Safety (car or counterweight safety)A mechanical device on the car (or counterweight) that grips the guide rails to stop and hold it in an overspeed, free-fall, or slack-rope condition. Sorted into Types A, B, and C by how it slows the car. Part 2.17.
Safety edge / photo eyeThe door protection that reverses a closing door: a physical bumper on older units, an infrared curtain on newer ones. First thing to suspect when doors reopen for no reason.
Safety gearA mechanical device on the car (and sometimes counterweight) that clamps onto the guide rails to stop it if the governor detects overspeed or a free-fall condition.
Safety zoneThe clear area at the entry and exit landings, kept free of obstacles. Width: distance between handrail centerlines plus 200 mm. Length: twice that distance from the end of the newel. Absolute minimums per 6.1.3.6.4.
Safety, Type AAn 'instantaneous' safety: it grips the rails hard and stops the car in a very short distance, using nothing to soften the grab. Allowed only on slow units (up to 0.75 m/s / 150 ft/min). Part 2.17.5.1.
Safety, Type BA safety that applies a limited, controlled rail pressure so the stopping distance stays reasonable for the car's weight and speed. Used across a wide speed range; stopping distances are tabulated against governor tripping speed. Part 2.17.5.2.
Safety, Type CA Type A instantaneous safety working together with oil buffers between the car frame and the safety plank. The buffers' stroke supplies the controlled stopping distance. Part 2.17.5.3.
SCC — Safety Codes Council (Alberta)Alberta's Safety Codes Council. Delegates elevating-device safety in Alberta to AEDARSA.
Seismic detection deviceA device that senses ground motion and, on a qualifying elevator, escalator, or moving walk in a seismic-zone building, removes power from the driving-machine motor and brake. Required at least once per unit or group. Part 8.4.10.1.1 (elevators); Part 8.5.4 (escalators and moving walks).
Seismic operationOn earthquake detection, cars move away from the counterweight, stop at the nearest safe floor and shut down — the counterweight leaving its rails is the danger, not the shaking itself.
SelectorThe device (older units use a mechanical tape/wheel; modern units use encoders) that tracks the car's exact position in the hoistway for leveling and dispatch.
SheaveA grooved pulley the suspension ropes run over. On a traction machine, the drive (traction) sheave grips the ropes by friction to move the car. Part 2.24.2.
ShutdownA unit out of service and unavailable to the building, distinct from a callback, which is the visit. One callback can cause no shutdown at all; one shutdown can last weeks waiting on a part.
SIL — Safety Integrity LevelA rating (1 to 4, with 4 the most stringent) for how dependable an electronic or programmable safety function must be. Comes from the external IEC 61508 series. Section 1.3.
SillThe threshold plate at a car or landing doorway that the doors slide across.
Simplex / duplex / triplexHow many cars are working as one group: one, two, or three. It's the first thing that determines what service a building can expect at peak.
Skirt deflectorThe brushes running along the skirt panel that keep feet, bags and clothing away from the gap between step and skirt. Mechanics call them skirt brushes.
Skirt deflector deviceOptional rigid or flexible element parallel to the skirt panel that steers feet and clothing away from the loaded gap. Geometry rules in 6.1.3.3.10. Allows a higher step/skirt index limit.
Skirt obstruction deviceStops the escalator if an object becomes caught between the step and the skirt as the step approaches the combplate — the trap that catches shoes and loose clothing right at the end of the run.
Skirt panelThe vertical panel on each side of the escalator step band, between the balustrade interior and the steps. Must be smooth, extend at least 25 mm above the tread nose line, and deflect less than 1.6 mm under a 667 N load (6.1.3.3.6).
Slack rope switchA switch that cuts power if the hoist ropes go slack: the sign that the car has landed on something, or a drum machine has kept paying out rope with nowhere to go.
Sling (car frame)The steel frame the car sits inside. The platform, safeties and ropes all attach to it — the cab you stand in is really just a finished box bolted into the sling.
Speed governorAn elevator device: continuously running, it monitors car speed and trips the car safety when the car goes too fast — the spinning watchdog that tells the safety when to grab (Part 2.18). Escalators have no car safety and no governor in this sense; their overspeed protection is the speed-monitoring device, which cuts power to the driving-machine motor and brake once speed exceeds rated by more than 20% (6.1.6.3.2). Where a governor is present on an escalator, it is tested at periodic inspection by manually operating the trip mechanism, then the adjustment means is sealed and tagged (8.6.8.15.5).
Speed-monitoring deviceElectrical safety device per 6.1.6.3.2 that cuts power if the unit's speed exceeds rated speed by more than 20%. Manual-reset.
SpliceA joint in a handrail or belt-type treadway. Must produce a continuous, smooth, unbroken surface: no pinch points, no bumps, no taper. Per 6.1.3.4.4 (handrail) and 6.2.3.6.1 (belt).
SSPI — Step/Skirt Performance IndexCombined friction-and-clearance figure of merit used to judge how safely the step interacts with the adjacent skirt panel. Computed from the polycarbonate-specimen friction coefficient and the step-to-skirt clearance under controlled load. Every escalator in service is tested; the installation era and the code edition in force in the jurisdiction set the thresholds it must meet, and whether the loaded-gap limit applies at all, never whether the test happens. Test procedure: 8.6.8.15.19. Pass thresholds: 8.6.8.3.
Standby power operationHow the group behaves on generator power, when the building usually can't run every car at once: cars are brought down and returned to service in a set order.
Static controlSolid-state motor control. Because there's no contactor opening the motor circuit by default, code requires two redundant power-removal devices, at least one electromechanical (6.1.6.10.4).
StepOne of the linked moving tread units that form the running surface of an escalator, with grooves that mesh with the comb plate at each end. Tread depth at least 400 mm, rise no more than 220 mm, width 560–1020 mm per 6.1.3.5.2.
Step bandAll the steps plus the means connecting them, taken as one assembly. When someone says the step band is out, they mean the whole loop, not a single step.
Step chainThe chains that connect the steps and pull the step band along the truss tracks. Cast iron links are prohibited (6.1.3.11), and a broken step chain must trigger the stop device in 6.1.6.3.3. Stretch and wear are measured, not eyeballed: a worn chain changes step spacing and comb engagement.
Step lateral displacement deviceSafety device required on curved escalators: cuts power if a step shifts sideways too far after a failure in its lateral guidance (6.1.6.3.14). On escalators with dynamic skirt panels, a companion device stops the unit if a skirt panel goes missing.
Step level deviceSafety device that detects a step dropping out of line (downward displacement of 3 mm or more at the riser end) and stops the escalator before that step reaches the combplate, so a sagging or broken step never reaches riders. Per 6.1.6.3.11.
Step nose lineThe line along the leading edge of each step's tread. Used as a reference for vertical-clearance dimensions including headroom (2 130 mm above), handrail height (900–1 000 mm above), and skirt height.
Step rollerThe rollers under each step that ride along the truss track system. If the support rollers sit outside the width of the step, a provision must keep the step from falling into the interior if a roller fails (6.1.3.5.8). Flat-spotted or seized rollers give the classic thump-thump on an otherwise healthy unit.
Step upthrust deviceSafety device that detects a step lifting where it shouldn't (upward displacement of more than 5 mm at the riser end near the lower landing, usually from something jammed under the step band) and stops the escalator. Per 6.1.6.3.9. Mechanics call it the buggy switch.
Stop switchManually opened/closed switch labeled 'STOP/RUN' with positively-opened contacts. Required in each machinery space (6.1.6.3.5) and adjacent to inspection controls (6.1.6.3.15).
Suspension (suspension means)The code's collective word for whatever actually holds the car up: steel wire ropes, coated steel belts, or chains. Worth knowing because “rope” is the habit and belts are common on machine-room-less units, so a requirement written about suspension applies to your belts too. See Rope (hoist rope) .
Suspension meansWhat the car and counterweight hang from — steel wire ropes, aramid fiber ropes, or noncircular coated-steel members — attached to the car frame. Carries a required safety margin (factor of safety). Part 2.20.
Escalator Field Guide
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