Which statement is true regarding sequence valves in a hydraulic system?

In hydraulic systems, sequence valves are designed to open at a predetermined pressure. This characteristic is essential because it allows for control over the sequence of operations in the system. By requiring a specific pressure to activate, sequence valves ensure that the hydraulic functions occur in a precise order, which is crucial in applications where timing and sequence are critical for safety and efficiency.

The preset value at which a sequence valve opens is adjustable, providing flexibility in system design. This feature allows engineers to design hydraulic systems where different components or processes are activated only after preceding operations have been completed, thereby optimizing the system's performance.

The other statements do not accurately represent the function of sequence valves. For instance, the idea that they open without a preset pressure mischaracterizes their intended operational control. Additionally, suggesting that they are exclusively designed for electrical circuits or are unsuitable for fluid power applications neglects the fundamental role sequence valves play in hydraulic systems.