International Dredging Review

International Dredging Review

Metso Pumps Help Aggregate Producers Mine Deeper Materials

By Albert “Bubba” Savage
Product Manager- Global Dredge Pumps
Metso Mining and Construction Technology

The majority of pumps Metso has sold to the U.S. dredging industry have been used in sand and gravel mining for the construction industry to produce concrete and asphalt for roads commercial building projects and residential building projects.

Since late 2008 the construction business in the U.S. has struggled to rebound from the economic collapse even as government has injected stimulus funds to help revive this labor-intensive industry.

While the market for new dredges for aggregate mining has been slow to rebound the equipment upgrading business has been active as aggregate producers strive to be more productive in the face of falling aggregate prices.

Metso was active in 2010 assisting dredge operators in replacing old inefficient and outdated dredge pumps with new Metso Thomas pumps.

Aggregate dredgers face four major operating costs: fuel labor resources or reserves and maintenance. While a new dredge pump cannot affect the price of the reserves directly it can affect the costs of fuel labor and maintenance.

Modern dredge pumps offer several advantages over older models. Advances in impeller vane designs have improved the hydraulic efficiency of today’s dredge pumps as much as 25 percent.

While straight type vanes have been the norm new design warped or Frances vanes have allowed pump designers to make impellers even more efficient while allowing for passage of large spherical objects desirable in a pump built for pumping whatever comes in close proximity to the suction opening. Fine tuning of entrance and exit angles of the impeller vanes allows pump designers to pinpoint the operation of the pump as close to the Best Efficiency Point (BEP) as possible. Operating close to BEP reduces the radial forces on pump shafts and bearings and reduces recirculative wear both of which can reduce labor costs associated with pump rebuilding and maintenance costs of pump wear components.

Aggregate mining dredges generally pump material 24 hours a day six to seven days per week. They make money only when they are running and producing material so uptime is vitally important to an aggregate dredger.

Product support by way of technical assistance and the availability of spare parts is key to many aggregate dredge operators. Metso offers technical assistance for dredgers in areas of project management pump and system calculations and troubleshooting of pumping issues. In the area of parts availability Metso inventories wear parts for standard dredge pumps in various locations throughout the U.S. and offers consignment inventories for customers who need onsite parts availability.

As mentioned previously material resources and reserves have become a major cost item for aggregate dredgers. The cost of land permits and environmental regulations has increased dramatically over the past years. The difficulty in acquiring new land for mining has forced aggregate producers to look deeper into their existing mining footprint to find additional reserves.

The efficiency of hull and deck mounted dredge pumps in mining material from depths over 40 feet is low due to dredge pump suction side losses. More and more dredgers who have good deposits of material at depths greater than 40 feet are using underwater ladder-mounted dredge pumps to increase operational yield and lower fuel costs. Metso has assisted several large aggregate producers to upgrade existing dredges with new more efficient underwater dredge pumps. These pumps enable a producer who struggled to achieve slurry 15 percent solids by weight in the dredge slurry to more than double their production with a underwater dredge pump capable of pumping slurry containing 32 to 38 percent solids. Higher production using less power means a lower cost per ton for the aggregate. In our market of falling aggregate prices increased production and lower cost can give the producer an advantage over the competition.

While the U.S. construction business has struggled in 2010 the market for pumps and dredges for export has exploded. Most U.S. dredge manufacturers are flush with work for dredges destined for points around the world. Since 2005 Metso has concentrated on marketing the Metso Thomas dredge pump to foreign markets through the Metso international sales units. These efforts have paid off in 2010 as Metso has exported pumps and components to Chile Iraq Germany Mexico Italy Brazil Canada Argentina China and Russia.
Dredge pumps in sizes H24 (10”x8”x30”: suction-discharge-impeller diameter) through X52WD (24x24x52) have been sent around the world to be used in retrofits of existing dredges and new dredge construction.

Many new dredges are being built to support operations associated with hard rock mining activities and associated tailings operations.

Pumps in the hard rock mining industry often transport high density slurry of ground and processed ore. Slurry concentrations of 50 to 60 percent solids by weight are typically pumped to cyclone banks for further separation or to new tailings deposit areas. These dredge pumps are selected because of their heavy sectioned wear parts made from highly abrasion-resistant materials. Pumps for this kind of service typically use five-vane impellers for higher efficiency and use pump cases with integrally cast side liners to protect wear points associated with the joints between mating parts.

As the cost of water for pump gland flushing becomes a major factor for many mining companies the use of low flow gland seals or mechanical gland seals that require little or no water to seal the shaft entrance into the pump are becoming part of the pump specification. Metso has incorporated mechanical seals in both dredge and booster pumps associated with mining and environmental projects.
While the mining and export markets have sustained our business in 2010 we eagerly await the rebound of the U.S. construction market. This is our “bread and butter” business that has helped build Metso’s dredge pump business. A healthy U.S. construction business means more jobs and an overall healthy economy.