Low Temperature Viscosity Testing

[MolaKule]

For machines that have to operate at low temperatures, or start from low temperatures, one needs to know how the fluids behaves at low temperatures.

This test measures the low temperature "apparent" viscosity in mPa.s or cP.

This test is especially suitable for fluids where power is transferred via these fluids.

What is the 1.) ASTM test designation, 2.) it's title, and 3.) the name of the machine used to execute this test?



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[jorton]

The ASTM test designation is ASTM D5293. Cold Crank Viscosity is the name of the test. And the name of the machine used to execute this test is the cold cranking simulator.

 

[weasley]

ASTM D4684
Standard Test Method for Determination of Yield Stress and Apparent Viscosity of Engine Oils at Low Temperature
Mini Rotary Viscometer (MRV)

In relation to engine oils this test is important to know if oil can be pumped out of the sump quickly enough when cold. If the oil won't flow well enough, exhibiting yield stress, then there exists the possibility that the oil pickup will suck up the oil around it, which won't infill quickly enough from the surrounding bulk, leaving a 'crater' in the oil surface and hence having air sucked up the pickup.

 

[MolaKule]

Another hint:

Quote:
This test is especially suitable for fluids where power is transferred via these fluids.

 

[Shannow]

Test ASTM D2983, Standard Test Method for Low-Temperature Viscosity of Lubricants, using a Brookfield Viscometer.

more appropriate for pumping, oil pick-up, and power transmission as it's a low shear rate test.

 

[jorton]

Oh, it's hydraulic fluid.

 

[MolaKule]

Originally Posted By: jorton
Oh, it's hydraulic fluid.


Originally Posted By: ASTM D2983-09
The Low temperature, low shear rate viscosity of automatic transmission fluids, gear oils, torque, and tractor fluids and industrial and automotive hydraulic oils are of considerable importance. Measurement of the viscometrc properties of these oils and fluids is often used to specify their acceptance for service.


If you look at ATF specifications you will see a Brookfield viscosity value listed. Recall that ATF is simply a specialized hydraulic fluid, as is Power Steering System fluid.

The Brookfield viscosity is measured for a viscosity range from 250 to 1,000,000 mPa.s (cP). The spindle speed can be varied from 120.0 to 0.6 rev. per minute, respectively. The Brookfield machine is calibrated with a calibration fluid of known viscosity.

The fluid to be tested is placed in a test cell tube of 22mm ID by 115mm long. It is then cooled to the test temperature for 16 hours, after which the spindle is rotated to determine the low temperature viscosity.

For example, we'll set a fluid to a temperature of -30F or -34.4C. The observed dial reading for the test fluid at 12 rev/m is 49.5. Reference fluid viscosity at -20F is 11,360. The reference fluid viscosity at -30F is 28,580. The Brookfield factor at 12 rev. per minute is 500. The Brookfield viscosity will then be 49.5X500 = 24,750.

For MaxLife ATF, the PQIA test was:

Brookfield Viscosity @ -40°C, cP: 20,000 cP Max, 17,511 cP AVG, and 11,560 cP for MaxLife.

http://www.pqiamerica.com/ATFdecember2012/valvolinemaxATF.htm


So the Piston Cup Lapel Pin once again goes to our BITOG member SHANNOW from the land of the Kangaroos, Wallabys, and the Sidney Opera House.

 

[userfriendly]

Quite often Brookfield viscosity will be stated as a low temperature limit
for Caterpillar drive train oils (TO-4s), manual transmission and final drive
lubricants on the product information data sheet.
The reason being, is that the maximum Brookfield viscosity limit at cold, is very close to the
channel point of the lubricant being tested.

The specification sheet will state Brookfield viscosity XXX@-20C for example.

That would mean that the particular lubricant is suitable for the application
intended for the product, at temperatures no colder than -20C.