Pumping Conditions Research Articles

A comprehensive comparison of the in vitro hemocompatibility of extracorporeal centrifugal blood pumps.

Purpose: Blood damage has been associated with patients under temporary continuous-flow mechanical circulatory support. To evaluate the side effects caused by transit blood pumping, in vitro hemocompatibility testing for blood damage in pumps is considered a necessary reference before clinical trials. Methods: The hemocompatibility of five extracorporeal centrifugal blood pumps was investigated comprehensively, including four commercial pumps (the Abbott CentriMag, the Terumo Capiox, the Medos DP3, and the Medtronic BPX-80) and a pump in development (the magAssist MoyoAssist®). In vitro, hemolysis was tested with heparinized porcine blood at nominal operating conditions (5L/min, 160mmHg) and extreme operating conditions (1L/min, 290mmHg) using a circulation flow loop. Hematology analyses concerning the blood cell counts and the degradation of high-molecular-weight von Willebrand factor (VWF) during 6-h circulation were also evaluated. Results: Comparing the in vitro hemocompatibility of blood pumps at different operations, the blood damage was significantly more severe at extreme operating conditions than that at nominal operating conditions. The performance of the five blood pumps was arranged in different orders at these two operating conditions. The results also demonstrated superior hemocompatibility of CentriMag and MoyoAssist® at two operating conditions, with overall low blood damage at hemolysis level, blood cell counts, and degradation of high-molecular-weight VWF. It suggested that magnetic bearings have an advantage in hemocompatibility compared to the mechanical bearing of blood pumps. Conclusion: Involving multiple operating conditions of blood pumps in in vitro hemocompatibility evaluation will be helpful for clinical application. In addition, the magnetically levitated centrifugal blood pump MoyoAssist® shows great potential in the future as it demonstrated good in vitro hemocompatibility.

1.8-µm laser operation based on femtosecond-laser direct written Tm:YVO4 cladding waveguides.

In this work, we have demonstrated tunable 1.8-µm laser operation based on a Tm:YVO4 cladding waveguide fabricated by means of femtosecond laser direct writing. Benefiting from the good optical confinement of the fabricated waveguide, efficient thulium laser operation, with a maximum slope efficiency of 36%, a minimum lasing threshold of 176.8 mW, and a tunable output wavelength from 1804 to 1830nm, has been achieved in a compact package via adjusting and optimizing the pump and resonant conditions of the waveguide laser design. The lasing performance using output couplers with different reflectivity has been well studied in detail. In particular, due to the good optical confinement and relatively high optical gain of the waveguide design, efficient lasing can be obtained even without using any cavity mirrors, thereby opening up new possibilities for compact and integrated mid-infrared laser sources.

Condition Monitoring of an Axial Piston Pump on a Mini Excavator

The focus of this paper is to show the process of developing a condition monitoring system for an axial piston pump mounted on a mini excavator. This work outlines some previous condition monitoring work on axial piston pumps but addresses the lack of research conducted on mobile hydraulics. The valve plate of the pump is chosen as a case study to demonstrate varying degrees of wear and damage to represent healthy and faulty pump conditions. The wear and damage of these valve plates is measured using an optical profilometer, and efficiency measurements were conducted to characterize the fault levels. Once the faults were characterized, the mini excavator was introduced and instrumented to demonstrate what parameters were being considered. Next, three duty cycles were introduced: controlled, digging, and different operator cycles. The controlled cycles are a very repeatable condition that eliminated the need of an operator. The digging cycle was more of a realistic cycle where an operator dug into a loose pile of soil. The different operator cycle is the same as the digging cycle, but a different operator was employed. The sensors that proved to be the most useful in detecting valve plate faults were the drain pressure, pump port pressures, engine speed, and pump displacement. Fault detectability accuracies of 100% were achievable under the controlled cycle utilizing the Fine KNN classification machine learning algorithm. The digging cycle could achieve a fault detection accuracy of 93.6% using the same algorithm and sensors. Finally, the cross-compatibility between a model trained under once cycle and using data from another cycle as an input was investigated. This study showed that a model trained under the controlled duty cycle does not give reliable and accurate fault detectability for data run in a digging cycle, below 60% accuracies. However, cross-compatibility may be achievable if more extreme faults are present. This work concluded by recommending a diagnostic function for mobile machines to perform a preprogrammed operation to reliably and accurately detect pump faults.

Ammonia masers towards G 358.931−0.030

ABSTRACT We report the detection of ammonia masers in the non-metastable (6, 3), (7, 5), and (6, 5) transitions; the latter being the first unambiguous maser detection of that transition ever made. Our observations include the first very long baseline interferometry detection of ammonia maser emission, which allowed effective constraining of the (6, 5) maser brightness temperature. The masers were detected towards G 358.931−0.030, a site of 6.7-GHz class II methanol maser emission that was recently reported to be undergoing a period of flaring activity. These ammonia masers appear to be flaring contemporaneously with the class II methanol masers during the accretion burst event of G 358.931−0.030. This newly detected site of ammonia maser emission is only the 12th such site discovered in the Milky Way. We also report the results of an investigation into the maser pumping conditions, for all three detected masing transitions, through radiative transfer calculations constrained by our observational data. These calculations support the hypothesis that the ammonia (6, 5) maser transition is excited through high colour temperature infrared emission, with the (6, 5) and (7, 5) transition line ratio implying dust temperatures >400 K. Additionally, we detect significant linearly polarized emission from the ammonia (6, 3) maser line. Alongside our observational and radiative transfer calculation results, we also report newly derived rest frequencies for the ammonia (6, 3) and (6, 5) transitions.

Numerical simulations of the flow of a kerosene gel: Effects of thixotropy and shear-thinning

The ability of a gel to act like a solid-like material at rest and flow like a liquid when sheared can be very useful in propulsion system. Numerical simulation of the flow of gel fuels can be used as a reference to assist experimental studies and applications of these materials. Non-linear rheological effects such as shear thinning, yield stress, thixotropy and viscoelasticity can create difficulties in the formulation and in the numerical investigations. This paper uses a thixotropic shear-thinning constitutive relationship while using a second-order kinetic equation for the structural parameter, where the Carreau–Yasuda model is used for a 5% organic kerosene gel. We study the simple shear flow to verify the accuracy of the numerical method, and the impact of the constitutive parameters on the apparent viscosity as a function of shear rate. To look at the thixotropic flow in more complex flows, we initially study the pipe flow of an organic kerosene gel for different pumping conditions. After performing a parametric study, we find that the thixotropy of the gel strongly affects the shear history, that is, the nonuniform aging distribution. The destruction of the microstructure can be accelerated by adjusting the flow intensity and the model parameters, but it seems that it is difficult to arrive at the equilibrium state within the time scale of the propulsion system; this poses a challenge to the design of the system.

Solar photovoltaic water pump performance optimization by using response surface methodology

AbstractThe constant depletion of the existing energy sources and their environmental effects have generated interest in employing renewable energy sources to power water pumping systems, such as solar‐photovoltaic. The research addresses the optimal photovoltaic (PV) power output, solar radiation, operating head, and tilt angle for maximum solar energy used to capture more solar radiation for solar water pumping for irrigation purposes. In order to get the best performance from the solar PV water pump, such as discharge (Q), hydraulic power (PH), pump efficiency (ήp), and overall efficiency (ήo), the design of experiments‐based response surface methodology was implemented in this work. The data required for the RSM model were obtained from the experimental work performed at location 28.67° N, 77.21° E, Delhi, India. The experiments performed at five different ranges of input variables PV power output (4000, 4250, 4500, 4750, and 5000 W), Solar radiation (200, 350, 500, 650, and 800 W/m2), operating head (15, 20, 25, 30, and 35 m) Tilt angle (5°, 10°, 15°, 20°, and 25°). The best output parameters The best conditions for a solar PV water pump (16.8 m3/h discharge, 1.85 kW hydraulic power, 81.15% pump efficiency, and 16.12% overall efficiency) were discovered to be Po 5000 W, SA 260 W/m2, Head 35 m, and TA 19°. The predicted result was validated using an RSM‐based solution, and the error% was found to be within acceptable limits (>5%). The desirability 0.963 of the model was indicating the good solution.

Artificial Neural Network-Based Fault Detection System with Residual Analysis Approach on Centrifugal Pump: A Case Study

Centrifugal pump is an instrument that is widely used in industry and has become the main driving component. A detection system is often needed to prevent damage to these pumps because they can interfere with the overall system performance. Therefore, this study discussed the development of a fault detection system for two centrifugal pump units, namely the Medium Pressure Oil Pump (MPOP) and the Water Injection Pump (WIP). In detecting the operating conditions of the pump, it was used a residual feature extraction technique in the time domain with a statistical approach. Residual was generated by using three sub-systems of a pumping system. Each sub-system was modeled using an artificial neural network with feedforward-back propagation architecture. Based on the feature values, the classifier was designed to classify pump conditions. Then the proposed fault detection system was applied in a condition monitoring system scheme. The test results (using data from the field) show that the fault detection system has an accuracy of 91.67% for MPOP and 94.8% for WIP cases. Meanwhile, the fault detection system has an accuracy above 99% during online monitoring simulations.

Terahertz Metasurface Modulators Based on Photosensitive Silicon

AbstractMetasurfaces solve the lack of materials in the terahertz (THz) band and control precisely the amplitude, phase, polarization, and transmission characteristics of THz waves, providing an effective way to realize THz functional devices. This article focuses on the design of THz metasurface modulators with a unit structure consisting of metal square rings, including resonance frequency, phase, and amplitude modulators. By embedding photosensitive semiconductor silicon (Si) in the unit structure, the unit structure is built from meta‐atom to molecularization model under the optical pumping condition, and the resonance frequencies are switched between high and low frequencies. The resonance frequency switchable characteristic is demonstrated using the equivalent LC oscillation circuit model, and the theoretical calculation results agree well with the simulations. Through theoretical calculations, the modulators achieve ultrafast switching times of less than 0.141 ps by the optical pumps, which have significant advantages in ultrafast THz modulators. By continuing to change the embedded position of the silicon in the unit structure, not only is a wide range of THz phase modulation achieved, but also multilevel modulation of the phase is realized. It is found that there is a strong relationship between the modulation depth and phase variation of THz waves, and a reasonable analysis is given. Further the amplitude modulator with a larger modulation depth (MD) is developed, and when the conductivity of photosensitive semiconductor silicon (σSi) reaches 2.5 × 106 S m−1, return loss (RL) is ≈0 dB, and the maximum MD reaches ≈100%; in order to gain insight into the nature of modulation, the modulation mechanism of THz waves under optical pumping conditions is analyzed. In addition, graphene‐based THz metasurface amplitude modulators are designed. When the depth of amplitude modulation is achieved by bias voltage modulation of the Fermi energy level of graphene, the maximum modulation amplitude is 23.42 dB, with a minimal modulation accuracy of 0.05 THz eV−1. In the article, the designed modulators have extremely excellent modulation performance. It has great potential applications in silicon‐based THz photonic devices, ultrahigh frequency electronic devices, high sensitivity sensors, and high‐precision imaging.

Investigation of a centrifugal pump for energy loss due to clearance thickness while pumping different viscosity oils

The clearance between the stationary volute and rotating impeller of a centrifugal pump is crucial; however, it affects the internal flow and deteriorates the pump performance. This study performed a flow investigation through a numerical simulation to understand the effect of clearance and pumping fluid viscosity under the design and off-design conditions of a centrifugal pump. Numerical simulations were conducted by solving unsteady Reynolds-averaged Navier-Stokes (URANS) equations and validated using experimental results. Five three-dimensional centrifugal pump flow domains were created, by varying the clearance thickness, and simulated with three different fluid properties. Consequently, the numerical simulation results aided in understanding the internal flow pattern and estimating energy loss due to disk friction and leakage through the clearance. It was found that the disk friction and leakage losses, which cause secondary losses in the pump, were highly affected by the fluid properties and clearance thickness. The clearance thickness drastically affected both the volumetric and hydraulic efficiencies to leakage; however, beyond a particular value, it became less significant. Furthermore, the viscous oils caused a high disk friction loss; however, the leakage loss was less affected by the clearance thickness.

Solving subsurface flow toward wells in layered soils using hybrid method of fundamental solutions

In this article, numerical solutions of three–dimensional subsurface flow toward wells in layered soils using a hybrid method of fundamental solutions is presented. The proposed boundary–type meshless method is based on using the superposition of the fundamental solution and general solution of governing equations from the subsurface flow and the radial flow to a well, respectively. To deal with the subsurface flow in a layered aquifer system, the method of domain decomposition is employed in which the continuity conditions of head and flux at the interface between layers can be satisfied. The validation of the proposed approach is conducted comparing with exact solutions and the USGS's modular hydrologic model, MODFLOW. The approach is then applied to investigate the leakage of the aquifer under pumping conditions for a real layered aquifer system in Taiwan. Results illustrate that the proposed approach exhibits high accuracy over the mesh–based numerical technique. We also demonstrate that the boundary–type meshless method is beneficial for the boundary discretization technique and reduces the computational complexity.

Detailed Thermo-Economic Assessment of a Heat Pump for Industrial Applications

Heat pump electricity costs grow with a power relationship as the evaporator temperature in the cycle decreases. The thermo-economic study of a solar thermal-assisted heat pump and storage system determines the minimum cost of the coupled system for an evaporator temperature. Through two case studies, one for the dairy industry and the other for 2G bioethanol production, the coupled system was evaluated for different temperatures in the evaporator, from 30 to 90 °C, and the minimum cost of the coupled system was determined. For the dairy industry, the lowest levelized total cost of a heat pump (LCOE) at 50 °C is 0.0799 USD/kWh. The evaluation carried out allowed us to determine the best operating conditions of the heat pump: 50 °C in the evaporator, COP = 4.2, and the work of the compressor of 211.3 kW. In the case of 2G anhydrous bioethanol production, the lowest levelized energy cost is 0.0409 USD/kWh for an evaporator temperature of 30 °C and a payback of 1.8 years. The study carried out makes it possible to guarantee the supply of the heat load at the operating temperature of the process and determines the impact of environmental conditions on the cost of the heat pump assisted with solar thermal energy.

Performance analysis and dynamic characteristics of a proton exchange membrane fuel cell with dual recirculation pumps for air-free applications

The exhaust gas recirculation strategy is usually used to ensure the stable and continuous operation of hydrogen–oxygen proton exchange membrane fuel cells (H2/O2 PEMFCs). However, few studies have focused on how the operating conditions of recirculation pumps affect the dynamic characteristics and performance of H2/O2 PEMFCs. In this study, a PEMFC system with dual anodic and cathodic gas recirculation pumps is investigated and the dynamic performance of the stack is also studied. The pump mode is proven to alleviate water flooding and enhance the stack performance effectively. When the rotating speed of recirculation pump reaches 5000 revolutions per minute, it can increase the gas flow rate inside the stack channel to 0.44 m s−1 (equivalent to a stoichiometric ratio of 2.85), which terminates the low-velocity flow inside the H2/O2 PEMFC and facilitates the removal of liquid water inside the stack. Moreover, the voltage undershoot during the current loading process is moderated by increasing the intake flow rate of the fuel gas through the pump-based recirculation subsystem, which could effectively solve the gas shortage problem of the stack. The presented findings are expected to provide more insights into the impact of the gas recirculation strategy on the performance of high-power stacks.

Interpreting Concentrations Sampled in Long-Screened Wells with Borehole Flow: An Inverse Modeling Approach.

New approaches are needed to assess contaminant mass based on samples from long-screened wells and open boreholes (LSW&OB). The interpretation of concentration samples collected in LSW&OB is complicated in the presence of vertical flow within the well. In the absence of pumping (i.e., ambient conditions), the well provides a conduit for flow to occur between aquifer layers or fractures as a result of head differences. Under pumping conditions, vertical borehole flow may vary with depth depending on far-field heads and hydraulic conductivity; furthermore, if pumping fails to overcome ambient gradients, outflow from the well to the aquifer may occur. Concentration samples thus represent flow-weighted averages of formation concentrations, but the averaging process is commonly unknown or difficult to identify. Recognition of the importance of borehole flow has motivated the use of multi-level wells, packers, and well liners; however, LSW&OB remain common for numerous reasons, including cost, multi-purpose design requirements (e.g., pump-and-treat, water supply), logging, and installation of instrumentation. Here, we present a simple analytical model for flow and transport within a well and interaction with the surrounding aquifer. We formulate an inverse problem to estimate formation concentration based on sampled concentrations and data from flowmeter logs. The approach is demonstrated using synthetic examples. Our results (1) underscore the importance of interpreting sampled concentrations within the context of hydraulic conditions and aquifer/well exchange; (2) demonstrate the value of flowmeter measurements for this purpose; and (3) point to the potential of the new inverse approach to better interpret results from samples collected in LSW&OB.

Calculation of Volume of Hot Water Storage Tank in Air Source Heat Pump System

Air source heat pump integrated with hot water storage tank may enhance the efficiency of heating, and the volume of hot water storage tank is closely related to the thermal efficiency of the hot water system. Referring to the relevant formulas of building water supply and drainage design standards, this paper simulates the operation conditions of heat pump, and combined with the measured annual data of hot water using in a hospital, systematically discusses the adaptability of heat pump water production and seasonal hot water usage, as well as the actual regulating volume of hot water storage tank. Assumed the heat pump is altered by the working condition of the vernal equinox, the daily storage and discharge of the hot water tank can be accurately calculated, the hot water tank should charge 2.94 times of average hourly water yield of air pump during the peak water usage period. considering the safety and economy of the air source heat pump system, it is strongly recommended that the volume of hot water storage tank can be designed as the 5 ~ 6 times of hourly average water yield of air source heat pump, which can meet the usage of hot water for most of the time and it is inspected under various accidental conditions.

Optimal capacity of variable-speed pumped storage for wind power consumption based on double-layer stochastic programming

Configuring a certain capacity of energy storage for the power system can effectively improve the reliability of the power supply and the level of wind power consumption. This paper takes pumped storage investment cost and wind power consumption demand as the optimization goal, realizes the coordinated operation of pumped storage units and thermal power units, and considers the uncertainty of wind power and load, the multi-timescale characteristics of different types of units and load demand response, and establishes a multi-timescale pumped storage capacity optimization model based on stochastic programming. The model consists of inner and outer layers. The outer layer is investment decision-making, which decides the allocation of pumped storage capacity. The inner layer is for optimization decision-making, and the system optimization operation is carried out in three stages: day-ahead short-term optimization, intraday ultra short-term optimization, and real-time optimization. An example of a typical scenario is established, and the planning results verify the effectiveness of the proposed model and method. The thermal-wind-hydro power system's total cost decreases first and then increases with the increase in the installed capacity of the pumped storage, and the curtailment rate gradually decreases. The total cost increases faster when the pumped-storage installed capacity is larger than optimal. For a pumped-storage power station of the same capacity, variable-speed pumped storage is better than fixed speed pumped storage in reducing the wind curtailment rate. The main reason is that its output is continuously adjustable under the condition of the variable-speed water pump, which is especially suitable for energy storage at night when wind power is high.

Ascertaining the Si-substitution on the tribo-corrosion behaviors of Ti3AlC2 in molten Solar Salt

As a promising working medium for thermal transportation, nitrate-based molten salts are widely adopted for current concentrating solar power (CSP) plants. However, their corrosive nature also brings severe safety hazards to the system, e.g., the impellers and cover in molten salt pumps. To study the potential application of MAX ceramics as a proactive coating for these parts, tribo-corrosion behaviors of Ti3AlC2 and its Si-substituted analogs against GCr15 steels are evaluated in the molten Solar Salt at 300 °C to simulate the operating condition of the cold-salt pump. The Si-substituted MAXs present higher anti-wear performance than pristine Ti3AlC2. With an optimal composition of Ti3Al0.6Si0.4C2, about a 25% reduction in mean wear rate to that of Ti3AlC2 is achieved. Through a comprehensive analysis of the morphological and chemical states of both tribo-corroded and static corroded surface, the effects of Si on the tribo-corrosion behaviors of Ti3AlC2 is illuminated. The enhanced performance after Si addition is ascribed to the facilitated formation of aluminosilicates as corrosion products on the surface, which act as a lubricant as well as impeding the dissolution of Al into the molten Solar Salt.

Determination of Exploitable Coefficient of Coral Island Freshwater Lens Considering the Integrated Effects of Lens Growth and Contraction

Groundwater on small coral islands (so-called freshwater lens) is an important water resource for residents and local ecosystems. However, an overexploitation of it may induce a contamination by saltwater. In this paper, we strive to determine the exploitable coefficient of the freshwater lens considering the integrated effects of lens growth and contraction and examine the impacts of well layout schemes on the evolution of the freshwater lens. For this purpose, a numerical model is setup to simulate the saltwater upconing and recovery process under pumping conditions during different evolution stages. Our results show that long-term and higher intensity pumping activities are suggested to be conducted at the latter stage of the lens evolution. Meanwhile, the seasonal contraction of the freshwater lens caused by the seasonal variation in rainfall is characterized by a quicker response of center thickness than maximum thickness of the lens, which further impacts the pumping intensity. The results also indicate that the exploitable coefficient (ρ) of the freshwater lens in small coral island is generally smaller than that in inland areas, ranging from 0.09 to 0.37 under different well layout schemes. Additionally, it is also affected by the uncertainty of hydrogeological parameters. Finally, a safe exploitable coefficient is proposed under the most unfavorable parameter combination for the studied island. The study has important implications for the protection and sustainable exploitation of subsurface freshwater resources on island.

Transient Hydrodynamic Behavior of a Pump as Turbine with Varying Rotating Speed

The working condition of a centrifugal pump as a turbine (PAT) is often unsteady. The rotating speed of a PAT constantly varies as the flow and load change, resulting in transient hydrodynamic behaviors between different working conditions. During the transition, the PAT undergoes a severe change in performance and complicated internal flow structures. In previous work, the fixed rotating speed of a PAT was mostly considered using computational fluid dynamics. To investigate the transient behavior of a PAT, relevant simulation tools are developed to depict transient flow conditions, and the corresponding transient speed of the impeller is calculated. Both large and small fluctuation transitions are simulated for the practical application of the PAT. The simulated results are first verified by experiments. The results show that the rotating speed significantly affects the performance and stability of the PAT. The rapid increment in flow rate and rotating speed lead to large energy dissipation in the internal flow field of the PAT. The range of high efficiency of the PAT expands and migrates to the high flow rate range. The efficiency in the transition condition started a cyclic growth after the flow reached 60 m3/h, and it reached a peak at around 80 m3/h, which was about 5% lower than the calculated value in a quasi-steady state. In the range of high rotating speeds, the rotating speed of the impeller and the operational stability are sensitive to flow fluctuation. The internal flow fields during transition conditions are analyzed as well. The obtained results can be utilized as a reference for studying the hydrodynamic characteristics and stability of fluid machinery in the transition under transient flow conditions.

Ultralow-threshold quasi-CW lasing from FAPbBr3 perovskite first-order DFB laser

Metal halide perovskites are emerging materials for integrated photonics. Here we report a quasi-CW pumped ultra-low ASE/lasing threshold formamidinium lead bromide (FAPbBr3) laser. The laser achieved stable lasing at 555 nm with a full width at half maximum (FWHM) of 0.6 nm, showing a low lasing threshold of 22.6 μJ cm−2 under 3.5 nanosecond quasi-CW excitation at room temperature. The material also showed an ultra-low ASE threshold of 46 μJ cm−2 under the same pumping condition. Through polymer doping, we showed that the material’s performance can be improved by increasing bimolecular recombination rate with reduced grain size.

PROPOSED DESIGN CRITERIA FOR A BILGE PUMPING SYSTEM: A CASE STUDY OF LARGE BULK CARRIER

In this study, the bilge pumping performance was investigated using the actual bilge pumping arrangement of a 180K class bulk carrier, and it was assumed that the No. 1 cargo hold was fully flooded. As a result of the calculation, the mean water velocity at bilge main could not satisfy the 2m/s requirement while discharging all the accumulated water from the flooded No. 1 cargo hold with the actual arrangement installed on the 180K class bulk carrier. As a result of the calculation by modified arrangement, it was found that the 2 m/s requirement could be satisfied when a pipe smaller than the required internal diameter according to the rule requirements of classification societies was applied to the bilge main under the same pump conditions. In addition, it was found that the flow rate of the pump should be increased by at least 40% when piping acceptable for the rule requirements of classification societies was applied to the bilge main. The bilge pumping system of 180K bulk carriers may be similar for every ship, and in our opinion, urgent modifications and repair are necessary for consideration of the characteristics of bulk carriers with a relatively high risk of flooding. According to the GBS structure, the rule requirements of classification societies regarding bilge pumping system should comply with the intended purpose of SOLAS Regulation II-1/35-1. It is proposed to revise SOLAS Regulation II-1/35-1 by applying the concept of Performance-Based Standard (PBS) in order to secure the performance of the bilge pumping system by applying a pipe smaller than the required internal diameter according to the rule requirement of classification societies. In particular, it is proposed that SOALS Regulation II-1/35-1.3.9, the requirement for the required internal diameter of bilge main, should be deleted so that any size pipe can be used if the bilge pumping performance can satisfy the 2 m/s requirement. Finally, “2 m/s Criterion” is proposed only design criteria to fulfill the intended purpose of the 2 m/s requirement of SOLAS.