Storage stacker cranes
Warehouse stacker cranes are a device that makes the most efficient use of storage space, offers extensive possibilities for mechanising and automating storage, order picking and transport, and reduces the number of workers involved. They are mainly used in large warehouses. They are machines specially designed for the automatic lifting and stacking of loads on racks. The task of the stacker crane is therefore to lift and transport them to other locations defined by the system. In accordance with the Ordinance of the Council of Ministers of 7 December 2012 on the types of technical equipment subject to technical supervision (Journal of Laws 2012 no. 0 item 1468), issued on the basis of Article 5(2) of the Act on Technical Supervision and the Ordinance of the Minister of Entrepreneurship and Technology of 30 October 2018 on the technical conditions for technical supervision in the operation, repair and modernisation of materials handling equipment (Journal of Laws. 2018 item 2176) all storage cranes are subject to technical supervision.
The design of a stacker crane can vary depending on the application, the type of product and the room in which it is installed. Despite the possible differences, most are structurally similar. Their common features are:
- Movement mechanism;
- Cargo trolley;
- Rotating platform;
- Gripping mechanism.
To ensure the safety of workers and protect the equipment from possible overloading, each stacker crane is equipped with:
- Emergency brake;
- Speed limiter;
- Emergency switch;
- Rope tension monitoring device.
Stacker cranes with cabs are additionally equipped with safety belts, cab locks and operator presence detection devices.
Advantages and disadvantages
The main advantages of the warehouse stacker cranes are: a significant increase in productivity; the possibility of working in an automatic cycle; high safety; the structure is robust and resistant to environmental influences and temperature variations; the use of a minimum aisle width, which allows the maximum number of racks to fit in the room; the system is very efficient, and can operate 24 hours a day and all days of the week. Warehouse stacker cranes also have disadvantages. One of them is the initial investment; automating the warehouse at the outset requires an input of greater costs. Also, to obtain maximum efficiency it is necessary to install several stacker cranes, one may not be enough.
Based on the type of construction, we can distinguish two types of stacker cranes:
- Pole - has a load-bearing structure in the form of a drive-through pole;
- Frame - has a load-bearing structure in the form of a drive-through door.
Based on the number of columns, we can divide them into:
- Single-column stacker cranes - designed to handle both containers and pallets; ideal for warehouses handling lighter loads;
- Twin-column stacker cranes - have two vertical columns between which a lifting trolley moves to provide access to different levels of storage; they are more reliable and stable; they are ideal for handling heavy loads; a feature is their high capacity.
Based on the type of work, three types can be distinguished:
- Automated - this type of stacker crane is the most common and popular choice; all the commands, directed by the management system, are taken by means of a microprocessor;
- Semi-automatic - in this case the stacker crane is controlled by a computer, the operator enters specific coordinates;
- Manual - the stacker crane is controlled from the cab and uses manual mechanisms; it is used for repair or maintenance work.
Testing of the storage stacker crane
All technical equipment should be systematically tested. These take place with the operator or his authorised representative and the maintenance person. During operation, equipment shall be subjected to such tests as:
- Periodic - equipment subject to a full form of supervision, during the periodic inspection it is checked whether the equipment is working properly, no damage has occurred, recommendations from the previous inspection have been carried out;
- Ad hoc operational - carried out within the timeframe required by current needs, the purpose is to confirm that the equipment is safe to operate after changes have been made;
- Ad hoc post-accident/post-failure - performed in the event of a dangerous damage or accident, the cause of the incident is then determined, conclusions are made and implemented.