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Key Features Of Hydraulic Oil And Application Of Hydraulic Pumps

Just because the wrong type of hydraulic fluid is used, the hydraulic pump can become inefficient or damaged. How do you know if you are using the correct fluid for your hydraulic pump? The answer to this question depends on several factors, including the type of pump, its maximum operating temperature, its maximum operating pressure, and even the type of material used for the pump's seals.



Hydraulic oil
Hydraulic fluids (sometimes called hydraulic fluids) can play multiple roles in hydraulic systems and their various components, including pumps. These purposes include:



Transfer energy
Prevent corrosion
Lubrication components in hydraulic systems
In most cases, the most important factor is the ability of the fluid to transfer energy, but if too much heat is trapped in the pump, internal components are corroded or not lubricated enough to prevent this, damage can occur. Damaged surface of internal components.



Why hydraulic oil is important for pumps

Hydraulic pumps are at the heart of any hydraulic system. Wrong fluid selection can seriously affect pump performance and life expectancy. In fact, the use of poorly matched fluids can lead to catastrophic failures that can lead to problems with cascading the entire system. Problems that can be caused by poor fluid selection include:



Excessive fever
Formation of sludge and varnish
Erosion and excessive surface wear
Reduced component life
Greatly reduced system efficiency
If the pump exhibits any of these symptoms, it may be time to research a more suitable hydraulic fluid for it.



Key characteristics of hydraulic oil
When choosing a fluid for your system, it is important to understand which attributes are important to your particular application. The most important characteristics of hydraulic oil include its viscosity, lubricity, thermal performance, flammability, stability and foaming properties.



Viscosity is a measure of fluid flow resistance. Honey is an example of high viscosity. Water is an example of medium viscosity. Most gases have a low viscosity. It is closely related to temperature. As the temperature decreases, the hydraulic oil becomes more and more viscous.



If the viscosity of the hydraulic fluid is too high, the system will not be able to operate effectively due to the loss caused by the movement resistance of the fluid. In addition, damage can occur because components within the system cannot be fully lubricated. However, if the viscosity is too low, there will still be lubrication problems, and the fluid will be less effective at transferring energy.



Lubrication method
Good hydraulic oil will be used as a lubricant in the system, protecting critical surfaces from damage and preventing metal-to-metal contact. In some cases, hydraulic systems or pumps may require hydraulic oil with additives to maintain their lubricity in the presence of high pressure.

Thermal performance
It is important to keep in mind the expected operating temperature range of the system to keep the hydraulic oil stable and to maintain the required viscosity. This can be a significant problem for equipment exposed to outdoor temperatures, especially when the temperature drops below freezing. In addition, the fluid needs to be able to dissipate heat generated by pressure drops and friction.



Fire-resistant hydraulic power unit
When used in explosive or highly flammable environments, hydraulic fluids should have a high flash point. Flash point is the temperature at which hydraulic oil releases enough vapor to ignite in the air. However, keep in mind that if hydraulic oils are discharged at a high enough pressure to create a fine oil mist, they can also easily catch fire. If flammable, the hydraulic oil should be non-petroleum or contain a large amount of water.



Ideally, the hydraulic fluid should be non-volatile. It should remain physically and chemically stable even under extreme pressure fluctuations, a wide operating temperature range, and even long-term storage.



Another potential problem with hydraulic fluid is foaming, which occurs when hydraulic fluid releases trapped gas. Foaming can cause the system to heat up and cause loss of hydraulic oil when gas is released.

Hydraulic oil type
There are three basic types of hydraulic oils: water-based, petroleum-based, and synthetic oils. Each type has its own special characteristics that make it ideal for some applications. In addition, some fluids are preferred for applications that may affect the environment.



The oldest type of hydraulic oil is water-based, but in modern times it is not used as well as other types of hydraulic oil. Keep in mind that although water may not be as effective in terms of lubrication, it is ideal for situations where the possibility of fire is important. In terms of price, water-based fluids are cheaper than synthetic fluids, but still more expensive than petroleum-based fluids.



Petroleum-based fluids are more commonly used than water-based fluids and are an inexpensive alternative to synthetic fluids. There are many types of petroleum-based fluids that are different from each other based on how petroleum products are processed:



Group 1: Production from solvent-neutral mineral oil
Type II: Composed of hydrotreated base oil
Type III: Composed of hydrocracked base oil
The higher base oil group has better corrosion resistance, stability and lubricity, which helps to extend the service life of the hydraulic pump. Although they may not provide the same level of performance as more expensive synthetic fluids, the inclusion of additives will enhance their performance. However, one of the problems with petroleum-based hydraulic fluids is the tendency to form sludge, which can compromise the performance and efficiency of hydraulic pumps.

Additives account for about 1% or less of petroleum-based fluids, but have a significant impact on the performance of hydraulic fluids. Key ingredients of additive packaging include antioxidants, anti-wear ingredients, foam inhibitors, viscosity modifiers and rust inhibitors.





Synthetic hydraulic fluids are man-made and specifically designed to provide high performance characteristics and work well in flammable environments. These fluids are the most expensive, but they work better than other types of hydraulic fluids when exposed to extreme temperature changes and high pressures. However, unlike petroleum-based and water-based fluids, they may not be compatible with certain sealing materials and may be toxic.



Hydraulic oil and pump types
The three most common pump types are gear pumps, vane pumps and piston pumps. The requirements for each pump are slightly different.



Gear pump
The gear pump works by compressing the fluid between the inner wall of the gear box and the retained air that meshes with the gear teeth. They are usually divided into internal gear pumps or external gear pumps, of which internal gear pumps are more reliable of the two. In addition, the internal gear pump can idle in a short time. Most gear pumps require fluids capable of withstanding a maximum temperature and pressure of 158 ° F, 500 psi. Gear pumps work best with fluids with a maximum ISO VG viscosity of 140 ° F between 15 and 32 and a maximum temperature of 158 ° F between 32 and 68.



Vane pump
In a vane pump, a slotted rotor is mounted on a shaft, which rotates eccentrically to a cam ring, thereby forming a vane cavity. The volume of the vane cavity on the discharge side decreases, forcing fluid to flow out; those pumps on the inlet side increase volume and draw in fluid. For vane pumps operating at 500 psi, the ISO VG viscosity ranges from 15 to 22. When the maximum operating pressure is around 1000 psi, the viscosity depends heavily on the maximum operating temperature. For operating temperatures up to 104 ° F, the viscosity should be between 10 and 15. For temperatures between 104 and 140 ° F, the recommended viscosity is 15 to 32. When the maximum operating temperature is expected to reach 158 ° F, higher viscosity fluids on the order of 22 to 46 are strongly recommended.



Plunger pump
Sampling and analysis of hydraulic oil
Piston pumps are much more complex than vane or gear pumps and can reach higher pressure levels. For low pressures of about 500 psi and temperatures up to 158 ° F, the viscosity should be about 15-22. For medium to high pressure (approximately 4,250 psi), the viscosity and condition of the vane motor are highly temperature dependent.



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