Shaft Seal Research Articles

Excessive shaft wear due to radial shaft seals in lubricated environment. Part I: Analysis and mechanisms

Within the last years, the amount of fluorelastomer (FKM) seals are increasing dramatically in industrial applications such as gearboxes due to its outstanding characteristics and superior performance. In terms of thermal stability resistance and compatibility towards lubricants FKM has wider application ranges compared to other sealing elastomers. However combined with low-viscosity, synthetic lubricants i.e. polyalphaolefin (PAO) or polyalkylene glycols (PG) macroscopic wear grooves were reported on hardened shafts. This can, but does not necessarily lead to leakage and the breakdown of a sealing system, which may cause serious damage to the environment and the machine, where the functionality of the seal is often crucial for the whole system. So far a clear explanation does not exist, just a few theories or assumptions, for this behavior can be found in the literature.Driven by that fact this article presents a detailed wear analysis of a critical combination for shaft wear in a system of fluorelastomer seal, polyalphaolefin lubricant and case hardened and twist-free ground shafts of AISI 5115 (1.7131,16MnCr5). The wear behavior of state-of-the-art radial shaft seals out of fluorelastomer seals was investigated. This wear phenomenon was reproduced using endurance tests on a multi-shaft test rig. Typical characteristic parameters and values of the sealing system performance were analyzed and correlated to shaft wear. For further understanding of this system, selected samples were analyzed with different recent methods of surface and thin film analysis.The results indicate that there is a clear relation between seal and shaft wear. The occurrence of shaft wear is also caused and influenced by a complex combination of lubricant-elastomer interaction. Based on this findings, a wear hypothesis is derived.

Reliability investigation of steam turbine critical components

Several aspects of maintaining and operating steam turbines at the palm oil mill areas have historically resulted in unreliable performance and repetitive failures. The reliability analysis using Weibull probability distribution for various components of steam turbine is discussed extensively. The objective of this reliability assessment is to identify the potential failure path of steam turbine components. The intent herein is to focus on critical components of steam turbine to successfully improve the integrity and reliability of turbines in those components. Areas discussed will be bearing failures, Shaft Seal failures, Control/stop Valve, Main Oil Pump, and Reducing Gear. It is necessary to improve the reliability indices of the steam turbine components by taking some measures such as well-planned and routine maintenance of equipment’s as well as training and retraining of technical human resources of the major equipment like steam turbine.

ATMOSFERİK PLAZMA İŞLEMİ KULLANILARAK FARKLI KAUÇUK VE NONWOVEN MALZEMELERİN YAPIŞMA DAVRANIŞININ İYİLEŞTİRİLMESİ

When bonding two different materials, if one of the materials has low surface energy, adhesion problems are observed. It may be necessary to increase the surface energy in order to obtain the desired strength when bonding the rubber material with a different material. In this research, within the scope of efforts to increase energy on the surface of the material using atmospheric plasma treatment, the quality and quantity changes of the adhesion formed between the surface of different rubber materials (NBR / HNBR / ACM / FKM) and nonwoven surfaces were examined. Adhesive bond rotary shaft seals should be protected without deteriorating bond structure even under ambient conditions. According to the results of this study, atmospheric plasma application provides significant improvements in rubber material-nonwoven material bonding processes.

Development of a Low-Friction Radial Shaft Seal: Using CFD Simulations to Optimise the Microstructured Sealing Lip

The sealing of shaft interfaces in machine housings against oil leakage is commonly realized by radial shaft seals, hence they are used millions of times in technical systems. However, with increasing speed they cause significant friction losses, which reduce the efficiency of the system significantly. In addition, the prevailing trend towards higher speed levels in electrified drive trains is already pushing sealing technology to its performance limits. Therefore, friction reduction offers a chance to extend the current performance limits and increase efficiency within existing applications. In this paper, a methodology for friction reduction is proposed, which is based on microstructuring and surface treatment of the seal sliding surface. Since experimental structural design is linked to high costs and time, a simulation-based method is proposed. Computational Fluid Dynamics (CFD) simulations are performed to analyze the influence of the structural geometry on local fluid flow. It is shown that for increasing sliding speeds, the analysis and the subsequent optimization of deterministic microstructures require the numerical solution of the complete Navier–Stokes equation in order to take inertial effects into account. Based on these results, an optimal geometric shape for the microstructure is found depending on the operating conditions.

Experimental study of radial lip seals with different sleeve coatings

Lip seals are vital components. Found on a range of machines, they are used to keep oil or grease within a system and help to prevent the ingress of contaminants. This article describes research that looks at the performance of various seal–shaft combinations by testing four different sleeve coatings – tungsten carbide, chrome oxide, hard chrome and stainless steel – in conjunction with radial lip seals pressured by preloaded garter springs. To find optimum sleeve coating and seal combinations, leakage and performance are investigated using an experimental test-bench.

Research on Variable Operating Characteristics of Condenser Considering Vacuum Tightness

Considering the effect of vacuum tightness on the performance of condensers, the influence of various operating parameters on condenser pressure and terminal difference was studied by establishing a calculation model of variable operating conditions of condensers. The results show that the change of heat load has a greater impact on the vacuum, and the effect is more pronounced when the initial temperature of the cooling water is higher. Therefore, it is necessary to strictly control the internal leakage of the valve, reasonably adjust the steam parameters of the shaft seal, and minimize the additional heat load on the condenser. The cooling water flow and initial temperature directly affect the condenser vacuum and have a greater impact. The initial temperature of the cooling water is not easy to control. When the initial temperature is high, most power plants use a method of increasing the flow to increase the condenser vacuum. The cleaning coefficient and air leakage have a great impact on the quality of the vacuum. Therefore, regular operation of the rubber ball cleaning system and timely vacuum leak detection are necessary measures to ensure the vacuum of the unit, which can effectively improve the economic efficiency of the unit.

ANALYSIS OF REPLACEMENT PART TIME INTERVAL DETERMINATION OF CRITICAL IN ENGINE WATER COOLANT PUMP TYPES KRI FPB57

Maintenance management is required and has a very vital role for a KRI types FPB57, considering the type KRI is one Alutsista Navy who have a high frequency activity, as well as the broad range of operations support capabilities are varied so that the automatic machine is also high activity and in the end reliability will decrease. Methodology Failure Mode Effects and Criticality Analysis (FMECA) is a widely recognized tool for the study and analysis of the reliability of the design or process. Many authors in the field have emphasized specifically the usefulness of this method and its limitations. At this writing considering the lifetime of the machine and the elements therein specifically the components of the water coolant pump has had a lifetime of more than 20 years, because it can be said that the components have entered a critical period. Based on the steps Failure Mode Effects and Criticality Analysis (FMECA) through the calculation of Risk Priority Number (RPN), so we can determine the critical components of acquired 9 of 19 chances damage that has critical component is Angular Bearings, Cylindrical Bearings, Spacer Ring, Water Seal, shaft Seal, Seal Slip Ring, Impeller, O'Ring and shaft. These components if damaged can lead to engine breakdown. From the optimization results indicate that the component replacement Cylindrical Bearings have the fastest time, ie 98 days. While the replacement of components with the longest time, which is a component Impeller 134 days. Besides obtain the most optimal replacement time of each component, also produced the cost of replacement is effective, it is proved by the value of the optimal CBR. CBR value for all types of components is less than 1 (CBR <1).Keywords : FMECA, Risk Priority Number, Reliability, Replacement Intervals,CBR.

Thermoelastohydrodynamic Lubrication Simulation of Radial Shaft Sealing Rings

Abstract Regarding the increasing demand in seal lifetime and energy efficiency, a detailed microscopic simulation is necessary—as an addition to experimental investigations—to better understand and improve radial shaft seals. For this purpose, typically thermoelastohydrodynamic lubrication (TEHL) simulations are used. The published models range from rather simple elastohydrodynamic lubrication (EHL) models to very sophisticated TEHL models. Only very few models take into account the roughness or microstructure of both contact surfaces, though, since this would require the consideration of transient effects. In this article, a transient TEHL model for the contact of radial shaft seals is presented. Studies of the sealing contact are conducted, and the possibility of investigating shaft microstructuring is shown.

On the Estimation of the Dynamic Leak-Tightness of Shaft Seals with Hydrodynamic Sealing Aids through a Hydrodynamic Parameter

On the Estimation of the Dynamic Leak-Tightness of Shaft Seals with Hydrodynamic Sealing Aids through a Hydrodynamic Parameter

Coupled hydromechanical (H-M) performance of in situ shaft sealing components for nuclear waste disposal

Decommissioning and closure of Canada’s Underground Research Laboratory (URL) involved installing a full-scale 5 m diameter by 12 m long seal in the main access shaft. The seal consisted of clay and concrete components spanning a major water-bearing fracture zone (FZ2) located at a depth of around 275 m that isolates two hydrogeochemical regimes. This paper presents results of coupled hydromechanical (H-M) numerical modelling that simulated measured performance of the seal. Parameters for the H-M modeling were determined from previously measured laboratory test data. Results from the modelling were compared with field data for water uptake and total pressures in the system. They show that hydration of the clay seal was dominated by the groundwater flow from FZ2. The simulations showed good agreement with field readings and provide an improved understanding of various interrelated physical processes that take place during hydration.

Optimization of shaft-seal water system of cutter suction dredger based on high-efficiency centrifugal separation technology

The shaft-seal water system (SSWS), as one of the critical systems for slurry pump protection, is widely used to provide shaft-seal water in cutter suction dredger. In general, the shaft-seal water obtained from gravity clarifier always accompanies with numerous sand with large size (>10 μm), resulting in the inevitable intense wear of components in the slurry pump, especially, the shaft sleeve and L-shaped rubber ring in back shaft seal. Even worse, the high temperature caused by unstable shaft rotation in the present of sand will aggravate the degree of this wear. To address the above thorny problems, in this study, water-sealed hydrocyclone (WSH) was unprecedentedly applied to optimize SSWS for high-efficiency sand centrifugal separation. The dimension and structure of WSH were designed and optimized before final industrial application. High-efficiency separation zone (the separation efficiency >90%) with Re ranged of 1.88 × 104–2.23 × 104 was also confirmed by introducing the optimal structure of the WSH (5° of cone angle and 10 mm of bottom apex diameter). For the improved SSWS in the actual application, the Dv(50) of the shaft-seal water decreased from 38.0 μm to 9.1 μm, and the corresponding solid concentration declined from 0.51 g/L to 0.051 g/L. Furthermore, it was verified that the optimized SSWS could significantly reduce the wear of the shaft sleeve and L-shaped rubber ring, and extend the service life of L-shaped rubber ring, up to 4 months. This finding provided a new insight for the optimization of the SSWS for slurry pump, which could improve the operational stability and reliability of cutter suction dredger in the construction of marine infrastructure.

Analysis and Treatment of Abnormal Pressure of Shaft Seal of Small Steam Turbine

In the commissioning of power plant, this paper finds that the shaft seal pressure of small steam turbine does not match the shaft seal pressure of steam turbine, and the shaft seal pressure of small steam turbine is high. On the basis of on-site verification and theoretical calculation, the problem of abnormal shaft seal pressure of small steam turbines was solved by modifying the steam turbine shaft sealing point access point and increasing the small turbine shaft seal overflow device, which provided a solution for similar problems in the future.

Effect of roughness on sealing performance of oil seals with surface texture

PurposeThis paper aims to obtain the film thickness, friction torque and pumping rate and analyze the effects of roughness and surface micro-dimple texture (circular, square and equilateral triangle) on the performance of the oil seal.Design/methodology/approachOn the basis of elastohydrodynamic lubrication and the pumping mechanism of rotating shaft seal, this paper establishes a numerical model of hybrid lubrication of oil seal in sealing area. The model is coupled with fluid mechanics, rough peak contact mechanics and deformation analysis.FindingsThe results show that surface texture significantly improves the lubrication properties of the oil seal. The oil seal with the square texture has the largest oil film thickness, while the equilateral triangle texture has a better effect on the pumping rate.Originality/valueTo get closer to the real working environment of the oil seal, based on the surface roughness, this paper studies the effect of the texture shapes applied to the oil seal lip surface on the performance of the oil seal. The critical roughness and rotational speed values with zero pumping rate are obtained, which provides a theoretical basis for the correct selection of oil seals.

Analysis and Treatment of Shutdown Due to Bearing Vibration Towards Ultra-supercritical 660MW Turbine

During the normal operation of an ultra-supercritical 660MW steam turbine in a power plant, the temperature of low-pressure shaft seal steam inlet gradually increases, and the vibration of steam turbine bearing suddenly increases, leading to the steam turbine shutdown. The diagnosis and troubleshooting of major vibration faults of steam turbine bearing are carried out, and the causes of faults are accurately analysed through collecting field data, checking maintenance records and disassembling inspection of relevant equipment. Taking corresponding effective measures to eliminate the potential equipment safety hazard.

Engineering Development and Application of Hydrodynamic Mechanical Seal of Reactor Coolant Pump

The shaft seal of reactor coolant pump (RCP) consists of three same hydrodynamic mechanical seals in series. It is the heart of RCP and its leakage directly determines the normal operation of the RCP. This paper introduces a new extruding deformation lapping method to manufacture the hydrodynamic mechanical seal. The stationary ring is deformed by using the extruding deformation tool and metallic gasket, and nine waveform grooves are produced on the seal end face. The function test showed that the low-pressure (LP) leakage meets the design requirement of the shaft seal under the examination pressure. Meanwhile the impact examination under the saltation pressure showed that the liquid film between new hydrodynamic mechanical seal friction pair was intact, and no failure occurred on the seal. The operation of this hydrodynamic mechanical seal in the nuclear power plant shows that the operation performance agrees well with the function test results, and proves that this new hydrodynamic mechanical seal is with a high reliability in engineering application.

ANALISIS TERJADINYA SLIP PADA KOPLING DI UNIT SCANIA P 124 CB 8x4 NZ 420

In the operation of the unit whose successor does not use a hydraulic system, the role of the clutch is very important in transmitting power from the engine to the transmission. However, the clutch can only slip so that it can no longer function to forward power from the engine to the transmission. This can be caused by several things, including: wear on the clutch material, the presence of oil in the field of clutch surface, and spring damage to the clutch. On Scania P 124 CB 8x4 NZ 420 units this slip on clutch problem also occurs so research needs to be done to find the main cause. The method used in this study is to carry out checks and measurements and then the results are compared with the standard values that have been determined. The result shows that the cause of the slip on the clutch on the Scania P 124 CB 8x4 NZ 420 unit is 1) the presence of oil that wet the coupling surface is caused by a damaged seal shaft; 2) wear on clutch components namely clutch disc and pressure plate. To keep the seal shaft in good condition, regular and regular oil changes must be made and when the replacement of the seal shaft must be in accordance with the part number so that the possibility of the same problem can be reduced.

The Design, Control, and Testing of an Integrated Electrohydrostatic Powered Ankle Prosthesis

This paper presents a prototype powered ankle prosthesis that can operate passively in most of the gait cycle and provide powered assistance for toe push-off and subsequent foot dorsiflexion. The use of an electrohydrostatic actuator (EHA) gives the ability to switch quickly and smoothly between passive and active modes. In this new powered ankle prosthesis, the motor-pump unit is integrated with the ankle joint and the battery and controller are held in a backpack. A 100 W brushless dc motor is used to drive a 0.45 cc/rev gear pump, controlling flow to an ankle cylinder through a bespoke manifold. The motor runs wet, pressurized to 6 MPa, avoiding the need for a pump shaft seal and a refeeding circuit for external leakage. A dynamic system model has been develop to help analyze the EHA performance. A motor control method is proposed based on heel strike recognition and a middle stance time delay. The prosthesis has been tested with a 70 kg transtibial amputee, and results are presented for walking on a treadmill at three different speeds (2.8, 3.8, and 4.8 km/h). The amputee has provided positive subjective feedback. We conclude that the hybrid passive-active approach has significant advantages for prosthesis design, and we outline future testing and development requirements.

New Designs of Centrifugal Magnetic Fluid Seals for Rotating Shafts in Marine Technology

Abstract The centrifugal magnetic fluid seals have important advantage over the conventional centrifugal seals. They maintain very good sealing capacity at static, medium and high speeds of shaft rotation, with the increased seal lifetime, and minimum torque and static friction. These seals are particularly useful in cases when the angular shaft velocity varies and sometimes decreases to nearly or exactly zero, such as in flywheel applications, ship propeller main shafts, etc. Unique properties of the magnetic fluid give rare opportunities for application in marine design, where perfect sealing together with reliable lubrication are required. The paper presents a typical design and operation principle of a centrifugal magnetic fluid shaft seal, along with new design solutions. Not only in ocean technology and underwater robotics. Some cases of application of centrifugal magnetic fluid seals in modern sealing technology are included.

The Calculation of the Contact Force and the Contact Width of Shaft Seals

Abstract The aim of the article is to point out the sealing efficiency of the two-language seal of the water pump bearing when radially deflecting the shaft within radial clearance. In order to obtain a radial displacement of the shaft at a location under a two-language seal, dynamic bearing simulation was performed using the MSC Adams program. The largest radial deviation of the shaft was applied in final seal analysis where the contact pressure changes on the individual tongues of the seal were recorded.

Centrifugal compressors for He circulation loops for ITER

Thermal shields of ITER machine and cryopumps are cooled by two forced-flow helium cooling loops using helium at 80 K as a cooling media and liquid nitrogen as a source of cooling. Two-stage integrally geared centrifugal compressors provide mass flow of up to 4 kg/s per each machine with a suction and discharge pressure of 1.6 and 1.8 MPa correspondingly. This is the first in the world use of such machines for helium, and therefore an extensive testing program was developed to demonstrate as much as possible that the required performance is achieved. This paper presents the details of chosen construction of machines, as well as explains particularities of using centrifugal compressors for He and specific problems which were required to be solved, in particular to meet strict leak tightness requirements and overcome rotordynamics issues. Factory testing program and achieved results regarding machines’ performance and treatment of shaft seal leaks are also described.