Hydraulic mounting and dismounting is a procedure using a pressurized fluid fo joining and separating cylindrical or tapered surfaces, the fluid being forced between the surfaces. The fluid used is eigther a hydraulic oil or machine oil. Mounting work should be performed with a rather thin oil having a viscosity of about 100 E at 200 C (75 cST at 680F). A thin oil will clear better from the fitting area (than a high -viscous oil) after completion of mounting. For dismounting, a thicker oil can used -about 200E at 200C (150 cST at 680F). If the contact areas in the fitting joint are damaged, a high viscosity gear or cylinder oil of about 1500E at 200 C (about 1140 cSt at 680 F) can be used. Fretting corrossion can be dissolved by adding anti-corrosive additives to the oil.
The oil presure must be exceed the presure existing acros the interference fit. This will cause an oil film to build up in the contact area.This presure film greatly reduces the friction between the connecting parts which can be conveniently displaced in relation to one another without the risk of damage to the surfaces. Since at the edges of the contact surfaces, the unit pressure is higher than over the central portion, the oil film will stay on for a little while.When mounting is completed the oil escapes from the joint and full frictional contact is re-established.
