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.

ESP Mechanical Shaft Seals: Trials and Tribulations of Lab Testing

Mechanical Shaft Seals (MSSs) are critical sub-components in Electric Submersible Pump (ESP) Seal Chamber Sections (SCSs), as they are the primary barriers used to isolate wellbore fluids from the motor oil. However, several ESP operators have observed relatively high MSS failure rates in certain applications, resulting in significant impacts on overall ESP system reliability and operational costs. In some cases, during teardowns, wellbore fluids were found in the lower chambers of the SCS, without any signs of damage to the MSSs or the bags/bellows in the SCS. Thus, to improve the run-life of ESP systems in their applications, operators identified the need to better understand the main influential factors affecting leakage rates through the MSS, including factors associated with the MSS characteristics and its operational conditions. To accomplish this, a test apparatus was built to allow the testing of MSSs in a wide range of operational conditions. This paper summarizes the technical challenges and key learnings that arose from building and commissioning such a test apparatus, as well as conducting several tests on multiple MSSs of a single design. Through commissioning of the test apparatus and subsequent testing, several limitations of the apparatus were identified and corrected through upgrades. Many of these upgrades were related to ensuring reasonably accurate measurement of the leakage rate through the MSSs, in both directions. Unexpected behaviours of the MSS were also observed during some tests. One example is the interesting phenomenon of reverse-pumping where, under certain conditions, leakage occurs in the opposite direction of the applied differential pressure. Finally, questions arose about the importance of certain aspects of quality control for MSSs and/or SCS assembly procedures. The above effort to build and commission a MSS testing apparatus has resulted in unique insight into shaft seal behaviour and continues to shine light on gaps in the industry understanding of factors affecting leakage through MSSs. It certainly provides evidence that there are many ‘unknown unknowns’ about MSS performance under challenging downhole operating conditions, and that the effort is worth continuing to support better MSS design/selection, and SCS assembly, as part of improving ESP system reliability.

Einfluss von Gruppe I Grundölen auf die Elastomerverträglichkeit von Radialwellendichtringen

Gear oils on the basis of Group I base oils are the most widely used lubricant in industrial drive systems. With dynamic friction torque tests, the influence of Group I base oils from different regions/refineries on elastomer compatibility of radial shaft seals is investigated by dynamic friction torque tests. The results show a significant influence of base oil on the development of frictional torque in the sealing gap and the elastomer compatibility.

Qualification of Barrier Fluidless, Sealless Seawater Canned Motor Pumps

The oil and gas industry continues to push toward subsea pumping technologies that minimize required support systems and increase system reliability. Canned motor technology has been applied successfully in other applications to achieve similar objectives including driving a subsea twin-screw pump. Applied subsea, canned motors eliminate the need for any barrier fluids within the motor, the myriad of systems and complexities necessary to store and replenish these fluids, and the mechanical shaft seals required to prevent the leaking and/or contamination of these fluids within the motors. As a direct adaptation of proven applications, see Figure 1, subsea water treatment is ideal for canned motor technology. Therefore, a development has been initiated and environment qualification testing of the first truly barrier fluidless, sealless subsea pump solution is complete. This purpose of the paper is to highlight the novel elements of this technology, review the system configuration, and document the system performance in accordance with the TRL 4 qualification initiative.

Analysis of Fluid Flow in the Sealing Gap of Radial Shaft Seals and Elastic Deformation of the Sealing Surface

The function of a radial shaft seal bases on interactions between the sealing edge and the shaft counterface. To better understand these mechanisms, a look inside the sealing contact was taken. The procedure and the testing facility are presented in this paper. In addition, a research methodology was developed, to systematically analyse the fluid flow and the distortion of the sealing surface of shaft seals. The results of the test procedure are documented in an evaluation matrix that allows the comparison of sealing systems with different worn sealing edges. For example, the tests show an influence of the rotation direction of the shaft during running-in on the formation of leakage channels or oil collecting chambers within the sealing contact.

Development and Optimization of a Tribometer for Radial Shaft Seals

In order to systematically investigate the tribological behavior of machine elements, several different tribometers based on simplifications of the contact situation have been developed and used successfully in the past. Many of these tribometers have become a standard testing equipment for tribologists. For the contact of radial shaft seals (RSSs), currently no such tribometer exists that can be used to characterize their behavior in a satisfying manner. In this paper, a tribologically equivalent system for RSSs is presented. The contact between the sealing lip and shaft is reproduced using a ring-shaped sample prepared from elastomer test slabs of the respective application material in contact with a conical shaft. The cone angle is chosen to properly represent the contact angles of the RSS under investigation by means of finite element (FE)-simulation of the contact pressure. The test rig allows for the on-line determination of friction, contact temperature, and wear progress. Results show good agreement of friction coefficient and wear behavior for the pairing of two typical elastomers with synthetic and mineral-based lubricants.