Engineering Essentials: Cartridge Valves

Fig. 1. Slip-in cartridge for pressure reducing consists of biasing spring, poppet, sleeve, seals, and cover plate (unshown).

Valve cartridges can be thought of as "bodyless" - valves without an integral housing - because they consist of only the internal moving elements of the valves. After a cartridge is inserted into a cavity, such as a manifold with appropriate flow passageways, the resulting valve performs like any conventional valve. Slip-in cartridges are held in the cavity by a cover plate, Figure 1; screw-in-type cartridges mate with threads in the cavity, Figure 2. Another type of insertable cartridge has circumferential grooves. After it is inserted into the cavity, it is held in place by swaging internally with a tapered pin that expands the cartridge diameter into interference contact with the bore.

Versatility

A wide variety of cartridges allows engineers to find almost any hydraulic control function in cartridge form - with very few limitations. Here are the control functions readily available in cartridge configuration today:

• relief valves
• sequence valves
• pressure-reducing valves
• check valves
• pilot-operated check valves
• load-control valves
• counterbalance valves
• flow-control valves (pressure- and non-pressure-compensated, fixed, priority, proportional divider)
• solenoid valves in 2- or 3-way poppet or spool type, and 4-way, 2- or 3-position versions, Figure 3
• electro-proportional directional, flow, and pressure controls, and
• specialty valves — such as shuttle valves and velocity fuses.

One innovation in cartridge valve technology today is the incorporation of two or more functions into a single cartridge housing — for example, check valves with flow-control valves, dual crossover reliefs, etc.

Custom valve packages