Heavy-duty pumping systems are the norm in mining, but newer equipment designs and materials are aimed at lightening the load – in terms of weight, opex, mechanical complexity and service requirements
By Russell A. Carter, Contributing Editor
The number of pump types used at any large-scale metal mining operation might only be surpassed by the range of sizes, body materials, power demands and maintenance requirements associated with them. Pumping tasks can differ greatly — pit dewatering vs. mill discharge, slurry vs. sludge, for example — and like the human workforce that installs, inspects and services them, some pumps are generalists capable of handling a variety of jobs, while others are specialists, designed to handle dedicated pumping tasks.
They’re are among the oldest and most tradition-bound equipment types used in mining. As Harvinder Bhabra, head of the fertilizers, metals, mining and chemical process business segment at Swiss pump builder Sulzer, pointed out in a white paper last year, pumps have been used to transfer fluids for centuries, progressing from early Egyptian shadoofs — basically a pole and a bucket — to the Greek Archimedean screw and on to the highly engineered designs available now.
They’re also a major part of the picture in any future vision of Industry 4.0. Bhabra noted that over time, as industry processes became increasingly sophisticated, specifications for various pump types demanded innovative manufacturing techniques to keep pace. Some of these include hydraulic profiling, CAD/CAM, computational fluid dynamics, finite element analysis and 3D printing. Most recent developments link to the advent of the Internet of Things (loT) and the collection of pump operating data and condition monitoring. Real-time visibility of a pump’s performance provides a reduced risk of unplanned downtime caused by a failure. Mine-site pumps also may be required to operate long after mining activity ceases, for care and maintenance purposes; reliability and remote monitoring capabilities are critical factors in those applications.
Next-generation models will likely not just transfer media more efficiently but will also be capable of sending performance and machine health data at unprecedented levels to a variety of digital platforms and devices, as mining companies continue to shift from capex to opex-based models that demand constant and comprehensive data flows for maximum effectiveness. Increasingly, companies are regarding pumps and the piping, valving and control networks they’re part of as an integrated fluids management system that can be used innovatively to help resolve broad industry issues of water usage and energy consumption, along with specific ongoing concerns about life cycle costs, leakage and repair frequencies.
Design innovations that support this approach are proliferating rapidly, encompassing features ranging from easier access for inspection and adjustments to quicker changeout of wear-prone components.
Integrate for Efficiency
Mine and plant pumping requirements can span a range of demands that vary from simple and straightforward to multidimensional, and obvious system choices aren’t always the complete answer to a pumping problem: For example, the favorable economics offered by a properly sized, efficiently powered and well maintained pump can be degraded by a piping setup that causes severe water hammer incidents resulting in leakage or pump damage; or a crucial heavy-duty valve may be so large that it requires extra vertical clearance to install and operate — and a crew of workers to safely maintain it; or perhaps a failing critical pipe section that was assumed to be protected against corrosion by its fusion bonded epoxy (FBE) lining should have been roto-lined instead for better performance.
These are all reasons why an integrated approach to pump-system design usually pays off. (As an example, see the accompanying sidebar describing how one pump supplier’s methodology solved multiple system demands at a Mexican gold mine.) All major pump manufacturers offer various levels of needs analysis, design consultation and on-site support both before and after system startup. And, as we’ll see further along, third-party participants such as electrical and engineering contractors, pump component suppliers and others can provide significant value to customers through advice and services related to pumping facility location and layout, monitoring and maintenance.
Recent pump models coming through the product pipeline offer end users a constantly expanding range of options for pump-system flexibility. Tsurumi, for example, has been particularly active during the past year, adding to its LH series heavy-duty submersible pumps for mining applications and introducing the GPN 837 heavy sand pump.
The new LH-D-series features two-pole, 110/185 kW motors and a double-suction impeller to deliver reliable performance in high-volume, high-head applications. The company said the pumps, with a maximum capacity of 14 m3/min and a maximum head of 92 m, meet the needs of open-pit and underground mining, heap leaching and large-scale tunnelling work.
According to Tsurumi, an important feature of the new LH-D series is the ability to draw large volumes of water from both the upper and lower sides of the double suction impeller, thus reducing thrust load, extending bearing service life and increasing the stability of pumping operations. The pumps have a flow-through design that actively cools the motor during extended operation at low water levels and a useful inspection window at the bottom of the stuffing box.
The top-of-the-line GPN 837 heavy sand pump is rated at almost 2,400 gallons per minute (gpm) and is designed for use whenever large amounts of solid matter are involved, Tsurumi said, noting that the unit can pass up to 30-mm rocks. The 1,800-lb (815-kg), 39-in.-tall (1-m) pump is powered by a 50-hp (37-kW) motor and features an oil filter that uses centrifugal force to lubricate in any position. The GPN 837 pumps vertically up to 78 ft (24 m) and when submerged is pressure-resistant down to 30 m.
Tsurumi recently began to promote its Tandem Kit, a pumping innovation developed for high-head applications where the need for strong output — and thus, larger pumps — collides with a lack of installation space, a situation not uncommon in underground mining.
As a solution, Tsurumi developed the Tandem Kit, which is attached to the casing of the LH and LH-W series pumps and enables two pumps of the same model to be easily connected in series, providing twice the total head of a single pump at a fixed flow rate. The operating principle of this method is the same as that of a multistage pump, according to the company, which has six 4- to 40-hp (3- to 30-kW) pump models that are compatible with the kit, with most featuring a dual impeller design. The standard kit, which can be easily attached to the pumps at the work site, provides a maximum 833-ft (254-m) head, and a 400-m head is achievable with optional equipment.
Weir Minerals has launched several new products, including the VL axial pump, horizontal process pump and vertical high-pressure molten salt pump, all in the company’s Lewis line. In addition, it introduced the mobile Multiflo LF pump range, available in different configurations to meet varied demands including applications where liquids may contain high percentages of solids or acidic conditions with low pH values. Mounted on either a trailer or a skid, the pumps are available with Tier 3 or 4 diesel power or an electric motor.
Weir said the pumps’ impeller design and larger-diameter pump shaft enables efficient handling of large solids while reducing operational and maintenance costs. This is achieved through an advanced, high-efficiency pump-end that requires less energy to process fluids.
The MultiFlo LF offers flow rates ranging from 100 m3/h to 3,200 m3/h, and discharge heads of 10 m to 210 m. The line’s robust bearing frame and pump shafts have been proven to result in fewer seal failures and shaft breakages under extreme conditions, according to the company.
Vertiflo announced the Series 1600 horizontal close-coupled, vortex end-suction pump line, offering capacity up to 1,600 gpm, heads of up to 170 ft, and capabilities for handling temperatures of up to 250°F. The pumps, offered in cast iron, stainless steel or alloy construction, feature a convenient, cost-saving back pull-out feature for easy inspection or maintenance, and an impeller design that facilitates better passage of solids, reduces axial loading, and prevents dirt from entering the sealing area.
Innovation Leads to Optimization
Innovative applications of existing technologies and improved material properties are also contributing to pump performance and reliability. Sulzer recently reported that, by using bearing manufacturer SKF’s fiber-optic sensing system to validate new pump designs, it can confirm product performance using actual measurement data previously unavailable. Sulzer said it used the SKF system to verify the design of a new centrifugal process pump.
The sensing system measures loads directly in the bearing, which gives a deeper insight into a pump’s actual operating conditions. “Design verification, using real load data, is enabling Sulzer to further improve its pump designs, and enable product design verification with real-time data rather than calculated scenarios. It improves physical test confidence and reduces time to market” said Daniel Perreng, sales and market champion, fiber optic sensing at SKF.
The system uses load-sensing bearings with fiber optic sensors, fitting the most commonly used bearing sizes used in heavy-duty process pumps. Only minor modifications are needed to install the sensors in the bearing housing, according to SKF, which explained that it measures bearing loads, and changes in loads and directions, accurately and repeatably. The system can also determine housing and impeller qualities and alignment.
It was tested and validated on a Sulzer mechanical test rig. SKF said that while Sulzer used the system in a research capacity, an end user can also use it to collect detailed data in the field. SKF will offer global support for setting up the system and training of Sulzer staff at their R&D sites as well as provide data analysis.
Gorman-Rupp recently developed a new integrally mounted diaphragm priming assembly as an option on select 4- through 12-in. (100–300 mm) Prime Aire and Prime Aire Plus pump models. Offered as an alternative to the venturi/compressor priming system on Gorman-Rupp’s priming-assisted pump models, the diaphragm primer delivers up to 60 cfm (1,700 lpm), a vacuum to 30 ft (9.1 m) and is rated for temperatures as low as 15°F (-9.4°C).
The company said the new primer assembly, with fewer components, offers reliability and increased efficiency, as well as higher lifts. Reversed air flow and thinner valves help any liquids entering the primer to escape easily. The new primer’s single-bearing housing has fewer leak paths and alignment issues compared with dual-bearing housing alternatives.
New synthetic-based products such as SealRyt Corp.’s Style 2017 stuffing box packing and South Africa-based Vesconite Bearings’ Hitemp 160 can provide better performance in tough mine pumping applications, according to both suppliers. Style 2017 packing consists of pre-twisted high-carbon yarn with monolithic polyester filament that is interbraided with an asymmetric matrix. According to SealRyt, Style 2017 exhibits very high tensile strength, is “shaft friendly” and resists picking and fraying wear, along with offering significant heat dissipation properties. Its pre-twisted configuration allows all beneficial material characteristics to be present throughout the entire product matrix.
Earlier this year, Vesconite reported that a pump containing three sleeve bearings made from its new bearing material, Hitemp 160, which can operate at temperatures up to 160°C (320°F) and is resistant to abrasion, was tested and received South African Bureau of Standards (SABS) certification.
The pump tested, according to the company, is part of a range of large vertical spindle suction pumps that will be primarily used in mining. “The pump manufacturer tested and included our proprietary Hitemp 160 material, which has excellent abrasive properties, negligible water swell and allows the pump to run dry periodically,” said Phillip de Villiers, Vesconite pump applications specialist. “Having a material that could aid in the pump’s need to run dry occasionally for short periods of time was a priority, and our material could serve that need in this specific application,” noting that the new material fills a gap in the market for high-temperature bearings that are able to operate in immersed conditions.
Ehouses Enter the Picture
Project owner reluctance to construct permanent structures at remote mine-site locations is converging with the industry’s attraction to digital solutions and modular design to drive increasing interest in Ehouses and similar movable enclosures for pump power, control and protection. As E&MJ reported in the November 2020 issue (see 3 Takes on Tailings Technology, pp. 54-56), Weir now offers a skid-mounted pumphouse that features towable relocation capability, adjustable leveling, an internal gantry crane, pump component lifting jigs and multiple access points for ease of maintenance. One of these mobile systems, recently delivered to a client, incorporates an integral gland water supply system and a three-point pump base-mounting system, which allows the base and skid to act independently, minimizing the risk of pump and motor shaft misalignment during operation and the relocation process.
Ehouses — transportable prefabricated electrical equipment structures containing medium- and low-voltage switchgear and motor control electronics — are gaining popularity, in part because the reduced size of this gear due to digitalization allows more of it to be packaged efficiently in smaller spaces. E&MJ asked Brian C. Literski, electrical engineer with engineering and professional services group Morrison-Maierle, to describe some of the advantages Ehouses can provide in pumping applications.
Literski, who has designed a number of Ehouses for Morrison-Maierle clients over the past 8-10 years, said project scheduling benefits are the primary driving factor for Ehouse orders from mining clients. “Mines identify a project, get it funded through their process, and then hurry to get the project installed within the fiscal period. The Ehouse approach enables the owner to procure long lead-time items — medium-voltage VFDs, for example — and have them shipped to the Ehouse manufacturer. The Ehouse manufacturer concurrently works on the building structure and once they receive the equipment they can install, test and wire most of the components in a matter of two to three weeks.
“Another plus for Ehouses is that once the design is bid and priced, we have seen very few change orders on them. Pricing is firm except for shipping rates, which are usually determined in the last few weeks before delivery,” Literski explained. Quality control and labor costs also enter into the equation: “Having qualified trades people working [on an Ehouse] in a manufacturing facility helps with quality control of the installations, and labor costs are lower” because project owners may avoid having to pay on-site workers overtime or per diem, he noted, particularly when conditions at the installation site can result in schedule disruptions. And, he continued: “The systems contained in the Ehouse are also more ‘plug and play.’ The entire unit arrives ready to be set in place and have external wiring connected. The internal wiring is already completed with equipment mounted and tested.”
Ehouse sizes vary, Literski said, with typical dimensions in the range of 12 ft wide x 40 ft long x 12 ft high or less, which makes shipping logistics easier. He also designed a unit that measured 14 ft 2 in. wide x 46 ft long x 13 ft high, weighing about 90,000 lb with equipment installed. “I’ve also seen two structures bolted together to make a wider Ehouse with pass-through doors to access each side. And when the pumping station only uses low voltage (480 volts or below), we can use a Conex style — 8 ft wide, with varying lengths — to house the equipment.”
These enclosures can easily meet the industry’s need for expanded instrumentation, data collection and security, said Literski. “We’ve included control panels and communications equipment in every Ehouse we’ve designed. The data links we provide to these units have enough bandwidth for process control data delivery as well as security cameras. And Ehouses are not just limited to pumping stations; any remote location that requires electrical power, data acquisition, or a combination of both are good candidates.”
Valves: Less is More
Valves may not be the largest cost-per-unit item in a piping system, and their selection may not be at the top of project engineering focus, but the wrong choice — either from cost considerations or misapplication — can have a disproportionate effect on process efficiency and facility safety. Lack of corrosion resistance, inappropriate pressure ratings and pressure loss throughout the system, or unnecessary system weight and stress are all problems that can contribute to poor piping-system performance.
Weir Minerals, for example, unveiled the Isogate WR knife-gate valve line, which the company said is designed to provide higher reliability at considerably less weight than equivalent mining valves.
“We’ve optimized the Isogate WR knife gate valve’s body design, by reinforcing the areas subjected to the harshest wear and pressure. At the same time, we’ve reduced the weight elsewhere to produce a robust, long-lasting mining valve that’s significantly lighter than comparable products,” said John Abbott, global product manager, valves and tailings. “The weight reduction can be especially significant in situations where a number of valves are used on a specific installation, such as in a hydrocyclone cluster, or where lightweight piping systems are used.”
The gate has also been redesigned, with stronger materials resulting in a thinner gate that can still withstand the pressure of mining slurries. This combines with a unique gate guide that reduces deflection by ensuring smooth gate movement and less stress on the sleeve elastomer during blade transition.
The Isogate WR knife gate valve features the IsoGate WSL sleeve, which, according to the company, uses proprietary Linard HD 60 silica-reinforced natural rubber to solve three common problems with sleeved knife gate valves: leakage during cycling, tearing and load distribution ring (LDR) failure due to corrosion and erosion. The Isogate WSL sleeve fully encloses the LDR to prevent corrosion. By allowing the rubber to move as the blade cycles, the design reduces the chance of tearing while reducing slurry discharge by up to 75%. The sleeve, according to Weir, also can also be used in existing Isogate WS knife gate valves, improving wear life and decreasing discharge on cycling.
“When designing the Isogate WR knife gate valve, we focused on features that improve the everyday experience of working with our valves. This includes important things like improved grease distribution and improved body flushing when used on high solids concentration applications. In-depth finite element analysis (FEA) enables us to ensure the product’s integrity, while making it lightweight. There are also a lot of smaller features to make life easier, such as a larger grease reservoir, ISO mount standardization and an external visual indicator for the valve’s status,” Abbott said.
Last year, Flowrox introduced a major design change for its larger (>DN 900) slurry knife gate valves. The traditional valve-actuator tower design, according to Flowrox, usually works well with this range of valve sizes, but also results in extremely tall units. Flowrox’s new design eliminates the cylinder tower and repositions the actuator cylinders to the side, significantly reducing valve height.
As an example, a DN 1200 valve with the traditional tower design could be as tall as 5.6 m (18 ft) in open position, making the valve more difficult to handle, less stable during assembly and harder to access for maintenance. The new Flowrox design for valves from DN 900 to DN 1500 has actuator cylinders on each side of the valve. Compared to the conventional design, a Flowrox DN 1200 knife gate valve is only 3.6 m (12 ft) tall in a fully open position. All maintenance access points are located less than 2 m from the ground, making them easily accessible.
Another change affects the valve body, which in conventional designs comprises two pieces that are bolted together, increasing the possibility of leakage and requiring tedious unbolting/bolting during maintenance. The new Flowrox valve body is cast in one piece, reducing the risk of leakage and containing fewer parts, for savings in spare part inventory and maintenance time.
Red Valve’s long-established and popular Series DX slurry knife gate valve was designed to be durable and user-friendly for difficult slurry applications, according to the company. The fully elastomer-lined DX prevents slurry buildup or dewatering by eliminating the seat cavity. Reinforced elastomer sleeves seal against each other, providing a 100% full-port opening, minimizing turbulence and wear when the valve is open. Seats isolate and protect metal parts from contacting process media. When closed, the sleeve provides a drop-tight seal in both directions.
Designing a System to Meet Multiple Challenges
An open-pit gold mine in Sonora, Mexico, planned to expand after discovering additional mineral deposits. To support increased production, the mine needed an efficient water management solution that would boost the pumping capacity for the mine’s process water and dewatering systems while ensuring the operation had a minimal impact on the local environment.
Xylem along with Bombas y Suministros del Norte, the local Xylem distributor, were tasked with a twofold challenge. The first goal was to develop a process water-pumping solution capable of feeding the high-pressure pumps that irrigated the extracted mineral to leach the gold from the ore. The second goal was to avoid contaminating the recovery pools with cyanide.
Working closely with the customer, the team engineered a system incorporating three products from Xylem’s portfolio: Goulds Water Technology vertical turbine pumps and Flygt submersible dewatering pumps, paired with Aquavar IPC variable-speed controllers.
Twelve Goulds Water Technology turbine pumps were installed on four custom-built raft units, three pumps per raft, floating on reservoirs containing process recovery water and well water. The pumps feed high-pressure pumps to irrigate the extracted mineral ore.
They were paired with Aquavar IPCs, which are specifically designed for submersible and groundwater applications and enable the pumps to respond smoothly and efficiently to fluctuations in demand, minimizing wear and improving pump life. In this application, they control pumps speed based on water demand, energy savings and efficiency.
Two 60-hp Flygt NS3202.180 submersible pumps were also installed, as part of the dewatering system. These units come into play when the site has heavy rainfall, pumping water from one recovery pool when it fills to a second recovery pool. The Aquavar IPC ensures that all pumps operate as efficiently and consistently as possible, pumping 6,000 gpm.
Jessy Parmar, business development manager, Xylem Industrial Solutions, said, “We recommend a holistic approach to mine water management, examining all aspects of the system to maximize productivity, reliability and sustainability. An optimized system includes built-in protection against downtime caused by equipment failure. The first line of defense is effective monitoring and maintenance.
“However, the most critical equipment requires contingency planning and emergency backup. In this case, two CD150 Godwin diesel automatic self-priming pumps were installed as a backup for the Flygt submersible dewatering pumps. This provided peace of mind that, in the unlikely event of a pump failure, a solution was on hand to ensure the safety of the surrounding environment.”
Since being installed, the process water and dewatering pumping solutions have operated reliably and efficiently. Having efficient and powerful pumps in place, suitable to this specific application and optimized by Aquavar IPCs, has ensured hassle-free operation.
Parmar continued, “Our mining customers take their environmental responsibilities seriously. As well as securing the safety of the surrounding ecosystem by ensuring the cyanide used to extract mineral ore did not leach into the recovery pools, our solution enhanced the productivity of the operation. Smart mine water management makes sense on many levels.”