Hydraulic oil starts breaking down at around 140☏. Operating Temperature as a System Health Indicator Oil life is cut in half at 140☏ – 155☏.System noise may increase due to thinner oil.As a good rule of thumb, I recommend these temperature mile markers. Individual pump manufacturers specify their own viscosity requirements and operating temperature ranges. To make a high VI fluid (with a VI considerably more than 100), the oil supplier can use a high VI base oil, viscosity modifiers, or both. With high VI hydraulic fluids, the optimum operating range of acceptable viscosities spreads over a wider temperature range, and the temperature range for the highest overall efficiency is also wider. Be careful not to get too heavy or too light of oil, or it could result in excessive heat.Īddress this dilemma by using high-viscosity index fluids. But it must also be heavy enough at high operating temperatures to avoid wear and internal leakage inside the pump, resulting in inefficient operation. Hydraulic oil must be light enough at very low starting temperatures to be easily sucked into the pump, preventing cavitation. Catastrophic pump failure and distribution of pump fragments throughout the system will occur. This reaction generates tons of pounds of force per square inch and can produce destructive micro jets of oil that collide against the internal pump surfaces at extremely high velocities. The little gas pockets released not only do not lubricate well but when exposed to high pressure at the pump outlet, the cavity walls of the bubbles collapse or implode. When the viscous oil restricts the fluid’s flow enough at the pump’s inlet, the pressure drops low enough (vacuum increases) that the liquid can’t exist as oil but vaporizes or boils into a gas. The main issue with cold oil is pump cavitation. Cold, thick oil will cause the system to operate sluggishly or erratically. This bypassing causes additional heat and a slowdown of the system. Too hot oil will easily bypass through pumps, valves, and cylinders. Controlling operating temperature reigns as the predominant viscosity-affecting variable. This means that operating temperature is king. This is because oil viscosity reduces rapidly with the increasing temperature of the oil and increases with decreasing temperature of the oil. Selecting the correct viscosity is a balancing act that requires juggling two conflicting requirements. The typical viscosities of hydraulic fluids are ISO VG 32, 46, and even 68, but they are available in an even wider range of ISO VG 22 to 100, which are also used in hydraulics. This definition is based on a specific liquid’s molecules having more or less internal friction. Viscosity is a measurement of a fluid’s internal resistance to flow. Viscosity is the most crucial property of lubrication, yet it is shrouded in mystery and confusion. Hydraulic oil must contain the correct viscosity, or the system cannot develop that power or operate properly. Therefore, flow and pressure together define the total power of the hydraulic system. The old battle cry in the hydraulics world is “flow makes it go.” However, pressure determines the ability of actuators to move heavy loads.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |