If hydraulic pressure is lost in the primary circuit, how does the secondary piston actuate?

The secondary piston actuates through mechanical pressure from the primary piston when there is a loss of hydraulic pressure in the primary circuit. This mechanical linkage allows the secondary piston to respond to movement of the primary piston, which means that even in the absence of hydraulic pressure, some degree of mechanical movement can still transfer force from the primary to the secondary circuit.

In systems where both circuits are interconnected, the mechanical action of the primary piston can continue to ensure that components dependent on the secondary piston can still function to an extent, allowing the overall system to maintain some level of operation. This behavior is important in hydraulic systems designed with such redundancies or fail-safes to ensure that a total failure does not result in a complete loss of function.

Other choices relate to different mechanisms of operation. The compensating port typically helps regulate flow or pressure and wouldn’t directly actuate the secondary piston in the event of primary pressure loss. Similarly, the statement that primary pressure loss affects both circuits is inaccurate in this context, as the mechanical connection can still allow for some actuation despite the loss. Hydraulic pressure from the primary piston is not applicable here since the question specifies the condition of lost hydraulic pressure.