{"id":6952,"date":"2024-03-21T17:05:03","date_gmt":"2024-03-21T17:05:03","guid":{"rendered":"https:\/\/northamericanmining.com\/?p=6952"},"modified":"2024-03-21T17:15:53","modified_gmt":"2024-03-21T17:15:53","slug":"lets-talk-about-slurry-pump-wear","status":"publish","type":"post","link":"https:\/\/northamericanmining.com\/index.php\/2024\/03\/21\/lets-talk-about-slurry-pump-wear\/","title":{"rendered":"Let\u2019s talk about\u2028 slurry pump wear"},"content":{"rendered":"\n

Handling slurry inevitably exposes equipment to wear. The question is thus how to manage \u2028and minimize that wear. North American Mining<\/em> spoke to four experts about issues in slurry \u2028pump wear protection.<\/strong><\/p>\n\n\n\n

By Jonathan Rowland<\/em><\/p>\n\n\n

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Digital solutions are helping bring more transparency to pump performance and condition monitoring, allowing problems to be identified earlier and solutions implemented that unlock new levels of efficiency in pump operation and maintenance. Photo: Metso<\/em><\/figcaption><\/figure>\n\n\n

Introduction: the three types of wear<\/strong><\/h3>\n\n\n\n

There are three main categories of wear to which a slurry pump may be exposed: abrasion, corrosion and erosion. Abrasion occurs \u201cwhen particles are forced between two solid surfaces and moved relative to at least one of the surfaces,\u201d explained Quinton Sutherland, divisional senior product manager, Pumps, for Weir Minerals. \u201cErosion is the wear that results from particles within a slurry flow contacting a solid surface and causing a high contact stress on the surface. Corrosion occurs when components of a slurry cause the wear material to chemically react, which then causes the material to gradually deteriorate. In a slurry pump, abrasion and corrosion often coincide and result in accelerated wear.\u201d<\/p>\n\n\n\n

All three mechanisms \u201cwear away the parts, changing their original dimensions and geometry, resulting in degraded performance,\u201d concluded Sutherland.<\/p>\n\n\n\n

Abrasion<\/strong>
Abrasion \u201ccan come in many different forms, depending on the size and concentration of the solids, as well as the nature of the flow,\u201d Leo Perry, lead product manager \u2013 GIW Slurry Pumps for KSB, told NAM<\/em>.<\/p>\n\n\n\n

A common case is caused by \u201cparticles between the rotating impeller and stationary suction liner (throatbush),\u201d noted Weir\u2019s Sutherland. Another example may arise \u201cbetween the shaft sleeve and packing (Figure 1),\u201d added Nicole Bessett, applications engineering manager, KREBS Pumps, Cyclones & Valves, for FLS. \u201cIn some cases, the gland follower is too tight, causing the packing to extrude into the sleeve. In other cases, the gland water supply is clogged or has a high concentration of solids. Both scenarios result in ineffective sealing, lower wear life, and more maintenance requirements.”<\/p>\n\n\n\n

Another example can \u201coccur between the impeller and the throatbush,\u201d continued Bessett. \u201cAs flow recirculates on the suction-side to the low-pressure zone at the impeller eye, mechanical grinding of solids occurs between the throatbush and the impeller.\u201d<\/p>\n\n\n

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Availability of spare parts and location of local service centers are key factors to consider when selecting a pump supplier. \u2028Photo: KSB<\/em><\/figcaption><\/figure>\n\n\n

Corrosion<\/strong>
Corrosive wear is a \u201cchemical process that leads to the gradual deterioration of materials,\u201d said Bessett. \u201cOne common form is pitting, which refers to localized corrosion that can eventually develop into cavities.\u201d As slurry chemistry can vary widely depending on the application, selecting an appropriate wear material is a key part of managing corrosion.<\/p>\n\n\n\n

\u201cWhen metal liners are required, hypoeutectic chrome alloys offer enhanced resistance against corrosive agents; options such as CD4MCuN and 300 series stainless steels are also available to further meet the specific demands of the application,\u201d added Bessett. \u201cA wide range of elastomer materials can also be provided, which are suitable for various chemical, pH levels, concentrations, and temperatures.\u201d<\/p>\n\n\n

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Figure 1. Abrasion on a shaft sleeve. Photo: FLS<\/em><\/figcaption><\/figure>\n\n\n

Erosion<\/strong>
Erosion occurs when material is removed through repeated impact of particles. Key factors here include flow velocities, particle characteristics, and pump sizing.<\/p>\n\n\n\n

\u201cWhen suction velocity \u2013 the speed at which slurry flows into the suction of the pump \u2013 is too high, particles do not have sufficient time to change direction before striking the back shroud of the impeller,\u201d explained Bessett. \u201cThe impact becomes more severe as the average particle size increases and the consequence becomes apparent when holes start to form in the back shroud of the impeller (Figure 2). These holes create a low-pressure path, allowing the flow to recirculate which, in turn, reduces pressure and increases wear. This is all indicative of an undersized pump.\u201d<\/p>\n\n\n\n

Oversizing \u201chappens when the flow rate is too low for the given pump size, causing the pump to operate to the left of the Best Efficiency Point (BEP),\u201d Bessett continued. \u201cAccording to Bernoulli’s principle, there is an inverse relationship between pressure and velocity. Therefore, high velocity at the cutwater point of the casing from oversized conditions means there is low pressure. Oversizing can cause reduced efficiency and increased erosive wear at the cutwater point of the casing.\u201d<\/p>\n\n\n

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Slurry pumps are exposed to various conditions that result in wear, including abrasion, corrosion and erosion.\u2028Photo: Weir Minerals<\/em><\/figcaption><\/figure>\n\n\n

Factors in wear rate<\/strong><\/h3>\n\n\n\n

\u201cAll hydraulic (wetted) surfaces are subject to wear,\u201d said KSB\u2019s Leo Perry, \u201cbut that does not mean all wear is even. There are many factors that determine wear rate.\u201d These can be broadly categorized into pump efficiency, pump maintenance, and pump configuration and material selection.<\/p>\n\n\n\n

Pump efficiency. A \u201cless efficient pump can be thought of as a pump that is doing a disproportionate amount of work compared to the useful output (flow and head),\u201d explained Perry. \u201cThe design of the pump is an important factor in pump efficiency, but of equal or greater importance is how well the pump matches the system requirements. Therefore, pump selection is critical: in general, the closer a pump operates relative to its BEP Flowrate (BEPQ), the better the wear performance.\u201d<\/p>\n\n\n

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Figure 2. Holes in the back shroud of the impeller caused \u2028by high suction velocity. Photo: FLS<\/em><\/figcaption><\/figure>\n\n\n

\u201cOperating the pump away from the BEPQ will increase the wear rate,\u201d agreed Tiago Oliveira, vice president, Pumps Services, for Metso, \u201cfor example, on the inlet liner, which is subject to sliding bed, crushing and grinding abrasion, and the impeller, which is subject to impact wear mainly in the eye, as well as sliding bed abrasion and low angular impact along the vanes between the impeller shrouds.\u201d<\/p>\n\n\n\n

Pump maintenance. Similar to efficiency, \u201cthe way a slurry pump is maintained plays a large role in how well it performs, both in terms of output and wear life,\u201d the KSB\u2019s Perry continued. \u201cFor example, the operating clearance between the rotating impeller and stationary surface of the casing or throatbush, otherwise known as nose clearance, should be continually maintained and adjusted over the course of the operating life of a slurry pump. This helps reduce harmful recirculation, which can accelerate wear, while maximizing the output and efficiency of the pump.\u201d<\/p>\n\n\n\n

Perry also emphasized the importance of nose clearance \u2013 the gap between the stationary throatbush and the impeller \u2013 to maximizing the operating life. \u201cSlurry pumps are designed in ways that facilitate nose gap adjustment. Many OEMs have introduced ways to perform these adjustments without shutting down the pump. In heavy-duty slurry applications, it may be beneficial to perform these adjustments up to 20 \u2013 25 times over the life of the parts.\u201d<\/p>\n\n\n\n

Pump configuration and material selection. Depending on the slurry characteristics, \u201cmaterial selection and pump configuration can also play key roles in the longevity of the equipment,\u201d Perry added. \u201cFor example, the size and quantity of impeller vanes and suction diameter may be considered variables in pump configuration that can be optimized based on slurry particle size distribution and observed wear characteristics of the pump. Different materials may have better or worse wear properties in the presence of large particles, or with consistently fine slurries.\u201d<\/p>\n\n\n\n

In addition to standard duty conditions, such as head, flow, specific gravity, and percent solids, FLS Pump Applications Engineer Nicole Bessett offered the following factors to consider when it comes to selecting appropriate wear materials:<\/p>\n\n\n\n

    \n
  • Solids concentration, size, mass, hardness: these parameters play a crucial role in determining the behavior of the slurry and its impact on the equipment.<\/li>\n\n\n\n
  • Slurry properties: consider the chemicals present, pH\/ concentration, temperature of the slurry, and the presence of tramp material from process upsets, as these properties can significantly affect the longevity of the pump.<\/li>\n\n\n\n
  • Solids shape: consider whether the particles have a spherical, angular, or sharp fractured surface. The shape of the particles can influence the wear and tear on the pump parts.<\/li>\n\n\n\n
  • Contact conditions: evaluate the velocity, angle of impact, and impact occurrence. Understanding these factors allows for pump selection and design able to withstand the expected conditions.<\/li>\n<\/ul>\n\n\n\n

    Considering all the above slurry characteristics, \u201cthe material properties (the hardness, tensile strength, durometer), then provide insight into the equipment\u2019s ability to withstand wear and operate efficiently,\u201d concluded Bessett.<\/p>\n\n\n\n

    There is \u201cno one-size-fits-all solution when it comes to wear materials,\u201d agreed Perry. \u201cWear materials range from the aforementioned steels and elastomers, to cast iron of various compositions and production methods, and ceramics.<\/p>\n\n\n\n

    \u201cWear performance is also just one factor to consider when selecting a material; other factors include the cost of procurement, total cost of ownership, ease of maintenance and supply chain considerations. The best course of action is to work with your trusted OEM to analyse the system and unique characteristics of each application and, from there, determine the best solution to meet both operational and budgetary targets.\u201d<\/p>\n\n\n

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    The three main parts of a slurry pump exposed to wear are the suction liner (throatbush), impeller, and the shell or casing.\u2028 Photo: KSB<\/em><\/figcaption><\/figure>\n\n\n

    And when premature wear is \u2028causing an issue?<\/h3>\n\n\n\n

    As a general rule of thumb, when the pump and system are matched, the casing will last about twice as long as the impeller, and about three times as long as the throatbush. However, \u201cpump design parameters are often adjusted to achieve a desired result, such as 1:1:1 replacements to match planned maintenance intervals,\u201d concluded Perry.<\/p>\n\n\n\n

    \u201cTypically, the impeller and\/or throatbush are the parts that experience the highest wear rates,\u201d agreed Weir Minerals\u2019 Quinton Sutherland. \u201cThe impeller is the moving part inside the pump that imparts the energy into the slurry, so it takes the brunt of the wear from redirecting and accelerating the solid and fluid mixture. When the slurry reaches the higher-pressure discharge region of the pump, it tends to seek the lower-pressure suction region of the pump through the gap between the impeller and the throatbush. As a result, the impeller acts like a grinding disc against the throatbush when slurry enters this interface region.\u201d<\/p>\n\n\n\n

    And when premature or excessive wear is an issue? \u201cThe wear patterns may be localized and\/or follow certain patterns that can be used in diagnosing the root cause of the premature wear,\u201d replied KSB\u2019s Perry. \u201cDiagnosing the root cause of accelerated wear can lead to sometimes counterintuitive solutions, such as \u2018downsizing\u2019 the pump to match lower flowrates, simultaneously improving wear performance on the whole.\u201d<\/p>\n\n\n\n

    \u201cWhenever I visit site, one area that always piques my interest is the scrap yard,\u201d added FLS\u2019 Nicole Bessett. \u201cIt never fails to amaze me the sheer number of worn impellers and throatbushes that end up there. I am always on the lookout for a throatbush that exhibits a Swiss-cheese like appearance or has wear epoxy, often applied to extend the wear life. Additionally, I pay attention to wear patterns that resemble a flowering at the eye of the impeller and question marks on the leading edges of the vanes (Figure 3). These patterns are telltale signs of recirculation and grinding.\u201d<\/p>\n\n\n\n

    Pump operating practices<\/h3>\n\n\n\n

    It has already been noted that operating the pump away from its BEP can cause wear problems. On the flip side, \u201cgood operating practices can also significantly extend the wear life of the pump,\u201d said Metso\u2019s Tiago Oliveira. Best practice advice from our experts included the following:<\/p>\n\n\n\n

      \n
    • Periodically adjust the axial clearance of the impeller to the inlet and back liner to maintain it at a 1-2 mm gap. This helps to avoid turbulence and internal recirculation, which reduce pump efficiency and increase wear.<\/li>\n\n\n\n
    • Maintain good inlet flow conditions, avoiding pre-rotation of the flow or air suction, and free outlet flow conditions in the discharge side.<\/li>\n\n\n\n
    • Maintain the water flow and gland seal system pressure as per OEM requirements to allow good flushing of the gland area and backliner.<\/li>\n\n\n\n
    • Continuously adjust pump speed to pump at the BEP, being careful to avoid:<\/li>\n\n\n\n
    • Exceeding maximum tip speed to prevent issues including hysteresis damage to the lines, a torn elastomer lining, and cracked impellers.<\/li>\n\n\n\n
    • Exceeding suction velocity limitations.<\/li>\n\n\n\n
    • Periodically replace wear parts to avoid efficiency loses.<\/li>\n\n\n\n
    • Continuously monitor the condition of pumps by regularly assessing temperature, vibration, pressure, and other parameters through digital services. This approach aims to swiftly identify deviations and implement proactive maintenance programs for optimal pump performance.<\/li>\n<\/ul>\n\n\n\n

      Slurry pumps are \u201cthe workhorses of many industries, relentlessly pushing abrasive mixtures day and night,\u201d added Oliveira\u2019s colleague at Metso, Alan Varghese, product head, Digitalization, Pumps & Hydrometallurgy. \u201cHowever, their lifespan and performance directly depend on how we treat them. Operating practices thus play a crucial role in determining their wear rate, making them a delicate balancing act between efficiency and longevity.\u201d<\/p>\n\n\n\n

      It is also common for operating conditions to change as plant operations evolve. \u201cA pump that was properly selected at the time of commissioning may not be the correct pump five years into the project,\u201d noted KSB\u2019s Leo Perry. \u201cIn these cases, the pump OEM can assist in finding solutions that minimize impact to the existing installation. In other scenarios, material selections may be reviewed after the first few maintenance cycles to better match the wear life to the mission run targets. Pump manufacturers are quite accustomed to these realities, and must design their product offerings with a certain amount of flexibility in order to facilitate these changes, to keep the pump well optimized to the ever-changing conditions in the field.\u201d<\/p>\n\n\n\n

      \u201cAlways be aware of the real condition of the system, and be open to adapting the pump as required to maintain optimal performance,\u201d concluded Perry. \u201cThere is always a best fit solution to the requirements of a slurry pump application, but that solution can change significantly from one year to the next over the life of the plant.\u201d<\/p>\n\n\n\n

      Inspection and preventative maintenance<\/strong><\/h3>\n\n\n
      \"\"
      Figure 3. Top: question mark wear patterns from recirculation: impeller after 1008 hours of operation when the wear ring \u2028(suction side clearance) was not adjusted. Bottom: Impeller \u2028after 984 hours of operation when the wear ring (suction \u2028side clearance) was adjusted. Photo: FLS<\/em><\/figcaption><\/figure>\n\n\n

      That last point provided a neat segway into the next discussion point: inspections. \u201cDuring the mission run of the pump, inspections provide important information to help diagnose problems that may be experienced later,\u201d said Perry. \u201cOftentimes, the parts are not observed until very late in the run, when wear has accelerated to the point that diagnosis of the root cause becomes difficult. Any mid-cycle inspections can provide clues to how wear starts, before becoming severe enough to require a shutdown, and may lead to solutions that can delay or prevent the onset of this wear.\u201d<\/p>\n\n\n\n

      Slurry pump wear is often a \u201cnon-linear function,\u201d added Weir Minerals\u2019 Quinton Sutherland. \u201cIt is thus important to take consistent measurements during shutdowns to create a trend history of wear rates and the resulting predicted wear life. Even if maintenance intervals are driven by another piece of equipment in the process (e.g. the SAG mill), instead of running the slurry pump to failure, understanding wear trends can allow an operator to estimate how long their pumps will last, giving them peace of mind between shutdowns.\u201d<\/p>\n\n\n\n

      \u201cWhen inspecting a pump\u2019s wet-end, start by checking which of the three mechanisms is creating wear,\u201d said Metso pump services expert, Tiago Oliveira, who guided us through the inspection process. \u201cThe side liners should then be inspected to understand the wear pattern between the impeller and liners, which is one indication of whether the pump is operating at BEP. Other indications of off-BEP operation can be gleaned by inspecting the casing volute and the location of the sliding bed and low angular abrasion patterns, as well as the impeller, looking for the wear pattern on the eye and on the vane tips, which can also indicate sizing limitations.\u201d<\/p>\n\n\n\n

      The importance of inspections and preventative maintenance \u201cholds especially true for unlined pumps, where the casing has dual the functions of containing both pressure and wear,\u201d added Bessett of FLS. \u201cIt is important to dispel the misconception that only lined pumps are safe, as unlined pumps can be perfectly safe when regular thickness measurements are recorded and tracked. Additionally, unlined pumps have a much smaller footprint, have fewer components, and are much easier to maintain.\u201d<\/p>\n\n\n\n

      Digital solutions are also providing new avenues when it comes to monitoring slurry pumps over time. These technologies essentially enable \u201cpump manufacturers and equipment operators to gather key operating and performance data much earlier in the process, and with much greater clarity and frequency than before,\u201d said KSB\u2019s Perry.<\/p>\n\n\n\n

      \u201cBy continuously monitoring the health of the equipment, it becomes possible to diagnose problems earlier and improve the outcomes in near real time,\u201d the KSB engineer continued.<\/p>\n\n\n\n

      \u201cIn addition, digital condition monitoring provides new data streams that help build a more complete picture of how the equipment performs and responds to changes in operating and design parameters. Armed with this information, it is possible to unlock previously hidden efficiencies in the operation and maintenance of the equipment, reducing costs, downtime, and uncertainty.\u201d<\/p>\n\n\n\n

      Selecting a pump supplier<\/strong><\/h3>\n\n\n\n

      When it comes to selecting a pump supplier, the \u201cmost important factor is trust,\u201d began Perry. \u201cTrust in the reliability of the product, reliability of the supply chain, and reliability in the technical expertise of the equipment provider. There are many challenges when operating a slurry pump, many of which can be foreseen, but some of which cannot. In times of need, it is always best to have a trusted partner who has seen it before and can help identify timely and effective solutions.\u201d<\/p>\n\n\n\n

      When selecting a slurry pump provider, \u201ca mine should consider the level of innovation and technical support available to improve the total cost of ownership over the pump lifecycle,\u201d according to Metso\u2019s Oliveira. \u201cThen it is important to have a supplier in full control of the supply chain, manufacturing its own parts and building its own pumps with genuine parts. It is also important to ensure that such genuine OEM parts comply with strict quality and performance standards; this ensures efficient operations leading to reduced power consumption and unexpected shutdowns and production losses. Finally, it is important to have a global supply chain and inventory stock available to supply the right parts in a timely manner, combined with knowledgeable field services teams and repair center capabilities close to the installed base.\u201d<\/p>\n\n\n\n

      \u201cAvailability of spare parts is critical to successful pump operation, as well as the presence of service and rebuild centers located close to your mine site. This cuts lead times and ensures your pump is only ever down for as short a time as possible \u2013 or ideally not at all,\u201d echoed Nicole Bessett of FLS. \u201cA key part of this is how the OEM integrates data from sales, inventory, and production department to allow it to stay up to date with stock levels and customer demand.\u201d<\/p>\n\n\n\n

      Selecting a slurry pump provider that \u201cunderstands the unique needs of each customer is critical,\u201d added Weir Minerals\u2019 Sutherland. \u201cFor example, some customers prioritize uptime above all else. They may be willing to pay a premium for the most advanced materials available, since their downtime costs are orders of magnitude higher than the premium parts prices, especially if they do not have a standby pump available. On the other hand, some customers have standby pumps installed and run their pumps to complete failure in a stable process, so they may require a more standard material selection. These are examples of how an OEM combines both the unique operating needs of a customer with the optimization of their total cost of ownership (TCO).\u201d<\/p>\n\n\n\n

      \u201cOne piece of advice is to view the operator-supplier relationship as a partnership,\u201d concluded Sutherland, bringing the discussion full circle and back to trust. \u201cThe trust between both sides allows for open communication on the wear life history, operating data, and future wear targets. This allows the OEM to work efficiently to offer solutions that help the operator meet their desired goals.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

      Handling slurry inevitably exposes equipment to wear. The question is thus how to manage \u2028and minimize that wear. North American Mining spoke to four experts about issues in slurry \u2028pump wear protection. By Jonathan Rowland Introduction: the three types of wear There are three main categories of wear to which a slurry pump may be exposed: abrasion, corrosion and erosion.…<\/p>\n","protected":false},"author":8,"featured_media":6957,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_themeisle_gutenberg_block_has_review":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[4],"tags":[2780,2781,1158,533,532],"coauthors":[1635],"class_list":["post-6952","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-features","tag-krebs-pumps","tag-ksb","tag-metso","tag-slurry-pump","tag-weir-minerals"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t