Gears Instead of Belts


Gravel plant cuts costs and reduces maintenance expenditures by using gearmotors. In many gravel pits, stone crushing plants and similar operations, shaft and belt drives provide motive power for conveyor belts. Until recently, this was the situation at the gravel plant of NorStone AS in Tau, located in the southwest region of Norway. Recently NorStone, a subsidiary of Heidelberg Cement AG, decided to change to robust gearmotors. This option promised lower investment costs and increased operational reliability, along with better process security. Reduced energy consumption was also anticipated, thanks to higher efficiency.

NorStone is Norway´s largest producer of gravel products. The company supplies aggregates for concrete and asphalt, pipe cover gravel for coastal regions, and other special products. Each year NorStone´s production facilities produce over 6.6 million tons of gravel products in various sorts and quality classes. The demand is large, and even with its present annual production capacity of 2.3 million tons of material the Tau plant can scarcely meet the demand. This makes it especially important to ensure that the plant is operational as much as possible and to minimize unplanned downtime.

Familiar advantages plus increased reliability with direct drives

Gearmotors are not new in gravel pits. Direct drives of this sort were commonly used in the 1980s. In subsequent years, many plants changed to belt drives because spare parts for these drives were always quickly available while manufacturers and suppliers of gearmotors were unable to offer stocks of spare parts with the same availability. "We have found that service and spare parts for gearmotors are now available to us very quickly. We hold some parts in stock ourselves, and for all of the rest we have complete trust in NORD Drivesystems as a supplier," explained Ivar Ullestad, Maintenance Manager at Tau, as the reason for going back to the former solution. "This allows the known advantages of drive solutions with gearmotors to be fully exploited. In particular, direct drive leads to higher reliability, which means less downtime and therefore less lost production time. Another important aspect is that less maintenance is necessary. In addition to reducing maintenance costs, this increases safety in the plant," added Ullestad.

Working conditions are a significant factor in such considerations. "You have to bear in mind that we work outdoors all year round. Most of the locations for the conveyor belt drives are open and unprotected. Due to the harsh weather conditions in the west of Norway, with wind, rain and sleet, as well as the dusty and rather unpleasant environment at the site, we try to minimize repair and maintenance times for our maintenance staff.» The Tau plant runs seven days a week, 24 hours a day in shift operation. The 168 production hours include 16 hours of scheduled maintenance. The plant is only shut down for the winter break. During this break, annual maintenance inspection and overhaul tasks are performed in two to three weeks. The direct drives have contributed to a distinct increase in reliability, amounting to approximately 4.5%, in the last three years. "We are very satisfied with this trend. With the change from shaft and belt drives to direct drive with gearmotors from NORD Drivesystems, in the first place we eliminate the aspect of belt wear, which is considerable. Furthermore, no water or dust can enter the drive mechanism. This means that the decision in favor of compact, robust gearmotor unit´s yields clear advantages and has therefore proven to be an intelligent move," summarized Per Thu, Production Manager of the NorStone plant. The direct drives brought more than just higher reliability and reduced financial and labor expenditure for maintenance activities. The relative investment costs for purchasing new gear units also proved to be lower. Replacing a complete package, consisting of a shaft-type gear unit along with belt pulleys, belts, a shed, belt cover and motor, turned out to be more costly than purchasing a comparable geared motor. As a series of periodic gear unit replacements was anyhow in the works, a comprehensive switch from shaft and belt drive to direct drive was a logical choice for Ullestad. He is currently working to standardize drive components. "With a staged cutback in drive systems for the conveyor belts, we are standardizing aspects such as motor size, shaft size and drum diameter in order to limit diversity and thereby simplify maintenance, stock management and service. We are also developing backup solutions, which among other things involves keeping components in stock ourselves," according to the maintenance manager.

NorStone AS

The Norwegian company NorStone AS (http://www.norstone.no/) is a fully owned subsidiary of HeidelbergCement AG, one of the world´s largest producers of building materials such as cement, sand and gravel. The plant in Tau monitors, mixes, controls, and delivers high-quality aggregates for concrete and asphalt as well as base course materials with consistent quality in various grades. The materials are split and cut into graduated sizes, after which they are mixed to obtain particle size distribution curves meeting specific customer requirements. In this process, compliance with EU standards is monitored by in-house laboratories. Among other things, NorStone supplies ballast for the railway industry, road building materials, and base course materials for coastal regions. The Tau plant produces 2.3 tons of material each year, of which around 75% is exported.

Company background

NORD was founded in 1965 to develop, produce, and market drive technology. As an industry leader ranking # 2 in US & Canada and # 2 as the Global Leader, NORD reaches nearly all markets. With 2600 employees and 35 assembly factories worldwide, sales and support is available in 60+ countries. This ensures short delivery times and services close to you. NORD supplies application-specific concepts and solutions; including but not limited to energy-saving drives. NORD provides wide range of products to meet your needs; such as gearboxes with torque ratings from 8.5 lb-in to 1,770,000 lb-in and electric motors with power ratings from 1/6 HP to 250 HP. In addition, the product line consists of high performance AC Vector Drives and AC Drives for panel mount or distributed motor mount.

www.nord.com

NORD Gear Corp

P.O. Box 367 - 800 Nord Drive

Waunakee, WI 53597

HOUDEK Barbara

Phone: + 1 608 849 7300

Fax: + 1 608 849 7367

barbara.houdek@nord.com

Getriebebau NORD GmbH & Co. KG

Rudolf-Diesel-Straße 1

22941 Bargteheide/Hamburg

Germany

NIERMANN Jörg

Phone: +49(0) 45 32 / 401 - 360

Fax: +49(0) 45 32 / 401 - 254

Joerg.Niermann@nord.com

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