should be checked by measuring deflection at the midpoint of the longest span. What is the correct procedure?

Answer: Apply a specified force perpendicular to the belt span and measure deflection — typically 1/64 inch per inch of span

The standard method is to apply a known perpendicular force at the belt midpoint and measure deflection; the target is approximately 1/64 inch of deflection per inch of free span.

In electrical motor theory, what is 'slip' in an induction motor?

Answer: The percentage difference between synchronous speed and actual rotor speed

Slip is the difference between the rotating magnetic field's synchronous speed and the rotor's actual speed, expressed as a percentage; slip is necessary for torque production in induction motors.

A welder is using the GTAW (TIG) process on stainless steel. Which shielding gas selection is correct?

Answer: 100% Argon

Pure argon is the standard shielding gas for GTAW on stainless steel; CO2-containing mixes are used for GMAW and cause oxidation that is incompatible with the TIG process.

When using an angle grinder with a cutting disc, which PPE item is most critical beyond standard safety glasses?

Answer: A full face shield rated for grinding operations

Cutting discs can shatter and eject fragments at high velocity; a full face shield protects the entire face from debris that safety glasses alone cannot cover.

A pipefitter is making a branch connection using a weldolet fitting. What is the primary advantage of a weldolet over a standard tee fitting for this application?

Answer: It allows a branch connection of any size without cutting and replacing the run pipe with a full tee

A weldolet is an integrally reinforced branch fitting that welds directly onto the run pipe with only a hole cut, eliminating the need to cut out a full pipe section and insert a tee.

In precision metalwork, surface finish is measured in microinches (µin) Ra. A drawing calls for a surface finish of 32 µin Ra. Which process would typically produce this finish directly?

Answer: Precision grinding (8–32 µin Ra)

Precision cylindrical or surface grinding routinely achieves 8–32 µin Ra, placing 32 µin Ra at the coarser end of the grinding range, making it the correct matching process.

An HVAC technician is commissioning a newly installed split-system air conditioner. Before charging refrigerant, why must the system be evacuated to at least 500 microns?

Answer: To remove air and moisture that would contaminate the refrigerant, raise condensing pressure, and cause acid formation

Air and moisture are non-condensables that raise system pressures and reduce efficiency; moisture reacts with refrigerant and oil to form acids that destroy compressor components.