Mechanical Seal Failure Research Articles

Dynamic Models of Mechanical Seals for Turbomachinery Application

One of the primary causes of mechanical face seal failure is rotor vibration. Traditional dynamic seal models often cannot fully explain failure mechanisms. The dynamic models of seals proposed in this paper, including those developed by the authors, are valuable for predicting seal dynamics during operation in specific turbomachinery and for explaining the causes of seal failure. The single-mass dynamic model is suitable for analyzing the dynamics of contact mechanical face seals and simply designed dry gas seals. The two-mass dynamic model is used to investigate the operational dynamics processes of classical dry gas seals under complex loading conditions. The three-mass dynamic model is used to study various complex types of mechanical face seals. This model can determine the normal operating condition range and explain leakage mechanisms in the presence of excessive rotor vibrations.

Analysis of Friction and Wear Properties of Friction Ring Materials for Friction Rings under Mixed Lubrication

Aiming at the problem of mechanical seal failure due to serious wear and tear in operation, the numerical model of the thermal–solid coupling wear of the seal ring is established by taking the friction sub-material as the research object, and the hardness, wear coefficient, and friction coefficient of different soft-ring materials are obtained by a test to verify the accuracy of the numerical model of wear. Additionally, the temperature field and deformation field of the seal ring of different materials are calculated, and the effects of the material parameters, such as elasticity modulus and thermal conductivity, on the temperature, relative deformation, and axial deformation trend are reported. The wear relation of the mechanical seal was optimized, and the correction coefficients of several materials were calculated. The results show the following: the main wear of the seal ring is due to adhesive wear leading to particle shedding and extrusion, adhesive wear causes material transfer, which alters the composition of the worn surface.in turn leading to cratering, which also causes the wear of the seal ring; the friction performance is better when the soft-ring material is graphite (C); the temperature, as well as the deformation, is smaller when the soft-ring material is silicon carbide (SIC); the correction coefficients for the life of SIC are calculated to be 0.23, for C, to be 0.14, and for stainless steel (Ss), to be 0.31, and the corrected equations can more accurately predict the corresponding material. The corrected equation can more accurately predict the service life of the corresponding material.

Analysis of Internal Flow Characteristics of the Bearingless Direct-Drive Centrifugal Pump System during Transient Start-Up

Traditional shaft-sealed centrifugal pumps exhibit problems, such as liquid leakage and reduced efficiency, due to mechanical seal failures. To address the issue, the bearingless direct-drive centrifugal pump system (BDDCPS) has been designed with bearingless motor technology. This may cause a new issue of rotor eccentricity displacement, which can lead to a reduction in pump performance. Compared to a stable state, the changes in characteristics, such as flow rate, head, and pressure, during the transient start-up process are more severe, increasing the likelihood of system failure and requiring greater attention. In order to ensure safety and reliable operation during the transient start-up process, this paper investigates the working principle of the BDDCPS and analyzes transient start-up characteristics with three different start-up methods. The external characteristics, pressure field distribution, velocity field distribution, and hydraulic losses analysis of the pump are determined for comparative analysis. Finally, it is found that the linear acceleration start-up method is the most suitable and efficient for the BDDCPS.

Research on stator current characteristics of centrifugal pumps under different mechanical seal failures

Mechanical seal failure has a great negative impact on the operation of a centrifugal pump system. A method to analyze the stator current characteristics of the motor in a centrifugal pump system is proposed to monitor the internal flow of the centrifugal pump and to identify the failure status of the mechanical seal. Experiments were conducted under different mechanical seal states. Based on sensorless technology, the stator current signal of the motor is collected, processed by windowing function, anti-aliasing filter, singular value decomposition, Hilbert–Huang transform, and the marginal spectrum of correlation quantity is drawn. The results show that according to the external characteristic curve of the centrifugal pump, after the failure of the mechanical seal, the head and efficiency of the centrifugal pump decrease, and the head is greatly affected by the degree of failure, while the degree of mechanical seal failure has little effect on the shaft power of the centrifugal pump; the centrifugal pump has good operation stability under design conditions or near slightly large flow; the stability of centrifugal pump operation decreases with the aggravation of mechanical seal failure; the corresponding maximum amplitude in the marginal spectrum can be used as an index to diagnose the damage degree of the mechanical seal.

Analysis of Vibration Characteristics of Centrifugal Pump Mechanical Seal under Wear and Damage Degree

Mechanical seal is a kind of shaft sealing equipment. Face wear is one of the main causes of mechanical seal failure. Mechanical seal condition is also related to the reduction of energy consumption and carbon emission. Therefore, we need to detect the centrifugal pump seal condition. At present, vibration signal is a common method for fault monitoring and diagnosis of centrifugal pump. In this paper, the vibration signal under the condition of damaged centrifugal pump seal is measured by studying the characteristics of vibration signal after the end face damage of centrifugal pump. Statistical indicators such as RMS and kurtosis were taken to analyze the average energy and shock wave energy of vibration signal. The time‐frequency characteristics of vibration signal are analyzed by frequency spectrum. The results show that there are a large extent variation of vibration amplitude in the direction of base and axis and a weak variation of vibration amplitude in the direction of radial and vertical. With the increasing of flow rate, the RMS of vibration signal falls at first, then keeps steady, and mounts at last when the flow rate is over the design flow rate. It can be shown from the time‐frequency spectrum that there is a shock wave and pause signals caused by the shock wave, which are reflected by the higher frequency band components of the vibration signal that can provide a reference to the diagnosis of the occurrence of damaged mechanical seal. From the analysis, the energy of vibration signal is related to the running condition, we can find that the occurrence of mechanical seal wear makes the centrifugal pump to produce high‐frequency vibration signal, and the axial vibration is the strongest and the instability in the fluid makes the vibration signal produce high amplitude characteristics. Analyzing the vibration signal characteristics of centrifugal pumps with damaged mechanical seal is of great significance to find the mechanical seal failure of the centrifugal pumps and adjust the operating parameters.

Reliability estimation of mechanical seals based on bivariate dependence analysis and considering model uncertainty

The reliability estimation of mechanical seals is of crucial importance due to their wide applications in pumps in various mechanical systems. Failure of mechanical seals might cause leakage, and might lead to system failure and other relevant consequences. In this study, the reliability estimation for mechanical seals based on bivariate dependence analysis and considering model uncertainty is proposed. The friction torque and leakage rate are two degradation performance indicators of mechanical seals that can be described by the Wiener process, Gamma process, and inverse Gaussian process. The dependence between the two indicators can be described by different copula functions. Then the model uncertainty is considered in the reliability estimation using the Bayesian Model Average (BMA) method, while the unknown parameters in the model are estimated by Bayesian Markov Chain Monte Carlo (MCMC) method. A numerical simulation study and fatigue crack study are conducted to demonstrate the effectiveness of the BMA method to capture model uncertainty. A degradation test of mechanical seals is conducted to verify the proposed model. The optimal stochastic process models for two performance indicators and copula function are determined based on the degradation data. The results show the necessity of using the BMA method in degradation modeling.

Technology Update: New Instrumented Docking Gun System Maximizes Perforating Performance

Technology Update Accidental detonation of a perforating gun at surface can have catastrophic consequences. To decrease risks, layers of procedural controls have been implemented to reduce the inadvertent application of power caused by human error, stray voltage, or the presence of radio frequency (RF) energy. Explosives handling procedures and controls, such as locking out the firing panel and acquisition system, are used to mitigate the human error risk. Mitigating RF risks requires establishing RF-free exclusion zones, with all RF transmissions shut down. Exclusion zones are effective, but adhering to them relies on strict procedural controls. With increased industry and personal reliance on RF transmitters, such as cellular phones, RF silence is becoming more difficult to achieve. Although RF-immune initiators were introduced more than 20 years ago to allow wellsite operations to continue without RF silence imposed, their complex initiation technologies require high power levels, which improve the safety margin to stray volt-age but significantly reduce overall system reliability. Perforating has always been a hands-on operation that relies on supervisor experience. Over the last decade, perforating reliability has continued to improve as service companies and operators have implemented detailed training programs, procedural checklists, and advanced hardware. However, these reliability improvements have begun to plateau, acting as an impetus to develop new perforating systems that would be more effective than procedural controls in addressing the main causes of perforating misruns: damaged or improper wiring, mechanical seal failures, and initiator malfunctions. Plug-In Design With Built-In Safety With a focus on resolving these issues, Schlumberger developed the Tempo instrumented docking perforating gun system—the industry’s first perforating system that fully integrates a plug-in gun with real-time advanced downhole measurements for monitoring and confirming operations to mitigate risk while increasing safety, reliability, and efficiency (Fig. 1). Created for all environments, the system uses modularized initiators combined with RF filtering mechanisms and an addressable switch to provide an enhanced level of safety to operations. Proprietary docking components are the key element of the gun system’s plug-in design. They streamline assembly and eliminate the major cause of perforating misfires: technique-sensitive crimping and wiring. The initiator can be plugged into a perforating gun by using simple mechanical and electrical connections without requiring complicated assembly. The new system eliminates all complex field wiring connections and crimping, which simplifies the arming process that has a direct impact on both wellsite efficiency and reliability.

Producing pore pressure profiles based on theoretical models in undrilled, deepwater frontier basins

A working petroleum system was established on the shelf in offshore Labrador with the Bjarni H-81 discovery in 1973 in the Hopedale Basin. The same reservoirs as those targeted on the shelf are present in the deep water, which is currently receiving attention as the result of newly acquired seismic data. To date, only a very small number of wells have been drilled in the deep water, i.e., Blue H-28, Orphan Basin, and none off mainland Labrador. The wells that were drilled in the deep water had encountered significant overpressure, e.g., kicks that indicated overpressures of 26,850 kPa in the Mid-Cretaceous. Therefore, it was reasonable to assume that pore pressures be similarly high for any new deepwater prospects identified. To help reduce the risk in unexplored environments, we developed an approach that can be adopted to model pore pressure in deepwater settings, with Labrador as the main case study area featured, but also we discussed other global examples such as the Vøring Basin, Mid-Norway. Our results indicated, as a first approximation, that seismic velocity-based pore pressures in shale-rich intervals were similar to the geologic model down to the Lower Tertiary. Deep lithologies were, by regional analogue, likely affected by cementation that will act to preserve overpressure generated by disequilibrium compaction by reducing permeability but will not generate additional pore pressure. The cements (and any carbonate or volcanic lithologies) will, however, result in faster shales and will underpredict pore pressure by mimicking low porosity. A theoretical or “geologic modeling” approach can be used to sense-check any pore pressure interpretation from seismic velocity. The geologic approach also can be used to assess the risk for mechanical seal failure by allowing for estimates of the pore pressure, and related fracture pressure, to be made without the effects of cementation that affect the logs and seismic velocity data.

A Review of Mechanical Seals Heat Transfer Augmentation Techniques

A mechanical face seal is one of most widely used components in rotating machinery such as pumps, mixers, blowers, and compressors. The primary function of a mechanical seal is to prevent leakage of the process fluid from the pump housing and shaft to the environment. Excessive heat generated at the face seal interface has been recognized as one of main causes of failure of mechanical seals. In the past few decades various efforts have been attempted to remove heat from the interface uniformly in order to reduce the interfacial temperature, eliminate thermally-induced failure, and thus increase the life of a mechanical seal. In this paper, a class of the pertinent patents on mechanical seals that use heat transfer augmentation techniques are reviewed and discussed. Also presented are several new approaches recently proposed by the authors specifically developed for enhancing heat transfer augmentation in mechanical face seal.

An Analysis of Mechanical Seal Failure of HTM Pump and its Improvement

Regarding the issue of short service life of mechanical seal of HITM pump in polyester production, this paper analyzes its causes, carries out the modeling, theoretical analysis, and discussion concerning the temperature flow field of seal faces, and puts forward the measure for improving the mechanical seal unit.

Failure Mode Analysis of Mechanical Seals

Mechanical seals are important to prevent leakage and entry of foreign particles into the system. Therefore, failure of mechanical seals can be hazardous to the system. Understanding the various failure modes or symptoms will facilitate improvement in design, operation, and reliability of the mechanical seals. Failure modes of mechanical seals are analyzed by using the 'Digraph Modeling and Matrix Approach'. Mechanical seal failure logic diagraph (MSFLD) is prepared for failure modes of mechanical seals and is described by contributing cause events (direct and indirect) and their inter-relations. The connection and reachability matrix is used to analyze the digraph model. The mechanical seal failure connection matrix (MSFCM) is obtained from the MSFLD, and the MSFRM is derived from it, which helps in identifying the stage relationship among various cause events and their importance. This helps in taking appropriate steps to minimize the failure and improve the reliability of the mechanical seals.

The performance of mechanical seals used in a high vibration environment

Cooling pumps found in high-power diesel engines experience high levels of vibration. Combined with long operating periods this can lead to the failure of mechanical seals used in these pumps. This feature article discusses a test facility, which was set up to investigate the problem, and the test results obtained from a wide range of mechanical seal designs. The performance-to-price ratio of the seals was then established to help users choose the best and most economical seal for their specific application.

Failure of mechanical seals in centrifugal pumps — part two

The previous article in this troubleshooting series on seals from Stan Shiels dealt with the pump's design, the piping system and vessels, and the fluid characteristics. This time an approach to two of the remaining areas will be addressed: the pump's operating envelope and process transients, and the pump's start-up procedure.

Failure of mechanical seals in centrifugal pumps

This fourth paper in the troubleshooting series deals with mechanical seals. Often a seal failure is diagnosed through visual inspection of the failed seal's components; this may yield the condition that existed in the seal cavity prior to, or at the time of, failure. The events that led to this condition are usually linked to the real cause of failure, which often requires us to move beyond the vicinity of the seal itself in our search for cause of failure. The extensive nature of this topic does not allow full coverage of all aspects of diagnosis, but this first of three discussions by Stan Shiels will deal with the prime areas associated with seal failure. His next article will address some specific in more detail.

Contact elimination in mechanical face seals using active control

Wear and failure of mechanical seals may be critical in certain applications and should be avoided. Large relative misalignment between the seal faces is the most likely cause for intermittent contact and the increased friction that eventually brings failure. Adjustment of the seal clearance is probably the most readily implemented method of reducing the relative misalignment and eliminating seal face contact during operation. This method is demonstrated with the aid. of a noncontacting flexibly mounted rotor mechanical face seal test rig employing a cascade control scheme. Eddy current proximity probes measure the seal clearance directly. The inner loop controls the clearance, maintaining a desired gap by adjusting the air pressure in the rotor chamber of the seal. When contact is detected the outer loop adjusts the clearance set point according to variance differences in the probes signals. These differences in variance were found to be a reliable quantitative indication for such contacts. They are complimentary to other more qualitative phenomenological indications, and provide the controlled variable data for the outer loop. Experiments are conducted to test and verify this active control scheme and strategy. The analysis and results both show that contrary to intuition for the seal under investigation, reducing seal clearance can eliminate contact, and the outer cascade loop indeed drives the control toward this solution.

A New Method in Acoustic Health Monitoring in Mechanical Seals©

Mechanical seals are a vital component of rotating equipment in the process and power generation industries. Due to the mechanical seal's wide range of application, mechanical seal failures constitute a large proportion of the overall mechanical failures resulting in unscheduled machinery shutdown and even catastrophic consequences. This paper outlines the development of an acoustic measurement procedure in detecting damage in face seals in a centrifugal pump. The acoustic measurements described allowed the elimination of extraneous background noise from nearbly operating machinery and other mechanical components without losing the main acoustic characteristics of the damaged seal. The background noise elimination significantly improved the accuracy of the analysis for the detection and identification of wear/damage in mechanical seals. The results are demonstrated on a set of damaged seals in a ANSI centrifugal pump in a laboratory environment. Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

Mechanical seal failures in process plant

Mechanical seal failures in process plant

An Investigation of the Operation and Failure of Mechanical Face Seals

Research Papers An Investigation of the Operation and Failure of Mechanical Face Seals F. K. Orcutt F. K. Orcutt Mechanical Technology Incorporated, Latham, New York Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information F. K. Orcutt Mechanical Technology Incorporated, Latham, New York J. of Lubrication Tech. Oct 1969, 91(4): 713-725 (13 pages) https://doi.org/10.1115/1.3555029 Published Online: October 1, 1969 Article history Online: August 23, 2011