More than 40 years ago, Germany's WOHWA set up the first blending and loadout systems in Europe. About 18 months ago, WOHWA opened a sales, service and spare parts supply center in Vancouver, Canada, where the company provides support to its dealers in the United States and Canada.

Take note

Automatic systems for loadout to trucks, ships and trains are gaining increasing popularity because of their significant cost-savings potential. Costs for fuel, personnel, maintenance and operation can be reduced substantially by the use of automatic blending and loadout systems. Also, throughput rates can be increased with the use of these systems. Automatic control systems are often used in fractionated plants for the automation of blending and loadout processes where the aim is a high degree of accuracy and repeatability.

For decades, companies such as Heidelberg Cement, Vulcan Materials, Lafarge and Holcim, have been purchasing WOHWA components or turnkey blending and loadout systems. WOHWA says it's the only company that can offer customers complete solutions. All essential components — discharge gates, belt feeders (reclaim and blending), belt scales, control systems, software and automation solutions with card readers — are engineered, manufactured and custom-tailored by WOHWA. Clients benefit by avoiding the potential conflict associated with using interfaces from different systems. WOHWA loadout systems are completely provided by one supplier.

Product features

This loadout station for trucks features a WOHWA user panel, allowing drivers to handle loadout themselves.

All systems are based on the WOHWA reclaim, blending and feeding devices: discharge gates and belt feeders that are fully hot-dip galvanized and bolted (not welded). Discharge gates are available with opening widths ranging from 8-in. x 8-in. to 32-in. x 32-in. and can be equipped with water drainage sieves, allowing drainage of the area directly above the discharge gate to prevent fines from spilling into the reclaim tunnel. Emergency shut-off gates are available for installation above all WOHWA discharge or feed devices facilitating repair and maintenance work or the complete replacement of a device.

Water drainage can also be applied when using belt feeders. For this purpose, a discharge gate is mounted above the belt feeder, which can be closed before the feeder stops, preventing wet sand spilling from the stockpile into the reclaim tunnel while the belt feeder is not in operation. This technique has been successfully applied in Europe for many years and it is gaining popularity in North America, according to WOHWA. It has been successfully introduced by Lehigh Northwest at its Sechelt gravel operation and by Polaris Minerals Corp. at its Orca Sand & Gravel operation.

With WOHWA blending and control systems in combination with WOHWA belt scales, a high degree of accuracy can be achieved when loading trucks. The belt scales communicate directly with the loadout system and transmit a stop signal just at the right time. This is a result of the automatic in-flight compensation, which is computed from the average belt load and the distance in time between feeding device and belt scales.

Weather and other influences can be compensated for with this dynamic feature. Conventional systems relying on preprogrammed, static time intervals for stopping the loadout process cannot match loadout accuracies achieved by WOHWA systems, according to the company. A WOHWA blending and loadout system with the in-flight compensation feature has been installed in Lehigh Northwest's Steelhead Aggregates Ltd. plant outside Vancouver. In this plant, the overloading of trucks has been practically eliminated.

All WOHWA loadout systems offer the additional possibility of volumetric blending: different fractions can be blended to produce product blends that meet the individual requirements of each customer. This technique can also be used for single-product stockpiles. Several reclaim devices are used simultaneously under a stockpile to avoid segregation problems caused by the formation of a too-large funnel. Reclaim occurs evenly from three outlets below the stockpile. This technique was successfully introduced by Polaris Minerals Corp. at its Orca Sand & Gravel operation on Vancouver Island.