HYDRAULIC SYSTEM BASICS: Episode 2 - PUMPS

Hi, welcome to our second episode of Hydraulics Basics. So in the first episode we talked about hydraulic tanks and their purpose and why they're important. We're moving on to the heart of the system now, which is the pump, right? So pumps are something that I'm going to try to put into a short video so I don't bore you guys to death, but there's a lot going on with pumps. I'm going to stick to some basics. There's different kinds of hydraulic pumps, right? You have vane type pumps, gear pumps, piston pumps, variable pumps, fixed displacement pumps, you name it. There's a wide variety of different pumps that can be used for different applications. Of course, we want to be able to showcase a wide variety of different pumps. So we have a piston style pump on our training boards that's capable of doing other things like load sensing and pressure compensation. And in order for it to do those things, of course, it has to be a variable pump. So this is a variable piston type pump. So just the basics of the pump. Pumps create flow, right? A lot of people say the pressure coming from the pump. Well, technically, I mean, I understand what people mean when they say that, but pressure is not created by a pump. Pumps create flow. Pressure is caused by the restrictions that that flow encounters, right? So the load, the size of the valves, the size of the all of that contributes to the pressure in a system. So hydraulic pumps are designed, their purpose is very simple, create flow, right? So all hydraulic pumps create flow. Another thing all hydraulic pumps share is that they have to have some internal leakage. Internal leakage helps to lubricate and cool the interior components of the pump. If you don't have internal leakage, then what happens is in these pumps without the internal leakage, they're going to get hot and they're going to burn up, right? So you have to have it. Now you might've heard terms where they talk about pump efficiency. So a pump efficiency is like if a pump is supposed to put out 10 gallons per minute, and you only see nine gallons per minute coming out of the pump. And that means that you probably have one gallon per minute of internal leakage, and that would be a 90% efficient pump because nine out of 10 gallons is making it to the outlet. In a gear type pump, around a 90% efficiency rating is where they are when they're brand new. And then you get into vane type pumps and then piston pumps, those efficiencies are even higher brand new because they don't require as much internal leakage. So internal leakage is something all the pumps must have. They have to have pumping chambers, meaning that they have to have a way for fluid to come in and get out. So in a gear, that would be between the housing and the gear teeth, and then the gears pushing the fluid toward the outer housing to the exit. In a vane, it would be the changing size of the elliptical that the vanes are in that causes the vanes to widen, which pulls fluid in and then contract to push the fluid out as they rotate. And then pistons are obvious as the piston is coming inward, then there's creating a vacuum and pulling fluid into it. And then as it rotates on a swashplate, it pushes the piston out, creating the flow that leaves the pump. Pumps can be tested by putting the pump under a load and checking the flow rate. So if you lift a heavy object, the back pressure is going to cause more internal leakage in a pump than if it was just sitting there running without lifting a load. So if I was going to test this pump right here, what I would do is call a test graph where I would run it at a certain flow rate and a certain amount of system pressure. And then I would gradually increase that system pressure and then compare the flow rate each time I raise the system pressure. And if it drops below a certain efficiency rating during that test, then I know I have a bad pump. But there's so much more I could talk about in pumps, but I just wanted to address some of the basic issues just to make people familiar with them. And then if you have any specific comments about pumps, please put them in the comments or let me know and I'll either make another video or just answer your question in the comments. So please like and subscribe. Let me know if there's any other special videos you guys want to see and have a good day.