Scale-Tron, automation, sensors and weighing systems

CUSTOM CONTROL AND WEIGHING SYSTEMS

Scale-Tron's engineering team has over 40 years experience in custom systems in weighing, automation, scales, force measurement and many related applications.

Expertise includes load cells, scales, industrial controls, computer and PLC programming, computer system set-up, electrical and electronic circuit design, motor power circuit design, including variable speed AC drives, load cell mounting, travelling hopper design, explosion-proof systems, bag and box filling, loss in weight feeders, Autocad drafting, technical writing and production documentation.

Unique project examples: 

Aggregate cooling system

Wet belt for aggregate cooling in concrete plantsConcrete for large civil engineering projects such as dams needs to be cooled to below 10°C (50°F).  The aggregates are cooled by passing them through a "wet belt"; a conveyor belt punched with thousands of holes with cold water sprayed on the aggregates as they pass.  The water produced for this cooling can also be used in the batching process.  Sand can be cooled in a modified kiln dryer or a fluid bed system using cold air as the cooling medium.  The batch plant bins are maintained in a partially filled condition by regulating the quantity of each aggregate that is fed to the wet belt.  After the wet belt these aggregates are re-screened to send them to the appropriate bins.  When the plant stops for more than a few minutes, the cold air is diverted from the sand cooler to help keep the batch plant bins cool.  Temperature sensors in the aggregate and sand bins, plus infra-red sensors in the mixer control the whole process, saving energy on cool days when maximum cooling is not required.

The control system uses a PLC and touch screen, similar to the BatchTron controller, to monitor all the processes and control the speeds of the aggregate feeders with Variable Frequency Drives (VFD) or inverters.  A connection with the batch controller can further enhance the control strategy by slowing down the feeds when batching is erratic, acting as a predictive control.

Systems have been installed at several high production plants;  examples are the Shimmick / Obayashi Joint Venture at the San Vicente Dam, southern California, Thalle Construction at the Kentucky Dam and Ruhlin Construction at the Willow Island Dam, West Virginia.  The wet belts are supplied by Ocmer Impianti, our Italian partners.

Scale-Tron and Ocmer are partners of ConCool Inc., the world leader in concrete cooling, providing controls and wet belts.


Powder batching system.

A unique powder batching system was designed for Rehau Industries’ Baie D’Urfe, QC plant.  The objective was to weigh up to 7 materials, with weights varying between 50g to 4 kg, into plastic bags and seal them. The soluble bags are then hand-added to plastic materials in a mixer, creating specific blends for different jobs.

The batches had to be completed within 120 seconds at most, with an accuracy of 0.5% of each ingredient weight.  These two conditions made it essential to use three separate weigh hoppers, discharging through a chute into the plastic bag which is held by a pneumatic clamp.  Ingredients are stored in bins standing on seven vibratory screw feeders, supplied by Vibra Screw Corp.  This type of feeder guarantees consistent feed of powders, some of which tend to clump and bridge.  The feeder discharge tubes are closed positively at the end of feed by sealing pads on spring-return cylinders.

The three hopper scales, shown in the picture, have capacities of 300g, 1500g and 4000g, are mounted on a single load cell each and have removable hoppers.  Discharge is activated from outside the hopper with a unique mechanism that only contacts the hopper during discharge, eliminating the forces and subsequent errors created by pneumatic tubing.

The system was controlled by our BatchTron-II controller, which handles both the speed and accuracy with ease.  Innovations were too numerous to list here, but we can discuss them with you.

Our wide experience in load cells, coupled with integrated mechanical and electrical design skills, give the ability to design load cell-based systems from scratch and guarantee their performance in advance.


Travelling weigh lorry, Thailand

Bayer Premier Co. needed an automatic weighing system for their new plant near Bangkok.

The stainless steel weigh hopper had to be capable of withstanding an internal explosion without rupture and was to travel between 12 overhead hoppers, gathering materials, and four mixers where it would discharge the completed batches. Extendable seals were to make contact with hoppers and mixers before transfer of material, to contain dust. The hopper, mounted on load cells on a wheeled trolley and weighing over 10,000kg when loaded, had to travel on rails, powered by a variable speed AC motor. Weight data with an accuracy of 0.05% had to be transmitted over a festooned cable 200 ft in length to the controlling PLC. 

The whole was to meet Class 3, Division 2, Group G requirements for hazardous areas.

The system was delivered on time and was started up without requiring our presence on site. It has been operating successfully for five years.

We specialize in all sizes of job, big or small, in any location.


Scale platforms, Optimal Robotics Inc. (later Fujitsu), Montreal

A critical part of Optimal's (later Fujitsu's) automatic checkout counters for supermarkets (trade name U-SCAN), a load cell weigh platform checks the weight of every item dropped into the shopping bag after it is scanned by a bar code reader.  The item weight is verified by the computer without the customer even being aware of it;  if a cheap item is scanned and then an expensive item is dropped in the bag in its place, the operator is warned instantly.

Optimal-Fujitsu's U-SCAN has been chosen by Kroger, A&P, Costco, Price Chopper and many other leading U.S. chains as well as Canadian Tire and the Loblaw's chain in Canada, plus a large market in Europe.


Carousel control system, Tunneling Systems Inc., Ontario.

A production "carousel" for moulding concrete sections for a Toronto subway tunnel required a control system.

The carousel system comprised a production line where moulds were to be sequenced through 12 separate stations, shunted via a transfer car to one of two alternate curing kilns, shunted through the kilns and out to another transfer car where they would be returned to the production line again.

Batching of concrete for seven different sizes of mould was also controlled by this system. Since the production line was crowded with unskilled workers, the potential for accidents was high and a special ultrasonic/microwave motion detection system was incorporated to prevent movement of the line when personnel were present.

The control system, operated from a graphic touch screen and PLC, ran fully automatically without a breakdown for the 2 year production cycle. This was the second such automation system designed and installed by Scale-Tron, the first being at Concrete Systems Inc's tunnel plant in Hudson, NH which produced a 9 mile 25 ft. diameter tunnel for the Boston Harbour sewage outfall project. 

This project (which did not involve load cells or weighing) demonstrates our knowledge of the precast concrete industry and its unique challenges.  We have the capability to handle both concrete batching and the more intricate controls that are required in highly automated plants.  Other examples include pick and place, travelling hoppers and automation of casting machines.        Tunnel Liner Plant Controls


Special expertise includes load cell application. There are few if any load cell applications which we have not undertaken over the past 40+ years. From the smallest, milligram sensitivity to the largest, half million pound capacity, we have designed load cell based weighing systems for applications ranging from gold and silver to mining and hazardous waste. Call or Email for application information.

Safety of personnel and protection of plant equipment is our primary concern when engineering a new system. We ensure that our designs meet OSHA and other national and local standards for safety, as well as plain common sense. In the past we have refused to produce equipment as requested by customers when we judged it as potentially unsafe; instead, we have recommended design changes to remove the hazard. The Carousel system above is an example.

Cost effectiveness and reliability are our next concern. Our practical experience includes a vast knowledge of shop practices in a great many industries, from food, drugs and alcohol to chemicals, steel and aluminum mills. We know the special conditions in which equipment must operate and survive. As a result, we can build equipment which is suitable for the environment and which will work from the day of installation for many years until it is retired, to be replaced with a new generation of equipment. Often, we have been the supplier of the new generation, replacing our own original equipment after 15 or 20 years of use.