Jiangsu Haifa Machinery Manufacturing Co., Ltd.

At chemical plant sites, we often encounter a situation where the pump is still running, bearing temperatures aren't too high, and the mechanical seal shows no obvious leakage, yet motor current is higher than normal, discharge pressure is unstable, vibration is elevated, and actual flow rate falls short of the original requirement. Users typically say, "This pump has been in service for many years—can we just improve its efficiency without replacing the whole unit?" I'm a technical specialist at Jiangsu Haifa Machinery Manufacturing Co., Ltd., with long-term exposure to API610 chemical process pumps, OH2 petrochemical process pumps, BB series high-pressure process pumps, VS series vertical pumps, molten urea pumps, urea hydrolyzer feed pumps, low-flow high-head pumps, pitot tube pumps, and jet-spray pumps. When we undertake energy-saving retrofits for old pumps, we don't immediately recommend replacing them with new ones. Many old pump casings, bearing housings, baseplates, motors, and piping foundations can still be reused. What truly affects efficiency is often the impeller hydraulics, volute flow passages, wear ring clearances, internal recirculation, cavitation, and deviation of operating conditions from the design point. In recent years, we've placed increasing emphasis on CFD simulation in old pump retrofits. CFD isn't just about creating a pretty streamline diagram—it helps us see the real flow issues inside the pump. Where we once relied on experience, we can now analyze data such as flow field velocity, pressure distribution, vortex zones, impeller inlet incidence angle, blade outlet flow, volute tongue impact, and cavitation risk. The resulting retrofit plan isn't a simple patch-up job but a hydraulically optimized solution based on computational evidence.

1. Why Does Old Pump Efficiency DeclineEfficiency decline in old pumps is generally not caused by a single factor. During our on-site measurements, common issues fall into several categories. First, the pump has long operated away from its high-efficiency zone. Many chemical plants have undergone capacity expansions, modifications, or pipeline adjustments, so the original pump no longer runs near its best efficiency point (BEP). Some pumps operate at low flow for extended periods with the discharge valve barely open, leading to significant internal recirculation; others run at excessive flow, increasing shaft power, reducing available net positive suction head (NPSHa), and raising vibration and noise. Second, impeller wear or corrosion. Thinning of blade leading edges, wear on trailing edges, and erosion of impeller shrouds all affect head and efficiency. Especially with media containing trace particles, mild corrosives, or high temperatures, the impeller geometry can deviate significantly from the original design after years of operation. Third increased wear ring clearances. As clearances enlarge, high-pressure liquid recirculates from the discharge side back to the suction side, increasing volumetric losses. The pump may appear to be running, but some energy is consumed internally in a closed loop. Fourth, local erosion or scaling in the pump casing and volute passages. When some old pumps are disassembled, we find corrosion pits, scale deposits, or weld repair marks in the volute passages, disrupting smooth flow and increasing local vortices, naturally reducing efficiency. Fifth, mismatch between motor and pump. In some cases, the motor or impeller has been replaced without recalculating flow, head, and power, resulting in an oversized motor driving a small load or the pump's actual operating point deviating from the original design. Sixth, cavitation issues being overlooked. Cavitation doesn't always manifest as severe damage initially; sometimes it's just slight noise, vibration, and efficiency loss. Especially with high-temperature condensate, light hydrocarbons, solvents, liquid ammonia, cryogenic liquids, and suction under vacuum, NPSH must be recalculated. So, when we work on efficiency improvement for old pumps, the first step isn't to design a new impeller directly—it's to identify why the pump is inefficient.

1. 

   What Can CFD Simulation Do in Old Pump Retrofits?

CFD simulation technology primarily helps us examine four things. First, whether the impeller inlet is smooth. If the inlet incidence angle is improper, it can cause inlet recirculation, local low pressure, and cavitation risk. After years of operation, the impeller leading edge may be worn, or the on-site flow rate may have changed, causing the inlet flow pattern to deviate from the original design. Second, whether there is flow separation and vortices within the blade passages. If the blade wrap angle, blade outlet angle, or passage width is unreasonable, the liquid can separate within the passages, leading to significant energy loss. CFD reveals areas of excessive velocity and stagnant flow. Third, whether the volute and impeller outlet are well-matched. Many old pumps are inefficient not solely due to the impeller but because of a mismatch between the impeller outlet and the volute passage. High outlet velocity from the impeller impacting the volute tongue can cause pressure pulsations, noise, and vibration. Fourth, efficiency variation at different flow points. Chemical pumps don't operate at a single point; actual installations have normal flow, rated flow, minimum continuous stable flow, and possible off-design conditions. CFD allows analysis at multiple flow points, avoiding optimization at just one point while worsening performance elsewhere. For us, CFD simulation doesn't replace testing—it gives testing direction. By screening options through simulation first, then combining machining, assembly, dynamic balancing, and performance testing, we can reduce trial and error.

1. Efficiency Improvement for Old Pumps Isn't Just About Replacing the Imp

Many users, upon hearing that an old pump is inefficient, ask, "Can't we just replace it with a high-efficiency impeller?" That's only half true. The impeller is certainly important, but the pump is a system. The impeller, casing, wear rings, cover, seal chamber, bearing housing, suction piping, discharge piping, motor speed, and medium density and viscosity all affect efficiency. If you only replace the impeller without considering the volute and system conditions, efficiency gains may be minimal, and you might even introduce vibration and cavitation issues. Our typical approach is: first, verify on-site operating conditions—actual flow, head, suction pressure, discharge pressure, motor current, medium temperature, density, viscosity, and vapor pressure. Second, perform detailed measurements of the old pump—record impeller outer diameter, impeller width, number of blades, blade angles, wear ring clearances, shaft diameter, casing passage dimensions, and volute tongue position., create a 3D model of the impeller, volute, suction chamber, and discharge chamber. Fourth, conduct CFD flow field calculations to analyze pressure field, velocity field, turbulent regions, recirculation zones, low-pressure areas, and hydraulic losses. Finally, based on the results, optimize impeller outer diameter, blade outlet angle, blade leading edge, passage width, wear ring clearances, and necessary volute modifications. If the user's site doesn't allow major casing modifications, we try to optimize the impeller and wear rings while keeping the original casing, baseplate, motor, and nozzle positions unchanged. This keeps retrofit costs low, minimizes downtime, and makes it easier for the site to accept.

1. API610 Chemical Process Pumps Are More Suitable for Systematic Retrofits

API610 chemical process pumps differ from ordinary water pumps; they serve continuous operation in refining, petrochemicals, coal chemicals, fertilizers, metallurgy, environmental protection, and fine chemicals. In many plants, stopping a pump affects the entire production line, so reliability must come before efficiency, and efficiency gains cannot compromise safety. Jiangsu Haifa Machinery Manufacturing Co., Ltd. primarily produces API610-OH1/OH/OH3, BB1–BB5, VS1–VS6 series HES-type chemical process pumps, as well as sixth-generation ultra-low carbon stainless steel high-quality molten urea pumps, urea hydrolyzer feed pumps,-flow high-head pitot tube pumps, and jet-spray pumps. When we undertake efficiency retrofits, we incorporate API610 design principles, focusing on bearing life, rotor stability, NPSH margin, seal chamber pressure, thermal expansion, material corrosion, and on-site maintenance. For example, our HXP jet-spray pump (pitot tube pump) has published parameters covering flow rates of 1–40 m³/h, heads of 80–1800 m, temperatures from -40 to 150°C, and design pressures up to 26 MPa, suitable for low-flow, high-head, high-pressure applications. For such extremely low specific speed pumps, hydraulic efficiency and internal flow losses are, and experience alone can't accurately judge every detail—CFD simulation plays a key role. Another example is our HES(U) ultra-low carbon stainless steel high-quality molten urea pump, with published parameters covering flow rates of 2–0 m³/h, heads up to 300 m, temperatures from -80 450°C, design pressures of 2.5–26 MPa. For these high-temperature, high-pressure, crystallization-prone media, efficiency improvement isn't just about hydraulics; it also involves materials, insulation, anti-crystallization measures, axial thrust, seal systems, and long-term operational stability. Therefore, improving old pump efficiency isn't simply about saving electricity—it's essentially a comprehensive redesign of hydraulics, mechanics, materials, and site conditions.

1. Where Can CFD Optimization Improve Old Pump Efficiency?

First, optimize the impeller inlet. Poor inlet design can cause impact losses and recirculation. By adjusting the blade inlet angle, leading edge shape, and front shroud passage, inlet losses can be reduced and suction performance improved. Second, optimize the blade outlet. The blade outlet angle affects head, power, and efficiency. Too large an angle may increase power; too small may result in insufficient head. CFD helps find the outlet angle best suited to on-site conditions. Third, optimize the impeller passage width. If the actual flow rate has changed, the original passage width may no longer appropriate. Adjusting it can reduce internal friction and secondary flow losses. Fourth, modify the impeller outer diameter. Many sites trim the impeller diameter to reduce head, but excessive trimming lowers efficiency. By recalculating the impeller diameter based on the system curve, the pump's operating point can be brought closer to the high-efficiency zone. Fifth, control wear ring clearances. Excessive clearances increase internal leakage and reduce efficiency. Restoring proper clearances during retrofits often yields direct efficiency gains. Sixth, optimize the volute tongue region. Flow impact between the impeller outlet and volute tongue affects pressure pulsations and noise. For old pumps with high vibration, tongue region analysis is important. Seventh, reduce internal recirculation. At low flow, recirculation can occur at the impeller inlet and outlet. Impeller modifications and operating point adjustments can improve low-flow stability. Eighth, reduce cavitation risk. CFD helps identify low-pressure zones at the impeller inlet, and by comparing NPSHa and NPSHr, we can determine whether to adjust the impeller inlet diameter, blade leading edge, or suction structure.

1. Parameters That Must Be Collected Before Improving Old Pump Efficiency

When developing retrofit plans for users, we typically need: pump model, original manufacturer, serial number; original design flow, head, speed, motor power; current actual flow, discharge pressure, suction pressure, motor current; medium name, density, viscosity, temperature, corrosiveness, solids content; on-site piping layout, valve openings, filter conditions; NPSHa or suction level, suction pressure, medium vapor pressure; impeller outer diameter, wear ring clearances, casing wear condition; vibration, noise, bearing temperature, seal leakage; and whether modifications to the impeller, wear rings, speed, motor, or piping are allowed. The more complete the data, the closer the CFD simulation boundary conditions are to the actual site, and the more reliable the final retrofit results. Some users only say "the pump is inefficient," making it hard for us to judge directly. Inefficiency could be due to the impeller, system resistance, or inaccurate flow measurement. We generally recommend on-site testing first, followed by 3D measurement and analysis.

1. Efficiency Improvement Isn't Always Better—Safety Margins Matter

Improving old pump efficiency shouldn't just chase impressive numbers. Chemical pumps require special attention to safety margins. If efficiency improves but shaft power exceeds the original motor's capacity, it's not acceptable. If head increases but discharge pressure exceeds the original piping or casing pressure rating, it's not acceptable. If flow increases but NPSHa is insufficient, leading to cavitation, it's also not acceptable. If the impeller is made too thin, compromising strength and corrosion allowance, it's not acceptable. If seal chamber pressure changes too much for efficiency, affecting mechanical seal operation, it's likewise not acceptable. So, when we perform CFD optimization, we always simultaneously check strength, shaft power, cavitation, seals, axial thrust, and rotor stability. For API610 chemical process pumps, reliability must come first. The of energy-saving efficiency improvement is to bring the pump back to a reasonable high-efficiency zone within safe limits, not to sacrifice operational stability for a single efficiency number.

1. What On-Site Benefits Can Be Expected After Improving Old Pump Efficiency?

If the retrofit plan is appropriate, users typically see several direct benefits. First, motor current drops, reducing energy consumption. For continuously running chemical pumps, even a few percentage points of efficiency improvement can yield significant annual electricity savings. Second, the pump's operating point moves closer to the high-efficiency zone, stabilizing discharge pressure and flow. Third, internal recirculation and impact are reduced, potentially lowering vibration and noise. Fourth, cavitation risk decreases, extending impeller and casing life. Fifth, the operating environment for mechanical seals and bearings improves, reducing maintenance frequency. Sixth, the value of old equipment is enhanced without major piping or foundation changes. However, I also honestly tell users: not all old pumps are worth retrofitting. If the casing is severely corroded, the foundation is deformed, the bearing housing is damaged, the original pump type deviates too much from current conditions, or on-site parameters have completely changed, it may be more appropriate to directly replace it with a new API610 chemical process pump.

1. Old Pump Conditions Suitable for CFD Efficiency Improvement Retrofits

From our experience, the following types of old pumps are well-suited for CFD simulation optimization: API610-OH2 chemical process pumps in long-term service; circulation pumps, feed pumps, and reflux pumps in refining, petrochemical, and coal chemical plants; pumps where flow and head are roughly appropriate but motor current is high; pumps with elevated vibration and noise but acceptable mechanical structure; pumps needing replacement parts due to impeller wear; pumps whose operating point has shifted after system modifications; pumps with low efficiency under low-flow high-head conditions; and pumps handling high-temperature, high-pressure, or highly corrosive media where reliability needs improvement. For these pumps, if the casing and foundation are still usable, good retrofit results can often be achieved through impeller hydraulic optimization, wear ring restoration, internal passage correction, and operating point adjustment.

1. Our Basic Process for Improving Old Pump Efficiency

Step one: Collect on-site data, including flow, head, pressure, current, temperature, vibration, noise, medium parameters, piping conditions. Step two: Disassemble and measure, inspecting the impeller, wear rings, casing, cover, shaft, shaft sleeve, bearing housing, and seal chamber. Step three: Create a 3D model based on actual measurements of the impeller, volute, and flow passages. Step four: Conduct CFD flow field simulation, analyzing pressure field, velocity field, recirculation, vortices, low-pressure zones, and efficiency losses. Step five: Propose an optimization plan, including impeller modification, blade angle adjustment, impeller diameter adjustment, wear ring clearance restoration, material upgrades, and necessary structural improvements. Step six: Manufacture new impellers or repair parts, ensuring dimensional accuracy, material quality, dynamic balance, and assembly precision. Step seven: Perform performance testing and on-site verification, confirming that flow, head,, vibration, and temperature rise meet requirements. This process may seem more complex than routine maintenance, but for large-scale chemical plants operating continuously, investing more in calculation and verification upfront reduces unnecessary downtime and rework later.

1. Conclusion

A decline in old pump efficiency doesn't always mean a new pump is necessary. With CFD simulation technology, we can identify invisible internal flow issues and, combined with API610 chemical process pump design experience, systematically optimize the impeller, wear rings, volute, and operating conditions. For Jiangsu Haifa, CFD simulation isn't just a marketing concept—it's a tool serving actual manufacturing and on-site retrofits. We care more about: why this old pump is inefficient, whether it can be improved on its original basis, whether current can be reduced after modification, whether vibration can be stabilized, whether seal and bearing life can be extended, and the entire chemical plant can more reliably. For old pumps in refining, petrochemical, coal chemical, fertilizer, metallurgical, environmental, and fine chemical plants experiencing efficiency decline, high current, elevated vibration, obvious cavitation, or operating point deviation from design, comprehensive retrofits can be performed using on-site measurement, CFD flow field analysis, hydraulic optimization, and API610 standardized design principles. Pump energy saving isn't just about replacing with a high-efficiency motor; pump efficiency improvement isn't simply swapping an impeller. Truly reliable old pump efficiency improvement analyzes the medium, piping, flow, head, cavitation, materials, seals, rotor, and hydraulic model together. Only then can an old pump return to reasonable operating conditions, allowing the equipment to continue creating value for stable plant operation.