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Selection and application of smoothing grease for construction machinery
Source: China Bearing Network Time: 2014-03-24
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2 Cone penetration: refers to the depth (in 1/10mm) of the experimental cone penetrating straight into the grease within 5s under regular temperature and load. It is the measurement target of the consistency and hardness of the smooth finger.
3 Colloidal stability (oil-extracting property): refers to the ability to keep oil in the skeleton of its thickening agent under the effect of external force; it is determined by the oil content. When the oil content of smooth grease exceeds 5%-20% Time; this smooth fat can not be used basically.
4 Oxidation stability: refers to the ability to resist oxidation in storage and use.
5 Mechanical stability: refers to the ability to resist the change of consistency under mechanical working conditions. Mechanical stability is poor; the consistency of easy to form smooth grease is reduced.
6 transpiration loss: refers to the percentage of the total amount of lost under regular conditions. It is an important factor affecting the life of smooth fat.
7 Water resistance: refers to the ability to not dissolve in water, not absorb water from the surrounding medium and not be washed away by water.
8 Similar viscosity: refers to the ratio of shear stress to shear rate when non-Newtonian fluid is active. When the speed is high, its viscosity is low; otherwise, the viscosity is larger.
2, the failure analysis of smooth grease (1) failure of the physical elements caused by the smooth grease in the application will be affected by mechanical shear and centrifugal force, smooth grease will be pulled out of the conflict interface to make it oil; Reduction, taper reduction and hardening; to a certain extent, smooth grease will completely fail, under mechanical shearing effect; smooth grease layout loves damage (such as soap fiber disengagement or orientation); causing softening, consistency reduction and The addition of oil is added; the end causes failure. Under normal conditions; smooth grease is added 2000r/min by transfer rate; its life will be cut by about half. Under high shear stress; the speed is doubled; the service life is only equivalent. 1/10 of the original life.
(2) The chemical smoothing factor causes the failure of the smooth fat and the oxygen in the air to chemically attack the acidic substance; it is firstly the antioxidant additive in the fat; but to a certain extent; the organic acid formed will corrode the metal component and damage The layout of the fat; the drop point, the viscosity increase of the base oil and the deterioration of the activity. Many experiments indicate; the higher the temperature; the more the life of the smooth fat decreases. For example, the temperature is between 90 and 100 degrees; Increase by 19 degrees; the fat life is reduced by about half; and at 10 to 150 degrees; for every 15 degrees increase in temperature; the fat life will be reduced by half.
In addition, the use of moisture, dust and harmful gases in the environment of smooth grease is also an important factor for its deterioration. For example, the grease is mixed with wear particles such as copper, iron, lead and bronze; the oxidation of the ground fat acts as a catalyst. There are many reasons for the failure of smooth fat; sometimes it can be caused by a certain cause; but more is the result of the same effect of multiple elements; perhaps with a reason as a breakthrough; then other causes together.
3. Reasonable selection of smooth grease When selecting smooth grease; the first thing to consider is the conflicting conditions (load, speed, temperature), working conditions (continuous operation, intermittent operation, presence or absence of oscillation and impact) and working environment (humidity) , temperature, air pollution, etc.).
(1) The application temperature of smooth grease should be at least 20-30 degrees below its dropping point when the operating temperature is high; the fat with good antioxidation function, small transpiration loss and high dropping point should be selected, when the operating temperature is low; Low-torque, low-viscosity grease; such as grease based on oil.
(2) The selected smooth grease should be compatible with the speed of the smooth conflicting pair at high speed; the smooth grease with a large taper degree made of low viscosity base oil should be selected for the low speed grease; High-coneness logo made of high-viscosity base oil.
(3) The selected smooth grease should be compatible with the load size.
When heavy load; smooth grease with high viscosity of base oil and high content of thickener should be selected. When the load is uniquely large, attention should be paid to the selection of smooth grease with extreme pressure additive or filler (molybdenum disulfide, graphite). Generally, the smooth fat of the short and medium viscosity base oil is laid out with the No. 2 consistency soap fiber.
(4) The selected smooth grease should be compatible with the environmental conditions to be used in an environment where the air is wet or touched with water; the water-resistant grease such as calcium-based, lithium-based or lithium-based composite should be selected, and the dust should be used for a long time; Select a thicker (ie higher trademark) grease; this seal better; avoid impurities mixed into the conflict.
In a strong chemical medium environment; oil-like smooth grease such as fluorocarbon smooth grease should be used.
(5) The selected smooth grease should be compatible with the lipid supply method of the conflicting pair to collect the grease; the smooth grease of 00~1 should be selected, and the greased grease, grease cup, etc. should be selected for timing; Smooth grease No. 1~3, for the long-term use without changing the fat; the smooth grease of No. 2 or No. 3 should be used.
(6) The selected smooth grease should be compatible with the working condition of the conflicting pair, such as when the oscillation is large; use a grease with high viscosity, adhesion and vibration damping; such as high viscosity cycloalkyl or mixed base smooth oil thick Compound soap base smooth grease.
(7) The selected smooth grease should be adapted to its intended use. The grease used for smoothing should be selected in detail according to the type of conflicting sub-type, working condition, working condition, environmental conditions and fat supply method. Grease; should be useful to protect the metal from corrosion; such as parts that are protected from sea water; should choose aluminum-based smooth grease with strong adhesion and high water resistance, usually the solid grease can be thickened with solid hydrocarbons. Grease made of viscosity base oil. Regarding the sealing grease; should pay attention to its function against the solvent of the sealed medium.
(8) The selected smooth grease should try to ensure the reduction of the type of fat; improve economic benefits.
In the condition that meets the requirements; try to use lithium-based grease, complex soap base, polyurea and other multi-effect universal smooth grease. This way, it not only reduces the type of fat; it simplifies the handling of fat; Long life can reduce the cost of using fat; cut repair costs.
4, the correct use of smooth grease (1) the amount of smoothing should be properly increased fat; the conflict torque will increase; the temperature rises; the amount of fat consumption increases, and the amount of fat is too small; Obtaining a firm and smooth conflict. Generally speaking, the suitable amount of fatliquoring is 1/3 to 1/2 of the total empty space in the bearing. However, depending on the condition; sometimes the grease should be applied at the margin of the bearing to smooth the cavity. .
(2) Pay attention to avoid the use of different kinds, trademarks and old and new smooth grease to avoid the use of fat-filled containers and things; otherwise; reduce the drop point of fat attack; increase the degree of coning and reduce the mechanical stability.
(3) Pay attention to the replacement of new fat operation because the type and quality of fat-removing are constantly improving and changing; when the old equipment is changed to new smooth grease; it should be tested first; after trial, it can be officially used, when replacing new fat; Remove the waste smooth grease; clean the parts clean. When adding smooth grease; the waste grease should be squeezed out; stop when the new smooth grease is seen at the grease outlet.
(4) Pay attention to the process of adding smooth grease before collecting and filling smooth grease; pay strict attention to the hygiene of containers and things; the grease supply on the equipment should be cleaned beforehand; beware of the mixing of mechanical impurities, dust and sand.
(5) Pay attention to the timely replacement of the season fat. The winter and summer plum and temperature difference of the equipment environment change greatly; if it is used in the summer, the fat in the winter may be the opposite; the results will be boosted.
(6) Pay attention to the timing of the replacement of smooth grease smooth grease according to the detailed application conditions; it is necessary to ensure a firm and smooth and not to cause grease dregs.
(7) Do not pack smooth grease in wooden or paper containers to avoid oil loss, hardening, mixing or contamination; and should be stored in a cool and dry place.
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