Philadelphia Gear gearboxes are an industrial workhorse, found on oil refineries, drilling platforms, chemical plants and paper mills. Most companies run them to failure, which often times is an impressive 10+ year run before a repair is needed. Their one weakness is the lip seals that are installed. Oil seal are able to contain forced lubrication systems or oil bath lubrication environments. They do however wear out in about 6-8 months on continuous use. On top of that, the lip seal wears a grove into the shaft, making it necessary to either refurbish the shaft or get a new one when it's time to repair. Regular labyrinth isolators don't scar the shaft but perform poorly in forced lube systems or flooded environments.