Gear PumpsĪlthough gear pumps are classed as the most inefficient out of all of the pumps, they are still able to function through a large amount of contamination. Piston pumps work best with viscosities ranging between 10 to 160 centistokes (cSt) at normal operating temperatures. They are manufactured for durability and are able to operate at higher pressures, usually up to 6,000 psi.

Piston pumps are more suited to harsh conditions. Vane pumps work best with viscosities ranging between 14 to 160 centistokes (cSt) at normal operating temperatures. Because of this, vane pumps are usually less cost-effective when it comes to maintenance, however they are useful for keeping a stable flow. When in operation, the vanes can wear out, due to the constant contact between two surfaces. There are rotors inside vane pumps that include slots attached to a shaft that is rotating erratically to a cam ring. Each pump is utilised in different ways for different applications. There are three main types of pump that can be found within a hydraulic system: vane pumps, piston pumps and (internal and external) gear pumps. The table below shows the classifications of viscosity against different temperature ranges:ĭifferent pumps require different viscosities. An incorrect viscosity could result in damage to hydraulic equipment, problems during operation and reduced service life. This is true even if the oil has properties include anti-wear, anti-oxidisation or anti-corrosion. The viscosity must be accurate for your application and the temperature. Moreover, if the viscosity is high, the oil will be better suited to an application which is used in harsher environments, exposed to a variety of operating temperatures. A lower viscosity index means that the oil may be more susceptible to change than if it were a higher viscosity index. The viscosity index helps us to measure the change in temperature in hydraulic oil. The measurement of viscosity in hydraulic oil is taken in Centistokes (cSt) and most commonly at temperatures of 40☌ and 100☌. On the other hand, lower viscosity means the oil is easier to pass through the system.

Moreover, high viscosity means the oil is thicker and is more difficult to transport through a system. For example, if viscosity increases, then it will take longer for the oil to pass through the hydraulic system. The hydraulic oil viscosity depends on how smoothly it flows. This is particularly important as applications become more demanding. Hydraulic oil viscosity needs to be able to work effectively to enable smooth operation no matter the temperature. A temperature drop makes the oil move less easily and it becomes more viscous. Similarly, when you put cooking oil into a pan and heat it up, the oil moves faster the longer it is heated. For instance, if the temperature of the oil increases then the viscosity decreases. In hydraulics, there’s a direct relationship between hydraulic oil viscosity and its temperature. Hydraulic oil viscosity is vital when choosing the right hydraulic oil for your system.

Definition of viscosity in oil and gas