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Application of non-metallic bearings in vertical pumps
Source: China Bearing Network Time: 2013-04-22
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Non-metallic bearings have been successfully used in vertical pumps. The consideration of non-metallic bearing lengths is generally 1~1. 5; from the perspective of shaft column dynamics; in the pump shaft of general scale scale; The stiffness value of non-metallic bearings is appropriate with metal bearings.
The load of the vertical pump bearing is difficult to dissect; it is properly light under normal conditions; therefore, the stability of the bearing can be an important problem. However, the speed of the pump is generally not high; it will not be severe and significant. Stable appearance; and bearing instability will shorten its service life.
The grooves in the bearing can cause centripetal force; during the assembly of the bearing; the accumulation of public service can incur small lateral loads. In this case; the smaller device offset is more suitable; higher operational stability can be obtained.
Bearing clearances must be large (but not too large); ensure bearing self-conversion; then offset the important shaft support structure of the bearing supply. Generally speaking, the working clearance is 0. 0115 mm / mm (relative shaft diameter); the smallest gap 0. 08 mm. Regarding non-metallic bearings; it is also necessary to consider liquid absorption and thermal expansion. These margins need to be considered; and can be reduced to a minimum by reducing the wall thickness. In any case; pump operation The variable mechanics depend on the correct working gap established between the shaft and the bearing.
Standard pump kit information such as 400 or 300 series stainless steel and non-metal materials can work well together. For salt or salt water; 300 stainless steel and duplex stainless steel have better corrosion resistance. If pumped The liquid contains a lot of abrasive particles; the hard pump sleeve can extend the service life of the bearing.
In general; the bearings should be grooved; these grooves ensure that the fluid is passed through the bearing; then the abrasive particles pass smoothly. Some smaller bearings (shaft diameters less than 50 mm) that work in sanitary fluids can be used without grooves Good work under the conditions. In either case, it is advocated that hygienic water can flow through the bearing; it is guaranteed to be smooth and cool.
Don't forget that the pump bearing space is the responsibility of a pump painter; but if the bearing information is different; this will also be a problem that pump repairers often have to think about. The best way is to set a shaft/bearing system stiffness; The first-order tortuosity critical speed is 10%~20% more undulating than the working speed (depicted by the rigid axis); however, the smaller shaft uses more flexible bearings; for example, bearings made of rubber; generally first-order and second-order tortuosity critical The working speed between the rotational speeds is based on the depiction (flexible axis depiction).
The critical limit of the shaft is necessary to be determined by the stiffness values ​​of the bearing and the support system. The stiffness of many non-metallic bearings is related to the typical tortuous stiffness of the shaft is high; therefore, when setting space requirements; can be the same as metal bearings The use of lower strength rubber data can require tighter bearing space or conversion to a flexible shaft depiction.
Most of the installed vertical pumps in the world do not require any horizontal layout support under the pump plane. This indicates that the pump casing supporting the bearing (which also supports the shaft assembly) is itself flexible; Resonance within the energy. If this problem is not carefully investigated in the process of depicting the machine; the bearing can fail; this rare form of wear can be mixed with the failure form.
Many vertical pump units are in the puddle; the flow rate of the water or the gap between the pump adjacent to the bottom, the reverse side, and the side surface is not properly considered; these rules are supplied in the operating manual and supporting literature; neglecting these The rules can cause cavitation and/or separation; then incur excessive oscillations in the operation and can cause bearing damage. Others; assuming that the depth of the minimum sinking proposed by the pump manufacturer is violated; the vortex can occur; the inlet fluid is trapped Air; and cause mechanical oscillations.
Many pumps operate on a functional curve; instead of thinking about the optimum power point correctly, excessive pumping can also cause overheating and bearing damage if the pump is highly economical or operates outside the highest power point.
The general practice is to dynamically balance the impeller of the vertical pump; to ensure smooth operation without oscillation. However, if the impeller moves during the casting process, it will not only cause mechanical imbalance; it will also cause hydraulic imbalance. The latter; dynamic balance can not improve this situation anyway; it will lead to excessive oscillation; shorten the service life of the bearing.
The use of non-metallic bearings for non-metallic bearings has many advantages; including impact civil service, low conflict, self-smoothing characteristics and marginal load. Most non-metallic bearings, including Thordon, have significant electrical resistance; thus; stray current is not a bearing An element of corrosion; the contact point does not call for corrosion.
Only need different pump and system rendering challenges through careful study and thinking; non-metallic bearings will ensure that the pump has many years of excellent service life. Totally; whether in the original pump depiction process or repair period; should be invested in equipment Think about the pump's depiction puzzle before use.
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