I just have to say that these guides are pure gold for anyone interested in learning hydraulics. Im currently studying to become an hydraulic technician in norway. From reading my books, i learn very little. From your videos, a great deal. Even though it's in english and it can sometimes be hard to understand or follow since english is not my native language, you still speak straight to the point, explaining well and in funny ways which makes me laugh and having fun while learning contrary to being bored to death reading native language books and learning nothing. I have no previous experince or knowledge to hydraulics. But your method of teaching is so simple even a 10 year old could learn from you. Im going to continue watching everything and then perhaps move on to your electricity tutorials. Cheers.
Hi Jim. Thank you for this lecture. Helluvalot easier to understand than the 1 or 2 paragraph descriptions in the textbooks I found. As you mentioned, most valves are devilishly clever and require effort to understand properly. You're doing a great job. I'm into numerical simulations of coupled systems involving hydraulics and multibody dynamics at large time steps. In this context, poppets and small spools pose problems -- small masses, very small range, etc. -- so I use alternative modeling techniques suitable for large time step size. My current relief valve is an array of biased check valves with different opening area. What kind of (numerical) experiments should I do to figure out whether that's close enough to a pilot operated relief valve. My model has only a small difference between cracking and fully opened pressure and reacts instantly in simulation time. If you know what that means, it's a fixed step implicit method so the states are consistent at each step, without slowdown. Whether there's an actual poppet or not in the simulation is irrelevant, as long as I can figure out the overall equations and inequalities which capture the behavior. Also, could you perhaps construct a lecture about simulation software for hydraulics or even electronics and share your experience with and opinion of them? Most people studying your lectures will work with simulation software at some point -- everyday for many -- and as with anything else, much guidance is needed to choose the right package for a given job. With best wishes.
I love the intel you pour in the explaining. As compared to many out there trying to tackle the same topics. With the following two questions I want to get deeper into explaining the "why"-s of the Pilot Operated Valve. Q: What in essence is different/better in the relief that the pilot offers? Is it just the small diameter of the orifice? Because of it being small, it senses the same pressure, while a much smaller force, allowing for a proportionally smaller spring dimension, therefore increasing the capacity of the valve?). Q: The associated decrease in the pressure override, is it because of the small volume and therefore time, it takes to refill the area upstream the orifice, after the pilot is extended back to the seat, once it has released the overpressure?
You basically answered your own question. Yes, the pilot chamber spring is smaller and as such presents a quicker and more linear reaction than a directly operated pressure relief valve with a larger spring and passage designed to handle full flow.
Slide @ 11:29 has numerous blockages on some of the channel ways that make the flow hard to understand. Also, i think there should be some sort of notation on the springs themselves, are they in a compression or tension scenario to make it easier to understand the physical forces on the springs. Some sort of Force vector arrow showing the amount forces. Spring force vs fluid force.
Jim, I can't understand why the pilot spring is a light biasing spring. Let's consider the pressure system 500 psi and the set pressure as 600 psi. In normal conditions, both sides of the spool and the dart fells the same pressure and the valve remains closed by the primary spring, right? Then, the pressure reaches 600 psi and the pilot spring open unbalancing the spool and the valve opens. Think this way the pilot spring must be a heavy biasing spring and there are no advantages over the direct pressure relief valve when thinking about the spring size and power.
Good point. The terms "heavy" vs "light" are relative in nature. It'd probably more appropriate to say the pilot operated spring is "lighter than" a direct acting spring because the pilot passage doesn't need to be sized for full flow but rather merely upsetting the balance of the primary which actually passes full flow to tank.
A way to think about it is Force = pressure x area. The spring is on the force side of the equation so if you make the area smaller that the pressure is “pushing” against the force of the spring is also smaller. The smaller the spring the more accurate it becomes at opening at the correct set pressure.
@@bigbadtech Well, I think I could not understand it yet. I've understood the cracking pressure as a mark that when the system pressure overcomes it the valve opens. And search on google I've read the set pressure is "The set pressure, also called the opening pressure, of a safety or relief valve is the inlet pressure at which the valve begins to open as required by code" what sounds me the same thing as cracking pressure. "When the cracking pressure is reached, the valve will open to allow flow of the material, when it drops, the valve will close."
Here's a simplified example: Let's say a fixed displacement pump produces 2gpm of flow and the pressure relief valve is set to 100psi. Let's say the cracking pressure is 80psi. Below the cracking pressure 80psi the system receives all 2gpm of flow. Above 100psi all 2gpm of flow is dumped through the pressure relief valve. In between 80 up to 100psi less flow goes to the system because more and more is diverted through the pressure relief valve. Assuming linearity (which it isn't), at 85psi, 0.5gpm goes through the pressure relief valve and 1.5gpm goes to the system, at 90psi, 1gpm goes through the pressure relief valve and 1gpm goes to the system, at 95psi, 1.5gpm goes through the pressure relief valve and only 0.5gpm goes to the system, finally, at 100psi all 2gpm is going through the pressure relief valve.
Please Jim can you tell me the exact difference between a differential area pressure relief valve and the normal direct acting poppet pressure relief valve ? Why is it called a differential area PRV ?
Excellent question. I actually cover this application in the unloading valves lecture. This link should send you to the exact section: ua-cam.com/video/eJ05rODkYFg/v-deo.htmlm42s
Great stuff Jim ! But I had a more specific valve in mind and it was my fault for not correctly stating it . I wanted to know more about the differential area direct acting poppet relief valve and its differences with a normal direct acting poppet pressure relief valve . I may have already understood the meaning of the term differential from your great explanation in unloading valve video . The valve im asking about is a valve that operates in the opposite direction to the normal PRV due to its construction . Thank you .
Aha, I'm actually not super familiar with these type of valves, however, I know this style is often used in cross over pressure relief valves because of their quick response as detailed at: ua-cam.com/video/zWRFibp6WnU/v-deo.htmlm29s If I remember correctly these style valves are better suited for intermittent applications rather than continuous applications as would a balanced spool style pilot operated pressure relief valve.
It all depends on what you want to do and the application. Differential area RVs can handle little more flow that regular direct acting. Pilot operated RVs can handle good amount of flow depending on its size and are used mainly as the Main RV of a system because they tend to be stable and pressure raise is almost flat. Pilot RVs, these are small RVs (0.5 GPM) that are used with logic elements to achieve a high flow RV function. Also the way the respond is not the same. Direct acting RVs have a small spike when the suddenly open in comparison with differential area RVs. this last kind has a slight higher spike when suddenly opens.
I just have to say that these guides are pure gold for anyone interested in learning hydraulics.
Im currently studying to become an hydraulic technician in norway. From reading my books, i learn very little. From your videos, a great deal.
Even though it's in english and it can sometimes be hard to understand or follow since english is not my native language, you still speak straight to the point, explaining well and in funny ways which makes me laugh and having fun while learning contrary to being bored to death reading native language books and learning nothing.
I have no previous experince or knowledge to hydraulics. But your method of teaching is so simple even a 10 year old could learn from you.
Im going to continue watching everything and then perhaps move on to your electricity tutorials.
Cheers.
there should be more lecturer like you. your expression and examples are enjoyable and very understandable. thanks for hydraulic context
This guy is good thank you
I don't even wanted to watch whole video, but I get attached by your teaching skills. I like it!
Thank u very much for sharing quality educational videos Mr. Jim. Clear scams for relief v/v’s. Very clear explanation.
Best intro music, I had ever seen.
Fantastic Jim! Excellent for this beginner/novice. You Perfectly and concisely answered "All" my questions on this topic..Thank you!
Hi Jim. Thank you for this lecture. Helluvalot easier to understand than the 1 or 2 paragraph descriptions in the textbooks I found. As you mentioned, most valves are devilishly clever and require effort to understand properly. You're doing a great job.
I'm into numerical simulations of coupled systems involving hydraulics and multibody dynamics at large time steps. In this context, poppets and small spools pose problems -- small masses, very small range, etc. -- so I use alternative modeling techniques suitable for large time step size. My current relief valve is an array of biased check valves with different opening area. What kind of (numerical) experiments should I do to figure out whether that's close enough to a pilot operated relief valve. My model has only a small difference between cracking and fully opened pressure and reacts instantly in simulation time. If you know what that means, it's a fixed step implicit method so the states are consistent at each step, without slowdown. Whether there's an actual poppet or not in the simulation is irrelevant, as long as I can figure out the overall equations and inequalities which capture the behavior.
Also, could you perhaps construct a lecture about simulation software for hydraulics or even electronics and share your experience with and opinion of them? Most people studying your lectures will work with simulation software at some point -- everyday for many -- and as with anything else, much guidance is needed to choose the right package for a given job.
With best wishes.
I love All of your videos... Very knowledgeable
Thank you sir
Excellent Jim!
Thank s for great lecture
thanks for great lecutre...!
I love the intel you pour in the explaining. As compared to many out there trying to tackle the same topics.
With the following two questions I want to get deeper into explaining the "why"-s of the Pilot Operated Valve.
Q: What in essence is different/better in the relief that the pilot offers? Is it just the small diameter of the orifice? Because of it being small, it senses the same pressure, while a much smaller force, allowing for a proportionally smaller spring dimension, therefore increasing the capacity of the valve?).
Q: The associated decrease in the pressure override, is it because of the small volume and therefore time, it takes to refill the area upstream the orifice, after the pilot is extended back to the seat, once it has released the overpressure?
You basically answered your own question. Yes, the pilot chamber spring is smaller and as such presents a quicker and more linear reaction than a directly operated pressure relief valve with a larger spring and passage designed to handle full flow.
Slide @ 11:29 has numerous blockages on some of the channel ways that make the flow hard to understand. Also, i think there should be some sort of notation on the springs themselves, are they in a compression or tension scenario to make it easier to understand the physical forces on the springs. Some sort of Force vector arrow showing the amount forces. Spring force vs fluid force.
amazing video. thanks a million
Thank you.....this helped me to a great extent
Jim, you are awesome! Incredibly valuable information on your channel. I'm very grateful!
Thank you. Fantastic
Very good information...thank you very much
This is insanely valuable! 😁 thanks🤗
Thanks! Please tell your friends these free resources exist.
@@bigbadtech kindhearted person，thank you
Good info
you are saving me!
awesome.
I like how you said "stupid pump"
thanks
Fantastic explantions, thanks a lot!
Great!!
Sir,
Please explain, relief valve with 3 numbers of pressure setting.
Hi Jim, I am confused about how did you make the narrow pilot passageway in the pipe?
Jim, I can't understand why the pilot spring is a light biasing spring. Let's consider the pressure system 500 psi and the set pressure as 600 psi. In normal conditions, both sides of the spool and the dart fells the same pressure and the valve remains closed by the primary spring, right? Then, the pressure reaches 600 psi and the pilot spring open unbalancing the spool and the valve opens. Think this way the pilot spring must be a heavy biasing spring and there are no advantages over the direct pressure relief valve when thinking about the spring size and power.
Good point. The terms "heavy" vs "light" are relative in nature. It'd probably more appropriate to say the pilot operated spring is "lighter than" a direct acting spring because the pilot passage doesn't need to be sized for full flow but rather merely upsetting the balance of the primary which actually passes full flow to tank.
A way to think about it is Force = pressure x area. The spring is on the force side of the equation so if you make the area smaller that the pressure is “pushing” against the force of the spring is also smaller. The smaller the spring the more accurate it becomes at opening at the correct set pressure.
Jim, is the preset pressure equal to the cracking pressure?
Nope. Cracking pressure is just a little bit before the full open pressure.
@@bigbadtech Well, I think I could not understand it yet. I've understood the cracking pressure as a mark that when the system pressure overcomes it the valve opens. And search on google I've read the set pressure is "The set pressure, also called the opening pressure, of a safety or relief valve is the inlet pressure at which the valve begins to open as required by code" what sounds me the same thing as cracking pressure.
"When the cracking pressure is reached, the valve will open to allow flow of the material, when it drops, the valve will close."
Here's a simplified example: Let's say a fixed displacement pump produces 2gpm of flow and the pressure relief valve is set to 100psi. Let's say the cracking pressure is 80psi. Below the cracking pressure 80psi the system receives all 2gpm of flow. Above 100psi all 2gpm of flow is dumped through the pressure relief valve. In between 80 up to 100psi less flow goes to the system because more and more is diverted through the pressure relief valve. Assuming linearity (which it isn't), at 85psi, 0.5gpm goes through the pressure relief valve and 1.5gpm goes to the system, at 90psi, 1gpm goes through the pressure relief valve and 1gpm goes to the system, at 95psi, 1.5gpm goes through the pressure relief valve and only 0.5gpm goes to the system, finally, at 100psi all 2gpm is going through the pressure relief valve.
@@bigbadtech Disregard what I just said! Now I can understand. Thanks
@@bigbadtechan explanation that's too generous. I love your style of teaching.
Please Jim can you tell me the exact difference between a differential area pressure relief valve and the normal direct acting poppet pressure relief valve ? Why is it called a differential area PRV ?
Excellent question. I actually cover this application in the unloading valves lecture. This link should send you to the exact section: ua-cam.com/video/eJ05rODkYFg/v-deo.htmlm42s
Great stuff Jim !
But I had a more specific valve in mind and it was my fault for not correctly stating it .
I wanted to know more about the differential area direct acting poppet relief valve and its differences with a normal direct acting poppet pressure relief valve . I may have already understood the meaning of the term differential from your great explanation in unloading valve video .
The valve im asking about is a valve that operates in the opposite direction to the normal PRV due to its construction .
Thank you .
Aha, I'm actually not super familiar with these type of valves, however, I know this style is often used in cross over pressure relief valves because of their quick response as detailed at:
ua-cam.com/video/zWRFibp6WnU/v-deo.htmlm29s
If I remember correctly these style valves are better suited for intermittent applications rather than continuous applications as would a balanced spool style pilot operated pressure relief valve.
It all depends on what you want to do and the application. Differential area RVs can handle little more flow that regular direct acting. Pilot operated RVs can handle good amount of flow depending on its size and are used mainly as the Main RV of a system because they tend to be stable and pressure raise is almost flat. Pilot RVs, these are small RVs (0.5 GPM) that are used with logic elements to achieve a high flow RV function.
Also the way the respond is not the same. Direct acting RVs have a small spike when the suddenly open in comparison with differential area RVs. this last kind has a slight higher spike when suddenly opens.
Why is the little orifice in the piston? Why can't it be an independent path to the poppet (e.g. like vent port).
There are several ways of making this work of which the balanced piston with a hole is one type.
fluid gospel
8:21
not the stupid pump hahhaah
My lab partner sent me this 🤔?!
What's he trying to tell you? Send it back.
Some ai-generated lectures!!
If they were AI generated the images would be much better.
stupid pump eh
Hi
Can you help me?
Lengthy and overexplained for the begginer