The hydraulic system is based on fluid dynamics, achieving transmission through a liquid fluid. The pressure and flow are two important and variable parameters in a hydraulic system. It is important to understand their difference and relationship, which will help you build or maintain hydraulic systems better. This article will introduce you to the pressure and flow in a hydraulic system.
What are Pressure and Flow in Hydraulic Systems
In the hydraulic system, the hydraulic motor turns the pump, allowing hydraulic oil to flow in and start to flow along the hose. Flow is the amount of hydraulic oil delivered by the pump. As the liquid continues to flow, it needs to overcome various resistances from the inner surface of hoses, valves, and actuator pistons. Therefore, producing pressure to push the rod connected to the piston, converting hydraulic energy into mechanical energy.
The Pressure in Hydraulic Systems
What is the Pressure in Hydraulic Systems and How is it Produced?
The flow generates the pressure in the hydraulic system, which is produced by the hydraulic oil overcoming various resistances during flow. The fluid flows from high pressure to low pressure; therefore, the pressure will also flow and transfer in the circuit. It can promote the hydraulic pump actuators’ operation, converting hydraulic energy into mechanical energy.
Factors Affecting Pressure
Some factors may affect the pressure in your hydraulic system.
The load
Load is the object of pressure; it contains the force required by the hydraulic system to push the object, and various resistances in the system. Usually, when the load is greater, the pressure will also be greater.
Operation temperature
The temperature will also influence the pressure. It usually affects the pressure by affecting the hydraulic oil. When the temperature is too high, the oil will become thinner and reduce the oil sealing, resulting in low pressure. While the temperature is too low, the oil viscosity will increase and reduce its fluidity. The pump can’t provide enough flow, also resulting in low pressure.
Hydraulic oil pollution
If there are impurities or other pollutants in the hydraulic oil, it will also lead to an elevation of the pressure.
Component wear
If the components in your hydraulic system have been damaged or worn, this can cause hydraulic oil leakage, therefore reducing the pressure level.
How to Adjust Pressure in a Hydraulic System
You can adjust the pressure in the hydraulic system through pressure management devices, like adjusting a hydraulic relief valve and a pressure reducing valve. The relief valve can release pressure to protect components, avoiding overpressure in the system. The pressure reducing valve can reduce upstream pressure and output a stable pressure downstream.
Relationship Between Hydraulic Cylinder and Pressure
The hydraulic cylinders can convert hydraulic energy to mechanical energy. The area of the cylinder is inversely proportional to the hydraulic pressure. That means when you push the same object, the smaller the area the cylinder is, the higher the pressure needed to lift the load is.
How to Calculate Pressure in a Hydraulic System
You can calculate hydraulic pressure through the formula: P=F/A. Its unit is pounds per square inch (psi). The “F” is all the force exerted on the hydraulic system, including the piston or other external pressure. The“A” is the area under the force, like the area of a piston or hydraulic cylinder. This can help you estimate the pressure needed quickly and adjust the pressure in the hydraulic system.
The Flow in Hydraulic Systems
What is the Flow in Hydraulic Systems
In the hydraulic system, the flow means the hydraulic oil flow in the system. The hydraulic pump delivers the flow, and the flow occupies the space of the piston in the hydraulic cylinder, which in turn makes the piston move under the action of pressure.
Implications of Flow
Flow usually contains two factors that can influence it.
Pump Speed
The speed of the hydraulic pump can influence the flow rate. Hydraulic oil comes out of the hydraulic tank and enters the system through the action of the pump. When the pump speed gets high, the volume of fluid flow will also get larger.
Hose
The oil needs to flow along the hose. In this process, the oil will contact the hose and generate friction. This will result in the back pressure, which means the variation of the pressure between both ends of the hose. When the hose becomes thin, the oil must flow faster to get enough flow to support the system operation.
Types of Flow in Hydraulic Systems
There are two main types of flow in a hydraulic system.
Laminar Flow
In a low-speed environment, the fluid flows in a structure of parallel layers. The flow rate of each layer is relatively even, and there may be slight differences between layers. It is a highly efficient and relatively idealistic flow type.
Turbulent Flow
The inner surface of the hoses in the hydraulic system can’t be absolutely smooth. Fluid flows in, usually needing to overcome the friction caused by small defects on the pipe surface. This will disturb the laminar flow, therefore producing turbulent flow.
You can use bigger hoses to reduce the influence of these frictions.
Other Types
Other types, like steady flow, unsteady flow, rotational flow, and more. They reflect the flow characteristics of the fluid. Understanding these flow types can help you better deal with fluid problems encountered in hydraulic systems.
Relationship Between Pressure and Flow in Hydraulic Systems
According to Bernoulli’s principle, you can know that the pressure and flow in a hydraulic system are inversely proportional. When the flow increases, the flow will become lower. That means when the friction in this system is high, the flow needs to overcome much friction, resulting in decreased pressure. And then the flow will increase. Therefore, you need to design each component in this system to meet your requirements.
Conclusion
In conclusion, pressure and flow are two important factors in a hydraulic system. Whether you are a machinery manufacturer or an automobile manufacturer, fully understanding them will help enhance the quality and stability of your machines. If you have any questions, feel free to contact us or log in to Target Hydraulics to learn more
FAQ
What Dangers May Occur When Pressure Becomes Excessively High?
If the pressure is overhigh, your machine might explode and cause a safety accident. Because high pressure will produce a huge impact that the machine may not understand. So it is indispensable to install and maintain the hydraulic relief valve in your hydraulic system. This is a safety device that can release the redundant pressure.
What are the Reasons Causing Pressure Drop in Hydraulic Systems?
Hose
The direct size of the hose and the friction force on the inner surface both affect the pressure. Generally, the larger the pipe diameter, the greater the friction force, and the lower the pressure becomes.
Hydraulic oil
The viscosity of hydraulic fluid affects pressure. High temperatures will cause the viscosity of hydraulic fluid to decrease, therefore reducing the pressure.
System sealing
Every component and connection in the hydraulic system should be sealed well. Otherwise, this will result in oil leakage and pressure drop. Moreover, it can also cause a safety accident.
