PILGRIM NUT METHOD :

The pilgrim nut system with the shaft and bore surfaces dry and degreased (except for cast steel propellers where wiping of the bore with an oil soaked rag is recommended) achieves the correct push-up by a calculation based on the predictable friction on dry surfaces. The  hydraulic  pressure  is  applied  suitable  for  the  ambient temperature is constantly monitored and also the hub movement relative to the increase of jacking pressure is checked by a dial gauge. The pilgrim nut employed for propeller mounting has internal nitrile rubber tube which when inflated hydraulically, forces a steel loading ring against the hub. Outward movement of the loading ring from the flush position must not exceed one third of the ring width, to avoid rupture of the rubber tube. Temperature of the hub and shaft are recorded and also used to find the correct final push up pressure from the manufacturer's instruction table. The propeller boss after a check with blue marker on the tapered surface of the shaft is pressed up successively with a push of 25 mm in each time by hydraulic pressure on to the loading ring and when it reaches the final position, it is finally nipped up with a tommy bar. Then the pilgrim nut is locked in position by a locking plate and bolts. The pilgrim nut can be reversed and used with a withdrawable plate and studs for removal of the propeller. To safeguard against any violent movement at release, wooden blocks are inserted and a gap of only a little more than the push up distance is left.

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