Mounting hydraulic valves
In-line and subplate-mounted hydraulic valves are common. However, most in-line valves are screw-in cartridge type with aluminum or steel bodies. Figure 10-31 shows an example of an in-line cartridge valve. (This valve also could be screwed into the custom manifolds discussed later.)
Screw-in cartridge valves perform all directional and flow control, relief, sequence, counterbalance and reducing functions -- the same as in-line and subplate valves. Only their physical makeup is different. They normally handle flows less than 40 gpm, but some manufacturers offer sizes with up to 120-gpm capacity.
There are worldwide interface standards for subplate-mounted hydraulic directional control valves. The information in Figure 10-32 shows port and bolt locations and relative sizes for all standard sizes. The figure also lists the numbering systems for U. S. National Fluid Power Association (NFPA), worldwide International Standards Organization (ISO), European Committee for Oilhydraulics and Pneumatic Control (CETOP), and the NG part of the German DIN Standard, which relates only to port size in metrics. (Actually, the NG port size can be for any type valve.)
Interface standards cover both size and location for ports and bolts. A directional valve from any country or manufacturer using this standard is interchangeable with all other valves of the same size. The only difference should be whether the bolts have SAE or metric threads.
Figure 10-33 depicts typical subplate and bar-manifold mounting arrangements for subplate-mounted directional control valves. Subplates mount a single valve and are used in simple single-cylinder applications. They come in bottom- and side-ported models for piping convenience. Some side-ported models have bottom ports as well.
Subplates can be used for multi-cylinder circuits but require a lot of pipe connections that can restrict flow and may be potential leakage points. Many multi-cylinder circuits work well with the bar manifold shown in Figure 10-33.
Subplates are available for all the valves listed in Figure 10-34. Porting for larger valves usually involves SAE flanges on the valve body. When they have subplate mounts, a special subplate must be made or they are mounted on a custom manifold.
Bar manifolds come with series and parallel porting related to pump and tank connections. Series manifolds usually are limited to three stations or three valves maximum, while parallel manifolds can have as many as 16 stations.
When circuits are not too complex, bar manifolds and modular accessory valves can eliminate most pipe connections and put everything in one location. Symbols for these modular valves are shown for most of the types available. They are always at the end of a section for a particular accessory valve.
Bar manifolds are only offered in sizes D02, D03, D05, D05H, D07 and D08. Size D10 valves use subplates or specially made bar manifolds, or are mounted on a custom manifold.