Hydraulic systems a generation ago featured valves that were either threaded for pipe and tube mount, or used a flat gasket interface for sub-plate mounting. These systems were bulky, leaky, heavy, and downright messy. Over the last 20 years, however, many line-mounted components have given way to hydraulic integrated circuits (HICs) using cartridge valves mounted in manifolds. Cartridge valves are installed into a hole on a hydraulic manifold (typically a cube-shaped block of aluminum, steel, or cast iron), which contains internal passages to create all connections between the valves and work ports. Some cartridge valves have threaded bodies that screw into the manifold, while others slip into cavities and are held in place by a cover that is bolted down.

In terms of design, the modular capacity of cartridge valves sets them apart from other valves. For example, a single line-mounted D08 directional valve may be used to control a cylinder, while a hydraulic integrated circuit (HIC) employs four or five cartridge valves for the same job. Thus, each cartridge can be optimized for each of the functional aspects of the large single directional valve, such as asymmetrical cylinder flow, pressure intensification, decompression, soft shifting, etc. By making the cylinder’s cap end cartridges larger than the rod end cartridges (and changing other functions in a likewise manner), cartridge valves circuits can be significantly more energy efficient.

Cartridge valves provide circuit designers with a wide range of controllable flows. Slip-in cartridges offer high efficiency for flows ranging from 80 to 1600 gpm, and screw-in cartridges from 1 to 200 gpm. Therefore, not only do HICs increase power and control density, but they minimize volume and footprint.

Slip into slip-Ins

Slip-in cartridges are usually the best choice in industrial (stationary) systems, particularly when prerequisites include high flows, high pressures, and high duty cycles. Most slip-in cartridges fall into the two-port poppet-valve category, and they are either fully open or fully closed. These are sometimes referred to as logic valves because of their either-or functionality. 

All slip-in cartridge valves are pilot operated, meaning that a small amount of pressurized hydraulic fluid is used to shift the valve open or closed. The trick to designing slip-in cartridge circuits is to understand the importance of pilot pressures within the circuit, be able to read and comprehend pilot circuitry, and ensure pilot pressure is always present.

It’s also crucial to understand how orifices control the rates of opening and closing slip-in cartridge valves. Generally, at the circuit-design stage, default orifices that come with covers would be a good place to start. The ability to tune circuits for fast response and low shock by changing the size of control and damping orifices in the covers comes with experience

A slip-in cartridge poppet is normally open, normally closed, and can provide modulated control. Unlike valve spools, poppet valves provide a leak-tight seal when closed. Cartridges that shift from open to closed are directional cartridges, because they either allow flow between ports A to B, or block it. A set of four two-port cartridges can replicate the four-way P-A, P-B, A-T, and B-T functions of a directional valve.