Forced Draft Fan & Primary Air Fan are used for adjusting the blast volume of a blower fan. It consists of three sections Rotary sealing section, Distributing spindle/ spool section & Main cylinder.
Rotary section can draw high pressure oil as well as returning oil & lubricating oil in the main cylinder body rotating at high speed and consists of a stationary shell supported by roller bearings.
Distributing spindle section acts as a directional valve with negative overlap. In order to protect the sealing, cool oil circulating outside the body is necessary.
Main cylinder body section is a differential cylinder with 1:2 ratio of upper & lower area. When high pressure oil is simultaneously led into the upper & lower chamber, larger chamber will act as cylinder chamber & smaller one acts as a pump supplying the larger one with oil and vice versa. This function causes the cylinder running in both directions for the same time & having the same acting force outside.
Servo cylinder operation: As the distributing spool moves in inlet line connects to the upper & lower chambers of the cylinder, the return oil is fully closed. On the other hand, as the distributing spool is pulled forward for a stroke, the inlet line only connects to the upper chamber & the return line opens fully so that the cylinder body will move forward until it returns to its original relative position. In general, servo cylinder is a hydraulic amplifier which can generate power force with a small drive signal source.
