Hydraulic Schematic - please explain!

[Speedy]

Could somebody please explain the following Hydraulic Schematic?

There are 2 pumps. The left is simply for the heat exchanger. The main pump (on the right), I understand to be of constant speed with the pressure regulated by a proportional valve.

However the schematic would seem to indicate that the pump is variable displacement (symbol-slanted arrow across pump) with a mechanical feedback on pressure.

What does the 'P' represent? I assume it is pressure.
The max pressure is 300Bar with over-pressure protection from a relief valve on the supply side.

Any comments welcome.
Regards,
Speedy

http://photobucket.com/albums/c22/eohalloran/?action=view&current=PumpSchem.jpg

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[MintJulep]

I can't find anything like that in the ISO hydraulic symbol library.

I'm half tempted to suggest that it might be a pressure piloted clutch to drive the pump in the left block.

 

[crjones]

This may be representative of control of the internal pump relief. This relief can be modified with respect to the control requirements.

 

[maytag]

Speedy,
You might post your question on the International Fluid Power site-there is a forum there that is frequented by some fluid power professional and there is the fluid power forum here as well. I could find no symbols such as drawn to the left of the pump. I would assume that one of these is supposed to represent a relief valve as there should be one in close proximity to the pump and possibly part of the other unknown symbol representing the control option for the varible pump i.e. pressure compensated,load sensing etc Maytag

 

[Beggar]

There is also the

http://www.eng-tips.com/threadminder.cfm?pid=1083

forum here on eng-tips

--------------------
Bring back the HP-15

http://www.hp15c.org

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[JJPellin]

That basic pump symbol is used for the hydraulic pumps we use in several systems. Our pumps are made by Parker Hydraulic. In their literature it refers to this symbol specifically for a variable volume piston pump. I have heard this called a swash plate pump. The extra symbols to the left of the pump suggest that is uses remote pressure compensation and perhaps load sensing or torque limiting capability. I am not an hydraulics expert. Perhaps you can use some of this terminology to Google for more information.

 

[ARenko]

The schematic does show it as variable displacement. This doesn't mean the pump is not driven at a constant speed. The swash plate angle changes to change the displacement, but it still rotates at constant speed.

The symbol that the P is in indicates a control method - it is a general symbol without indication of control type (types can be push button, foot pedal, lever, etc...). This is then connected to the pilot w/ adjustable spring (on the schematic). Perhaps it it is the pressure compensator with a manual lever in addition to the spring-adjustable pilot. I've never noticed a P symbol in one before, but I guess someone just meant it to mean that it is the pressure compensator controller. The pressure compensated pump will put out a variable flow to maintain a constant pressure according to the setting of the pressure compensator.

 

[budt]

Speedy;

Can you find a manufacturers name on the pump? A part number?

The best place to look for a symbol that is not covered in ANSI or ISO symbol literature is in the manufacturers catalog. They have the symbol and usually post an explanation of what is happening with each component in the symbol.

Symbol literature like ANSI and ISO are for general info and do not and cannot cover every type of combination that can be made by using available components. On top of that, when someone has to make a symbol to cover a device they produce it always is up to their interpretation of standard symbols. I look back at some I have put together over the years and wonder what I was thinking when I made that one.

If I had to interpret it from what the symbol indicates I would say it is a Variable Volume Uni-Directioonal Pump with a Proportional Control for Volume Output and a Manual Override at the pump to operate the displacement for setup.

"P" could mean Proportional for the Manual Operator to the left of the square it is in????

Find a catalog and if it is Parker, Vickers, Rexroth there will be a fairly comprehensive explanation of all their control types.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us