Outdoor Platform Lift Gate Interlock and Sill Mismatch
An outdoor inclined platform lift serves a 1.2 m rise at a public library. It was installed in 2014 and has a 900 mm by 1,200 mm platform, a folding seat, and a key-operated control. During a rainy-day call, the librarian reports that the lift “sometimes stops halfway” and that the gate at the upper landing can be pulled open about 50 mm while the platform is moving. You find the platform sill is 25 mm above the upper landing when leveled, the gate interlock striker is loose, and the fault log shows three “gate open” faults in the past week. The lift is the only accessible entrance to the children’s section; the main entrance has a 200 mm step and no ramp.
1. Assess the gate and sill conditions against the platform-lift code and decide whether the lift can remain in service.
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The gate condition is a critical non-compliance. A platform lift gate must be provided with a positive interlock that prevents movement unless the gate is closed and locked, and the interlock must not be capable of being bypassed by pulling the gate open. A 50 mm opening with a loose striker means the gate can be opened while the platform is moving, so a passenger could reach into the hoistway or fall from the platform. The 25 mm sill mismatch is also a tripping hazard and may exceed the allowable clearance between the platform and the landing; it must be measured against the applicable CSA B355 requirement. The lift should be removed from service immediately, locked out, and tagged. The library’s lack of an accessible route does not override the hazard; the owner must arrange a temporary accessible entrance or alternate service while repairs are made. The three “gate open” faults in one week support the conclusion that this is a recurring interlock failure, not a one-time adjustment.
2. What root-cause checks and repairs would you perform before returning it to service?
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I would first inspect the interlock switch, striker, wiring, and terminal connections for misalignment, moisture ingress, corrosion, and loose fasteners. Because the lift is outdoors and the call occurred in rain, I would check the enclosure gaskets and drain paths as well. I would adjust or replace the striker and switch so that the gate cannot be opened until the platform is at the landing and the lift is stopped, then test the interlock from every operating position, including the upper and lower landings and with the platform at mid-travel. I would correct the platform leveling and sill mismatch, verify the platform stops level within tolerance, and check the slope and landing transitions for water damage or frost heave. After repairs I would perform the required function tests, load test, and documentation, and I would record the fault log entries and corrective actions before releasing the lift.