Pump Stage Research Articles

Improving the Efficiency of Submersible Multistage Pumps Based on the Hydrophobization of the Flow Part Surfaces

The paper presents an experimental study of an assembly of five stages of an electric centrifugal pump (ECP) installation, the flow part of which is modified according to the principles of biomimetics, namely using the “lotus leaf effect”. The object of the study was a 5A-35 ECP. The surfaces of the blade systems of impellers and guide devices of stages 5 A-35 were hydrophobized using the method of applying surfactant layers. The degree of impellers hydrophobicity was estimated by the wetting angle average value measured by three drops at three different points on the impeller surface. The impellers surface roughness under study was determined by the arithmetic mean profile deviation Ra and the profile height irregularities Rz. The issues related to the surfactant coating modification effect salt deposition and corrosion were studied. For this purpose, the surfaces of the original and modified impellers were subjected to intensive forced salt deposition as a result of prolonged exposure to saline solution. The conclusion about the samples corrosion resistance degree was made by changing their mass, which was due to the salt deposits formation during 15 hours of stay in solution, as well as using the drop method. Both methods have shown that the surfactant coating can serve as a salt deposition inhibitor, and the pump impeller modified by it has increased corrosion resistance. Thus, during comparative tests, a smaller mass of salt was deposited on the modified impeller sample during 15 hours of exposure in saturated saline solution than on the original sample. This indicates that the surfactant layer prevents the salt deposits fixation on the working surfaces of the pump stage. On the modified sample examined by the drop method, the indicator color changed in 20 minutes, and on the original one – in 2 minutes. Experimental studies have been carried out, during which the operation energy parameters of a five stages 5A-35 pumping package with initial and modified surfactant-coated impellers have been determined. The studies have shown a 2 % increase in efficiency in the pum-ping package of stages with modified impellers. The results of the study can be useful in the oil production, chemical industry, as well as in the housing and communal services sector.

Experimental investigation of a novel gas-liquid homogenizer methodology for ESP in high GVF flow applications

This paper presents a new homogenizer for Electric Submersible Pumps (ESP). Experiments were carried out using a two-stage radial-type pump with perforated vanes running at 3400 RPM. A test rig was designed to measure pressure and observe flow patterns. Results showed excellent performance for intake GVF ranging from 25 % to 89 %. Using the proposed homogenizer in the multistage ESP improves pump performance for gas-liquid mixtures. The study explored parameters to improve pump performance in high GVF conditions. The proposed homogenizer is more cost-effective and efficient by integrating into the existing pump stage and allowing customizable perforations. This design flexibility improves performance while avoiding the need for extra space or components. Moreover, numerical simulations with a helico-axial rotating multiphase pump and ANSYS-CFX software were conducted to prove the concept numerically. The focus was on gas-liquid two-phase flow and the effects of inlet GVFs. Modifications to the impeller blades, such as grooves, slits, or holes, were designed to enhance performance. The study found that CFD simulations accurately predict pump performance and that modified impellers improve performance in specific GVF ranges.

Hydrohelical ESP Gas Separator Increases Flow Range, Improves Reliability

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214723, “New High-Performance ESP Gas Separator,” by Barry Nicholson, SPE, and Scott R. Harryman, SPE, Oxy, and Donn J. Brown, SPE, Halliburton, et al. The paper has not been peer reviewed. _ The complete paper presents research, design, and field testing of a new type of mechanical gas separator for electrical submersible pump (ESP) systems that increases operating flow range and separation efficiency while decreasing erosion problems and improving reliability. The hydrohelical separator system has been proved effective in different types of wells. Background Several methods and techniques exist for avoiding gas in ESPs, including inverted shrouds, passive separators, mechanical gas separators, and tandem gas separators. Most share the limitations of limited flow capabilities and reduced performance at higher total flow rates. The many variables associated with complex two-phase flow behavior, internal and external pressure variations, separation methods, velocity and viscosity of fluids, effect of the pump bolted above, inherent erosion issues, and single vs. tandem designs add to the challenge of basic mechanical gas-separator operation. In 2016, a program was initiated that featured investment in both experienced personnel and advanced testing technology to unravel the aforementioned challenges and improve understanding of the operation of downhole mechanical gas separation. The team investigated innovative methods of testing and created a transparent testing system that allowed visual observation of individual internal flow regimes as well as component performance. Using a combination of high-speed photography, computational fluid dynamics validation, and specialized instrumentation, every component of a mechanical separator system was enhanced for higher flow capabilities, improved separation efficiency, and higher reliability for a variety of downhole conditions. The result was the development of a new type of mechanical gas separator for ESP use. Development Most gas separators ingest multiphase fluid into a separation chamber, separate the gas and liquid phases, eject the separated gas phase into the well annulus, and provide sufficient liquid phase fluid to the pump to enable efficient pumping. Existing designs vary, but they share separation methods that result in decreased efficiency at higher flow rates and low maximum flow rates compared with the pumps they feed. The hydrohelical gas separator is the first downhole, dynamic gas-separator design improvement in more than 30 years designed to address these deficiencies (Fig. 1). The design was aimed at the following main objectives: - Increase total fluid flow rate through the separator - Maximize efficiency of every internal and external component of the system - Reduce erosion characteristics common in traditional gas-separator designs - Improve reliability The design of the hydrohelical gas separator is based on a stationary helical vortex inducer and pump stages that enable movement of large quantities of fluid while remaining immune to gas locking. The stationary helical vortex inducer design enables increased efficiency and flow rate through the separator by reducing turbulence in remixing regions within the helical inducer and separation chamber.

Optimization of low-temperature multi-stage submersible pump based on blade load

The multi-stage submersible pump is a power conveyor for low-temperature media, which is conveyed by the rotating of centrifugal impellers. In this study, the impellers of a multi-stage submersible pump were optimized to improve the efficiency under the premise of the constant total blade load and head. Based on the analysis of performance and flow for each stage of the 18-stage submersible pump, the optimization scheme composed of the first stage, the middle stage, and the last stage was determined. The blade outlet angle, average blade wrapping angle, and blade wrapping angle difference were selected as optimization parameters through Plackett–Burman experimental design and significance analysis, and the blade profile was redrawn by changing the blade load distribution. The performance prediction model was built based on the Kriging response surface model, and then, the global optimal blade profile was found by non-dominated Sorting Genetic Algorithm II. The efficiencies of the 3-stage submersible pump and 18-stage submersible pump with optimized impeller increased by 2.35% and 2.01%, respectively. Under the design condition, the flow rate loss and pressure pulsation at the impeller outlet decreased and the stator–rotor interaction between the impeller and guide vane was weakened. This will lead to a reduction in unstable flow such as secondary flow and vortices, and an improvement of flow stability at the impeller outlet.

Sensitivity analysis on tailpipe design for mitigating terrain slug in horizontal wells

Terrain slugs are a common challenge faced in horizontal well completions, leading to significant operational difficulties and reduced well performance. The lateral wellbore can cause hydrodynamic slug problems, even severe terrain slug issues. With undulations along the lateral, gas pockets can build up within the peaks and valleys of the wellbore. These gas pockets can restrict liquid flow until bottom hole pressure builds up enough energy to push the liquid slug to the surface. The terrain slug flow not only frequently results in foaming or emulsions at the surface but also causes downhole equipment failures, especially for Electrical Submersible Pumps (ESPs). Even with the downhole separator and gas handling pump stages, the ESP system is challenged by the elongated gas pocket that results in gas locks and electrical failures. To mitigate these issues, the use of Tailpipes (TP) in combination with ESP has become a popular solution. This study aims to explore the impact of tailpipe design on the performance of ESP systems in horizontal wells. With the help of oilfield operating companies, 5 representative wells are selected from 24 horizontal ESP wells that are facing or will potentially face the slugging issue.A total of 284 simulations are conducted using the transient simulator (OLGA, 2019) to comprehensively investigate the tailpipe design methodology for well conditions that are comparable to this study, i.e., flow rate from 500 to 2000 bpd, GLR from 500 to 2000 scf/bbl, 5 ½” and 7” casing, 9000–12000 ft well depth. Different TP diameters and lengths are simulated to evaluate the TP effectiveness at different flow rates, Gas-Liquid Ratios (GLRs), and well conditions. The results of this study can provide valuable insights and recommendations to the ESP tailpipe design for a wide range of horizontal wells applications, and help to improve their overall performance and reliability.

О структуре гидравлических потерь при работе многоступенчатых лопастных насосов

The paper proposes methodology for assessing hydraulic resistance of the vane pump stages. The methodology makes it possible to reveal the hydraulic losses structure during liquid pumping and assess contribution of each type of these losses to the overall balance of the pumping stage energy consumption. Dependence of hydraulic losses on the width of the inter-vane flow channels is shown. Theoretical method was developed to predict the effect achieved by altering the vane design and production technology. Prospects of research, design, development and industrial production of the new type of multistage vane pumps with the oval-type stages are substantiated.

Numerical Simulation of a Three-Stage Electrical Submersible Pump under Stall Conditions

This paper focuses on investigating the stall phenomenon of a three-stage electrical submersible pump using numerical methods by examining the internal and external characteristics of the pump under design conditions and critical stall and deep stall conditions. The energy losses inside the impeller and diffuser are also discussed. The internal flow at all pump stages under stall conditions is analyzed, highlighting differences and correlations. Under critical stall conditions, multiple vortices appear in the impeller channel of the first stage, while the flow in the secondary and final impeller remains smooth. Flow separation occurs in the diffusers at all three stages. Under deep stall conditions, the inlet setting angle causes all stages to enter a synchronous stall state. The range and intensity of vortices in the diffusers of all stages are further increased, seriously affecting the mainstream. This paper provides valuable insights for the research of internal flow and optimal design of electrical submersible pumps.

A negative voltage generator with 4-stage configurable parallel switching for smart window film applications

ABSTRACT A negative voltage generator was developed that can be used in the drivers of smart window films (SWF), which have typical operating voltages of 8 to 10 V. It consists of four Negative Charge Pump (NCP) stages and a 4-phase non-overlapping Clock Generator (CG), where the 4 NCP stages are configurable by external digital signals. This generates a wide output voltage range necessary to control different SWF modes, such as opaque, transparent, and tinted modes. TSMC 0.18-m HV BCD (High-Voltage Bipolar-CMOS-DMOS) process was used to fabricate the proposed negative voltage generator on silicon. Measurement results demonstrate that at switching frequency (fsw) = 20 MHz, supplied voltage (VDD) = 4.5 V and Vin = GND, it generates a wide output voltage range of −3.9 to −14.0 V, achieving the widest voltage range among the prior works, which covers the required negative voltage range for SWF usage. The peak efficiency is measured on silicon to be 58.08% .

High-Performance Charge Pump Regulator with Integrated CMOS Voltage Sensing Control Circuit

This paper introduces a design for a charge pump DC-DC boost regulator with an integrated low-voltage control circuit. With a charge pump and feedback circuits implemented in 0.35 µm CMOS technology, the proposed DC-DC boost regulator offers an efficient device solution for low-power applications. The proposed design employs an error amplifier, oscillator, and comparator in the control circuit which is designed with a supply voltage of 1.8–3.5 V and 2 MHz frequency. Stability is obtained via a pole-zero compensation in the feedback circuit. The charge pump regulator with four pump stages and the whole regulator circuit are analyzed using the Cadence simulation tool. Measurements of the fabricated 0.35 µm CMOS regulator show that the transient time of the error amplifier is controlled within 1.0 µsec and the output voltage is accurately controlled from 7.8 V to 9.4 V with 27–38 mV ripple and 4.5 mA maximum current.

OPTIMIZATION OF THE GEOMETRIC PARAMETERS OF THE MOLECULAR STAGE OF A VACUUM PUMP WITH SCREW CHANNELS ON THE ROTOR

A technique for optimizing the geometric parameters of the molecular stage of a turbo molecular vacuum pump with helical channels made on the rotor is considered. In the axial section of the rotor, the channels have a rectangular shape. As a result of numerical experiments by the Monte Carlo method in the molecular gas flow regime, the influence of each geometrical parameter of the rotor on the main pumping characteristics of the molecular stage was established. The developed program makes it possible to optimize the geometric parameters of the helical channels of the molecular stage for given overall dimensions of the rotor in order to obtain the maximum speed of action and pressure ratio.

Online trained controller for Electrical Submersible Pumps in liquid–gas flow

The Electrical Submersible Pump (ESP) is an artificial lift method widely used in the oil industry. More than 150,000 wells worldwide are equipped with ESPs to produce cost-effective oil rates. An ESP unit usually includes an electric motor, a protective element, a gas separator (optional), and a multistage centrifugal pump. When free gas produced in the well reaches the pump stages, problems such surging and gas-locking can occur, leading to unexpected shutdowns in the oil production. In this work, a control based on Artificial Neural Networks (ANN) with online training is proposed as a solution to reduce these unplanned shutdowns. The proposed controller was designed using the direct inverse control method and the data obtained from an ESP working with a liquid–gas flow. The results of this work show that the controller can drive the operation of the ESP away from the regions where surging and gas-locking would occur. Since the controller is an online trained ANN, it was able to control the operation of two different pumps, namely the model P100 pump, the model P47 pump, and the model P23 pump.

OPTIMIZATION OF GEOMETRIC PARAMETERS OF HELICAL CHANNELS IN A MOLECULAR VACUUM PUMP

A method of optimization of geometrical parameters of a molecular stage of a turbomolecular vacuum pump with helical channels made on the stator under the molecular gas flow regime is considered. In axial section of stator the channels have rectangular shape. As a result of numerical experiments, the influence of each geometrical parameter on the main pumping characteristics of the molecular stage has been determined by the Monte-Carlo method.

Investigation of pressure pulsation induced by quasi-steady cavitation in a centrifugal pump

To study the pressure pulsations induced by quasi-steady cavitation in a centrifugal pump, the pressure pulsations at the pump inlet and outlet were experimentally investigated with the development of cavitation. Moreover, the internal flow characteristics in the pump during the process were numerically determined. The numerical simulation results agreed well with the results obtained from the experimental test, verifying the accuracy of the numerical simulation. Furthermore, the cavitation-induced pump inlet and outlet pressure pulsations of the centrifugal pump were analyzed by wavelet analysis and fast Fourier transform, and the cavitation incipient point and occurrence of the unstable cavitation point were obtained. The results of both wavelet analysis and fast Fourier transform show that in the quasi-steady cavitation stage of the centrifugal pump at the design flow rate, the pump inlet and outlet pressure pulsations are significantly increased at twice the axial frequency, while the other axial frequency components are weak and the internal flow is stable. With the development of cavitation in the pump, the pump inlet and outlet pressure pulsations at the axial frequency and its multiples afford some obvious broadband pulsations. To investigate the mechanism of quasi-steady cavitation-induced pressure pulsation in the centrifugal pump, the dynamic mode decomposition was used for internal flow field analysis. The results show that different inflow states lead to obvious differences in the internal flow and unsteady flow structures. There are complex pressure pulsation characteristics dominated by different frequencies in the centrifugal pump. Blade passing frequency plays an important role in the entire flow field, and its mechanism has been analyzed. This research will provide experimental and theoretical support for quasi-steady cavitation recognition and help researchers improve the operation stability of the centrifugal pump.

The Study of the Sound Waves Transmission along the Fluid Line through the TsN-2 Electric Pump

BACKGROUND: Noise at production site or at any other place where technical equipment operates is a huge issue. It has a strong negative effect on human nervous system, reduces average lifespan and causes a number of severe diseases. That is why reduction of noise, produced by pumps, is one of the current priorities of hydraulic engineering.
 AIMS: In this study, the experimental research of sound transmission through an operating pump and a non-operating pump was carried out. The aim of the research is to find out, whether the last stage of a multistage pump is the main source of hydrodynamic noise (HDN) in pressure line (or the first stage in suction line), or all stages somehow contribute to HDN.
 METHODS: The experiment was carried out on the TsN-2 two-stage impeller pump. In order to generate a sinusoidal signal, an imbedded generator, a vibration test rig and a power amplifier were used. Data acquisition for measurement of HDN and vibrations was performed with use of a conditioning amplifier, a hydrophone and an accelerometer. A 4-channel spectrum analyzer served as a device for processing the studied signal. In addition, a theoretical calculation, considering some physical assumptions, was carried out in order to obtain a more general and accurate concept.
 RESULTS: After completing the experiment, hydrodynamic noise levels and differences for three cases were obtained. These cases are for the switched-on pump, the switched-off pump and for the pump with the removed stage. The data obtained with hydrophones (hydrodynamic noise levels) was correlated with the data obtained with accelerometers (vibration levels). As the correlated data analysis result, the sound insolation distribution over the spectrum was obtained.
 CONCLUSIONS: According to the study results, it can be concluded that the absence of one of two stages ambiguously affected on the sound-insolation properties of the pump. Moreover, no firm conclusions can be drawn about the pump operation influence on the change in its sound-insolation properties.

Particle image velocimetry in a centrifugal pump: Details of the fluid flow at different operation conditions

Centrifugal pumps are present in the daily life of human beings. They are essential to several industrial processes that transport single- and multi-phase flows with the presence of water, gases, and emulsions, for example. When pumping low-viscous liquids, the flow behavior in impellers and diffusers may affect the centrifugal pump performance. For these flows, complex structures promote instabilities and inefficiencies that may represent a waste of energetic and financial resources. In this context, this paper aims at characterizing single-phase water flows in one complete stage of a centrifugal pump to improve our understanding of the relationship between flow behavior and pump performance. For that, a transparent pump prototype was designed, manufactured and installed in a test facility, and experiments using particle image velocimetry (PIV) were conducted at different conditions. The acquired images were then processed to obtain instantaneous flow fields, from which the flow characteristics were determined. Our results indicate that the flow morphology depends on the rotational speed of the impeller and water flow rate: (i) the flow is uniform when the pump works at the best efficiency point (BEP), with streamlines aligned with the blades, and low vorticity and turbulence in the impeller; (ii) the velocity field becomes complex as the pump begins to operate at off-design conditions, away from BEP. In this case, velocity fluctuations and energy losses due to turbulence increase to higher numbers. Those results bring new insights into the problem, helping validate numerical simulations, propose mathematical models, and improve the design of new impellers.

Особенности совершенствования конструкции лопастных рабочих колес для работы на газожидкостных смесях

The article analyzes the flow gas-liquid mixture features inthe flow part of the impellers of multiphase stages pumping gas-liquid mixtures. By analogy with the coefficient specific speed of a pump for a single-phase liquid and the cavitation specific speed, a specific speed for multiphase pump stages is proposed. It is shown that the operation of blade pumps on multiphase media depends on the characteristics of the flow of the working fluid in all parts of the flow path, including the conditions at the inlet to the impeller, the flow in the blade cascade of the impeller, the guide vane, the outlet elements of the pump. Design changes in traditional blade cascades are recommended, and a new type is proposed: a multi-row cascade system.

Optimal design and numerical analysis of multi-field coupling in a screw pump under wet gas compression.

During on-site operation under wet gas compression, the volumetric efficiency of a twin-screw pump decreases sharply, the temperature in the pump rises significantly, severe vibration and even jamming can occur. To solve the problems caused by wet gas compression structurally, a method for optimizing the design of a decompression screw is proposed in this paper based on the characteristics of a twin-screw pump and screw compressor. A fluid-solid multi-field thermal-coupling scheme is used to calculate the pressure, temperature, deformation, outflow, and volumetric efficiency of a screw pump before and after optimization. The average deviation between the calculated outflow and the experimental results was no more than 5%, demonstrating the accuracy of the calculation. After optimization, the return flow between the pump stages was significantly reduced and the outflow had increased. When the pressure difference between the inlet and outlet was 1 MPa, the maximum increase was about 18%. With an increase of the gas volume fraction from 95% to 99%, the average increase of the volumetric efficiency was about 14%. The temperature rise in the chambers at all levels and the temperature difference between the inlet and outlet of the decompression screw pump were lower than those of a traditional screw pump. The deformations at the three clearances were also less than those of a traditional screw pump, which helps to avoid jamming caused by thermal expansion.

Manufacturing of Complex-Shape PM Products Consisting of Several Powder Elements

The article’s primary purpose is to give a technological assessment of manufacturing complex-shaped parts using powder metallurgy. The process is considered in the example of a complex-shaped product consisting of several elements manufactured separately from the Fe-C-Cu powder mixture and then combined into a single structure. The joining was carried out by impregnation of porous structural elements with the fusion of copper-containing material. It has been demonstrated that the infiltration process is affected by many factors: porosity of structural elements, wettability of their pore channels, fluid flowability of the infiltrating material, and other factors. The research was carried out on the mass products - centrifugal pump stages for oil production. The elements compaction was carried out on hydraulic press at a pressure of 500 MPa, which ensured the average density of the parts after sintering up to 7.8-8.4 g/cm3. During sintering and impregnation, various types of defects of the pieces were detected, which were caused by the excessive thickness of the infiltrating material, different densities of the walls, and insufficient wettability in the connection zones of the elements.The investigations have shown that manufacturing complex components by prefabricating single elements and their subsequent sintering combined with infiltration is feasible. It can be done in a chamber furnace as well as with belt sintering. However, it is necessary to carefully prepare the mold before sintering, choose the infiltrating agent, and analyse possible disadvantages.

Development and research of a multistage hydraulic gear-multiplier drive for metallurgical presses

The paper presents one of the solutions to reduce the installed power and increase efficiency of hydraulic pump drive of high power pressing equipment used in metallurgical plants. The authors have developed a multistage hydraulic drive based on a block gear-multiplier. Plungers of all cylinders form a movable block, the cylinders – a stationary one. The mode of operation (reduction, multiplication) is provided by a combination of output cylinders supplying fluid to the power cylinder by switching some of them to drain. Analysis of a four-stage drive with a three-stage multiplier gearbox is presented in comparison with a simple pump drive. A four-stage drive with two output cylinders provides a reduction gear and two multiplier stages, with which a stage of fluid supply to the power cylinder directly from the pumps (pump stage) is combined. Power and kinematic parameters of the drive were determined by the power loading during the working stroke and speed mode during the working cycle (forward (idle and working stroke) and reverse stroke). It is advisable to use a multi-stage drive with a smoothly increasing load over the entire length of the working stroke (upsetting, drawing operations). Analysis of the basic and additional combination of stages for linearly increasing power load, which was determined by the pressure at the beginning of Р0 , and the maximum pressure at the end of the working stroke Рmax was carried out. In the basic version, a gear stage (idle stroke), pump stage and two multiplier stages (working stroke) are sequentially combined. With an additional combination, the reduction stage covers idle stroke and initial part of the working stroke. Analysis was carried out under the condition of equality of pressure and power of the pumps in stages and the condition of equality of direct stroke time of the compared drives. The ratio of pump capacities was estimated. Dependences of the main parameters of the developed drive, reduction and multiplication factors were obtained. With the accepted initial data, it is possible to reduce the pressure and power of the developed drive pumps (in comparison with the simple one) by 28 – 37 % with an additional combination of stages (increases with an increase of an idle stroke). It is lower for the basic combination by 5 – 9 % (reduction is greater at lower idle stroke values). The use of an additional combination is limited by the ratio P0/Pmax ≤ 0/4.

Closed-Loop Insulin Delivery Versus Sensor-Augmented Pump Therapy in Older Adults With Type 1 Diabetes (ORACL): A Randomized, Crossover Trial.

To assess the efficacy and safety of closed-loop insulin delivery compared with sensor-augmented pump therapy among older adults with type 1 diabetes. This open-label, randomized (1:1), crossover trial compared 4 months of closed-loop versus sensor-augmented pump therapy. Eligible adults were aged ≥60 years, with type 1 diabetes (duration ≥10 years), using an insulin pump. The primary outcome was continuous glucose monitoring (CGM) time in range (TIR; 3.9-10.0 mmol/L). There were 30 participants (mean age 67 [SD 5] years), with median type 1 diabetes duration of 38 years (interquartile range [IQR] 20-47), randomized (n = 15 to each sequence); all completed the trial. The mean TIR was 75.2% (SD 6.3) during the closed-loop stage and 69.0% (9.1) during the sensor-augmented pump stage (difference of 6.2 percentage points [95% CI 4.4 to 8.0]; P < 0.0001). All prespecified CGM metrics favored closed loop over the sensor-augmented pump; benefits were greatest overnight. Closed loop reduced CGM time <3.9 mmol/L during 24 h/day by 0.5 percentage points (95% CI 0.3 to 1.1; P = 0.0005) and overnight by 0.8 percentage points (0.4 to 1.1; P < 0.0001) compared with sensor-augmented pump. There was no significant difference in HbA1c between closed-loop versus sensor-augmented pump stages (7.3% [IQR, 7.1-7.5] (56 mmol/mol [54-59]) vs. 7.5% [7.1-7.9] (59 mmol/mol [54-62]), respectively; P = 0.13). Three severe hypoglycemia events occurred during the closed-loop stage and two occurred during the sensor-augmented pump stage; no hypoglycemic events required hospitalization. One episode of diabetic ketoacidosis occurred during the sensor-augmented pump stage; no serious adverse events occurred during the closed-loop stage. Closed-loop therapy is an effective treatment option for older adults with long-duration type 1 diabetes, and no safety issues were identified. These older adults had higher TIR accompanied by less time below range during closed loop than during sensor-augmented pump therapy. Of particular clinical importance, closed loop reduced the time spent in hypoglycemic range overnight.