Relief Valve Basics 

I'll try to clarify a little. The relief valve does indeed open when the system pressure is greater than the spring setting. You have that precisely correct. The first pressure level where that happens in a relief valve that has only one spring and one poppet, is not the highest pressure that the system will reach. As the overloading happens elsewhere in the system, perhaps at a hydraulic motor that is powering an increasingly overloaded winch, the relief valve poppet (single) will continue to compress the spring. The spring will in turn be pushing back with more force as it is compressed. The flow through the relief valve will increase as the poppet opens wider, as the motor/winch is overloaded to a point where the relief valve, wide open, with the spring compressed, will be the easier path for flow as opposed to the overloaded motor and winch. The pressure reached at that moment when the poppet is pushing the spring as far as possible, will be the true 'setting' of the relief valve, as that will now be the highest pressure that the system can reach. I hope that help.

Me too

A relief valve is meant to prevent an over-pressure condition, yes. I cannot say what type of action will solve your line burst problem, because I do not know the cause. What type or model of machine do you have? For the sake of safety, please be very careful not to make any adjustments to your system without first obtaining hydraulics training. Can you contact the manufacturer of your machine for assistance?

Drain pressure in many cases will be a value that is close to or the same as atmospheric pressure if the tank is vented. If there is a return line filter preceding the re-entry to the tank, then drain pressure might be 1 or 2 Bar (15 or 30 PSI) depending on the model of filter, and the spring tension in the bypass check valve within the filter housing.

I also believe the arrows of the first position were drawn incorrectly. They do not use a Hydraulics software for these videos (it is done manually on Flash) so this kind of mistake may happen.

Yes, I just wanted to check with someone else because I wasn't sure as I was fairly new to hydraulics. By now, I am sure it is a 'drawing mistake' because they just put a random valve in for presentation. Great videos tho, they've helped me tremendously!

Ah, yep! Good catch. I'll let the team know, so they can flip that symbol around. I'm thrilled to see you're paying such close attention to our animations, and I'm glad they're proving to be helpful.

They've really been helpful, especially to understanding the 'more complex' systems where it's really hard to imagine what's going on inside. I bet you've saved many students from hours of torture, myself included. Thanks again!

Our programmers and animators build all our simulations from scratch, using web technologies like SVG and JavaScript. We don't use any off-the-shelf program or tool. If you'd like to browse all our hydraulic simulations, head on over to our website: www.lunchboxsessions.com/explore/hydraulics

New Holland LB75? I haven't worked with that model. Do you have schematics or any manuals? What is the issue that you are dealing with, that requires finding the relief valve? Has the system pressure been too low? Please be careful with any adjustments, and follow all manufacturer's safety recommendations.

from famous hydraulic valve maker Eaton, on page one, in a paragraph that begins with "Graph 1 is..." It's a good explanation. www.eaton.com/ecm/groups/public/@pub/@eaton/@hyd/documents/content/pct_273384.pdf

LunchBox Sessions. I stand corrected.