Hydraulic Line

Hi all!,

I am currently working on a hydraulic project. One of the procedure requires me to setup a line as shown in the picture. I am fairly new to this field, I am not sure what does the symbol highlighted in red represents. I have used google image try to find it, no results.

Thank you for your help,


  • $\begingroup$ If this were a P&ID for a chemical process (and not hydraulics) I would definitely say check valve. For hydraulics, the check valve is sometimes drawn as a circle in a "V" shape. It's possible that this is meant to indicate a relief valve. Functionally they are similar, but the intended purpose of the two can be different, especially if the relief valve is meant for a safety function. $\endgroup$
    – Byron Wall
    Commented Sep 21, 2016 at 18:15

1 Answer 1


I worked in a hydraulics design field for two years and found that unfortunately there isn't a standard way to draw many components. Each manufacturer seems to choose their own route. Designers are left to redraw or interpret components and sometimes hybrid symbols are created making the problem worse.

Information about what your project does and what you think the component does would be helpful. Also knowing the vendor or a recommended manufacturer would be helpful in hunting it down.

My best guess is that it is a poorly drawn check valve. The little spring drawn on it, most likely means that it is spring actuated (spring closed) and has some backpressure. Here are some check valve symbols it is similar to. I suggest you evaluate your hydraulic circuit and see if a check valve makes sense in that location before fabrication.

ISO Spring-loaded ball-type non-return valve
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Check Valve Symbol on Wiki
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ProfiCAD Symbol Library
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ConceptDraw symbol library
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  • $\begingroup$ The hydraulic lines are hooked up to an Aileron Servocontrol Actuator on A320 planes. Starting from the left, the first pipe is connected to a servo valve, the middle is pressure in, the right is return pressure. It is hard, if not impossible, to get information from manufacture because my company doesn't not have subscription to their technical support. I think a check valve in this case make sense. $\endgroup$
    – Sean
    Commented Sep 16, 2016 at 16:20
  • $\begingroup$ That sounds much more interesting than the potato equipment I worked with ;-) Glad I could help! $\endgroup$
    – ericnutsch
    Commented Sep 16, 2016 at 22:52

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