Bulk handling system prevents contamination

The system prevents contamination due to incorrect filling of silos. Thanks to the smart key system, Limpens Elsloo can now rest assured that no errors will be made when filling and emptying over 100 silos.

Since 1930, Limpens Elsloo has grown from a haulage company into a full-service organisation which, besides bulk and tanker transport, provides cleaning, dry bulk handling and storage services involving a wide range of raw materials and products. The company operates more than 250 trailers for the national and international distribution of powders and granulates. The range of services also include the repackaging of bulk materials. For this purpose, Limpens Elsloo has a bag cutting machine with a 25 ton per hour capacity, a Dino bulk truck loader and a big bag filling and emptying station. The company operates 109 storage silos with a combined capacity of 29,500 m3 spread across two silo parks, which are located immediately adjacent to the A2 motorway and a very short distance from waterways and railway lines. For the storage and transshipment of all bulk goods they use state-of-the-art loading and unloading techniques. Recently, Limpens Elsloo secured the latest extension of their silo park and other silos with a Sofis interlock key system. This system ensures that no more errors can be made during the filling or unloading of silos.

Interlocks
Interlocking is a mechanical system for securing process systems which makes sure that valves and other components can only be operated in a certain, pre-defined order. It is operated with physical keys that can only be used in a single way. The enforced adherence to process flow sequences eliminates human error during the operation of process plants and guarantees a safe working environment. With some applications, especially in the gas and petrochemical industries, the process involved in start-up or shutdown procedures may consist of a number of steps. However, for safe dry bulk handling, the procedure is considerably more straightforward yet just as efficient and reliable.

Bulk handling
What is important at Limpens Elsloo is that no errors can be made when filling or emptying silos, because a mistake resulting in a product or raw material ending up in the wrong silo or bulk truck is extremely costly. To eliminate every risk, the logistics company decided to use the interlock system supplied by Sofis. This system features unique keys that only fit their own silo valves and can only be released the moment they are needed.

Key cabinet
At first sight, the key cabinet that forms part of the system can be compared to the conventional key cabinet that you might find in the control room of a silo park. The bulk truck driver shows the consignment note at reception and the operator hands him the key to fill or unload the corresponding silo. The linear key with its own unique shape and number is taken from the key cabinet. What makes the Limpens Elsloo system unique is that the logistics manager receives instructions about the silo in question on his computer screen and only the key for the corresponding loading or unloading station is released. The correct key is indicated by a green light. All other keys in the cabinet remain locked, which prevents them from being removed from the cabinet. The key that is handed to the driver will only fit the one valve on the relevant silo. Upon completion of the job, the key can only be returned to its own place in the key cabinet.

Electronic key cabinet linked to stock-control system
What characterises this particular solution is the combination of a robust, mechanical lock on the silo and an electronic key cabinet that manages and documents the issue of keys. The electronic key cabinet is linked to the customer’s stock-control system which specifies which silo can be filled or unloaded and which key is to be released. Both the locking system and the key cabinet are universal, which means they can be linked to any stock-control system whatsoever.

Control system
Not only does the system offer clear insight into the status of the keys present behind the transparent and lockable door, it also features many other benefits. For example, you can see when a specific valve is opened and closed and therefore measure the time that a valve has been open. In addition, sensors detect which keys are present in or absent from the cabinet. This information is easily linked to a to a distributed control system (DCS). Conversely, the interlocking system can be used to ensure that the key to a silo is not released if, for example, work is being carried out inside it. Other options include the release of local loading and unloading systems and checking whether people have been authorised to be given keys with methods such as PIN or iris scans.