slurry pump metso

Slurry pump side-liner wear: comparison of some laboratory and field results

Abstract

The current work compares some lab wear results with the wear found across different field applications with _d_ 85 particle size ranging from 100 to 4000 μm. Side-liner wear life data has been collected for two different geometries and two different material classes (cast iron and natural rubber). Different field wear patterns have been photographed and categorised on the basis of particle size. The field wear patterns showed close similarity to the lab wear patterns particularly in the areas of localised gouging. Wear rates are also compared for the different geometries. Overall trend of wear with particle size for the white iron parts was similar to the grey iron lab tests albeit at significantly lower wear rates. In general, the wear with the rubber side-liner was less at smaller particle sizes but greater for particles larger than _d_ 85 of about 700 μm.

Introduction

Centrifugal slurry pumps are used almost universally to move mixtures of abrasive solids and liquid around wet mineral processing operations. These pumps are generally of rugged construction and generous clearances to allow the passage of large solids. Pump useful life in these applications can range from a few weeks to a few years depending on the type of slurries handled. The direct cost of slurry pump wear parts for the mining industry and the associated down-time and labour costs are significant. Reducing these total ownership costs requires a better understanding of pump wear patterns and wear rates for different slurries and different geometries.

Previous work undertaken in the laboratory by Warman International has identified the effect of flowrate and particle size on the wear in a standard (STD) 6 in.×4 in. centrifugal slurry pump [1]. In this work it was found that the inlet side-liner wear did not change much regardless of particle size over the range _d_ 85=100–1000 μm. Most of the wear on the side-liner occurred on the face and around the periphery. The front expelling vanes on the impeller were presumed to be responsible for keeping particles away from the eye (centre) region. More recently a high efficiency style impeller (HE) geometry has also been tested in the laboratory [2]. Pump rotational speed and slurry concentration were varied and the results compared to the STD design. The lab testing has by practical necessity been restricted to a fairly narrow range of slurry conditions and soft cast iron materials were used to generate an acceptable wear rate in a short time period. Overall it was found that the slurry pump inlet side-liner experienced a greater wear rate than either the impeller or casing-liner for applications where the _d_ 85 particle size (screen size which passes 85% of particles by mass) was predominantly finer than 700 mm [1]. This particle size range represents a significant proportion of mineral processing and industrial slurry applications.

The focus of this current work is the side-liner as it represents the life-limiting component of the slurry pump for many applications. In order to verify and extend the findings of the previous lab tests, wear life data has been collected on the two different pump geometries (both STD and HE) from a range of different duties in the field and the results compared.

Measuring side-liner wear

The wear of the inlet side-liner is significantly influenced by the design of the impeller that rotates in close proximity to it. The majority of side-liner wear has been attributed to the slurry “leakage” which occurs from the high pressure casing periphery back to the low pressure inlet (or “eye”), across the face of the impeller [2]. The presence or otherwise of front expelling vanes on the impeller shroud, the clearance between the impeller and side-liner and the meridional profile of the

Results

The results for the wear patterns and wear rates have been considered separately.

Discussion

The major difference in the wear between the HE side-liner and the STD has been largely explained previously by the geometry differences [1], [2]. Because the HE design has no expelling vanes on the impeller front shroud and has a much larger front clearance over much of the shroud diameter it does not seal as well as the STD impeller. This in turn means a greater quantity of slurry returning through the gap between the impeller and side-liner.

Summary and conclusion

The experimental work outlined has compared the field wear performance of side-liners against some limited lab results. Overall it was found that the field results agreed with what was previously reported from the laboratory [2] and that the metal HE side-liner wears better than the STD for _d_ 85<300 μm slurries. It was also found from the field results that for smaller particle slurries (_d_ 85<700 μm) that rubber side-liners give lower wear rates than the metal. These results provide useful