The system circuit
The basic closed circuit
Hydraulic lines connect the main ports of the pump to the main ports of the motor. Fluid flows in either
direction from the pump to the motor then back to the pump in this closed circuit. Either of the hydraulic
lines can be under high pressure. In pumping mode the position of the pump swashplate determines
which line is high pressure as well as the direction of fluid flow.
Basic closed circuit diagram
Input
PV
MF
Case drain line
Output
Flow (Bi-directional)
Reservoir
P104 120E
Case drain and heat exchanger
The pump and motor require case drain lines to remove hot fluid from the system. The topmost port
drains the motor to ensure the case remains full of fluid. Fluid routes through the lower drain port on the
pump and out the topmost port to the reservoir. A heat exchanger, with a bypass valve, cools the case
drain fluid before it returns to the reservoir.
Service Manual
Series T90 Axial Piston Pumps
Introduction
©
Danfoss | March 2020
AX216086485386en-000101 | 9