Remove risk of human error in refractory powder dispensing plant
A case study identifying the pros & cons of using rigid IBCs (Intermediate Bulk Containers) as opposed to dosing from Big Bags.
Producers of refractory products face much the same pressure as any and all other process industries:
- Requirements for greater product variation
- Order quantities differentiate more and more
- Lead times get shorter – nobody wants to hold stock
- Cost pressure from lower salary based producers
- Tighter quality requirements
It is common practice for major producers of refractory linings in developed countries to automate the powder batching process, with the majority using big bag dischargers combined with screw feeders in a cluster or linear arrangement.
The formulas are often quite complex, typically including 10-12 different raw materials of varying quantities. Whilst the approach with big bags works very well for a single recipe; it leaves a lot to be desired when recipes change and half, or maybe all the raw materials need to be changed!
It is literally impossible to close off a big bag half empty and the natural result of such a set-up is “campaign production”, building up excessive finished goods inventory because it is so troublesome to change recipes. Customers do not order with regularity and stock may be sitting on the shelf for months – sometimes also losing its value because the client who it is intended for changes their method or supplier.
A global player in this field approached Matcon to enquire how Matcon’s Lean philosophy could be applied to refractory batching. Matcon are more well-known within the food and pharmaceutical industries but also have a solids handling background in heavy duty industries and applications including metal powders, brake lining and building chemicals.
The combination of very high capacity (several tonnes per hour) and demand for flexibility was certainly a challenge and novel ideas were required. The result of the conceptual study was a circulating track for “batch containers”, being fed from raw Material IBCs at an elevated frame.
The Core technology – Cone Valves
Once the concept was defined and agreed, the next step was to validate that the solution would actually work – this was achieved using our full scale testing facilities. As could be expected, many of the refractory ingredients proved very challenging – especially when combined with the demanding accuracy and high throughput requirements specified by the client. After several days of optimising parameters, both parties were satisfied that the proposed cone valve technology would work.
The cone valve solution for discharging and dosing powder is simple yet elegant by combining both dosing and discharge aid with the same unit: An active lifting probe docks with the passive Cone Valve in the transportable IBC (Intermediate Bulk Container) and once fully engaged, high accuracy dosing can be accomplished without any secondary feeder devices such as screws or vibratory feeders.
The key benefits of the cone valve in this application are:
Dust free connections each time a raw material IBC is docked or undocked from
the batching system.
- Powerful discharge aid – assures automatic discharge of all ingredients required.
- Reliable and accurate dosing – the basic project requirement.
- No secondary feeder required – raw material changeover can be done at a minutes notice.
- There is literally nothing to clean or empty once the IBC is removed, so a new recipe can be run within minutes of the previous one. Alternative solutions will typically take up to an hour for each ingredient to be changed.
All materials are received in big bags as they are the most versatile and cost effective method of shipping powders between manufacturing plants. When required, the big bags are transferred in full into 2m_ IBCs each equipped with Radio Frequency Identification (RFID) tags so that the Manufacturing Execution System (MES) control system can safely guide the operator when selecting the correct IBC for any given recipe. Raw material IBC movements are executed with heavy duty fork trucks, but AGVs or other automated IBC movement can be considered also.
A number of Batch IBCs circulate automatically below the raw material IBCs and collect various ingredients on demand as instructed by the recipe control system. Once the full loop is completed, the batch IBC is automatically emptied (also utilising cone valve technology) into the mixer. Once empty, the batch IBC is returned to the first dosing position for a subsequent batch, with a same or different recipe.
Raw material IBCs are removed from the Formulation System when empty or when the material contained in the IBC is not required imminently. By operating in this manner, a smaller number of dosing positions can provide automatic dosing for the 75 different raw materials
The system is very novel and innovative but has proven itself as state of the art for the client with additional installations now being considered. With hindsight, it has been possible to identify and address a couple of improvements including:-
- The powders handled behave differently based on the country of origin, time of year, moisture as well as storage time. Smart software was applied from day 1 trying to accommodate all extremes. However, some combinations were problematic and much improved “self-learning” software, combined with valuable input from the customer has resulted in substantially tighter standard deviation .
- The system was always designed to dose >20kg to an accuracy of +/-0.5% or better. In reality, there is always a risk that a very small amount of powder is required as a “top-up” from when an IBC runs empty, as well as a creeping demand from the market for smaller inclusions of “exotic” materials. Software improvements have also allowed for such smaller inclusions at very high accuracy levels.
- The system provides unprecedented flexibility in terms of recipe and ingredient changeover albeit this requires some additional fork truck handling. In 95% of cases, this can easily be justified in relation to time savings; but for the 1-3 biggest ingredients, a fixed conveying system should be considered for future plants.
The system is installed in Europe and can be visited as a reference on a case by case basis subject to competitive situation with the interested party and management approval.
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