How long does the grease in the pump bearing need to be replaced?
For bearings, lubrication is an important issue for performance. The suitability of the lubricant or lubrication method will greatly affect the life of the bearing. If the bearing is made of high grade grease, it can run for 15,000 hours or two years under normal operating conditions. For pumps with a motor power greater than 18.5 KW or under adverse conditions such as high ambient temperature, high air humidity, high dust, and aggressive industrial environment, the bearings should be inspected in advance, and if necessary, 5,000 hours of grease replacement can be arranged. The amount of grease filling varies with the structure and volume of the casing, and is generally filled to 1/3-1/2 of the volume. When the filling amount is too much, the grease deteriorates due to stirring and heating, aging and softening.
Misunderstandings in mechanical seal overhaul
1. The greater the amount of spring compression, the better the sealing effect. In fact, if the spring compression amount is too large, the friction pair may be sharply worn and burned instantaneously; excessive compression causes the spring to lose the ability to adjust the end face of the moving ring, resulting in seal failure.
2. The tighter the moving ring seal is, the better. In fact, the dynamic ring seal is too tight and harmful. One is to aggravate the wear between the seal ring and the bushing, and to leak prematurely; the second is to increase the resistance of the moving ring in the axial adjustment and movement, and it is not possible to adjust it when the working conditions change frequently; the third is that the spring is excessively fatigued and easily damaged; It is to deform the moving ring seal and affect the sealing effect.
3. The tighter the seal ring of the static ring, the better. The static ring seal is basically at rest, and the relatively tight seal will be better, but too tight is also harmful. First, the static ring seal is caused by excessive deformation, which affects the sealing effect. Second, if the static ring material is graphite, it is generally brittle, and excessive force is easy to cause chipping. Third, it is difficult to install and disassemble, and it is easy to damage the static ring.
4. The tighter the impeller lock is, the better. In mechanical seal leaks, leakage between the bushing and the shaft (interaxial leakage) is more common. It is generally believed that the leakage between the shafts is that the impeller locks are not locked. In fact, there are many factors causing leakage between the shafts, such as the failure of the inter-axis pads, the offset, the impurities between the shafts, and the larger shape of the shaft and the sleeve. Position errors, contact surface damage, gaps between components on the shaft, and excessive length of the shaft threads can cause leakage between the shafts. Excessive locking of the lock nut will only lead to premature failure of the inter-axis pad. On the contrary, the lock nut is moderately locked, so that the inter-axis pad always maintains a certain compression elasticity. During operation, the lock nut will automatically lock in time, so that the shaft is always in good condition. Sealed state.
5. The new one is better than the old one. Relatively speaking, the effect of using a new mechanical seal is better than that of the old one, but the quality or material selection of the new mechanical seal is not appropriate. The large dimensional error will affect the sealing effect; in the polymerizable and permeable medium, the static ring is not excessive. Wear or not replace it as well. Because the static ring is in a static state for a long time in the static ring seat, the polymer and impurities are deposited as one body, which has a good sealing effect.
The following items should be paid more attention when using bearings:
Bearings are precision parts, so they require a very cautious attitude when using them. That is, they use high-performance bearings. If they are used improperly, they can not achieve the expected performance and easily damage the bearings.
First, keep the bearing and its surrounding environment clean. Even if the smiling dust that is invisible to the naked eye enters the bearing, it will increase the wear, vibration and noise of the bearing.
Second, the use of installation should be carefully and carefully not allowed to force the stamping, the hammer is not allowed to directly hit the bearing, and the pressure is not allowed to pass through the rolling element.
Third, use appropriate and accurate installation tools to use special tools as much as possible, and try to avoid the use of cloth and short fibers.
Fourth, to prevent the corrosion of the bearing directly when taking the bearing by hand, you should fully wash the sweat on your hands, and apply high-quality mineral oil before operation, especially in the rainy season and summer to pay attention to rust.
How does the bearing fail prematurely?
According to the bearing industry leader SKF found in the study of extending the bearing life, only 25% of the bearing performance depends on the quality of the bearing. Other factors, such as installation, lubrication and maintenance, actually have the greatest impact on the bearings.
a.16% of premature failure of various bearings is caused by improper assembly and incorrect use of assembly tools.
b. Although “maintenance-free” sealed bearings can be installed, 36% of premature bearing failures are caused by incorrect technical application and improper use of grease.
c. Bearings are precision parts. If the bearings and grease are contaminated, they will not operate effectively, so at least 14% of all premature failure bearings are caused by pollution problems.
d. If the machine is overloaded, improperly used or maintained, the bearings will be affected, resulting in 34% of the bearings failing prematurely due to fatigue.
Why should the bearings be cleaned before adding new grease?
New grease and waste grease cannot be mixed at will, because the grease is oxidized due to mechanical shearing, agitation of metal catalyzed high temperature and other conditions, as well as mechanical impurities such as dust, oxide water and gas, etc. Metamorphic depolymerization and aging produce hydroxy acid, colloid, asphalt and other products. The color of the grease becomes darker, the viscosity and consistency change, the acid value increases, the corrosion increases, and the performance is reduced. Causes the properties of new grease to deteriorate.
1. The grease produced by different manufacturers of the same grade will have a change in properties due to different raw materials and processes.
2. Different kinds of greases can't be mixed. Because the thickeners, base oils and structures of the greases are different, the thickeners will be unevenly dispersed. It will not be easy to form a stable structure. The grease will become soft and the mechanical stability will be reduced.
The principle and advantages of ultrasonic cleaning?
1. Principle: The sudden change of sound pressure when ultrasonic waves propagate in liquid causes strong cavitation and emulsification of liquid, and millions of tiny cavitation bubbles are generated every second. These bubbles are rapidly generated in large quantities under the action of sound pressure. And continually violently blasting, producing a powerful impact and negative suction, enough to make stubborn dirt peel off, kill bacteria, viruses.
a, no holes. Since the action of ultrasonic waves occurs throughout the liquid, the surface of all objects that can come into contact with the liquid is cleaned, and it has a unique effect on objects with many complicated shapes and gaps.
b, autumn is not damaged. Traditional manual or chemical cleaning often results in mechanical or chemical corrosion, while ultrasonic cleaning does not cause any damage to the object.
c, wash everything, wash everything. In addition, when a suitable cleaning agent is used for an object of a different nature, the ultrasonic wave is strengthened by the penetration and dissolution of the cleaning agent, and the cleaning is completely refreshed.
Pump mechanical seal installation and technical requirements
1. Technical requirements for the cooperation of the machine, pump and mechanical seal:
a. The maximum bending of the shaft shall not exceed 0.05mm.
b. Each part in the part meets the drawing requirements. b. When tightening the gland, it should be done after the coupling is aligned. The compression screws should be tightened to prevent the flange surface from being skewed. c. The amount of compression of the spring is allowed to be ±2mm according to the drawings.
c. The amount of vibration of the shaft at the installation of the mechanical seal shall not exceed 0.1 mm. c. The axial yaw of the shaft must not be greater than 0.5 mm. d. Install the mechanical seal. The shaft has a manufacturing tolerance of h8 and a finish of 1.6. e. Install the end of the shaft (sleeve) of the moving ring seal and the end of the sealing gland (or casing) of the quiet ring seal to be chamfered and smoothed. 2. Installation requirements for mechanical seals for pumps:
d. After the moving ring is installed, it must be ensured that the moving ring can move flexibly on the shaft.
Cooling and flushing of pump mechanical seals
1. The first type of cooling consists of the outlet or high pressure end of the pump, which will transport the clean medium directly to the sealing end face, and then enter the pump cavity. Through the continuous circulation of the medium, the frictional tropical end of the friction end face will reach the cooling effect.
2, the second cooling method
On the basis of the first cooling form, a cooling water jacket is added to the back of the stationary ring, the cooling effect is improved, and the liquid can be collected and collected. When the temperature of the sealing medium is >150 °C, in addition to cooling in the cooling water jacket through the cooling water and the static ring back, forced cooling measures should be taken. That is, the clean medium from the pump outlet should be cooled to 50 °C in advance by a heat exchanger. Then enter the sealed chamber to cool and rinse, this form is the best cooling effect.
3. If the medium contains particles or impurities, filtration measures must be taken to input the normal temperature clean rinse liquid into the sealed chamber.
Technical requirements for mechanical seal installation and use
1. A clean layer of mechanical oil should be applied to the surface in contact with the seal during installation so that it can be installed smoothly;
2. The sealing cavity of the equipment should be kept clean during installation. The sealing parts should be cleaned to keep the sealing end face intact and prevent impurities and dust from being brought into the sealing part;
3. It is strictly forbidden to knock and hit during the installation process, so as to prevent the mechanical seal from being damaged and causing the seal to fail;
4. The dynamic jump of the equipment shaft should be ≤0.04 mm, and the axial yaw force should not be greater than 0.1 mm;
5. When installing the static ring gland, the screw must be evenly stressed to ensure that the end face of the static ring and the axis are perpendicular;
6. After the installation, push the moving ring by hand to make the moving ring move flexibly on the shaft and have certain elasticity;
7. After installation, the rotating shaft and the rotating shaft should be light and heavy.
8. The equipment must be filled with medium before operation to prevent dry friction and seal failure;
9. For easy crystallization and granular media, when the medium temperature is >80 °C, corresponding flushing, filtering and cooling measures should be taken. For various auxiliary devices, please refer to the relevant standards of mechanical seals.