A liquid with low viscosity, like water, flows easily compared to one with high viscosity, like honey. In general, viscosity for a liquid decreases as temperature increases.
Honey, for example, is very viscous if cold and would ooze from the jar if you tried to pour it. Heat the honey, though, and it becomes easy to pour. The poise is inconveniently large for most fluids, however, so the centipoise cP is more commonly used. Dynamic viscosity is often measured with a rotational viscometer, which uses a spinning probe immersed in a sample of liquid.
Depending on the nature of the test, the probe may be a cylinder, a sphere, a disk or some other shape. Viscosity is determined by the force needed to rotate the probe at a chosen speed. Because viscosity varies with temperature, any meaningful description of viscosity must also include temperature. A Newtonian fluidlike water, has a constant viscosity despite the amount of shear stress.
Non-Newtonian fluids have viscosities that vary with the magnitude of shear stress. Paint, ketchup and mayonnaise are non-Newtonian fluids that undergo stress-thinning, which means their viscosities decrease with stirring. In contrast, a mixture of cornstarch and water, sometimes called oobleck and used for some slime recipes, exhibits stress-thickening — you can slowly push your hand into oobleck, but it becomes rigid if struck quickly.
Unlike dynamic viscosity, kinematic viscosity measures the resistance to flow under only the influence of gravity and is primarily used for Newtonian fluids.
Saybolt viscosity, also called SSU viscosity, is measured with a Saybolt viscometer, which heats the liquid to a desired temperature and pours it through a calibrated orifice. Standard test temperatures are 77,and degrees Fahrenheit The time in seconds for 60 mL of the liquid to flow through the orifice is the SSU.
The method is derived empirically, and consequently it is somewhat complex. Converting kinematic viscosity to SSU requires the inverse relationship, which can be obtained by using the solution to the quadratic equation:. Lee is a writer, electronics engineer and owner of a small high-tech company. He also produces web content and marketing materials, and has taught physics for students taking the Medical College Admissions Test.
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Hydraulic oil viscosity
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Invalid email. This is required. Login to Your Account. Remember Me? Register Forgot password? What's New? Forum Manufacturing Today General Engler viscosity question. Results 1 to 8 of 8. Thread: Engler viscosity question. Thread Tools Show Printable Version. I have an big old 15 HP swiss lathe that says it needs 1.
What viscosity is that roughly equal to in either SAE motor oil or gear oil?
Viscosity Conversion Factors
Thanks for any and all help, Marc. What is the temp spec on the gearbox. This day and age, you prolly want to consider a synthetic oil to save power lost and to improve the lube characteristics. This is not even close to an SAE or gear oil range. ISO-7, 10, 15, and 22 are usually considered spindle oils. ISO is usually a hydraulic recirculating oil.
That's one hell of a range for viscosity. ISO from 2, And ISO from around 1, So, without knowing what speeds you're running, it's hard to make a recomendation. That's great. Thank you very much.
ISO Viscosity Grades
That is exactly the info.One of these other chemicals is a viscosity index improver. Viscosity index should not be confused with viscosity; it is an altogether different kind of rating.
The viscosity index number indicates the extent of thickness, or resistance to flow, with temperature changes. The time measured in seconds for a volume of 65 ml to flow through the orifice is the rating of the oil. Lower viscosity fluids will flow more easily and faster, while high viscosity fluids will flow more slowly.
If the tested oil takes more than 1, sec for the 65 ml to flow, the tested oil temperature is increased. As an example: 30W oil flows much faster at higher temperatures.
Image courtesy of Hy-Pro Filtration. The pump and hydraulic motor are most sensitive to viscosity, so you must be sure to only use suitable oil according to the manufacturer specifications. Other system components are less sensitive to viscosity. If the oil is too thin low viscosity not only is it hard to pump, but slippage will accrue due to leakage past clearance spaces, between gears, vanes, piston seals and valve spools, thus effecting overall system efficiency.
Viscosity also increases with pressure. Viscosity Index V. Thus 0 indicates an oil with the greatest change over a certain temperature while indicates an oil with the least change over a certain temperature. All other oils fall within these extremes. With the addition of chemical additives, the V. The most desirable hydraulic oils have the least amount of viscosity change and a V.
Finally, temperature can have a major effect on hydraulic oil. Keeping oil to a moderate temperature level is an important requirement for reliable operation.
High temperatures can also cause chemical reactions, such as oxidation, and reactions with minute quantities of acids present, also shorten oil life. I are critical for low temperature operation. It is important to monitor start-up and operating temperatures, allowing enough time for the machine to warm up before putting it into high speed or heavy operation.
Your email address will not be published. This site uses Akismet to reduce spam. Learn how your comment data is processed. Photo: Meg Schneider. Comments please what are the examples of viscosity index. Leave a Reply Cancel reply Your email address will not be published.ISO oil grades are identified by their viscosity grade or VG.
SAE grade equivalents to ISO grades are approximate, since they are based on viscosity measurements at different temperatures. Gear oil grades can also change with time due to viscosity changes that occur with usage. Gear oil lubricates gears in cars and industrial motor gear boxes.
Look for indications that the oil is multi-grade. Refer to the SAE grade marked on the container label. SAE grades identified by a number and then letter are multi-grade oils. Identify whether the oil is intended for use in crank cases or to lubricate gears.
Measure the viscosity with a viscometer if the conditions are far from the original test conditions on which the SAE or ISO grades are determined. You can verify extremely hot and cold temperatures with a thermometer. Extreme temperatures can result in very different viscosity than is standard for the grade.
Gear oil grades can also change with time due to chemical changes that occur with usage. Directly measure the viscosity to determine the correct ISO grade in either of these cases. Convert the measured viscosity to the ISO viscosity to determine the correct grade. SAE oil viscosity measurements are in Centipoise, abbreviated to cP. ISO viscosity grades are measured in centistokes, abbreviated as cST and measured in millimeters squared per second.
Fortunately, Centipoise and Centistokes have a one-to-one ratio. This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
To submit your questions or ideas, or to simply learn more about It Still Runs, contact us. Step 1 Look for indications that the oil is multi-grade. Step 2 Identify whether the oil is intended for use in crank cases or to lubricate gears. Step 3 Measure the viscosity with a viscometer if the conditions are far from the original test conditions on which the SAE or ISO grades are determined.
Viscosity variation within ISO oil grades is plus or minus 10 percent. Items you will need SAE grade marked on the container label viscometer thermometer.
Pirro, A. Wessol, J. About the Author This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.This arises because of the internal molecular friction within the fluid producing the frictional drag effect.
There are two related measures of fluid viscosity which are known as dynamic and kinematic viscosity. Dynamic viscosity is also termed " absolute viscosity " and is the tangential force per unit area required to move one horizontal plane with respect to the other at unit velocity when maintained a unit distance apart by the fluid. Note that the conversion from Absolute Dynamic Viscosity to Kinematic Viskosity depends on fluid density.
The conversions below are for fluid with density like water - or specific gravity like one. Viscosity conversions are based on fluids with specific gravity of one. Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro.
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There are several methods in use. The most acceptable method in the United States is the Saybolt viscosimeter Figure The time it takes for the measured quantity of liquid to flow through the orifice is measured with a stopwatch. Obviously, a thick liquid will flow slowly, and the SUS viscosity will be higher than for a thin liquid, which flows faster.
Since oil becomes thicker at low temperatures and thins when warmed, the viscosity must be expressed as a specific SUS at a given temperature. Where temperature extremes are encountered, the fluid should have a high viscosity index.
Summer numbers 20W, 30W, etc. Table is a chart of the temperature ranges. The following formulas may be used to convert centistokes eSt units to approximate Saybolt universal seconds SUS units. These viscometers can be used to test the viscosity of hydraulic fluids either prior to their being added to a system or periodically after they have been in an operating system for a while. Viscosity Index The viscosity index, VI, of oil is a number that indicates the effect of temperature changes on the viscosity of the oil.
In other words, the oil becomes extremely thin at high temperatures and extremely thick at low temperatures. On the other hand, a high VI signifies relatively little change in viscosity over a wide temperature range. Figure illustrates the relative change of viscosity with changes in oil temperature.
SAE to ISO Gear Oil Conversion
An oil having a high VI resists excessive thickening when the engine is cold and, consequently, promotes rapid starting and prompt circulation; it resists excessive thinning when the motor is hot and thus provides full lubrication and prevents excessive oil consumption. For the proper operation of the hydraulic control system, the hydraulic fluid must have a sufficiently high VI to perform its functions at the extremes of the expected temperature range.
The average hydraulic liquid has a relatively low viscosity. Fortunately, there is a wide choice of liquids available for use in the viscosity range required of hydraulic liquids.
The VI of oil may be determined if its viscosity at any two temperatures is known. These tables permit calculation of the VI from known viscosity. Pour Point Pour point is the lowest temperature at which a fluid will flow.
If the hydraulic system will be exposed to extremely low temperature, it is a very important specification. Your email address will not be published. Sections About. Categories Uncategorized. Posted on August 27, by admin Leave a comment.
SUS Viscosity For most practical purposes, it will serve to know the relative viscosity of the fluid. Selection process retrofitting to existing equipment:Motor suitability and de-rating. Pumps:Pumps in series switched to meet demand.
Actuators:selection and performance of cylinders. Energy and Efficiency:The complete isothermal formula. Particle degradation:Test rigs and data sources. Moisture and condensation:Air processes and Condensation in reception hopper. Operating problems:Existing plant and Positive pressure systems.Forum Rules.
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We'll bring you the most relevant peer-to-peer conversations happening in the trade and tips and tricks to help you get the job done. Invalid email. This is required. Login to Your Account. Remember Me? Register Forgot password? What's New? Forum Manufacturing Today General Saybolt oil equivilants? Results 1 to 11 of Thread: Saybolt oil equivilants? Thread Tools Show Printable Version. Saybolt oil equivilants? Any recommendations? BTW, the lathe is this: Page Title thanks!
I know this is niot an exact match but they are close.