If you work in lift or elevator safety, you’ve probably heard that an overspeed governor is the unsung hero that keeps cars from careening out of control. But if you’re like most people, you might not stop to think about all the built-in safety interlocks that make this part actually work—especially when you’re sourcing gear as reliable as the ones we supply. I get it: when you’re busy with inspections, installations, or troubleshooting, it’s easy to see the governor as just a spinning wheel and a rope. But those interlocks are what turn a simple speed-monitoring device into a fail-safe that stops a lift dead before disaster hits.
Let’s break this down without the jargon, okay? First, let’s make sure we’re on the same page: an overspeed governor (sometimes shortened to just “governor”) is the component that tracks how fast the lift car is moving, way before any other safety system kicks in. We sell a bunch of options, from our standard Overspeed Governor to ones tailored specifically for lift setups (check out our Overspeed Governor For Lift if you’re dealing with high-rise installs). But here’s the thing—no governor does its job alone. The interlocks are the safety layers that keep it from failing, even if something goes sideways.
The first interlock you’ll find on just about every overspeed governor is the electrical safety switch. Most people don’t realize this is the first line of defense, not the mechanical one. When the lift car speeds up past a pre-set limit (usually 115% of the rated speed, per global codes like ASME A17.1 or EN 81), the governor’s flyweights (little metal arms inside that pop out when speed spikes) trigger this electrical switch. The switch cuts power to the lift’s motor immediately—no waiting around. If that electrical switch didn’t exist, a spike in voltage could fry the governor’s moving parts, or a loose wire might keep the motor running even when speed is too high. I’ve seen this happen a couple times on job sites: a tech skipped testing the switch during a routine check, and when a car started speeding, the motor didn’t cut out, leading to way more wear on the braking system. That’s why we build our Lift Speed Governor units with redundant electrical contacts—so even if one fails, the other still trips to shut down power.
Next up is the rope grab interlock. The governor connects to the lift car’s safety gears via a steel governor rope that runs over a pulley at the top of the shaft and down to a weight at the bottom. When the flyweights pop out at overspeed, they lock the governor pulley from spinning. That’s where the rope grab comes in: it clamps down on the governor rope so hard that the rope can’t move. But here’s the interlock part—this clamping action has to be tied directly to the lift car’s safety gears, not just the rope. If the rope grab clamped but didn’t pull on the safety gear, the car would just stop the rope, not the car itself. We test every Elevator Overspeed Governor we ship by simulating rope slip: if the grab doesn’t lock both the rope and trigger the safety gear within a fraction of a second, it gets sent back to our shop. That’s why our Speed Governor For Elevator line has a built-in tensioner for the governor rope, too—if the rope is too loose, the grab won’t engage, so the whole interlock chain breaks. Tensioners aren’t just a nice add-on; they’re a critical interlock that prevents false disengagements.
Wait, let’s talk about the weight interlock, too. The governor’s bottom weight isn’t just for keeping the rope taut—it’s a check on the system. If the weight is too light, or someone removes it (I’ve heard horror stories of lazy mechanics skipping that step), the governor pulley won’t spin fast enough to trigger the flyweights, even if the car is actually going too fast. That’s a hidden interlock most people overlook: the weight’s mass is calibrated exactly to the governor’s trip speed. For example, a 1,000 lb. capacity lift needs a 2 lb. weight, not a 1 lb. one—swap that, and the governor trips too late. We include detailed weight installation guides with every unit, but we still get calls from guys who tried to “adapt” a weight from an old governor. Don’t do that. It’s a simple interlock, but one that prevents so many overspeed incidents.
Another one is the shaft limit switch interlock. No, this isn’t part of the governor itself, but it ties directly to how the governor works. If the lift car reaches the top or bottom of the shaft too fast (way before the governor would trip), a limit switch cuts power to the motor. But here’s the link to the governor: the governor’s electrical switch is supposed to trip at a slightly lower speed than the limit switch. That way, the governor acts first. If the limit switch trips before the governor, that means the governor is faulty, and techs know to check it right away. We work with lift manufacturers to wire these two switches in a series, so if either trips, the motor cuts out. It’s a interlock that creates a chain of accountability between the governor and the rest of the lift’s safety system.
Let’s get real for a second—most of the time, these interlocks work without anyone noticing, which is exactly how they’re supposed to. But last year, a small lift company in Chicago called us because their governor had tripped, but the car still kept moving. Turns out, their mechanic had modified the electrical switch to be less sensitive, so when the speed spiked, the switch didn’t cut power, and the rope grab couldn’t lock because the flyweights had to pop out harder. We sent a tech out to re-calibrate the switch, and we also walked them through checking all the interlocks during their next routine inspection. That’s why we make sure all our Overspeed Governor For Lift units come pre-calibrated, with clear instructions for testing each interlock—no guesswork.
A lot of people ask us: “Do I need to test all these interlocks every time I do a service?” Let’s be honest, code requires it. The electrical switch, rope grab, rope tension, and weight all need to be checked every 6 months (per ASME) or annually (per EU codes). Skipping even one is a safety hazard. I’ve seen a lift in a small apartment building fail a inspection because the weight was missing—they thought it was “unnecessary” because the lift “never goes fast.” Spoiler: it did go fast, when a kid ran around inside and the car lurched. The governor didn’t trip, and the safety gear only caught it at the bottom, leading to a damaged counterweight. That cost them $10k in repairs, not to mention the inconvenience of being out of service for a week.
If you’re a lift mechanic, facility manager, or anyone responsible for elevator safety, you know that the right gear makes all the difference. Our range of governors—from our standard Overspeed Governor to specialized Lift Speed Governor units—are built with all these interlocks integrated, so you don’t have to piece together parts that might not work together. But even the best gear only works if you check those interlocks regularly.
At the end of the day, overspeed governors aren’t just about monitoring speed—they’re about the network of interlocks that turn a single device into a full safety system. It’s easy to overlook these little parts, but they’re the reason a lift doesn’t become a hazard. If you’re in the market for a reliable overspeed governor, or you have questions about which interlocks to test for your setup, reach out to us today to talk through your needs.
References:
- ASME A17.1-2020: Safety Code for Elevators and Escalators
- EN 81-1:2020: Safety Rules for the Construction and Installation of Elevators
- National Elevator Industry, Inc. (NEII): Recommended Safety Inspection Practices for Elevator Overspeed Governors
- Elevator World Magazine: “Critical Interlocks in Overspeed Governor Systems” (2022)
- American Society of Mechanical Engineers (ASME): Overspeed Governor Performance Standards