Page 50 - MMI - MayJune2022 small-single

four-ball wear test but may fail
in the FE-8 and FZG tests.

Why FZG and FE-8 test
methods better than the
four-ball wear test
FZG Test (ASTM D 5182):
ASTM D 5182, A/8.3/90 method
is widely used to evaluate the
scuffing properties of industri-
Source: Anand Engineers Pvt Ltd A-type gears are loaded step-
al gear oils.
wise in 12 load stages between
Hertzian stress of Pc = 150 to
1800 N/mm². They are operated

Gear oils Steel Corrosion Test (ASTM D 665 A and B) Copper Corrosion Test (ASTM D 130) for 15 min at a pitch line velocity
of 8.3 m/s and a starting oil tem-
have to perature of 90°C in each load
withstand stage, under conditions of dip lu-
harsh en-
vironments tic for applications involving are used to determine the cor- brication without cooling. After
such as rust, water contamination. rosion property of the gear oil each load test, scuffing marks
water, and The demulsibility test (ASTM D before conducting trials. are evaluated on the gear flanks.
debris to 1401) was conducted on Moly- Molygraph’s Ultra Gear Syn Gear oil must pass load stage 12
hinder emul- graph’s Ultra Gear Syn 320 syn- 320 passes: (i.e., damage load stage must be
sification, thetic gear oil at 82°C. This oil • Steel corrosion test (ASTM D more than 12 stages).
foaming, passes the demulsibility test 665 A and B) for 24 hours In FZG, Molygraph Ultra Gear
and wear within 15 minutes. It indicates • Copper corrosion test (ASTM Syn 320 passes 12 load stages.
characteris- the extent of the hydrophobici- D 130) with 1a rating for 3 FE-8 Test (DIN 51819-3):
tics effect on ty of the formulated gear oil. hours at 100°C and 1b rating The wear behavior of rolling
gears. Of the Foaming in the gearboxes is the for 24 hours at 100°C. bearings is examined in the FE-8
four broad
categories most frequent complaint that wear test according to DIN 51819-
of gear oils, manufacturers come across. Wear characteristics 3 at an oil temperature of 80°C.
synthetic Foam does not circulate and re- Anti-wear and load-carrying In this test, axial cylinder roller
gear oils are duces the lubricant's effective- properties of gear oils are quite bearings of type D are subjected
best suited, ness by accelerating gear wear important. However, determin- to a speed of n=7.5 min-1 with
especial- and overheating. ing it only through a four-ball an axial force of Fa=80 kN at a
ly for the When tested, Molygraph Ultra machine test is not the right steady-state temperature of 80°C
demanding Gear Syn 320 shows 0ml foam approach as extreme pressure over 80 h. With a C/P<2, a very
applications height in sequence I at 25ºC, Se- additives, which give an 800kg high load is applied. Wear is then
of open quence II at 93ºC and Sequence III weld load in a four-ball test (i.e., determined gravimetrically. Gear
gears. at 25ºC as per ASTM D 892 test. ASTM D 2783), can fail in FZG oils in the FE-8 wear test, accord-

and FE-8 tests, while extreme ing to DIN 51819-3, have to show
Corrosion characteristics pressure additives, providing a roller wear of <=30mg cage wear
Oil additives are beneficial in 250kg weld load in four-ball tes- of <=200mg. Molygraph Ultra
adding certain properties to ters, can pass FZG and FE-8 tests. Gear Syn 320 clears DIN 51819-3
the oil. But sometimes it is also This is because sulfur, used as an at a temperature of 80°C.
harmful to the gearboxes. EP additive, gives higher weld load
additives that contain active points on four ball machines but Molygraph’s Ultra Gear
sulfur aggressively react with causes scuffing and pitting in Syn 320 gear oil for
the metal, causing wear and FZG and FE-8 tests. industrial gears
even failure. Moreover, the four-ball wear test Industrial gear oils are expect-
Some gearboxes have compo- (ASTM D-4172) is conducted for 1 ed to work under high tem-
nents made up of steel, bronze, hour while FZG is run for 15 min peratures and severe loads
and copper. Steel Corrosion for a minimum of 12 load stages, and in frequently contami-
Test (ASTM D 665) and Copper and the FE-8 test is run for 80 nated settings with dirt, de-
Corrosion Test (ASTM D 130) hours, so additives may pass the bris, and water. To address

50 | May-June 2022 Modern Manufacturing India