Auxiliary valves consist of multiple sections assembled together to form a stack to be used in mobile applications. A typical stack consists of 2 to 10 sections with each section being selected for a specific function. Sections consist of a directional control spool with or without a float position, proportionally actuated mechanically, hydraulically, or electrically. Sections may include workport reliefs, PO checks, pre or post pressure comp and flow limiters. Sections may utilize a load sense feature for pump control or be of an open center design for use with positive displacement pumps.

Titan has taken two approaches to test auxiliary valves. In one approach, the section is tested alone and then a very simple test is performed on the complete stack. A second approach is to perform section level testing after assembled into the stack. The approach is usually governed by the customer, although Titan can discuss the pros and cons of each.