What is Pressure Compensation?
In pressure compensation, the fluids flow through tubes and hoses at a rate that is determined by its pressure potential. When you take the measurement of the pressure at point A along with the measurement of point B at your actuator, you will notice that there is a variance in the pressure of point A and point B. The variance in pressures indicates the energy that is available for access by fluids to get from point A to point B. There will be more energy available for the flow of the fluids the larger the difference of pressure. The flow potential will be reduced as the pressure of point B gets closer to the pressure of point A. When handling hydraulic applications, your ability to reach velocity within your actuators is lost as the energy is lost to the flow of fluids.
The system of hydraulics allows for the oils to be pushed like a physical rod by the force given off by the pump. The transfer of force is taking place instead of containing the energy within the moving fluids. As a result of the fluid being pumped through one passageway, the flow is not hindered by the differences in the pressure of point A and point B, other than leakage loss. As pressure increases, the rate of leakage will also increase. This also occurs in hydrodynamic applications.
The problem that arises when the pressure changes at point B is that the differential pressure is altered from point A to point B. Flow rates are determined by the pressure differential and its consistency is critical.
Pneumatic hoses and tubes are used to control the flow of air to valves, actuators, tools and other devices. The sizes of the tubes and hoses vary by the types available on the market. It is important for engineers to understand these different factors when selecting the best hose or tube for the task at hand.
The supply of air along with the application provide a standard baseline for the performance of the product. When determining the sizing for hoses and tubing, the flow requirements aid in the selection process. Tubing for hydraulic applications is verified by wall thickness and the outer diameter and the hoses are quantified by the inner diameter. A result of choosing one with an inner diameter that is too small will hinder flow and cause losses in the pressure, future inefficiencies and high rates of fluid velocity. This can cause a shorter life span of service. On the contrary, if the diameter is too large, the weight, cost and size will be higher than needed.
It is best to start with the structure of the hose. There are a variety of common materials that make up thermoplastic tubing. Polymer formulations are also offered from a number of companies to accommodate your precise requirements. Pneumatic applications use tubing materials that are made of polyurethane tubing that is flexible, strong, resistant to kinks and abrasions and can hold up against fuel and oil contact. This type of tubing can be frequently found being used in logic and actuation systems, medical and laboratory applications, vacuum equipment and robotics and in a variety of semi-conductor engineering.
Nylon tubing is known for being light, tough and stable throughout its dimensions. Higher pressure pneumatics benefit from this type of tubing. As a result of its flexibility, nylon tubing can be used in tight spaces and for low water absorption. Pneumatic controls and low-pressure pneumatics benefit from polyethylene tubing. It is highly resistant to chemicals and other solvents, is very flexible and can be acquired at a low cost.
It is recommended for engineers to weigh all of the options available when it comes to the benefits, features and drawbacks of each material. Engineers must consider whether the fluids are compatible with the selected tubing. When looking at air systems, the air lubricators contain oils and other substances that will be consumed by the compressor. As a result, the inner tube could be affected. Exposure to environmental components will also have an effect on tubing assemblies. The environmental elements that can affect the tubing include: salt water, chemicals, air pollutants, UV radiation, ozone and other degrading elements.
Hose and tubing failure are sometimes caused by outside power-driven influences. When choosing tubing also keep in mind that flexing, vibrations and kinking can increase in high amounts. Tubes and hoses that are damaged should be replaced to avoid premature failure.
When building an assembly for pneumatic tubing, there are a wide variety of fittings available to connect various components. Some examples of these fitting include:
- Reusable versions
These fittings come in the form of brass, stainless steel, plastic, steel and other resources. When seeking to connect components, the compatibility of the parts should be ensured by the designers before assembly.
There are many variations to the standard products that are available for fittings. These variations are made to give strength to the tubes or hoses, offer resistance to abrasions and ensure that the materials are compatible against harmful chemicals.
To conclude, pressure compensation occurs when hydraulic components are ready to take on the load of system pressure while being able to adjust to the changes in the ongoing pressures. The adjustment can be made through the pump while it compensates for the pressure as the flow is reduced when downstream pressures reach levels that are too high. Another instance of pressure compensation happens when the downstream pressure rises as a result of increased flow potential from the flow control.