Hydraulic Fluids
Background & Properties
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May 2025
GPS
Industry Specifications
Importance of Filterability, Demulsibility and Foam Tests
In hydraulic systems, air can be treated as a contaminant and lead to failures in the hydraulic pumps,
including cavitation and air bubbles. e ability to demulsify air and disperse foam improves filterability,
leading to longer component life.
Types of Filterability, Demulsibility, and Foam Tests include:
Filterability (Denison TP 02100)
is test measures how quickly an oil will filter when dry and how quickly it will filter when contaminated with 2%
water.
Test Criteria
A. Dry 600 seconds maximum
to 75 ml
B. Wet (2%) 2xA seconds maximum
to 75 ml
Demulsibility (ASTM D 1401)
is test measures the oil:water cuff and the time it takes for the oil and water to separate. Equal amounts of
oil and water are agitated at 130°F and le to separate over a timed interval. It is run at 130°F with ISO VG
32/46.
Test Criteria
Oil-water-cuff (ml) 40-37-3
Separation time (min) 30
is test is very important to hydraulic fluid users. A good AW hydraulic fluid must separate oil and water
effectively and leave no creamy white cuff between the two fluids.
Foam (ASTM D 892)
is test measures an oil's ability to prevent excessive foaming in the presence of entrained air.
Test Criteria
No foam allowed aer 10 minutes
Air Separation (DIN 51381)
Test Criteria
Separation Time, min ISO VG 46/68 ISOVG 32
DIN 51524 Part 2 10 max 5 max
GM (LS-2) LH,03, 04, 06) 10 max 5 max
Denison HF-O 7/10 NR
C7
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