Unloading Valves (Full Lecture)

In this lesson we'll examine another member of the pressure control valve family known as the unloading valve. Unloading valves are commonly used to divert pump flow at low pressure. Additionally, we'll examine a differential unloading relief valve used exclusively for accumulator circuits and unloading schemes making use of pressure switches and solenoid operated valves. (Full Lecture)
___________________
If you wish to support this project please visit the Patreon page at: / bigbadtech
___________________
Copyright information: Use this lecture. Use it at home, at work, or at school. Put it in a playlist, embed it in a website, share it with your coworkers, family, friends, and enemies. I made this lecture and posted it on KZbin so users everywhere have free access to this information.
This being said, this KZbin channel is meant to be the sole point of distribution for this lecture. Users are not authorized to download it, change it, or charge for access. Don’t even think of downloading it and uploading to your own channel and pretending it’s your own work. Not cool. Use this lecture and let your friends know this free resource exists.
Use it. Don't steal it. Be cool.
__________________
For more FREE online technical training check out the following playlists available at the bigbadtech channel:
DC Circuit Analysis • DC Circuit Analysis
Single Phase AC Circuit Analysis • Single Phase AC Circui...
3 Phase AC Circuit Analysis • 3 Phase AC Circuit Ana...
Hydraulics • Hydraulics and Electri...
Pneumatics • Pneumatics
Motor Control • Motor Control
Motors and Generators • Motors and Generators
Motor Drives/Variable Frequency Drives (VFD) • Motor Drives
Programmable Logic Controllers (PLCs) • Programmable Logic Con...

[@helicopterpeace7434]

Hello Jim, thank you for your video lectures. They have very valuable. Anastasia

[@augustyn1967]

Very good video. helped me touch up on a few issues. I was looking for a cost affective way to use a gas operated positive displacement pump with closed center valves.

[@commenter5469]

Hey!!! There’s damn good restaurant at Petro truck stop. Called Iron Skillet! 😁

[@michaelcostello6991]

Unloading valve is also called accumulator charging valve. I searched this first on your channel but could not find this video. Perhaps give it both names so one can find it. Thanks for great video. mike

[@johnevan7737]

Hi Jim,again thanks for these lecture.These Differential Unloading Relief Valve is the same as Unloading Relief Valve?Also the difference in pressure is constant bet the pump side and accumulator side?Some hyd manufaturer dont carry these item.Ive encounter an Unloading Relief Valve w/ the check valve incorporated wit in.Really learns a lot from your lectures.More power!!

[@arslanahmad1195]

I read in a pump data sheet that starting pressure should not be more than 20 bar for that pump. Is this restraint induced by the pump mechanical design or the prime mover motor's electrical characteristics? Will this restraint prohibit the use of the third unloading method?

[@bigbadtech]

I'd hesitate to give you a definitive answer without looking at the specific data sheet but because this limitation is mentioned on the pump data sheet (rather than the prime mover's starting torque) this limitation would probably be because of the pump's mechanical characteristics. Provided the maximum starting pressure is above the low pressure limit for the pressure switch it would charge the accumulator.

[@commenter5469]

You probably looking at the LS controlled piston pump. For those LS margin or “stand by” is about 20 bar. The lecture is not talking about some specific pump type.

[@heavyjay]

Wouldn't it be more efficient to just have pump A turn off at 500 psi?

[@danalex2991]

In both scenarios, the pilot operated UV and the differential area UV there are pressure cycles that the accumulator goes through . The only difference i can see that is in the differential area UV you can control the pressure range and if possible minimize it but in the pilot operated UV you do not have that level of control . Is there any other advantage ?

[@bigbadtech]

Honestly that's it. With the differential unloading relief valve you basically operate off the accumulator between the high and low value while the pump is unloaded. Only when pressure drops below the low value does the pump recharge the accumulator.

[@commenter5469]

Turning pump on and off - will kill the motor very quickly. And will be even more annoying than listening to system load and unload. Just get a darn Pressure Compensated pump, and get rid of the whole shebang all together.