Shaft Seal Research Articles

Approach Uses Intentional Deadheading of ESPs To Improve Run Life

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204521, “Intentionally Deadheading SAGD ESPs: An Unconventional Approach To Improve Run Life,” by J. Daine Studer, Jesus E. Chacin, SPE, and Roger Walters, SPE, ConocoPhillips, et al. The paper has not been peer reviewed. _ Electrical submersible pumps (ESPs) used in steam-assisted gravity-drainage (SAGD) applications run at the highest motor temperatures possible. However, they cool very rapidly when shut down. High cooling rates promote motor oil volumetric contraction, eventually leading to wellbore fluid ingress and short-circuited motors. The complete paper discusses successful field tests designed to decrease ESP cooling rates by inducing controlled deadheads rather than shutting down ESPs. Various extended-deadhead field trials (of up to 70 or more days in duration) validated the approach while confirming that no deadhead-related ESP damage was induced. Introduction In conventional operations, when ESPs operate in deadhead mode (i.e., no flow into the production line), all useful lifting work turns into heat and the ESP can overheat rapidly. The tendency to overheat increases as the gas/oil ratio of the lifted fluid increases. This type of overheating failure usually manifests as burnt stage components and cable burns close to the pump. At the Surmont SAGD plant, however, anecdotal evidence when ESPs inadvertently ran for a few hours in deadhead mode showed that SAGD ESPs cooled during deadhead events. This was the genesis of the project presented in the paper, which is to intentionally deadhead, rather than shut down, SAGD ESPs to offset or partially offset naturally occurring rapid cooling. Application Background A typical Surmont ESP producer completion features wells that are surface-cased with 13⅜-in. casing to approximately 120 m, and 9⅝-in. to approximately 350–450 m true vertical depth. Horizontal sections range from 600 to 800 m in length and are terminated with 7-in. slotted liners or flow-control-device strings. ESPs produce through 3½-in. tubing and are set at an inclination angle of 75° to 82° in specially drilled tangent sections. A 21/16-in. guide string is used to protect and land as deep as possible an optical fiber string inside a protective coiled string (1¼ in.). This optical fiber is used to obtain distributed temperature measurements. A bubble tube is bundled inside the ESP power cable to provide single-point downhole pressure measurements at pump-setting depth (PSD) in the annular space. Most ESPs used at Surmont feature power ranging from 60 to 180 hp to lift total gross production rates to the 1,000–6,500 B/D range. Water cuts average from 70 to 73%. The most-common failure modes experienced at Surmont caused by temperature cycling include worn mechanical shaft seals, metal bellows overextension, and thrust bearing wear (Fig. 1).

A new rotor structural design method of rotating packed bed based on hydrodynamic performance analysis

The rotating packed bed (RPB) is a typical process intensification device. However, the unbalanced vibration of the rotor makes the rotor transmission shaft squeeze the bearing and shaft seal frequently, which may destroy the bearing and shaft seal and cause material leakage. In response to this situation, this paper proposes a new spherical rotor structure design method based on hydrodynamic performance analysis for the RPB. It establishes the CFD models, including a conventional rotor structure and a spherical structure. The gas-liquid flow field characteristics in the two kinds of structural equipment are analyzed from the CFD results. It is found that the gas-liquid flow field distribution of the RPB with a spherical rotor structure is consistent with that of the conventional RPB, and the residence time of the liquid is less than 1s. The RPB with a spherical rotor structure meets the fluid performance of the high-gravity reactor. The gas-phase pressure drop of RPB with a spherical rotor structure is 20−35% lower than conventional structural RPB, and it increases the liquid holdup by 30−50%. It can be concluded that RPB with a spherical rotor structure has the advantages of lower pressure drop and higher liquid capture ability.

Friction Performance Analysis of Reactor Coolant Pump Shaft Seal Based on Sensor and Computer Simulation

In recent years, the state has put forward a grand plan to develop nuclear power in order to control environmental pollution and carbon emissions. In nuclear power plants, mechanical seals for reactor coolant pump play an important role in nuclear power safety production. However, China cannot independently produce such mechanical seals, and they are blocked by foreign related technologies, which has seriously affected China’s nuclear power development plan and the overall safety of China’s nuclear power operation. Under this background, this paper studies the friction performance of the shaft seal of the reactor coolant pump, uses the sensor to obtain the data of friction factors such as low-pressure leakage, effectively monitors the low-pressure leakage through calculation and simulation modeling, truly reflects the operating state of the reactor coolant pump, and provides a new research direction and experimental basis for further analysis of the friction performance of the shaft seal of the reactor coolant pump. The results show that under the joint action of the pressure difference and the force generated by the deformation of the moving ring plate, the cone angle formed on the seal end face is 1300.9 μ convergence gap of rad. When the inlet water temperature is 65°C, the leakage rate is 1867.8 L/h. The deformation of the moving ring deformation ring plate can hinder the increase of the deformation cone angle of the moving ring. The greater the thickness of the moving ring deformation ring plate, the greater the seal leakage rate. The inlet temperature of the sealing medium and the friction performance of the material also have an impact on the sealing performance.

Development of an Integrated Electro-Hydraulic Machine to Electrify Off-highway Vehicles

Electrification of off-highway vehicles is notoriously challenging due to extreme power density requirements. This article proposes and develops an axial flux machine integrated with a hydraulic pump to realize a single modular, electro-hydraulic machine to electrify off-highway vehicle implements. This integrated machine eliminates redundant bearings, couplings, and shaft seals, reuses surfaces, and enables direct cooling of the electric machine with the hydraulic fluid, to significantly increase power density. Three popular axial flux machine variants are first compared using a finite element analysis based design optimization approach. The single rotor, single stator variant is identified to be the most promising for integration with the hydraulic pump. Next, a multiphysics framework of the complete integrated hydraulic pump and axial flux machine is developed to characterize the design space. The results indicate promising potential for this concept to realize efficiency over 85% and power density over 5 kW/kg for the complete machine (electric machine, hydraulic pump, and thermal management system), while utilizing conventional materials (thin gauge silicon steel, N45 magnets, and enamelled copper wire). A prototype axial flux machine has been experimentally characterized and integrated with a hydraulic pump to demonstrate the integrated electro-hydraulic machine concept.

Research on a Large Diameter Magnetic Fluid Seal With Thin-Wall Parts

Magnetic fluid seal is a new type of sealing method, which has been applied in many fields. For some fields, such as aviation and aerospace, high sealing performance, large shaft diameter, and small design space are required, which brings difficulties to the sealing design. Therefore, it is necessary to study a large diameter magnetic fluid seal with thin-wall parts. In this article, the effects of seal clearance and shaft deflection on the magnetic field distribution of magnetic fluid seal are analyzed by the finite element method. At the same time, the force of seal shaft in the assembly process is also simulated. The influence of the amount of magnetic fluid on the pressure resistance is analyzed. The low-temperature starting torque and high-temperature pressure resistance of magnetic fluid seal are experimentally studied, and the optimal injection amount of magnetic fluid is obtained. The research content of this article can be used as a reference for the design of a large diameter magnetic fluid seal with thin-wall parts.

Performance Analysis of the Self-Pumping Hydrodynamic Mechanical Seal with a Conical Convergent Diffuser Groove

Requirements such as high opening force, low leakage rate, and design without matching auxiliary flushing systems are expected of the modern fluid machinery shaft seals used in the process industry. A self-pumping hydrodynamic mechanical seal with a conical convergent diffuser groove is proposed and its sealing performance is studied by numerical simulation in this paper. Further, its sealing performance is compared to that of a flat-bottomed equal cross-sectional diffuser groove and the results have shown that the proposed seal has more superior sealing performance. The influence of structural and operating parameters on the sealing performance of the proposed seal is discussed and its working mechanism is explained. The results have shown that when the structural parameters of the spiral groove and the operating parameters are the same, the proposed design has a similar leakage rate and a higher opening force. The conical convergent diffuser groove has better wrapping properties, whereas the fluid energy is utilized more efficiently, improving the sealing interface opening force. The taper degree variation causes a slight change to the pressure at the root of the spiral groove, causing slight fluctuations in the seal leakage rate. The research results broaden the design of non-contact mechanical seals and provide a theoretical basis for the engineering application of the proposed self-pumping hydrodynamic mechanical seal with a conical convergent diffuser groove.

Approach to the Description of Macro Lead Formation by Means of a Kinematics Simulation Model

ABSTRACT The often-recommended plunge grinding of lead-free sealing counterfaces for rotary shaft seals, proposes a problem in the production. The recommendations in [1, 2] tend to longer spark out times which is not cost effective. Switching to more cost-effective alternative manufacturing methods can lead to a different unfavourable behaviour of a sealing system [3, 4]. Thus, a more detailed look at the machining process ‘plunge grinding’ with its influence on the sealing counterface can help to improve the process parameters. Therefore, the plunge grinding process is considered kinematically in a simulation model. Kinematically simulated and modelled sealing counterfaces are then evaluated with a statistical analysis software, where the resulting characteristics of the lead structures are compared with the input parameters of the process. Different parameter sets were also ground, analysed and evaluated to validate the results. With the good accordance between the kinematics simulation model the experimentally ground surfaces, this approach shows comprehensively the interrelationships between the manufacturing parameters and the resulting lead parameters.

Shaft seal for ships incorporates low-friction sealing ring and emergency feature

Canada's Thordon Bearings Inc has developed a low maintenance water-lubricated shaft seal. It incorporates a low-friction sealing ring which, says the company, is better suited to both variable and deeper draught vessel conditions. In addition, its design has an emergency feature that enables a vessel to return to the nearest port safely if the main seal on its propeller shaft is damaged.

Rotary Shaft Seals: Correlation of Wear Formation at the Sealing Edge and Shaft under Various Operating Conditions

Elastomeric rotary shaft seals are a common seal type for various industrial applications. They are comparably cheap and easy to use and offer an overall good performance. But the wear behavior of these sealing systems is not fully understood and not predictable so far. If a lip seal fails, it causes high maintenance costs and environmental damage. In this article, various tribological conditions are considered. For this purpose, the sealing systems are tested with multiple operating conditions relevant to practice. Three test series are conducted with rotary shaft seals BAUM5X7 75FKM585 on plunge ground shafts. The tests are carried out with two different circumferential velocities of the shaft (4.2 and 10 m/s), three different oil sump temperatures (40, 80, and 120 °C), two different lubricant types (FVA 3 and PG 3), and five different test durations (between 100 and 625 h). For a complete acquisition of the system condition, all shaft surfaces are measured in 2D and 3D before and after the test runs and the wear of the sealing edges is evaluated with a recently developed laser line triangulation method on the complete circumference of the sealing rings. Results show large amounts of wear, depending significantly on the operating conditions. A strong correlation of the wear effects in the tribocontact area of the sealing system becomes evident. This article helps to understand and avoid critical operating conditions concerning abrasive wear.

Design of Magnetic Levitation Shaftless Contra-Rotating Propeller and Feasibility Analysis of Drive System

In order to solve the problems of vibration, noise, shaft seal and complex structure of the marine propeller, the author proposes a new type of magnetic levitation(Maglev) shaftless contra-rotating propeller(CRP), analyzes the mechanical structure design and component layout of the propeller, and uses 3D modeling software to model and assemble components. The propeller is mainly composed of rotors, shroud, stator winding, sensors, control circuit and other components, and its control system is further divided into a levitation system and drive system. Then the drive system of the propeller is studied, its mathematical model is analyzed, and the drive system model is built in MATLAB/Simulink to analyse the feasibility of the propeller drive system, and a PID controller is added to make the system have good dynamic response performance.

Development and initial performance of a miniature axial flow blood pump using magnetic fluid shaft seal.

In this study, we developed a new catheter-mounted micro-axial flow blood pump (MFBP) using a new miniature magnetic fluid shaft seal (MFSS). The prototype of the catheter-mounted MFBP had a maximum diameter of 8mm and a length of 50mm. The new MFSS composed a neodymium magnet ring, an iron ring, and a magnetic fluid particularly designed for the MFSS. The new MFSS had outer and inner diameters of 4.0mm and 2.6mm, respectively, and a length of 3.0mm. The sealing pressure of the MFSS was calculated to be 432mmHg using FEM (Finite Element Method) result; therefore, the MFSS had sufficient sealing pressure for the catheter-mounted MFBP. The friction loss of the MFSS included the friction owing to the viscosity of the magnetic fluid and the magnetic force between the iron ring and ring magnet. The total friction loss of the MFSS was 0.08-0.09W in the pump operational speed range from 22,000 to 35,000rpm. From the in vitro experimental results, the catheter-mounted MFBP using the MFSS had a pump output of 3 L/min. against a differential pressure of 60mmHg, and the pump characteristics of the MFBP were almost the same as those of Impella 5.0.

Flow visualization of non-contacting mechanical seals with bidirectional rotation

Abstract Non-contacting mechanical seals are used as a shaft seal in a turbomachinery. A few micrometers thin lubrication film is formed by grooves on the seals. Various groove shapes were presented, and most of these grooves were designed for unidirectional rotation. However, reverse rotation occurs accidentally in the turbomachinery. In this study, the performance of two type unidirectional grooves was investigated by measuring the pressure in a chamber which means sealed fluid pressure and visualizing the flow in the lubrication film with bidirectional rotation. The measurement results of pressure under forward rotation showed that the pressures fluctuated as rotational speeds increased by hydrodynamic pressure. By contrast, under reverse rotation, the amount of fluctuation was smaller and almost not changed with increasing rotational speeds. In addition, the flow visualization results showed the increase of pressure drop areas and occurrence of gas phase. This indicates the decrease in load capacity and film stiffness. In contrast, the discharging flow from inner to outer side or the breakage of the film were confirmed and prevented fluid leaking. In summary, the results showed the degradation of lubrication characteristics though the no degradation of a sealing performance.

Investigation of Radial Shaft Seal Swelling Using a Special Tribometer and Magnetic Resonance Imaging.

Compatibility between the rubber material of radial shaft seals and the lubricants to be sealed is an important requirement that customers demand of their lubricant suppliers. Among other effects that may result from incompatibility, the penetration of lubricant components into the rubber (swelling) can impair the seal’s functionality due to changes in its geometry and mechanical behavior. Typically, the penetration of a lubricant into an elastomer is evaluated after an immersion test using volumetric, gravimetric, and extraction measurements. Due to the small changes that need to be detected, such methods may not be sufficient to obtain meaningful results. In this contribution, we use magnetic resonance imaging (MRI) to investigate swelling on special tribometer samples as well as a radial shaft seal that were previously used in component tests. Several combinations of rubbers and lubricants that have proven to be compatible were tested in addition to combinations with expected incompatibilities in real applications. The results indicate that MRI measurements can be used to quantify the penetration depth and potentially also the velocity with which the lubricant diffuses into the rubber, thereby yielding detailed insights into the swelling process of the seal.

Flow Conditioning to Control the Effects of Inlet Swirl on Brush Seal Performance in Gas Turbine Engines

When subject to highly swirling inlet flow, the bristles on the upstream face of a brush seal in gas turbine engines tend to slip circumferentially, which may lead to aeromechanical instability and seal failure. In this article, a new design of the front plate of brush seal, which mitigates this effect, is presented. Angled ribs on the upstream side of the front plate are used to reduce the swirl of the flow impacting on the bristle pack. The effects of the rib geometry, including angle of inclination and height-to-spacing ratio, are investigated using computational fluid dynamics, and a bulk porous medium model of the bristle pack, on a simple seal geometry. Results show that the ribs can effectively regulate the flow upstream of the bristle pack, reducing the swirl and channeling flow radially inward to the sealing section, resulting in decreased circumferential forces on the bristles. Ribs inclined at 20° to the radial direction and with height-to-spacing ratio of 0.4 were selected as the most effective of those investigated for the seal geometry under study. A model of an aeroengine preswirled cooling air chamber was created to give insight into the inlet swirl boundary conditions that a preswirl seal brush seal could be subjected to at a range of leakage flow rates and inlet swirl velocities. The new design and upstream roughness feature substantially reduced inlet swirl velocity incident on the bristle pack. The findings in this work could have a significant impact on brush seal design and, in particular, mitigate a significant operational risk of swirl-induced instability in high-pressure, high-speed shaft seal locations.

Analisis Kerusakan Trim Air Pressure Regulating and Shutoff Valve Pada Pesawat Boeing 737-800 Menggunakan Metode Failure Mode and Effect Analysis (FMEA) di PT.GMF Aeroasia,TBK.

Air Conditioning (AC) is the one of system in aircraft to make a passanger and all cabin crew comfortable. Trim Air Pressure Regulating and Shutoff Valve or also known as Trim Air PRSOV is a component on the Boeing 737-800 aircraft to regulate flow of hot air constantly before entering the aircraft cabin. Refering to the data for the last 6 years, the replacement of the component belonging to one of the Indonesian national flight carrier using Boeing 737-800 aircraft was the occurance of 84 times the cooling system failure which caused the light indiacator in the cockpit to light up. Among them happened 70 times unscheduled maintenance and 14 times scheduled maintenance. Thus, this essay was made to analyze the causes of the damage that occurred to the Trim Air PRSOV. The method used in this research is Failure Mode and Effect Analysis (FMEA) is the technique used to find, identify and eliminate failures or damage to a system or process. The first step is to analyze using a Pareto diagram and then continue with the FMEA method so that an analysis of the damage that often occurs is damage to the diaphragm with 42% damage with an RPN value of 389.1, erosion on the ring seal with 22% damage with an RPN value of 376 and shaft seal damaged with 12% damage with an RPN value of 295.1 for it requires aggressive treatment. Therefore, repairs with a long TAT of 14 days are expected to increase the reliability of the PRSOV Trim Pressure component. For this reason, repairs are carried out with a long TAT of 14 days, it is hoped that there will be an increase in the reliability of the PRSOV Trim Pressure componen.

Improvement of shaft seal performance using hydrophilic elastomer by addition of CNF

To prevent leakage of subject fluid or ingress of surrounding material at a rotating shaft, shaft seals such as oil seals or mechanical seals are commonly assembled in a lot of mechanical devices. Although these shaft seals are commercially available and replaceable, it is not always successful to be used for water sealing because they cause high friction and wear or leakage due to low viscosity and poor lubricity of water. In the previous study, a seal ring made of hydrophilic elastomer was developed so that it promotes hydrated lubrication under the boundary lubrication mode. Also, the fiber reinforcement of the hydrophilic elastomer was introduced to improve its elasticity with original material properties. In this work, partially reinforced seal rings with layered structure in addition to uniformly reinforced seal rings were developed and evaluated by sealing performance test. The results suggested that partially reinforced seal ring showed both characteristics of each single layer depending on the operational condition.

Three-dimensional structure-based approach for the analysis of macroscopic lead structures on sealing counterfaces

The seal failure of an elastomer rotary shaft seal is often caused due to lead on the shaft counterface. In sealing technology, the term ‘lead’ includes all structures on sealing counterfaces that are capable of transporting fluid in axial direction through the sealing contact and thus disrupting the sealing mechanism. Lead structures are created during the manufacturing process of the shaft surface or throughout the handling. They occur in various shapes and sizes. Depending on the characteristics of the lead structures, several specialized measurement and evaluation methods exist which have to be applied in combination. However, not all types of lead can be covered with the methods known so far. State of the art are frequency-based and model-based analysis methods, which are only able to detect periodic lead structures. Aperiodic and stochastically distributed lead structures cannot be detected due to the functional principle. This article provides an approach for a structure-based evaluation of macroscopic lead structures based on optical topography measurement data. This allows to detect all known types of macroscopic lead on the shaft surface and in future to measure microscopic and macroscopic lead with a single measurement procedure.

Influence of Dressing Parameters on the Formation of Micro Lead on Shaft Sealing Counterfaces During External Cylindrical Plunge Grinding

Influence of Dressing Parameters on the Formation of Micro Lead on Shaft Sealing Counterfaces During External Cylindrical Plunge Grinding

Gas film lubrication method on rotation shaft seal based on contact design

PurposeWear failure happens frequently in rubber seal of high-speed rotating shaft because of the dry friction. Some traditional lubrication methods are not effective because of the restrictions on the relative high speed, temperature and others. This paper aims to present a new method of lubrication with gas film for the rotation shaft seal based on the contact design.Design/methodology/approachTo obtain the generation condition of gas film and good effect of lubrication in the contact gap between the shaft and its seal, a series of micro-spiral grooves are designed on the contact surface of rubber seal so as to obtain a continuous dynamic pressure difference.FindingsThe result is that the distribution of the gas film in the micro-gap is continuous under the design of the spiral grooves and the contact with eccentricity because of the deformation of rubber seal, which is verified through the simulation calculation and experiment test. It is confirmed that the lubrication method with gas film through designing micro-spiral grooves on the contact surface is effective, and can achieve self-adaptive air lubrication for the high-speed shaft under the premise of the reliable sealing.Originality/valueThe method of gas film lubrication is realized through designing a microstructure of spiral grooves on the rubber surface to change the contact status, which can form a mechanism of adaptive lubrication to reduce the dry friction automatically in the contact gap. For the cross-scale difference between the rubber seal and gas film, a new modeling method is presented by building the mapping relation for the split blocks and repairing technique with integrated computer engineering and manufacturing, to reduce the possibility of nonconvergence and improve the efficiency and accuracy of calculation.

Test and evaluation method for greases in grease-sealing rotary shaft seals

Grease-lubricated sealing systems show starved lubrication much more frequently than oil lubricated sealing systems. Different greases provide different lubricity to the sealing system. A test and evaluation method was developed that allows to assess the lubricity of different greases and to compare them with each other. The test and evaluation method consists of a test run and a subsequent analysis of the test components. The test run comprises a 24-hour speed collective and is performed on a test rig using real sealing system components. For the evaluation method, eight criteria are analysed, which are rated suitable for evaluating starved lubrication. The criteria include parameters measured during the test run, such as friction torque and temperature, as well as parameters inspected in the subsequent examination of all test components. All criteria are assessed and combined to an overall score, that allows to directly compare different greases with each other. The test and evaluation method developed reveals significant differences between 23 greases examined. Thus, the lubricity of greases in sealing systems can be analysed and compared much more quickly than in the past. Thanks to the rapid testing and focused evaluation of the relevant criteria, greases can be tested much more cost- and resource-efficiently than before.