Elevator Mechanic Exam Vocabulary Flashcards

Latching Relays and Electrical Identification

• Definition and Usage: Latching relays are used for call registration, direction selection, or as selector relays.
• Types: There are two primary types of latching relays:
  • Set/Reset: These are electrical latching relays.
  • Mechanical: These are mechanical latching relays.
• Symbol Recognition: The symbol for a latching relay is a box containing a shaded triangle located in the lower right-hand corner.

Motor Speed and Electrical Formulas

• RPM Calculation: To determine the Revolutions Per Minute (RPM), use the following procedure:
  • Step 1: Multiply the constant 60 by the Frequency ($f$) in Hertz ($Hz$).
  • Step 2: Divide the number of Poles ($P$) by 2.
  • Step 3: Divide the result of Step 1 by the result of Step 2.
  • Formula: $RPM = \frac{60 \times f}{P \div 2}$

Resistance and Insulation Testing

• Megohm Meter (Megger):
  • Used to test the insulation properties of electric wiring, motor windings, and high-power antenna mounts.
  • Often referred to as "megging out" or using a "megger" to identify if equipment or wiring is shorted to ground or the frame.
  • Characteristics: It utilizes significantly higher voltages to check resistance than a standard Volt-ohm meter.
  • Minimum Resistance: The acceptable minimum resistance for insulation is $1\,M\Omega$.

Shunt and Overload Components

• Shunt Overload Definitions:
  • (1) A parallel connection.
  • (2) A resistive element placed across armature terminals to bypass a portion of the current.
  • (3) A flexible electrical conductor designed to conduct current around mechanical joints between two conductors.
  • (4) A resistive element (usually very low resistance) used in parallel with a DC ammeter movement to bypass a calibrated portion of the total circuit current.
• Temporary Run Box Hazards: Getting shocked while using a temporary run box is typically indicative of a bad ground.

Rigging and Hoisting Procedures

• Bridle Hitch:
  • Consists of two, three, or four single hitches used together to hoist an object.
  • Load Stress vs. Sling Angle:
  • A sling with two legs lifting a $1,000\,lb$ object at a $90^{\circ}$ angle results in a load of $500\,lb$ per leg.
  • If the angle decreases to $30^{\circ}$, the stress increases to $1,000\,lb$ on each leg.
  • Safety Recommendation: Sling angles should be kept greater than $45^{\circ}$. Angles approaching $30^{\circ}$ are extremely hazardous and must be avoided.
• Lifting Materials: Hoisting materials should be checked for defects before every pick.
• Eye Bolts: To determine the Safe Working Load (SWL), check if the eye bolt is being used for in-line loading (never use eye bolts for non-in-line hoisting).
• Clevis Usage: When using a clevis with a screw-type pin, the pin must be tightened and inspected before each lift.

Scaffolding and Fall Protection

• Securement: Scaffolding must be tied to the structure using #9 wire or specific tie-in devices.
• Tie-off Requirements:
  • The first vertical tie must be at a maximum height of 4 times the narrowest base dimension.
  • Additional vertical ties must not exceed $26\,ft$ apart.
  • Maximum horizontal distance between ties must not exceed $30\,ft$.
• Load Capacity: OSHA requires scaffolds to support 4 times their maximum intended load.
• Plank Stability: Planks used in shaftway scaffolding must have cleats to prevent movement.
• Personal Fall Arrest System (PFAS):
  • Components: Anchorage, Lanyard, and Body Harness.
  • Lanyard length is typically $6\,ft$.
  • PFAS must be inspected before each use.
  • Anchorage must be independent and capable of supporting $5,000\,lbs$ per worker attached.
• Fall Protection Threshold: OSHA requires fall protection when working on scaffolding at or above $10\,ft$ from the ground.
• Barricades: Safety barricades across hoistway openings should be installed after rough or finished floors are in place. Top rails should be at $42\,in$, mid-rails at $21\,in$, and include a $3\,in$ toe board.

Car Specifications and Counterweights

• Counterweight Balance: Counterweights are typically hung to balance the empty car weight plus $40\%$ of the capacity load.
  • Example Calculation: If a car weighs $7,000\,lbs$ with a capacity of $3,500\,lbs$:
  • $40\% \text{ of } 3,500 = 1,400\,lbs$
  • Total Counterweight = $7,000 + 1,400 = 8,400\,lbs$.
• Modernization Weight Changes: If adding $5\%$ to a $10,000\,lb$ counterweight frame:
  • $10,000 \times 0.05 = 500\,lbs$
  • New weight = $10,500\,lbs$.
• Guide Shoes: On a traction elevator, bottom guide shoes or roller guides are fastened to the safety plank.

Wiring and Cabling

• Wire Sizing Standards:
  • Minimum size for wires in traveling cables is #20.
  • Minimum size for wires outside of travelers is #24.
  • The largest wires are the feeders for the hoist or pump motor.
• Spare Wires: A $10\%$ spare wire count is standard when pulling wire.
  • Calculation for 52 wires: $52 \times 0.10 = 5.2$ (order 6 spares).
• Traveling Cable Installation:
  • The loop should be at least 30 times the cable diameter.
  • Vertical suspension must be a minimum of $4\,ft$ at both the hoistway and car hanger attachments before the loop forms.
  • If replacing a cable with a different size, the hanger must be adjusted "post-wise" to ensure the loop clears the platform edge.
• Voltage Drop: If a controller is moved (e.g., $30\,ft$ away), larger wire should be used to compensate for voltage drop.
• Strain Relief: Strain supports are required in vertical raceways every $100\,ft$. Fastening should begin at the lowest point and work upward to adjust tension.

Specialized Elevators and Dumbwaiters

• LULA (Limited Use/Limited Access):
  • Max Rise: $25\,ft$
  • Max Speed: $30\,ft/min$
  • Max Capacity: $1400\,lbs$
  • Max Platform Area: $18\,sq/ft$
• Residential Elevators:
  • Max Rise: $50\,ft$
  • Max Speed: $40\,ft/min$
  • Max Capacity: $940\,lbs$
  • Max Platform Area: $19\,sq/ft$
  • Escape Hatch: Not required unless manual operation is not provided.
• Dumbwaiters:
  • Max Platform Area: $9\,sq/ft$
  • Max Inside Height: $4\,ft$
  • Max Capacity: $500\,lbs$
  • Note: No riders permitted. If working on top, the main line must be OFF and work performed only partially in.

Hydraulic Systems and Calculations

• Mathematical Constants: $\pi \approx 3.1416$; there are $231\,in^3$ in a Gallon.
• Area of a Plunger: $A = \pi \times r^2$.
  • If diameter is $10\,in$, radius ($r$) is $5\,in$.
  • $A = 3.1416 \times 5^2 = 78.54\,in^2$.
• Volume and Oil Calculation:
  • Example: Moving a $6\,in$ jack (radius $3\,in$) for $25\,ft$ ($300\,in$).
  • $A = 3.1416 \times 3^2 = 28.27\,in^2$
  • $V = A \times H = 28.27 \times 300 = 8481\,in^3$
  • $Gallons = 8481 \div 231 = 36.71\,gallons$.
• Hydraulic Valves:
  • Relief Valve: Tested annually. Relieves pressure if car hits an obstruction, is overloaded, or hits the stop ring.
  • Check Valve: One-way valve allowing oil flow only in one direction.
  • Up Valve: Controls up start, acceleration, high speed, slowdown, leveling, and stop.
  • Down Valve: Depends on system pressure as the elevator motor does not run in the down direction.
  • Bypass and Relief: Often combined into a single unit.
• Tests:
  • Category 1 Oil Buffer Test: Plunger must return to normal position within $90\,seconds$.
  • Static Load Test: Performed on unexposed cylinders annually. Hold empty car for $15\,minutes$; movement suggests an underground leak.

Electronics and Circuitry

• Amplifiers (Op Amps):
  • Inverting: Input is supplied to the Negative terminal.
  • Non-Inverting: Input is supplied to the Positive terminal.
• SCR (Silicon Controlled Rectifier):
  • Three-terminal device pulsing the gate with positive voltage to act as a switch.
  • Remains ON until anode/cathode voltages equalize, are reverse biased, or voltage is removed.
  • Testing: Positive lead on Anode, negative on Cathode, jumper between Anode and Gate. A good SCR shows $0.7\,V$. Shorted SCRs show low resistance between anode and cathode when tested with an ohmmeter.
• Logic Gates:
  • AND Gate: Output is High (1) ONLY when all inputs are High.
  • Exclusive OR (XOR): Output is High if any but NOT ALL inputs are High (Comparator gate).
• Timing Circuits:
  • OFF Delay: Timing begins when current is removed. Relay picks immediately when switch closes.
  • ON Delay: Relay is delayed until capacitors are charged. Capacitors are connected in parallel.

Control Systems

• Ward Leonard System:
  • Uses a closed loop between generator and hoist motor armatures.
  • Car speed is controlled by the amount of current in the generator shunt field.
  • Provides nearly constant speed under changing loads and regenerates power.
  • If all three contacts close in the diagram, it runs high speed.
• Inductance in DC Brake Circuits:
  • R1: Controls the rate the magnetic field builds (time to energize/lift brake).
  • R2: Located in the discharge path; controls the time to set the brake and suppresses voltage spikes.
• Series Brake Circuit: Uses a resistor to limit initial current. Contact E opens to insert more resistance once the brake is lifted, preventing coil saturation.

Troubleshooting and Safety Inspections

• Noise Issues: If a hoist motor is making noise, inductors can be used on the AC input to filter "notch effect" or provide isolation. A growling/humming 3-phase motor that stalls may have a cracked/loose rotor bar.
• Blowing Fuses: A car blowing a $3\,A$ fuse at the same point in the hoistway suggests an exposed traveling cable.
• Phasing: A reverse phase relay detects loss of phase or phase reversal in building power.
• Door Problems:
  • If an elevator runs with center opening doors partially open, the gate switch was likely activated but the relating device failed.
  • Mechanical safety edges bumping at center opening suggests issue with the safety edge retracting mechanism.
  • Closing force limit for passenger doors per ANSI Rule 112.3: Max $30\,lbs$. (If at $50\,lbs$, it is out of compliance).
• Encoder Issues: A sawtooth waveform on an oscilloscope indicates a fault; a perfect encoder produces a square wave.
• Escalator Errors: An escalator falling $10\,in$ short usually indicates an incorrect benchmark or column line.

Equipment and Maintenance

• Measuring Tools:
  • Micrometer: US Mike reads in thousandths of an inch ($0.001\,in$); Metric reads in hundredths of a millimeter ($0.01\,mm$).
  • Caliper Rule: Used to measure the outside diameter of a pipe.
  • Convert Inches: $1\,inch = 2.54\,cm = 25.4\,mm$.
• Rail Data:
  • Standard rail length is $16\,ft$.
  • Weight Calculation: For 15 full $16\,lb$ rails plus two $8\,ft$ sections: $(15 \times 16) + (1 \times 16) = 16 \text{ total rails} \times 16\,lbs = 4096\,lbs$.
• Oil Types: Use non-detergent, single viscosity gear oil for machines.
• Escalator Safety:
  • Max angle of Moving Walkway: $12^{\circ}$.
  • Max angle of Escalator: $30^{\circ}$.
  • Step Level (Sag) Switch: Trips if step sags more than $1/8\,in$.
  • Demarcation lights provide visual indication for entering/exiting.
  • Skirt panel clearance: No more than $3/16\,in$.

Fire and Chemicals

• NFPA Labels:
  • Red Square (4): Severe fire hazard.
  • Yellow Square (0): Not reactive.
• Fire Classes: Class C extinguishers are for electrical equipment (motors/switches).
• Elements of Fire: Fuel, Oxygen, Heat.
• MSDS: Material Safety Data Sheets can be demanded from your elevator company Superintendent or Manager.

Questions & Discussion

• Q: How many points of contact on a ladder?
  • A: 3 points of contact must be maintained. Ladders should extend $3\,ft$ above the landing.
• Q: What is the tripping speed for safeties?
  • A: Minimum tripping speed is not less than $115\%$ of rated speed. (e.g., $500\,fpm \times 1.15 = 575\,fpm$). All elevators above $150\,fpm$ require an overspeed switch.
• Q: What to do if a coworker smells of alcohol?
  • A: Take action by informing the mechanic in charge, business representative, or supervisor.
• Q: Which drill method for soft soil?
  • A: Rotary (Auger) drill. Use Percussion Rotary with a Button Bit for hard rock.
• Q: Minimum clearance between facing controllers at 500V?
  • A: $36\,inches$.
• Q: Total PI's for a 12-floor building with 3 cars where 3 floors don't get PI's?
  • A: $(12 \times 3) - (3 \times 3) = 36 - 9 = 27$ PI's.
• Q: Formula for 3-phase Transformer KVA?
  • A: $KVA = \frac{V \times I \times 1.732}{1000}$.