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1、 Grease storage
There are many kinds and brands of lubricating grease with different properties. The grease is more likely to deteriorate than oil, and it is difficult to deal with after mixing impurities in the grease. Therefore, it is of great significance to strengthen the quality management in the storage of lubricating grease.
1. Quality changes in grease storage
After long-term storage, the quality of lubricating grease changes in the following aspects:
1) Color change;
2) Mixed with ash, sand, dust and other mechanical impurities;
3) Mixing or absorbing water:
4) After long-term storage, lubricating oil precipitates and forms hard blocks, resulting in oil Use Of Grease soap separation, acid formation, unqualified corrosion, etc.
2. Causes of deterioration of lubricating grease during storage
The reasons for deterioration of lubricating grease during storage Use Of Grease include: introduction of impurities and moisture from the outside; Physical or chemical changes in the grease itself.
3. Measures to delay deterioration of lubricating grease during storage
1) Lubricating grease shall be put into storage first to reduce the influence of temperature, moisture and dust;
2) Reduce the storage temperature;
3) Strengthen targeted management according to the characteristics of different types of grease;
4) Pay attention to sealed storage;
5) Pay attention to the cleaning of grease removal tools and containers;
6) For different users, large, medium and small packaging forms are adopted;
7) Pay attention to the regular test of lubricating grease in stock.
2、 Main forms of failure:
1. Oxidative metamorphism
2. Destruction of lipid colloid structure
3. Base oil play
4. Grease separation and loss
5. Foreign matter mixing
6. Grease aging (hardening, loss of lubrication)
Failure occurs when one of the following conditions is met:
1. When the consistency changes to ± (15 ~ 20)%, it is generally necessary to change the grease;
2. If the dropping point changes, the soap base grease will be judged as aging failure as follows:
Lithium grease below 140 ℃, sodium grease below 120 ℃
Calcium base grease below 50 ℃, composite aluminum below 180 ℃
Composite lithium below 200 ℃, others, change more than ± 20%
If the acid value of lubricating grease is more than 3mgkoh / g, it will become invalid
4. Mechanical impurity content, the following is failure
Fe>1％
Or Cu > 3%
Or ash content change rate > 50%
3、 Failure analysis of lubricating grease
(1) Failure caused by physical factors
In use, the grease will be subjected to mechanical shear and centrifugal force at the same time, and the grease will be thrown out of the friction
Wipe the interface and make it separate oil, resulting in the Use Of Grease reduction of lubricating grease, the reduction of cone penetration and hardening. To a certain extent, the lubricating grease will be completely ineffective; Under the action of mechanical shear,
the structure of lubricating grease is damaged (such as the separation or orientation of soap fiber), resulting in softening, decrease of Use Of Grease consistency and increase of oil separation, which eventually leads to failure. Under normal circumstances,
if the transmission speed of lubricating grease is increased by 2000r / min, its service life will be reduced by about half. Under high shear stress, the rotating speed is doubled and the service life is only 1 / 10 of the original life.
(2) Failure caused by chemical factors
The chemical reaction between lubricating grease and oxygen in the air produces acidic substances. Firstly, it consumes the antioxidant additives in the grease. However, to a certain extent, the generated organic acids will corrode the metal components and destroy the structure of the grease,
reduce its dropping point, increase the viscosity of base oil and Use Of Grease deteriorate its fluidity. A large number of tests show that the higher the temperature, the more obvious the decline of grease life. For example, when the temperature is 90 ~ 100 degrees,
the service life of grease will be reduced by about half for every 19 degrees of temperature increase, while when the temperature is 10 ~ 150 degrees, the service life of grease will also be reduced by half for every 15 degrees of temperature increase.
In addition, the moisture, dust and harmful gases in the environment in which the grease is used are also important factors for its Use Of Grease deterioration. For example, if the grease is mixed with wear particles such as copper, iron, lead and bronze, it will catalyze the oxidation of grease.
In short, there are many reasons for the failure of lubricating grease, sometimes caused by one reason, but it is more the result of the interaction of multiple factors, or take one reason as the breakthrough, and then other reasons work together.
4、 Correct use of grease
(1) The amount of lubrication should be appropriate
Too much grease will increase the friction torque, temperature and grease consumption; If the amount of grease is too small, reliable lubrication cannot be obtained and dry friction occurs.
Generally speaking, the appropriate amount of grease is 1 / 3 ~ 1 / 2 of the total void volume in the bearing. However, according to the actual Use Of Grease situation, sometimes the bearing edge should be greased and cavity lubrication should be implemented.
(2) Pay attention to prevent the mixing of different types, brands and new and old greases
Avoid the cross use of grease containers and tools, otherwise it will have adverse effects on grease, such as drop point drop, cone penetration increase and mechanical stability decrease.
(3) Pay attention to the replacement of new grease
As the variety and quality of lubricating grease are constantly improving and changing, when the old equipment changes to new lubricating grease, it should be tested first and can be officially used after trial;
When replacing with new grease, first remove the waste grease and clean the components. When Use Of Grease adding lubricating grease, the waste lubricating grease shall be squeezed out until new lubricating grease is seen at the grease discharge port.
(4) Pay attention to the management of grease filling process
Before receiving and filling lubricating grease, pay strict attention to the cleaning of containers and tools, and wipe the grease supply port on the equipment in advance to prevent the mixing of mechanical impurities, dust and sand.
(5) Pay attention to the timely replacement of grease in season
For example, the temperature difference between winter and summer plums in the environment where the equipment is located varies greatly. If winter fat is used in summer or vice versa, the results will be counterproductive.
(6) Pay attention to adding and changing lubricating grease regularly
The addition and replacement time of lubricating grease shall be determined according to the specific use conditions, which shall ensure reliable lubrication without causing waste of grease.
(7) Do not pack grease in wooden or paper containers
Prevent oil loss from hardening, mixing with water or being polluted and deteriorated, and store in a cool and dry place.