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GREASE CONSISTENCY

CONSISTENCY of the lubricating grease is very important. A too thick (high consistency grease) will have lower pumpability and smaller ability of the grease to reach in the areas where it needs to lubricate. If a grease is too soft, (consistency too small) then it could leak out and increase grease consumption. The National Lubricating Grease Institute (NLGI) classified greases Consistency after the worked penetration of the grease, which is measured after 60 double strokes working, in the grease worker, at 25°Celsius).

Also greases with consistency in between the NLGI grades can be produced, on request (often is used NLGI 00/000 and also the in-between class Grade “NLGI 2,5”) which is between the consistency for NLGI 2 and the consistency for NLGI 3.

NLGI GREASES CONSISTENCY GRADES

NLGI number represent a scale for comparing the consistency range of greases. The numbers are from NLGI 000 which is semi-liquid to NLGI 6 which is solid. For example:This range of greases and pastes products are intended for the extreme applications such as high power open gears for grinding mills, dryers and rotary kilns, lubrication of rolling element bearing exposed to severe operating conditions and steel industry; special paste for bushings of hydraulic and pneumatic hammer; copper paste for easy assembling/disassembling operations in automotive and industrial applications.

NLGI Grade Penetration after 60 strokes
000 445 - 475
00 400 - 430
0 355 - 385
1 310 - 340
2 265 - 295
3 220 - 250
 

Measuring of grease penetration in Verila Lubricants testing laboratory

 

The ISO grease classification: ISO 6743-9 – the part ISO 6743-9 L-X

(Class L - Lubricants; Family X). The reading of the grease specification is the following:
ISO –L –X –symbol 1 –symbol 2 –symbol 3 –symbol 4 -Numbers

Symbol 1 = Lower operating temp. range (see table for Symbol 1, A –E)

Symbol 2 = Upper operating temp. range (see table of symbol 2, A –G)

Symbol 3 = combination of resistance to water washout and rust performance, measured as per the ISO 11007 [EMCOR Test], see bellow table of symbol 3, A –I

Symbol 4 = Load carrying / performance symbol (see bellow table of symbol 4, A –B)

Numbers = NLGI Consistency Class by ISO 2137

Symbol 1, states the grease Lowest operating temp. Lower operating temp., (°Celsius)
A 0
B -20
C -30
D -40
E < -40
Symbol 2, states the grease Upper operating temp. Upper operating temp., (°Celsius)
000 445 - 476
00 400 - 430
0 355 - 385
1 310 - 340
2 265 - 295
1 220 - 250
Symbol 3, states the Water Resistance & Rust Protection Water Washout Loss, % At this Temperature (°Celsius) Rust-prevention Rating
A No Requirement 38 No Requirement
B No Requirement 38 1-1 max
C No Requirement 38 2-2 max
D < 30 38 No Requirement
E < 30 79 1-1 max
F < 30 79 2-2 max
G < 10 79 No Requirement
H < 10 - 1-1 max
I < 10 - 2-2 max
Symbol 4, states the ability to Lubricate under High Loads, by measuring the weld load in 4 ball test ASTM D2596 or IP 239 Four-Ball Weld Load Requirement, (kg)
A None
B ≥ 250
 

Example of reading of the ISO classification of a grease: VERILA Lithium EP 2 is ISO-L-XCCHB-2. This means: it works in temperatures down to -30 Celsius [letter - C] and up to 120 Celsius [letter - C], with very good water wash out resistance and rust prevention [letter - H], with EP properties [letter - B], in NLGI 2 consistency grade [number 2].

 

EMCOR Testing Rig in our laboratory


The DIN Grease Classification: DIN 51502

The reading of the grease specification is the following: DIN 51502–Character 1Character 2 –NLGI Grade –Character 3Lowest Temperature

Grease classification based on the applications Character 1
Greases for Bearings K
Greases for Closed Gears G
Greases for Open Gears OG
Greases for Friction Bearings / Sealing M
Lowest operating temp.
-10
-20
-30
-40
 
Information regarding additives and Base Oils utilized in the grease Character 2
dry lubricants added (MoS2, Graphite, etc) F
Ester based E
Fluor hydrocarbons FK
Synthetic or part synthetic base oil HC
Poly-glycols PG
Silicon Oil SI
EP additive P

Preparation of 4-ball Wel Load test

Character 3:
designating upper
operating temp.
and water resistance
Highest
Operating
temp
Celsius
Behavior in presence of water
according to
DIN 51 807 Part 1
C 60 0 at 40 Celsius to 1 at 40 Celsius
D 2 at 40 Celsius to 3 at 40 Celsius
E 80 0 at 40 Celsius to 1 at 40 Celsius
F 2 at 40 Celsius to 3 at 40 Celsius
G 100 0 at 90 Celsius to 1 at 90 Celsius
H 2 at 90 Celsius or 3 at 90 Celsius
K 120 0 at 90 Celsius or 1 at 90 Celsius
M 2 at 90 Celsius or 3 at 90 Celsius
N 140 Producer specific information
P 160 Producer specific information
R 180 Producer specific information
S 200 Producer specific information
T 220 Producer specific information
U > 220 Producer specific information

Low Tempearture Flow Pressure Test

 

Example of reading of the DIN classification of a grease:

VERILA Lithium EP 2 is KP2K-30 grease according to the DIN 51502.

This means: it is grease for bearings [Character K] with Extreme pressure properties [Character P], of NLGI 2 consistency grade, for temperatures up to 120 Celsius [Character K] and down to -30 Celsius.

 


The TYPICAL OPERATING TEMPERATURES, PER GREASE TYPES

 

A grease Operating Temperature Range for continuous operation depends on many factors:

  • continuous or temporary exposure to high temperature,
  • relubrication frequency,
  • if there are frequent cycles of high to low operating temp.,
  • evaporation resistance of the grease, and many more.
 

Highest operating temp. depending on product, re-lubrication interval, temperature fluctuations

 

Lowest operating temp. of a grease


 

This graph has general orientation character only, variations for particular products can occur. Some VERILA greases are specially formulated to be safely applied over or below the values presented in the graph. Please always refer to the Product Data Sheet.

The Grease DROPPING POINT

The dropping point of a grease measures the temperature at which the grease passes from a semi-solid phase into a liquid state, under the conditions of test and testing temperature. The dropping point range is specific for each type of thickener.

Dropping point is linked to the highest operating temp. that the grease can be used at, but the maximum operating temp. must be significantly lower than the grease's dropping point temperature.

Measuring of dropping point temperature in Verila Lubricants testing laboratory