Relationship Between Vibrations and Mechanical Seal Failures in Centrifugal Pumps

2005 ◽  
Author(s):  
David B. Stefanko ◽  
Robert A. Leishear
Keyword(s):  
Industrial Applications ◽  
The Other ◽  
Fluid Film ◽  
Operating Speed ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Centrifugal Pumps ◽  
Radial Vibrations ◽  
The Common ◽  
Bearing Design

A reduction of radial vibrations in mechanical seals increases the life of the seals in centrifugal pumps. Mechanical seals consist of two smooth seal faces. One face is stationary with respect to the pump. The other rotates. Between the faces a fluid film evaporates as the fluid moves radially. Ideally, the film evaporates as it reaches the outer surface of the seal faces, thereby preventing leakage from the pump and effectively lubricating the two surfaces. Relative vibrations between the two surfaces affect the fluid film, damage the faces, and decrease the life of the seals. In a series of industrial applications, different techniques were used to minimize vibration, and the life of the seals was shown to significantly increase. The operating speed was controlled in one case, the bearing design was replaced in another case, and the stiffness of the pump was altered in still another case. The common corrective action in each case was a reduction in vibration.

scholarly journals Relationship Between Vibrations and Mechanical Seal Life in Centrifugal Pumps

2007 ◽  
Author(s):  
Robert A. Leishear ◽  
David B. Stefanko
Keyword(s):  
Crack Growth ◽  
Fatigue Damage ◽  
The Other ◽  
Fluid Film ◽  
Time To Failure ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Centrifugal Pumps ◽  
Vibration Data ◽  
Cyclic Stresses

A reduction of vibrations in mechanical seals increases the life of the seals in centrifugal pumps by minimizing fatigue damage. Mechanical seals consist of two smooth seal faces. One face is stationary with respect to the pump. The other rotates. Between the faces a fluid film evaporates as the fluid moves radially outward across the seal face. Ideally, the film evaporates as it reaches the outer surface of the seal faces, thereby preventing leakage from the pump and effectively lubricating the two surfaces. Relative vibrations between the two surfaces affect the fluid film and lead to stresses on the seal faces, which lead to fatigue damage. As the fluid film breaks down, impacts between the two seal faces create tensile stresses on the faces, which cycle at the speed of the motor rotation. These cyclic stresses provide the mechanism leading to fatigue crack growth. The magnitude of the stress is directly related to the rate of crack growth and time to failure of a seal. Related to the stress magnitude, vibration data is related to the life of mechanical seals in pumps.

Analysis of Carrying Capacity and Friction Torque of Friction Pair Fluid-Film for High Parameter Bellows Mechanical Seal

2013 ◽  
Vol 455 ◽  
pp. 207-211
Author(s):  
Mutellip Ahmat ◽  
Zhi Wei Niu ◽  
Guzaiayi Abudoumijiti
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Influence Factor ◽  
Friction Pair ◽  
Scientific Basis ◽  
Friction Torque ◽  
Fluid Film ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
The Relationship

The friction pair for bellows mechanical seal as a friction element is one of the key components for it. In this research, by based on the computational fluid dynamics (CFD) numerical theory, using the Fluent software, corresponding model and parameters, the fluid-film between the clearance of the sealing ring friction pair for the bellows mechanical seal under such the high-temperature, high-pressure, high-speed as complex working conditions is numerically simulated, the relationship between the carrying-capacity of the fluid-film and the temperature, the viscosity of the fluid-film, the relationship between friction torque of the fluid-film and the speed, viscosity of the fluid-film, the influence factor of leakage are obtained. The researching results provide the scientific basis for the optimization designing of the high parameter bellows mechanical seals.

Optimum Design of Flat End Face Mechanical Seal Based on Coupling Analysis

2010 ◽  
Vol 37-38 ◽  
pp. 819-822 ◽  
Author(s):  
Jian Feng Zhou ◽  
Bo Qin Gu ◽  
Chun Lei Shao
Keyword(s):  
Optimum Design ◽  
Thermal Deformation ◽  
Coupling Effect ◽  
Design Method ◽  
Fluid Film ◽  
Outer Side ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Friction Heat ◽  
Bearing Force

The flat end face mechanical seals are widely used in shaft sealing at moderate rotational speed. The thermal deformation of the rotating and stationary rings initiated by friction heat of fluid film should be primarily considered in the design of mechanical seal. In consideration of the coupling effect among the thermal deformation of sealing rings, the fluid flow in the gap composed by end faces of sealing rings and the heat transfer from fluid film to sealing rings, the optimum design method for flat end face mechanical seal is established. The end faces are fabricated to form a divergent gap at the inner side of the sealing rings, and a convergent gap will occur at the outer side and a parallel gap will be obtained at where the original divergent gap is due to the thermal deformation. After optimization, the leakage rate can be reduced while the bearing force of fluid film is still large enough to keep the fluid lubrication of the end faces.

The Demonstrated Function of PLR Pump Mechanical Seal Under SBO Conditions

2017 ◽  
Author(s):  
Toshiyuki Yoshioka ◽  
Takashi Motani ◽  
Atsushi Fujimaru ◽  
Koji Yamada ◽  
Kunihiro Hasegawa ◽  
...  
Keyword(s):  
Nuclear Power ◽  
The Other ◽  
Leak Rate ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Reactor Coolant ◽  
Seal Failure ◽  
Coolant Injection ◽  
Regulatory Standards ◽  
Fukushima Daiichi

Generic Safety Issue 23 (GSI-23) by the U.S. Nuclear Regulatory Commission (NRC) was identified in 1980 as a result of staff concerns about reactor coolant pump (RCP) seal failure during Station Blackout (SBO), that is, seal degradation leading to a significant loss of reactor coolant in pressurized-water reactor (PWR) plants. Resolutions of GSI-23 have been considered at PWR plants. In 2000, NRC decided to close GSI-23 and issue Regulatory Issue Summary00–002 (RIS 00–002)[1], based on considerations such as; for example, the improvement of RCP seal performance[2], and the reduction of the risk of RCP seal failure in certain plants by the addition of alternate power sources. After the closure of GSI-23, some licensees were planning to make other associated improvements under their individual plant program. In Japan, the RCP seal was showed that leakage rate was low under SBO testing conditions[3] in licensing safety reviews conducted according to new nuclear regulatory standards after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant. On the other hand, a boiling-water reactor (BWR) is not included in GSI-23 because operating experience indicates that seal failures in BWRs result in smaller leak rates than seal failures in PWRs and, BWRs have the reactor coolant injection capability under SBO conditions, such as the reactor core isolation cooling (RCIC) and the high-pressure coolant injection (HPCI) system. In addition, for the particular BWR-2 type plants that do not have emergency makeup systems, the pump mechanical seal was tested under SBO conditions and successfully showed minimal leakage[4]. However, for the BWR-5 type plants which have the reactor coolant injection capability, such as the RCIC and HPCI systems, the pump seal had not been tested. In Japan, after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant, licensing safety reviews of BWRs and PWRs are being conducted according to new nuclear regulatory standards. We took this opportunity to test the leak rate from Primary Loop Recirculation (PLR) pump mechanical seals under SBO condition. The peak of leak rate was approximately 0.6ton/h (2.6gpm) during the 24 hours of SBO testing condition. Despite damage of O-rings in the mechanical seal by heated water which were ovserbed at post-inspection test, a very low leak rate was realized because the leakage path after passing through the damaged parts of the O-rings was limited by the other restricting pathway in the mechanical seal. This seal leakage was very low, compared with the reactor coolant makeup capability of the RCIC system and the reactor coolant release capability from main steam safety relief valve (SRV). Therefore, we reconfirmed that the result of this leak rate does not affect the safety evaluation for the reactor. It is shown in this paper that the leak rate from PLR pump mechanical seals is low under SBO condition by our demonstration test.

scholarly journals Research on the Dynamic Characteristics of Mechanical Seal under Different Extrusion Fault Degrees

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1057
Author(s):  
Yin Luo ◽  
Yakun Fan ◽  
Yuejiang Han ◽  
Weqi Zhang ◽  
Emmanuel Acheaw
Keyword(s):  
Film Thickness ◽  
Dynamic Characteristics ◽  
Fluid Film ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Rotating Speed ◽  
Analysis Process ◽  
Fluid Film Thickness ◽  
Object Of Study ◽  
Fault Mechanism

In order to explore the dynamic characteristics of the mechanical seal under different fault degrees, this paper selected the upstream pumping mechanical seal as the object of study. The research established the rotating ring-fluid film-stationary ring 3D model, which was built to analyze the fault mechanism. To study extrusion fault mechanism and characteristics, different dynamic parameters were used in the analysis process. Theoretical analysis, numerical simulation, and comparison were conducted to study the relationship between the fault degree and dynamic characteristics. It is the first time to research the dynamic characteristics of mechanical seals in the specific extrusion fault. This paper proved feasibility and effectiveness of the new analysis method. The fluid film thickness and dynamic characteristics could reflect the degree of the extrusion fault. Results show that the fluid film pressure fluctuation tends to be more intensive under the serious extrusion fault condition. The extrusion fault is more likely to occur when the fluid film thickness is too large or too small. Results illustrate the opening force is affected with the fluid film lubrication status and seal extrusion fault degrees. The fluid film stiffness would not always increase with the rotating speed growth. The seal fault would occur with the increasing of rotating speeds, and the leakage growth fluctuations could reflect the fault degree.

Predictions for Non-Contacting Mechanical Face Seal Vibration With External Excitation From Pump Vibration: Part II — Flexibly Mounted Rotor

2018 ◽  
Author(s):  
Clay S. Norrbin ◽  
Dara W. Childs
Keyword(s):  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Fluid Film ◽  
Axial Distance ◽  
Mechanical Seal ◽  
Seal Ring ◽  
Mechanical Seals ◽  
Running Speed ◽  
Frequency Dependent ◽  
Frequency Independent

Stability and response predictions are presented for a Flexibly Mounted Rotor (FMR) mechanical seal ring using the model developed by Childs in 2018. The seal ring is excited by lateral/pitch vibration from the rotor/housing. The model includes a frequency dependent stiffness and damping model for the O-ring and a frequency independent model for the fluid film. The dynamic coefficients are speed and frequency dependent. The mechanical seal is modeled after a typical FMR mechanical seal. Parameters for radius, fluid film clearance, and O-Ring axial distances are varied. The axial distance between the O-Ring and seal ring inertia center doz is found to couple lateral rotor motion and seal ring pitch vibration. The predictions show a dependency on both excitation frequency and running speed. The analyzed FMR has a critical region with high transmissibility in a region around a speed and excitation frequency of 70 kRPM. Another region of high transmissibility is predicted to be with sub-harmonic excitation frequency. The FMR seal ring also has an unstable region that is sub-harmonic of 1% running speed. Running back on the HQ curve for a pump causes broadband sub-harmonic excitaiton, which can cause rub failures for FMR mechanical seals.

Coupling Analysis of Fluid Film and Thermal Deformation of Sealing Members in Spiral Groove Mechanical Seal

2007 ◽  
Vol 353-358 ◽  
pp. 2455-2458
Author(s):  
Jian Feng Zhou ◽  
Bo Qin Gu
Keyword(s):  
Thermal Deformation ◽  
Critical Speed ◽  
Fluid Film ◽  
Hydrodynamic Effect ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Spiral Groove ◽  
Coupling Analysis ◽  
Rotating Speed ◽  
Bearing Force

The thermo-hydrodynamic effect in the spiral groove mechanical seal was investigated. The coupling analysis of the fluid film and the thermal deformation of sealing rings was carried out, the separation angle obtained, and the shape of the gap between the two deformed end faces determined. The results indicate that the increase of the temperature of the fluid film and the thermal deformation of the sealing rings cause the increase of the leakage rate. There exists a critical rotating speed, when the rotating speed is lower than the critical speed, the bearing force increases with the increase of the rotating speed, and once the rotating speed is higher than the critical speed, the bearing force decreases reversely. The thermal deformation weakens the hydrodynamic effect of the spiral groove mechanical seals.

Fuzzy Comprehensive Evaluation Method for Mechanical Seal Risk Assessment of Centrifugal Pumps

2011 ◽  
Vol 474-476 ◽  
pp. 1283-1287
Author(s):  
Ying Jie Hao ◽  
Bo Qin Gu
Keyword(s):  
Evaluation Method ◽  
Comprehensive Evaluation ◽  
Fuzzy Comprehensive Evaluation ◽  
Risk Level ◽  
Stable Operation ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Centrifugal Pumps ◽  
Fuzzy Comprehensive Evaluation Method ◽  
Comprehensive Evaluation Method

A failure analysis of mechanical seals of centrifugal pumps was presented with fuzzy comprehensive evaluation method. Both failure probability and failure consequence were analyzed to evaluate the risk grade of the mechanical seals. The potential risk level of a mechanical seal was estimated by the application of risk matrix. The proposed fuzzy comprehensive evaluation method can be used to judge the reliability of mechanical seals and provide an important reference for the safe and stable operation of centrifugal pumps.

Analysis of the Pressure and Carrying Capacity of the Friction Pair Fluid-Film for the High Parameter Bellows Mechanical Seal

2012 ◽  
Vol 522 ◽  
pp. 441-446
Author(s):  
Qiang Gao ◽  
Mutellip Ahmat ◽  
Li Chao Ren ◽  
Jing Luo
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Friction Pair ◽  
Scientific Basis ◽  
Fluid Film ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Numerical Theory ◽  
Sealing Ring ◽  
Relationship Of

In this research, by based on the computational fluid dynamics (CFD) numerical theory, using the Standard-Turbulence model and the Standard-Wall function, the fluid-film between the clearance of the sealing ring friction pair for the bellows mechanical seal under such the high-temperature, high-pressure, high-speed as complex working conditions was numerically simulated, the pressure fluid and the relationship of the carrying-capacity of the fluid-film between the pressure inlet of seal cavity and the width of the fluid-film, and the results of the numerical analysis was compared with the theoretical value. The researching results provide the scientific basis for the optimization designing of the high parameter bellows mechanical seals.

A Hydrodynamic Theory of Radial-Face Mechanical Seals

1973 ◽  
Vol 15 (1) ◽  
pp. 17-24 ◽  
Author(s):  
B. Stanghan-Batch ◽  
E. H. Iny
Keyword(s):  
Experimental Evidence ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
Fluid Pressure ◽  
Fluid Film ◽  
Hydrodynamic Theory ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Substantial Agreement ◽  
Seal Design

The existence of a lubricating fluid film between the faces of a mechanical seal has been amply demonstrated, but the mechanisms of lubrication and sealing have yet to be convincingly established. Experimental evidence to show that mechanical seal faces are most probably lubricated by a hydrodynamic action induced by the waviness of one of the surfaces has recently been published by the authors. Following this work a modified form of the narrow bearing approximation to Reynolds' equation for hydrodynamic lubrication has been applied to an idealized wavy faced seal. The resulting theory of seal face lubrication has been extended to include radial flows in the fluid film and predicts a net inward flow of fluid which may be utilized to oppose the flow due to the sealed fluid pressure. Predicted lubrication and sealing characteristics are in substantial agreement with measured values. It is suggested that the performance of mechanical seals can be improved by giving one face an appropriately wavy surface at the time of manufacture; a number of other observations on mechanical seal design are also made.

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