A skylight cleaning robot tether should be rated to at least 3-5x the unit’s weight, inspected before every shift, and paired with a ground exclusion zone. Operation should stop above roughly 12 m/s wind, or lower if the manufacturer states less.
Most people worry about the robot falling off the roof. The subtler risk is the tether failing under load or the robot swinging into the space below. Both are manageable with three habits.
How strong does the tether need to be?
Tether specs confuse buyers because there are two jobs: power/data delivery and fall arrest. Some systems use one cable for both; others separate them. For fall arrest, the working load should be several times the robot mass, so a 20 kg unit wants a cable rated well above 60 kg with documented inspection.
Check the rated load, the age of the cable, and any abrasion near anchor points. A frayed tether is a stop-work item, not something to swing on for one more panel.
What wind speed stops the job?
Most 2026 units list a maximum operating wind around 10-14 m/s, and many add a gust threshold lower than the steady limit. A gust can spike double the average in seconds. Carry a handheld anemometer and set your own stop point below the spec. On an exposed high-rise roof, that might be 8 m/s.
Wind matters more on tall, unsheltered roofs and on glass with a smooth coating, where cups have least grip.
Why do you need an exclusion zone?
Anything that can fall needs a zone underneath where people do not stand. A robot plus its tether and any tools can drop. Mark the area, brief staff, and post signage during operation. In public atriums and malls the floor below is the tricky part, because the zone moves with the robot.
- Inspect tether and anchors before every shift.
- Stop above roughly 12 m/s wind, or the manufacturer’s lower figure.
- Mark the ground exclusion zone and brief staff.
- Keep a rescue and recovery plan on file.
What should the daily log capture?
| Check | Before shift | Note |
|---|---|---|
| Tether condition | Yes | Frays = stop work |
| Anchor integrity | Yes | Torque test yearly |
| Wind speed | Yes + hourly | Handheld anemometer |
| Exclusion zone | Yes | Signage and brief |
| Cups and blades | Yes | Replace worn items |
Who gets this wrong?
Sites that treat the robot as low-risk because it is “just a machine”. That attitude skips the anchor torque check and the wind log, and those are exactly the items an incident report will ask about. Treat the robot like any other height-work asset with a documented regime.
Safety documentation for the K3, Y3 and S1 is available via the contact page.
What does a tether inspection actually check?
- Surface abrasion and cut strands along the full length.
- Connector and carabiner wear and correct locking.
- Anchor bolt torque and corrosion.
- Sheath integrity around any bend or edge.
- Load-test documentation within its valid period.
How does rain change the risk?
Wet glass cuts suction grip sharply, and rain adds weight to the tether as water soaks the sheath. A robot running on a rain-wet panel at speed can slide before the vacuum recovers. Most operators treat rain as a stop condition, not a nuisance, and reset for a dry window instead of pushing through.
Frost is worse. A thin ice film under a suction cup means almost no sealing, and the robot can break free without warning. In cold climates, treat frozen mornings as no-go until the glass clears.
What is a sensible exclusion zone size?
Size the zone to the potential swing, not just the drop point. A tethered robot pendulum-swinging from a tall roof can travel several metres sideways. For high roofs, mark a zone that covers the swing arc plus a margin, and keep it clear for the whole shift. In public spaces, use barriers, not just cones.
Who is accountable when something falls?
The site operator, not the robot maker. That is why the daily log, the anchor certificate and the exclusion-zone record matter. After any incident, investigators ask for exactly those documents. A team that kept the log finds the process straightforward; a team that did not has no defence.
How often should anchors be re-tested?
Most standards call for annual visual inspection and periodic load testing, often every 12 months depending on jurisdiction and use. Keep the certificate on file and note the next due date. An expired anchor certificate can halt a clean on the day and, worse, invalidate insurance after an incident.
Salt air and coastal sites accelerate corrosion, so inspect more often there. A rusted anchor thread that still looks sound can fail under load.
What does a rescue plan need?
- How to retrieve a stranded robot from the roof.
- Who to call and how fast they can respond.
- How to isolate power and reset the unit safely.
- How to clear a fallen unit from a public area.
How do you brief non-technical staff?
Most people who see the robot on a roof are not operators. A short briefing covering the exclusion zone, the meaning of the signage, and who to alert if the robot behaves oddly prevents bystanders from wandering underneath. Simple, repeated, and written down beats a lengthy policy nobody reads.
Key Takeaways
- Rate tether fall arrest at 3-5x robot weight.
- Carry an anemometer; gusts beat the steady wind limit.
- Mark a moving ground exclusion zone under the robot.
- Inspect tether, anchors and cups before every shift.
- Log wind, tether and anchor checks for audit.