One puzzling valve in a bad copy of a schematic 1

[brcuzz]

I'm resurrecting a bad (and only) copy of a hydraulic schematic for a Menzi Muck 5000 T2 spider excavator. It was apparently photocopied while folded, without bothering to unfold it, so the folded regions are blank, forming a thin blank cross on the reconstructed page. I've inserted the missing elements in color on the attached draft reconstruction, as well as some translations of the German in blue. But in the yellow-highlighted box there's a valve that has me baffled. Does anyone recognize this type of valve? And what ports would it normally have?

 

[hydtools]

A pilot operated check valve.

Ted

 

[brcuzz]

So the valve diagram should should be corrected to look like this?:

 

[hydtools]

OK, but you dropped the internal check valve symbol from the pilot side position of the valve.

Does it now match the circuit operation logic?

Ted

 

[brcuzz]

OK. Would this be the correct way to diagram it? And is there an ANSI standard for hydraulic schematics? I have not really gotten to the logic part of the project yet, just figuring out what's on paper so far.

 

[hydtools]

ANSI Y32.10
The International Standards Organization (ISO), standard ISO 1219-1:2012

Ted

 

[Jacc]

This is an improvised symbol, you won't find it in any standard.

This is a sectional Open Center valve manifold of Parker brand.
The weird symbol is probably because they butchered a standard spool/section or mid inlet section to achieve a certain function.

The function seems to be that if you start operating the slew function, the excess flow from the slew function is directed directly to tank.
The reason for doing this is to make sure the other functions downstream of the slewing valve will not affect the slewing speed. I.e. if you are slewing slowly and then lift the boom with a full load, the slew would suddenly speed up. This could cause all kinds of incidents on an excavator working on steep technical terrain and perhaps with people around.