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    Although I've already come across these newer Komatsu pumps (like this one), I could never get enough time to gut one right... Until today, when I finally got my chance with this little baby from (according to the owner) a PC 340 excavator.

    From my previous experiences I already discovered that these pumps have simple closed center load sensing controls, with the only major difference being the fact that Komatsu opted for the use of an external upstream LS signal, which on most "classic" LS pumps is connected internally to the pump's pressure outlet. And this one is no exception, as you can see from the diagrams - here you have a simple diagram, showing only one pump, and here is something I made to show the complete tandem unit, mainly to demonstrate locations of the test ports.

   Like its smaller sisters, it is equipped with two proportional pressure reducing valves, which provide pilot pressures to override the settings of torque limiter and LS delta P, which, as modern days dictate, are most surely controlled by a computer on the actual machine. The small block under one of the valves is a small spring-loaded accumulator. I would guess its function it to dampen the pilot pressure spikes.

    I said before that these controls are over engineered, but now, after I've looked into them in detail, I must admit that this is an elegant  solution for a torque limiter, I even made a small diagram of its function, which is out of proportion and only serves to show the principle of its operation.

   This solution is compact and simple, but it requires a lot of precise low-clearance machining (expensive) and most surely is less contamination tolerant than "classic" designs. If something goes wrong with the control, you will have to replace the whole servo-cylinder assembly, something you won't find anywhere but at the origin... Also, you can not access this part without partially disassembling the pump. I, personally, still am an adept of bulkier controls which are separated form the servo-cylinder, allowing for better serviceability, but this solution is VERY NEAT. I take my hat off  to whoever designed this control!

   The presence of all these plugs and holes in the servo-piston assembly is, from what I have seen, a weak place in these pumps. So far I have already seen them plugs come out (causing the displacement control to malfunction), and, on this particular pump, the Swiss cheese servo-piston simply split in half (yes, smack in the middle), which will be soon posted in the kaboom section.

    Nevertheless, upon looking further into the pump, I find a lot of very interesting engineering solutions, like the cartridge valve, (I do not know if the Komatsu has a name for it, but I baptized it "cartridge" as it looks like one), which is removable and therefore allows for some options, like orifice to tank, controlled restriction, check-valve, etc... This is only my speculation, though, but I still pointed it out in the diagram.

   The pump screams high quality and thorough research! I believe the Komatsu engineers have meticulously designed this pump to present the best efficiency and self-oscillations free control performance. As much as I hated old Komatsu designs, I am starting, well, not to "like", but rather to "find attractive" these newer ones.

   The only thing that still is a strong "NO" factor, is the fact that if something must be replaced, especially is the control area, there will be no cheap solution.

    Despite these drawbacks, these pumps are still on the top of the "quality pyramid", and like any quality hydraulics, will not brake "on their own", provided that a reasonable share of "quality maintenance" is involved.
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Komatsu pump from PC340, cartridge detail
Komatsu pump from PC340 hydraulic schematics
Komatsu pump from PC340 hydraulic schematics
Komatsu pump from PC340, torque limiter deatil
Komatsu pump from PC340
Komatsu pump from PC340
Komatsu pump from PC340
Komatsu pump from PC340
Komatsu pump from PC340
Komatsu pump from PC340
Komatsu pump from PC340, proportional valves
Komatsu pump from PC340, LS spool
Komatsu pump from PC340, servo-cylinder and torque limiter
Komatsu pump from PC340, servo-cylinder and torque limiter
Komatsu pump from PC340, servo-cylinder and torque limiter
Komatsu pump from PC340
Komatsu pump from PC340
Komatsu pump from PC340