Oil Hydraulics and Mechanical Leverage
How are oil hydraulic systems used to provide mechanical leverage? Learn about how oil pressure is translated into mechanical movement.
There are many similarities between hydraulic and mechanical systems. This section is 100 times longer than the one that represents 100 to 1. By adding 10 kg to the length of the lever, we can raise 1000 kilograms or 1 tonne. The hydraulic cylinder has a 100:1 area ratio between the pump and the cylinder. It is therefore one hundred times greater than the region. One ton or one thousand kilos more is found on this side than it is on the other. It can be lifted with 10 kg of force.
Distributed Nature of Hydraulic Systems
Hydraulics has the advantage of allowing for almost any distance between the pump and the lifting cylinder. Similarly to this, a mechanical system could be built in the same way. If a mechanical system was used to increase the weight at a distance, there would be wires and pulleys.
However, hydraulics makes things much easier. We will now discuss rotary actuators. The flow rate is what determines the number of revolutions per minute (rpm). A pump that is smaller and has a lower flow rate will result in a specific rpm. However, a pump with a higher flow will result in a higher rpm (revs per minute). Because of their rotational speed, rotary actuators and motors can be used for driving. Torque is the result of the force multiplied by the radius.
Torque in Hydraulic Systems
Torque is measured in Newton's meters, while force is measured in Newton's. When dealing with the radius, the radius is measured in meters. It is also fascinating. The hydraulic motor only produces torque when it is under load. There is no torque without a load. This is similar to turning a loose nut with no torque by applying a torque wrench. We can tighten the nut and create torque if we come across resistance. Someone once compared a hydraulic motor to a circular cylinder rotating in a circle. This seems reasonable. It was quite brilliant of that person to bring it up. Naturally, this is the reservoir at the rear.
The hydraulic cylinder, also known as a linear actuator, feeds hydraulic fluid into the hydraulic cylinder via the pipe to push the load. The resistance of the load creates pressure in the hydraulic cylinder. This is a common saying. This is why force equals pressure multiplied by area. Pi times D divided by four is the area. The force is measured using Newtons, while the pressure is measured using megapascals.
We will now examine a small hydrostatic drive. Because there is no control valve for direction, it is called a basic hydrostatic driver. The pump starts to work and power the hydraulic motor when the electric motor is turned on. The result is that everything stops when the electric motor is turned off at the end. There is no forward motion and no backward motion. It just rotates in one direction. We have left the intake filter intact for this short experiment.
A suction filter is rarely used. The return line filter follows the pressure filter. This is a very important filter. Small indications will be found. The indications must be placed closest to the pump if a suction filter exists. The filter must be removed from the seat if it becomes clogged. Although the spring is low-pressure, you will notice a vacuum here. This will act as a gauge. This is an example. The blocking of filters has been enabled. Before there is pressure here, we must remove the ball from its place.
This filter would be 10 microns for the normal hydraulic system, similar to the previous one. Naturally, if the filter is blocked over there, the pressure will be displayed here as we compress the spring. They are now at very low pressure. It is just a pressure difference. The spring's pressure difference is generally around 100 kilopascals. The relieving valve is next. We'll be looking at it shortly, as well as our gauge isolator, pressure gauge, and pressure gauge.
A gauge isolator is recommended unless the pressure gauge is being constantly checked. We do not use a gauge isolator. The gauge isolator can be used to stop the pressure gauge from working if it is inspected more than once per week or once per day. Remember the hydraulic pressure gauges? One that's filled with glycerine is always on hand; this unique pressure gauge has a dampening effect that affects internal systems, gears, and other components. Now we will take a look inside our three-stroke, two-directional control valve and move it manually over there. The right-hand envelope is removed to show how the sign is read. Next, activate the gauge oscillator (3/2 valve). Let's do it again.
This has happened many times before. The envelope on the right disappears. The left-hand envelope goes in, and there is pressure. We then repeat the process and bring it back. The pressure will be displayed when the button on the manual control gauge has been released. Let's do it again. The gauge will fall to zero when the button is released. The envelope will move, and the spring will take control. We can see that it happens this way. Another example is when we used the three-to-two valve for expanding the cylinder. Let's pretend that the envelope shifts and high-pressure oil enter the cylinder to lengthen it. We want to remove the cylinder. The spring will take over when we release the button. The cylinder also retracts with its weight.
Cylinder with a Single Functioning Piston
This is an example of a cylinder that has a single functioning piston. We'll now take a closer look at the relief valve. This relief valve has direct action. These are usually based on the recommendations of the companies in their catalogs. These pipes typically have a quarter-inch BSP thread, a six-millimeter diameter, and a flow rate of around 12 liters per minute. They are sometimes used at a higher flow rate by businesses. The force of the spring is opposed to the hydraulic pressure at Port P.
Hydraulic Oil Relief Valve
When the spring's setting exceeds that of the relief valve, it opens, allowing fluid to flow from Ports P and T to the reservoir. Imagine a pump passing through this area. As pressure rises, the valve opens and allows air back into the tank. Calculating the spring force required to keep the poppet cone from bursting against the valve seat can be done by multiplying the pressure at Port P by the area. Force equals pressure divided by area. There is only a small area that can bear the pressure. The sign is a diagonal line, indicating that the spring can be adjusted. P indicates that the spring is under pressure. Then there's the T.
Downsides of Pressure Relief Valves
This particular relief valve has a downside. If our pump were ever to get into the system's plumbing, it would cause the relief valve to explode. Pressure energy is created when there is pressure. When it blows off, the pressure energy transforms into kinetic energy and interacts with the poppet, closing it. This happens continuously. If we had a pressure gauge, it would constantly be moving around. It is not a good idea to constantly blow off a relief valve, as the poppet will eventually wear against the hardened seats.
The seat is extremely hard, and the poppet is reinforced. As an example of a relief valve blowing up, you might imagine getting into overload and blocking the outlet to prevent oil from reaching a pump below. We press the arrow down and return to the tank as the pressure increases. Let's do it again. Assuming that the stroke of the hydraulic oil cylinder is complete, pressure builds and the tank is emptied. I had previously indicated that this was an imaginary pilot line.
Opening Relief Valves
To open the relief valve, you only need to apply force. This is a special type of relief valve. The poppet of the direct-acting relief valve, as shown in the above image, will oscillate while relieving. While the damping plunger acts as a shock absorber, it maintains a constant fluid flow across the valve seat. The direct-acting relief valve has a damping plunger.
What exactly happens here? The poppet and plunger are interchangeable. Pressure increases, and there is more space around the plunger. Pressure builds up behind the relief valve and pushes it forward as the relief valve blows away. The pressure energy is still converting to kinetic energy, and the poppet still tries to close, but it must extract the oil.
The pressure gauge shows that it rises and stays at the same level without any fluctuation. This is just an example of the pump releasing into the system. This is the pump that is going through here. We interpret it the same way. It goes into a high pressure, shifts over, and then the pressure rises. At that point, we release it back into our tank. As shown by the adjustable arrow, the spring can be adjusted. We now have a valve that can be used in two directions and has two strokes. Two positions, two ports We will discuss both a normally closed and an otherwise open valve with animated examples. Next is the usually closed valve. Let's go over this again as we read a sign. These are the envelopes.
The roller is sometimes called a cam follower, but it is commonly referred to simply as a roll. The lines that represent hydraulic pipework are drawn against an envelope controlled by an outside force. This is the situation where the spring has authority over the envelope. This envelope is responsible for providing the plumbing to the outflow and inlet. We move our camera until it meets the camera follower. The roller is pressed on, and the bottom envelope disintegrates. So let's do it again. The cam moves, the cam follows, and this pumps down. Flow is also present.
The cam controls the cam follower and the roller. This causes the lines that represent hydraulic tubing to be drawn on the envelope being controlled. We can now see it. The cam can be removed from the follower. It is currently happening; it is closing. There is currently a flow. We will stop it, and it will close. The cam follower is deactivated by the normally closed valves. The cam follower is back. It is possible to imagine a cylinder with a camera attached. It ends naturally. This is the valve that is usually closed. Let's take a look at this one.
This is often accessible. You can close a valve that is normally open by engaging its cam follower. What happens next? The cam slides onto the roller and the cam follower. The bottom envelope disappears, and the envelope is sealed. Let's do it again: The cam slides out onto the roller and the cam follower; the bottom envelope vanishes, and we seal the envelope. To open the normally open valve, the cam follower of the cam is deactivated.
It is now closed, resting there. Assumes command. The pipes are being used to open the envelope, which has been commanded externally. Once we have reached this point, the cam follower can travel backward and the spring will be opened. This is how the symbols are interpreted. This is how it looks. We'll now do a quick exercise to show how the hydraulic system works.
Direct Acting Relief Valve
In the circuit that shows the operation of a direct-acting relief valve, there is not enough pressure in the pressure line. The pump is therefore now operating. This circuit is an experiment. It is not intended to be used in hydraulic systems. The hydraulic oil is cycling, so it's just rising and returning to the tank. We now activate the solenoid. Before, we had a cam follower. The lower envelope will disappear now that there is a solenoid.
The upper envelope will close, stopping oil from returning to the reservoir. Here, we are descending. Pressure here increases. The relief valve opens, and pressure is registered on the gauge. Let's look at it again. The solenoid is activated, the lower envelope disappears, the upper one slides down, system pressure develops, and the relief valve blows out. The pressure gauge shows the pressure. Let's say we need a high flow rate. We need a direct-acting relief valve.
Potential Issues with Direct Acting Relief Valves
The diagram below shows the potential issues that could arise when using a direct-acting relief valve at high flow rates. The valve will need a four-ton spring, which is strong evidence for a pilot relief valve. This diameter is 50 millimeters. There is an estimated 20 MPa there. This is why we need to install the four-ton spring. Although we have shown how to tighten the spring, I believe it would require a very long lever that would have to be rotated by a person to tighten it. This is a little absurd. This is why it's off-screen.
Let's now examine this. The force in Newton equals the pressure in megapascals divided by the area. We will assume that the pressure in Newtons is 20 MPa and that the diameter of the circle is 50 millimeters. It is therefore 20x50 squared, 5x50 squared divided by 4, and 50x50 squared divided into 4. This is the area. Three nine six nine nine Newtons are obtained by multiplying three nine six nine nine points. This can be converted to kilograms or tons by multiplying by 9.81 kilograms per newton to convert it to kilograms, and by 1000 to convert it to tons. This is a four-ton spring. It is absurd to try to seal the valve.
PIlot Relief Valves
Instead, a pilot relief valve can be used, which we will do. It will have an opening of approximately 0.5 millimeters. When the system is running with the pump working up here with the pipe and then there is pressure on this side, both pressures will be equal, so the spring is holding the valve poppet in position. This could be the large diameter of 50 millimeters, which is necessary for high flow rates. The pump will experience resistance, and the pressure will build up, causing the poppet to fall off its seat.
The pump is attempting to pass through a 0.5-mm hole. This causes the pump to strain and pushes the poppet out of its way. This little valve controls it. We might be able to squeeze in a three-millimeter-square, 20 MPa (60 Newton) spring there. This is significantly more than the 4-ton spring that we talked about a moment ago. This is why I interpret the sign slightly differently. This is the location where the valve leaks. There is oil in the area. They have therefore added a dot on this line.
Pilot Relief Valve Demonstration
Our pilot demonstrated the pilot relief valve. It is springtime again, of course. This is where the correction takes place. This has been discussed before. By the chain dot, everything is one unit. The spring's diagonal arrow may need to be adjusted. This was discussed just a moment ago. This is the sign for this type of valve. This valve is the only one that can handle a high flow rate. Let's look at it.
Here is the circuit that illustrates the operation of the pilot relief valve in an area where the pressure line isn't flowing. This is how it works: This area is currently experiencing flow. Once the solenoid is activated, the lower and upper envelopes disappear, respectively, and pressure rises. The relief valve opens, and pressure is indicated by the gauge. Let's do it again: turn on the solenoid to restrict pump flow. The relief valve will burst when pressure builds up due to resistance. As the pressure gauge shows, we are blowing across there.
This is the basic hydrostatic drive. We've just shown the intake filter. Now let's turn on a pump to see how the oil flows. It also enters the hydraulic motor, which rotates it. The reservoir is then refilled with the returned oil. It may seem a bit confusing after looking at the examples. There are reservoirs here, there, and everywhere else, and there is also a reservoir.
There is also a reservoir in addition to the hydraulic motor drain. Here is a diagram of the circuit. These lines do not have to be displayed back to the reservoir. The drawing would be difficult to read and would be cluttered if we did. A well-designed circuit will always try to minimize the number of unnecessary lines. This is exactly what we did here. Now we know that they all go to the reservoir. This would be shown differently on a pipe diagram. This is just a circuit diagram.
Draining the Hydraulic Motor
It is important to drain the hydraulic motor. Every hydraulic motor must have a drain. Some people have put hydraulic motors where the oil leaks out. They have a small red plastic stopper at the drain port. The oil pulls out the plug, and they replace it with a steel one. However, the motor is only good for a few days before it needs to be replaced. Several times I have been told that there is a hydraulic motor and that the item is useless. It's not clear what is going on. It turns out that there is a blockage in the drain line where it should be. We don't want to create unnecessary back pressure, so the drain line should be wider than the drain coming from the hydraulic motor. We will discuss this further. The only reason the pressure will rise is that the motor wears down over time. This allows oil to get around the clearances. This is sometimes called a leaky line by some businesses.
Lubricating Oil Drain
This is called a lubricating oil drain. It will return to its tank. Our pump currently does not have a drain. The drain for a vein pump or gear pump is internal. However, a piston pump drain is external. I've also seen people with piston pumps without the plugs. The problem is, the pump will only last for a few days before it needs to be replaced. All piston pumps should have an external drain. Let me continue. External drains are required for every hydraulic motor.
Open Circuit Hydrostatic Drives
Oil Hydraulics Cylinder Design & Maintenance