润滑脂固体物质含量

DIN 51813 Prüfung von Schmierstoffen;

Bestimmung des Gehaltes an festen Stoffen in

Schmierfetten; Teilchengr??en über 25 μm, 1989.

润滑脂固体物质含量

Solid particles in greases cause severe problem during

the operation of lubricated units. They influence the

noise behaviour of ball bearings and enhance the wear

rate of interacting components. Solid matter content in

lubricating greases is given in DIN 51813 . The

method employing the hydraulic grease press

we describe here is applicable to greases not containing

any solid lubricants. Operating pressure of hydraulic

grease press is up to 150 bar, and the test load at the

piston is ca. 60 – 70 kN.

Mean quantity 500 g of a grease sample is pressed

through the test sieve (Fig. 5). The squeezed grease is

dissolved in a solvent mixture and in acetic acid and

then filtered. After washing out and drying the filter

crucible, a mass difference is used to determine the

fraction of solid particles contaminating the grease.

Test sieve with a mesh size of 0.025 mm is made of

stainless steel, e.g. according to DIN 4188, and could be

214 ? VOL. 43, No 3, 2015 FME Transactions

used not more than for two tests. Base fabric on the

sieve bottom is of the same steel, whereas its mesh size

is 0.5 mm (Fig. 5).

Precision of the method is characterised by

repeatability and comparability as it is shown in the

following Table 1.

Table 1. Repeatability and comparability of the test method

(mass fraction in mg/kg)

Solid matter content    Repeatability   Comparability

    < 10.0            5.0        10.0

   ≥ 10.0            7.5        15.0

Some additional controls integrated into the hydraulic

grease press make also possible testing the filterability of

greases. These include adjustment of the flow rate at the

test sieve and the pressure within the grease cartridge.

The adjustment range of both characteristics is based on

the range of parameters prevailing in filters. Results of

such tests show user whether grease is suitable for an

application. Adjustable flow rate at the test sieve ranges

from 0.5 to 1.5 m/min; adjustable maximum of filtration

pressure is 60 bar, whereas pressure measurements at the

test sieve lie in the range from 0 to 60 bar.