Take a long look at the hydraulic equipment parked inside a construction site. A heavy load needs lifting, so the mobile lifting gear accommodates the work order. Hydraulic oils flow in the rigid metal tubes, flexible hoses strain, and the fluid lifeblood facilitates the movement of a steel-latticed boom. Considering the importance of the fluid medium in this scenario, just how do we choose hydraulic oils?
Revisiting Hydraulic Oils
First and foremost, the energy transmitting fluid is expected to responsively manipulate unwieldy payloads, which is why oil compressibility is a major consideration when the equipment requires new oil. But there are several other equally important functional requirements that govern the selection process. The non-compressible feature obviously equals a shorter response time, so the actuators move as soon as a control is manipulated back inside the operator cabin. What about cooling? Energy transmitting prowess is all very well but not if the fluid is running hot. Does the oil still convey that energy if contaminants are penetrating the hydraulic lines? These issues, among others, must be considered when choosing hydraulic oils.
Leveraging the Multigrade Difference
Here’s a few additional features to look out for when the time comes to pick out a new hydraulic oil type. The ‘Bulk modulus’ ratio refers to the volumetric reduction of the fluid when pressure is applied. Again, this is a compressibility issue, so the Bulk Modulus should be high while a temperature-resistant high-viscosity index keeps the oil thick enough to transmit the required kinetic energy. Next on our selection agenda, let’s assess multigrade oils. This oil family adds two or more viscosity grades to the hydraulic system, which is considered a beneficial feature when the equipment operates in areas where temperature extremes could influence the flow rate of the oil. However, multigrade oils employ complex VI Improvers (Viscosity Index Improvers). These additives are known to break down or ‘shear’ over time. Avoid VI Improver shear by employing a first-class monograde oil. Speaking of additives, do select a hydraulic oil that has a useful additive, perhaps one that acts as an anti-wear formula.
In simple terms, hydraulic oils pick up the negative characteristics generated by the equipment. If that oil is wrong for the selected machine, it’ll run hot. The equipment’s lifespan, controlled by the machine lifeblood, will be reduced. A suitable Bulk Modulus rating, plus a matching high-viscosity index helps to maintain the system while also optimizing the response time of those all-important moving parts. Incidentally, when choosing hydraulic oils, do remember that the fluid is also a lubricating agent, a grease for the hard-working mechanical components.
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