An Investigation of Oil Column Separation in the Return Line of Large Free Forging Press

Abstract

In a large free forging press, the high speed operation of a directional control valve often causes an oil column separation in the return line just after the valve. The process of oil column separation from the start of valve operation to the contact of oil columns is analyzed by the numerical calculation, and the relation between the valve closing time of linear closing mode and the surge pressure due to the contact of the oil columns is obtained. The expression of flow characteristic of the valve can be simplified by use of an effective stroke of the valve. The general relations between the oil column separation caused by the linear mode closing of the valve and the dimensionless parameters which describe the characteristic of pipe system are obtained.