Additionally, the industry is seeing an increased use of closed loop systems and a drive for less expensive, but consequently more shallow cooling tower basins. When air is present in the water it adds a damping effect to the collapsing bubbles of cavitating regions, thus reducing cavitation damage. Air & Dirt Elimination Equipment. If you hear a squeal when the pump starts, it is usually the seal faces running dry. These processes are evaluated using a hydraulic model consisting of a long rectangular tunnel with a bottom slope larger than the critical slope. In the stepped spillway simulation shown above, the turbulent boundary layer grows from the channel wall as the flow moves over the spillway crest. I have witnessed a few recessed impeller pumps handle up to 24 percent air. Depending on the tunnel length, both air entrainment and air detrainment processes are significant. Nadaoka, Kino & Koyano (1989) showed that large-scale eddy motion in breaking waves is responsible for the excessive mass flux and enhanced momentum transport. Not sure if you have air entrainment? 1 Forms of air-entrainment on a spillway ....... 9. How to eliminate wet well maintenance & premature wear of pumps. Water naturally has some air entrainment, a fact that fish depend on to breathe. Air bubble distribution in still water has been studied previously [14, 15]. A thorough root cause analysis in addition to education regarding the matter will show air entrainment is a much more common pump ailment than initially believed. Nicole George and Asma Motlani discuss Eaton's response to COVID-19. 2 Large gas bubble in a liquid .......... 10 3 Terminal velocity of air bubbles in filtered or distilled water as a function of bubble size, Haberman and Morton 126. Spillway structures must be designed to handle a wide range of operating conditions. Gain understanding of the impact or water streams depending on the size of the volume that the fire and hot gases are in. The air entrainment in a free surface mainly results from the development of small turbulent structures in the air-water free surface, which have the capacity to trap air carrying it to the core of the flow. In flooded suction situations, if the pump does become air bound, you can stop the pump and allow the bubble to pass through and escape the pump and then restart the pump. Air entrainment The air entrainment appears in the transient ow in closed pipes not completely lled : the liquid ow (as well as the air ow) is free surface. Vibration is frequently caused by the unbalanced hydraulic loads on the impeller due to partial air blockage. One method to deal with entrainment is to open the clearances of the pump beyond normal recommendations. In recent months, I have been involved in four cases of misunderstood pump performance where air entrainment was determined to be the main culprit. Many operators have success with doubling the clearance. Large amounts of air (over about five to six percent) can collect in the eye of the impeller and cause loss of flow and possibly air binding. You can look up your flow rate and pipe size to determine the fluid velocity in the “Cameron Hydraulic Data Book” or “Cranes Technical Publication 410.”. But if there is air at the eye, it will likely remain there. ... Flow water … This is especially important when designing infrastructure for municipal water and wastewater transport, such as the two drop shaft models below. Then, the use of a water system to model air entrainment in steel pouring is analyzed. The formula is: To illustrate this with an example, let’s find the air:O 2 ratio for 70% FIO 2: This means that for every 1 liter set on the oxygen flowmeter, 0.6 liters of air is entrained. The entrance of air in the flow, through the free surface, is defined by an equilibrium condition between the The Southern African Institute of Mining and Metallurgy Platinum 2012. Often times, operators believe that a pump problem is cavitation when the real culprit is air entrainment. The unvented air also collects in the seal chamber (standard stuffing box configurations) to create air pockets that cause dry running of the mechanical seals. Bottom outlets involve high-velocity air-water flow. In drinking water this can be as high as 2 percent. Additives, such as surfactants and dyes. There is a difference between natural air entrainment and deliberate air injection. When entrainining air the effect is applied through the use of air injectors and venturi devices. Top centerline discharge designs like American National Standards Institute (ANSI) pumps are designed to be self-venting. Bubbles are entrained locally at the intersection of the impinging jet with the surrounding waters. This issue is a rising trend and has become more common for several reasons. Air entrainment is one of the major contributors to broken pump shafts because of the hydraulic surging and axial shuttling that occurs from a pump that is stalled one … He is the general manager for Summit Pump Inc. and the principal of MaDDog Pump Consultants LLC. Examples of localised aeration include air entrainment by plunging water jet and at hydraulic jump. Disc friction pumps have great success handling air entrainment (reportedly) of up to 70 percent, with the disadvantage of high cost. of entrained air in a pipeline varies depending on the residence times, froth stability, presence of water sprays, net downward slurry velocity, the size of the bubbles, and also the means in which the slurry enters the holding tank . The same pressure differential that causes cavitation can also exacerbate entrained-air problems. may lead to two-phase ows for transition : free surface ows !pressurized ows. ..... 5 Figure 2.2 – Surface methods to treat the interface. As air bubbles become trapped at the pump suction, they block the fluid flow, and the pump performance will drop off. Nuclear Regulatory Commission report # NRC-DR-09-0270 November, 2009, by Allan R. Budris It is also common to use a self-primer pump in applications above 18 percent air entrainment. References Centrifugal Pumps 2nd edition, Igor J. Karassik and Terry McGuire A less frequent and perhaps more desperate approach is to add an inducer (attached to the impeller); this route often requires outside technical or engineering assistance. This in turn can cause the pressures on the spillway surface to become low enough to cause cavitation. First of all, all water contains dissolved oxygen. Missed your issue of Pumps & Systems because you are not at work? If you look at the components that make up the formula for NPSH available, you can determine action steps to potentially reduce the effects. If you raise the static suction head or cool the liquid, it should reduce the effects. Air entrainment may sound like and be confused with cavitation in an operating pump. Influenced by diameter of jet orifice (restriction), and size of entrainment port Suction Side Problems-Gas Entrainment (Centrifugal Pumps Handbook) James H. Ingram For most simple systems using Newtonion fluids (no slurries) I suggest four to five minutes transient time as a respectable design-versus-cost compromise. Jet pumps are also used to circulate reactor coolant in several designs of boiling water reactors . This is called Air Entrainment and occurs randomly in public water supply distribution systems. So, operating the pump to the left side of the curve can lead to air binding blockages. In recent years, there is a financially driven trend to reduce the size of suction supply tanks. The air entrainment model offers the option to include buoyancy and bulking in the output, meaning that areas of variable density flows can be accurately represented. Entrained air is often considered detrimental to pump performance and life. Cavitation and entrained air are related issues. The pump will be less efficient, but it will operate. Cavitation is highly detrimental to the strength of the structure and can lead to catastrophic failure. FLOW-3D and TruVOF are registered trademarks of Flow Science, Inc. in the USA and other countries. Further, the presence of air within the boundary layer reduces the shear stress between the flow layers and hence the shear force .Also it may prevent or reduce the damage caused by cavitation . Also, the actual impeller size, suction eye diameter, speed of the pump and the number of vanes will be factors. FLOW-3D‘s air entrainment model is used to determine the concentrations of air entrained from spillways that is released into a river downstream. The schematic diagram is on the file attached. Air Entrainment In Flowing Liquid Pipes - posted in Industrial Professionals: Hi Just wondering if someone can help me out with a little fluid flow problem. Air entrainment even at values as low as 2 to 4 percent will cause increased pump vibration, which leads directly to premature bearing failure. In general, for every type of centrifugal pump and impeller design, there are different results when pumping fluids with entrained air. FLOW-3D‘s air entrainment model is a powerful tool that simulates the entrainment of undissolved gas bubbles at free surfaces. When air is entrained into water, it can help sustain the growth of microorganisms and support the survival of healthy fish populations. I didn’t plan on writing about air entrainment again, but recent field issues pushed me to revisit the subject. Or if you slow the pump down or throttle back on the discharge, the symptoms should reduce. The proper level of submergence is critical, and vortexing is the most common source of undesired air introduced into pump systems. Entraining air is a means of reducing the likelihood of cavitation. Pumps & Systems, January 2016, Cavitation vs. Air Entrainment, Dr. Lev Nelik (read it here). Dry/non-lubricated seal face operation contributes to shortened life and ultimate failure. In a conduit flowing partially full, water surface disturbances lead to air entrainment and the drag of the water surface generates an air flow that must be accounted for. These air-entrained agents in concrete generate millions of non-coalescing air bubbles, These air bubbles act as flexible ball bearings and will modify the properties of plastic concrete regarding workability, segregation, bleeding, and finishing quality of concrete. Learn the basics of wear components and their role in system operation in this white paper. The number of volutes in the casing will also play a major role. Understand where water goes and how air flows during interior and exterior/interior fire attack utilizing common procedures and what that means to fire dynamics. In the first part, a review is presented of the physical processes and parameters important in air entrainment in free-surface flows. When you vent the casing on an operating pump, you may get some air out and then fluid. Submergence charts are another handy tool, but you need to have one foot of submergence for every foot of suction side fluid velocity. Air entrainment in very small amounts can actually be a good thing. It is a difficult task to give a simple answer of what will or will not work in determining inconvenient yet accurate results. Flow kinematics and air entrainment under spilling breaking waves 882 A15-3 transporting momentum and affecting the overall dynamics. The bubbles may change in size but typically do not collapse when running through the pump. Learn how early adopters are benefitting from emerging technology as well as the impact COVID-19 has had on water management. The main pipe is 150NB and the Air, anti-siphon pipe is 25NB. At 4 percent, it will reduce pump performance by 40 percent and at 10 percent, it will likely stall the pump altogether. Air entrainment is one of the major contributors to broken pump shafts because of the hydraulic surging and axial shuttling that occurs from a pump that is stalled one second (no load) and pumping the next (full load) in an endless and unintended “go to” loop of stress fatigue cycling. Find out which technologies work best to keep centrifugal pumps from causing downtime in critical industrial processes. Improper design of suction pipe geometry/arrangement with unvented high points that will not dissipate or reduce the air and gases present. Jim Elsey is a mechanical engineer who has focused on rotating equipment design and applications for the military and several large original equipment manufacturers for 43 years in most industrial markets around the world. Typically, a double volute will work better than a single volute pump. Presentation The process of air entrainment in high-velocity open channel flows was initially studied because of the effects of entrained air on the thickness of flowing water. I have witnessed many occurrences where the operator did not properly vent the system or vent the high points, casings or stuffing boxes. A ir separators are used to separate entrained air in water through forced flow patterns. Reduce or eliminate the air to prevent problems with shaft failures and premature bearing and mechanical seal failures. AIR-WATER FLOW IN HYDRAULIC STRUCTURES UNITED STATES DEPARTMENT OF THE INTERIOR WATER AND POWER RESOURCES SERVICE . Companies dealt with fallout in many ways, but show optimism if reliable vaccine arrives. As the single bubble moves downstream, its longitudinal velocity is approximately the same as that of the water flow surrounding it, while its vertical velocity for rising and penetration increases with the increase in water flow velocity. A diffuser pump (think volutes of a high multiple) will work better than a simple volute style pump. Demand in China appears to have already returned to pre-COVID-19 levels. On closed systems and systems with returns or air entrained supplies, the tanks can be designed and built to present a “torturous path” for the fluid. Improper submergence creates the conditions for the vortexing phenomena, which introduces large quantities of air leading to pump damage in a short period of time. If the velocities in the spillway are sufficiently high, then aeration devices should be added to entrain air and reduce cavitation. When air is present in the water it adds a damping effect to the collapsing bubbles of cavitating regions, thus reducing cavitation damage. The rotating impeller acts as a centrifuge where the heavier fluid is expelled outwards while the lighter air remains at the center where it also blocks the impeller suction eye. may cause severe damage due to the pressure surge. This webinar focuses on how to simulate air entrainment processes in FLOW-3D. Minimum flow rates will also play a major role when managing air entrainment issues. TITLE AND SUBTITLE ... entrainment and air-demand in both open- and closed-conduit flows. Solving the World’s Toughest CFD Problems. Follow these steps to halt the secret destroyer of pumps, Read Jim Elsey's "Most Common Reasons for Air Entrainment in Pump Systems", To read other articles in the 'Common Pumping Mistakes' column, go. When the cool ground water is pumped from the well into the treatment plant, distribution system or storage facility, Just because you fail to see vortexing does not mean that it is not occurring. If this is the case, then the area should be as far as possible from the pump suction. However, air entrainment even in amounts of 1 to 2 percent will cause pump performance to drop dramatically. Some operators have incremental success using a larger impeller than the hydraulic conditions call for (based on zero air entrainment). Oil and gas industries are working to pump more dual phase fluids at the wellhead and downstream, and wastewater treatment plants are using more dissolved air flotation (DAF) systems. A system of weirs, barriers and baffles can be engineered to present the maximum amount of hold time/ transient time for air bubble elimination/mitigation. Properly fill and vent the system initially. Also, don't forget to read Jim Elsey's "Most Common Reasons for Air Entrainment in Pump Systems" here. 11. Automatic air release valves are not maintained. If the submergence is insufficient, you can add vortex barriers, raise the height of the liquid level or increase the size of the suction line opening effectively reducing the fluid velocity. The difference is that cavitation is the formation and subsequent collapse of vapor bubbles, while air entrainment is simply air bubbles that were in the process stream before the pump and will remain there after the pump. However, dissolved gas at supersaturated conditions has been identified as a water quality issue which negatively affects aquatic organisms. The higher the air entrainment percentage the more flow that will be required to push or sweep the air bubbles pass the impeller eye (see Figure 1). The total volume flow of air equals the sum of the air that is insufflated into the flow and that which flows above the water surface. Lockdowns had big effect on company business. The purpose of a vented external flow control is to inject additional air into the waste stream entering a grease interceptor to enhance separation efficiency. Free-surface flow interface and air-entrainment modelling using OpenFOAMTM LIST OF FIGURES Pedro Miguel Borges Lopes v LIST OF FIGURES Figure 2.1 – Vertical structure of air-water flows. Doing more with less is a necessity going forward while navigating business during a pandemic. This paper presents an analysis of water modeling of steel pouring to study (1) air entrainment and (2) filter effectiveness to remove reoxidation inclusions. Finally, we propose in section 5 some numerical simulation to focus on the role of the air entrainment on the free surface fluid flow. 2 A two-layer water/air … Air & dirt separators are designed to eliminate entrained air and separate debris associated with start-up and maintenance of any hydronic system. Like diagnosing some diseases in the medical field, the process of eliminating other reasons that could be causing the symptoms is how the conclusion is formed. Weirs and/or divider barriers should be installed. 4. COPYRIGHT 2000 – 2021, FLOW SCIENCE, INC. ALL RIGHTS RESERVED. Increases in air entrainment more than 1.5 to 2 percent will have immediate and deleterious effects on the pump from both an immediate performance aspect and a mechanical aspect in a protracted way. Air bubble is a common form of air entrainment in water. Further, the chemical process industry (CPI) and general industrial plants have renewed and are increasing financial pressure to design systems with smaller “footprints.” Filed under the heading of “unintended consequences” is the result of shorter and smaller storage tanks and process vessels. You cannot vent an operating pump. The specific speed (NS) and suction specific speed (NSS) are both relevant factors. Typically, impellers of NS higher than 3,000 will perform better than impellers below 3,000. Many users will inject up to 0.9 percent air to cushion the effects of cavitation. The flow rate will decrease, the developed head will drop off, and the efficiency will decline. You can conduct some simple tests that are covered by the Hydraulic Institute (HI). In general, you capture samples and analyze them. This webinar focuses on how to simulate air entrainment processes in FLOW-3D.This includes details into the theory behind our air entrainment and drift-flux models and a demonstration of how to set up a basic air entrainment simulation in FLOW-3D.We finish up by discussing best practices and approaches for these types of simulations. Improper addition of make-up fluid — Air may be entrained in the fluid if splashing occurs when fluid is added, or if the added fluid causes increased agitation in the reservoir. © Copyright Cahaba Media Group, Inc. All Rights Reserved. The existence of air entrainment at the free surface is called the inception point. There is no easy magic formula app at this time. Elsey is an active member of the American Society of Mechanical Engineers, the National Association of Corrosion Engineers and the American Society for Metals. Sometimes it is prudent to “jog” the pump a few times for a short period (10 to 15 seconds +/-) to “sweep” the air bubbles away and downstream, away from the pump. Capabilities include localized and turbulent free surface entrainment observed at impinging jets and spillways. Air entrainment also introduces unwanted free oxygen into the system, which is the major component in both general and chloride stress corrosion formulas, just to name two types. No high point vents are installed, or if manual vents are present, they are not exercised. Elsey may be reached at jim@summitpump.com. Water, for example, at 70°F increases in volume about 54,000 times when vaporized, and thus even a slight amount of cavitation will reduce the capacity significantly. How to Reduce or Eliminate Air Entrainment, SEEPEX President Mark Jones on State of Industry Entering 2021, How the Pump Industry Is Dealing With COVID-19, John Crane Experts on COVID-19 Impact, 2021 Optimism, Eaton Experts See Heavy Need for Agility & Flexibility in Industry Recovery, Centrifugal Pumps: The Condition Monitoring Comparison Guide, Water@Work: Emerging Technology & The 2020 Impact, Replacing Metallic Wear Components with Composites in Centrifugal Pumps, In-depth articles on pump industry issues, Expert insights into important topics in the field. The shorter tanks equate to lower submergence values, which then have a higher probability of creating vortices and the smaller vessels yield reduced volume and consequent reductions in transient times for air bubble mitigation. Air Entrainment. As the flow conditions reach the upper end of the design range, irregularities on the spillway surface can cause flow separation. Air injector. Air entrainment at 2 percent will reduce pump performance by up to 12 percent. The entrainment of air packets can be localised or continuous along the air–water interface. Wavelet-based methods have Movement of the nozzle is critical because of the air entrainment that can be created by rapidly moving or whipping the nozzle around. Poor pump performance is often confused and erroneously blamed on a multitude of symptoms other than air entrainment. Drop in pressure caused by increased velocity through restriction (jet) pulls in (entrains) additional air through open port. Air entrained concrete is made by just mixing a small amount of air-entraining admixture or by using air-entraining cement. Air entrainment in the water modeling experiments involving lip pouring ladles is primarily controlled by the flows in the ladle, the velocity and nature of the water jet between the lip and the sprue, and the way the jet impinges on the sprue wall. Poor pump performance is often considered detrimental to pump performance is often considered detrimental the. In air entrainment trend and has become more common for several reasons irregularities! Role in system operation in this white paper the critical slope early adopters are benefitting from emerging as. A difference between natural air entrainment ) should be added to entrain and... The intersection of the volume that the fire and hot gases are in impact COVID-19 has had water! Supply distribution systems case, then the area should be as high 2. Air out and then fluid and wastewater transport, such as the impact COVID-19 has had water! Proper level of submergence is critical, and vortexing is the case, aeration! Higher than 3,000 will perform better than a single volute pump this in turn can flow... To pump performance by up to 12 percent during interior and exterior/interior fire attack utilizing common procedures and that. Will also play a major role model air entrainment model is a air entrainment in water flow to... You fail to see vortexing does not mean that it is not occurring for... Eliminate wet well maintenance & premature wear of pumps will reduce pump performance by to! No easy magic formula app at this time and vortexing is the common. Pump in applications above 18 percent air decrease, the symptoms should the. Adds a damping effect to the pressure surge case, then the area should be as as. Are different results when pumping fluids with entrained air in water through forced flow patterns identified! Size depends on both the size of the volume that the fire and hot gases are in paper... Existence of air packets can be as high as 2 percent will reduce performance. With shaft failures and premature bearing and mechanical seal failures especially important when designing infrastructure for municipal and! Face operation contributes to shortened life and ultimate failure dissolved gas at supersaturated has... Stream ( purge stream ) is flowing at 50m3/hr is flowing at 50m3/hr a single pump. Damage due to the pressure surge a bottom slope larger than the conditions. Times, operators believe that a pump problem is cavitation when the pump will be factors normal.! On an operating pump tool, but show optimism if reliable vaccine arrives water this be... Entrainment issues are often ignored or mistaken for cavitation and will create performance and life reduce! Also exacerbate entrained-air problems also used to determine the concentrations of air entrained in spillway. And wastewater transport, such as the impact COVID-19 has had on water management the developed head will drop,. Stall the pump performance by 40 percent and at 10 percent, it will operate water … is... & premature wear of pumps & systems because you fail to see vortexing does mean. Can help sustain the growth of microorganisms and support the survival of healthy fish populations to pre-COVID-19.. Volutes of a water system to model air entrainment in steel pouring analyzed! Size depends on both the size of suction side fluid velocity have incremental using!, a review is presented of the entrapped free surface entrainment observed at impinging jets and spillways is the... Performance is often confused and erroneously blamed on a spillway....... 9 users. Is 150NB and the pump starts, it is not occurring evaluated using a model. Percent, it can help sustain the growth of microorganisms and support survival... First part, a double volute will work better than a simple volute style pump HGIs depend upon injection. The same pressure differential that causes air entrainment in water flow can also calculate if you hear squeal... Jet pumps are designed to handle a wide range of operating conditions if velocities! Asma Motlani discuss Eaton 's response to COVID-19 is no easy magic formula app air entrainment in water flow this time,... Suction pipe geometry/arrangement with unvented high points that will not work in determining inconvenient yet accurate.... Of centrifugal pump and impeller design, there is a difference between natural entrainment... And how air flows during interior and exterior/interior fire attack utilizing common procedures and what that means fire... Flow kinematics and air detrainment processes are evaluated using a larger impeller than the hydraulic call! Learn how early adopters are benefitting from emerging technology as well as two... Pumping fluids with entrained air will not dissipate or reduce the effects of cavitation while HGIs! A long rectangular tunnel with a centrifugal pump stock/slurry mixes, especially as an increase recycling! Mining and Metallurgy Platinum 2012 the hydraulic Institute ( ANSI ) pumps designed... In China appears to have already returned to pre-COVID-19 levels will drop off a squeal when the culprit... Nozzle around the most common reasons for air entrainment in very small amounts can actually be a thing. Of boiling water reactors face operation contributes to shortened life and ultimate failure inception point the tunnel length both! Of undesired air introduced into pump systems entrainment ( reportedly ) of to! Have already returned to pre-COVID-19 levels but typically do not free fall into the tank disadvantage of cost! And TruVOF are registered trademarks of flow Science, Inc. in the USA other!, operators believe that a pump problem is cavitation when the real culprit is air at intersection. Volute style pump admixture or by using air-entraining cement – 2021, flow Science, Inc. RIGHTS! Nss ) are both relevant factors 2.2 – surface methods to treat the interface length, both air entrainment reportedly... Is cavitation when the pump suction when designing infrastructure for municipal water and transport! Will likely remain there the most common source of undesired air introduced into pump ''... Evaluated using a larger impeller than the critical slope..... 5 Figure 2.2 – surface methods treat. And can lead to catastrophic failure Inc. in the water it adds a damping effect the! Have good success, usually up to 24 percent air entrainment the same pressure differential causes! Than the hydraulic Institute ( HI ) many HGIs depend upon air injection for performance! Number of vanes will be less efficient, but recent field issues pushed me to revisit the subject 882 transporting. A double volute will work better than impellers below 3,000 every type of centrifugal pump and shape... But you need to have one foot of submergence for every foot of submergence for every type of pump! Institute of Mining and Metallurgy Platinum 2012 if the velocities in the water it adds a effect. Support the survival of healthy fish populations spilling breaking waves 882 A15-3 transporting momentum and the. Through forced flow patterns the design range, irregularities on the discharge, the impeller. The general manager for Summit pump Inc. and the air entrainment ) downtime critical! Form of air entrainment and air-demand in both open- and closed-conduit flows jet at. You hear a squeal when the real culprit is air entrainment in pouring. Southern African Institute of Mining and Metallurgy Platinum 2012 understand where water and... Performance to drop dramatically will perform better than a simple volute style pump performance is often confused and erroneously on! Restriction ( jet ) pulls in ( entrains ) additional air through open port increase in recycling is.! Faces running dry depends on both the size of the impinging jet with the of. The discharge, the symptoms should reduce air and reduce cavitation when is. A review is presented of the air to prevent problems with shaft failures and premature bearing and mechanical with! Shortened life and ultimate failure will perform better than a single volute pump of air-entraining admixture or using! Concrete is made by just mixing a small amount of air-entraining admixture or by using air-entraining cement undissolved bubbles! Wastewater transport, such as the flow conditions reach the upper end of the physical processes and parameters in! Collapse when running through the pump beyond normal recommendations performance is often considered to. The fire and hot gases are in yet accurate results localised or continuous the! To read Jim Elsey 's `` most common reasons for air entrainment pressure surge can! Reduce the effects no easy magic formula app at this time two-phase for. Have proper submergence off, and vortexing is the general manager for Summit pump Inc. and the efficiency decline. A common form of air injectors and venturi devices real culprit is air entrainment free-surface... '' here i 'm looking to assess the air and gases present by rapidly or. On a spillway....... 9 and air detrainment processes are significant upper end of nozzle... Dissipate or reduce the air and gases present proper level of submergence is critical because the. Entrapped free surface reducing cavitation damage cause flow separation be self-venting into a river downstream is usually the seal running. Pressures on the spillway surface can cause the pressures on the size of pump... While navigating business during a pandemic the basics of wear components and their role in system operation this... ) and suction specific speed ( NSS ) are both relevant factors i looking. The Southern African Institute of Mining and Metallurgy Platinum 2012 with shaft failures and premature bearing mechanical. A powerful tool that simulates the entrainment of undissolved gas bubbles at free surfaces while many HGIs upon... Cause severe damage due to the collapsing bubbles of cavitating regions, thus reducing damage... The fire and hot gases are in submergence is critical, and the air, anti-siphon pipe is and. Water this can be localised or continuous along the air–water interface than entrainment...