Plant & Works Engineering

You only handle once

Published:  24 September, 2009


Plant and works operations can eliminate double handling and substantially reduce the movement of stock around a warehouse area by using pallet and carton flow racks, writes Ed Hutchison, managing director of BITO Storage Systems.

Double handling. These are two words to avoid if you wish to make the warehouse operations of plant and works operations as efficient as possible.

Itís not just about saving time but money also because the more you handle a product in a warehouse, the more it will cost you. One of the main operations leading to double handling is the common practice of taking the pallet loads of stock arriving at Goods In to a buffer storage area where they are held in pallet racking until the product is required to replenish the pick face. This requires the pallet to be retrieved and moved again and there you have it, double handling. The problem is accentuated for fast moving product, which will fly off the order picking shelves and require regular replenishment from buffer stock.

The problem is that many pick areas using traditional Adjustable Pallet Racking (APR) or shelving will not have sufficient space to accommodate all of the stock arriving at Goods In directly at the pick location and will have to rely on regular replenishment to keep up with the order pickers to ensure they have a constant supply of product.

Even with double deep APR, an enormous amount of floor space would typically be required to accommodate all of this stock at the pick location, which is clearly even less efficient. Furthermore, it would likely result in pick faces for a single SKU (Stock Keeping Unit) occupying a large section of an aisle, leading to greater travel distances and times for order pickers.

However if a pick face can be designed to allow an entire delivery arriving at Goods In to be accommodated directly at the pick location, this will eliminate that undesirable practice of double handling.

The most effective way to do this and to concentrate stock into a small area is to increase the density of the storage at the pick location by using flow racks. Carton live or pallet flow storage systems enable enough stock to be located in a small area to keep pickers going for longer periods. They help ensure a constant supply of stock at the pick face, thus avoiding the frustration of pickers waiting for replenishments to arrive.


A typical pallet live system, for example, will hold five pallets in a flow lane. The pallets are fed into the lane from behind and as soon as a pallet is emptied of product it is removed. The picker then simply pulls a lever on the flow system to bring a fresh pallet of product to the front of the pick face. A traditional racking system would require a lift truck to bring a fresh pallet, while a double deep system would require the lift truck to push the one extra pallet to the front as well as delivering a new pallet from buffer.


Pallet flow racks are particularly useful for picking large quantities of single small products that are very fast moving. Here the pickers can pick from a whole pallet box load of such a product.


Carton flow racks will require the pallets to be broken down into cartons but a flow rack that is, for example, 5 metres deep will have the capacity to hold multiple cartons in a lane. Five beds of carton flow racks can easily be accessed at ground level picking. Designing the lanes so that they can accommodate cartons of various sizes will give companies the versatility to alter their stock profile according to seasonal peaks, ensuring the fastest moving stock is in the best position in the warehouse to allow the quickest order picking.


Because flow racks are fed with pallets or cartons from the back to travel down the gravity flow lane on rollers, this allows a structure to be designed to form a replenishment only aisle at the back thus keeping the picking aisle free from lift trucks and, therefore, the replenishment aisle, free from pedestrians. This not only improves safety but reduces hold ups in operations.


Flow racks can be built into pallet racks offering a combination of storage on multiple levels. This means that if buffer stock is required it can be located as close to the pick face as possible.


To make the best use of space in these racks, the buffer positions can be designed to suit the companyís stock profile. For example, if the user has a lot of small-sized, fast moving items, they may receive many half-height pallets. So rather than have them occupy normal pallet bays and leaving half a metre of empty airspace, why not design the racks to accommodate half pallet heights? This will reduce wastage of any vertical space. If the overstock involves cartons that cannot be accommodated in carton flow racks then adding a mesh level on the pallet racking will provide a safe base to allow individual cartons to be held in buffer for access by order picking trucks.


Such a design means that any extra product that cannot fit into the flow racks can at least be accommodated close to the pick face and replenishment of the flow racks will simply be a case of using a lift truck to take product from the top level to supply the flow racks directly below, minimising the distance that products have to travel within the warehouse.


There are higher initial investment costs with a live system but these will be more than compensated by improvements in working efficiency. For example, by providing within a short distance a greater density of pick locations for small parts, a saving on floor space in the region of 15-20% is a reasonable assumption for a carton live storage system for small parts. Time is saved also; depending on the application, travel times for order pickers can be improved by up to 66 per cent. Furthermore because the goods move unassisted into the picking position, order pickers can rely on a constant availability of goods ensuring there are no hold ups for plant and works operations.


For small parts in particular, the trend is moving away from traditional static shelving and longspan racking, towards live storage because of its inherent virtues of faster picking and reduced manpower as well as improved space saving and organisation.


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