Pumps and Valves: Integrate for Efficiency

by russell a. carter, contributing editor

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 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.

All major pump manufacturers offer various levels of needs analysis, design consultation and on-site support both before and after system startup. And, 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 2-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. 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.

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.

The Tandem Kit attaches 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. 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.

Innovation Leads to Optimization

Innovative applications of existing technologies and improved material properties are also contributing to pump performance and reliability. SKF’s fiber-optic sensing system, for example, has been used to validate new process pump designs.

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 [the manufacturer] to further improve its pump designs, and enable product design verification with real time data,” 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.

New synthetic-based products such as SealRyt Corp.’s Style 2017 stuffing box packing can provide better performance in tough mine pumping applications. 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.

Valves: Less is More

Weir Minerals recently unveiled the Isogate WR knife gate valve line, which the company said is designed to provide high reliability with considerably less weight.

“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.

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.

This article was adapted from an article that was published in the April 2021 edition of Engineering & Mining Journal (E&MJ).