With the vigorous development of online shopping, express delivery has become a big problem. Because most express deliveries are not scheduled, there can only be an approximate delivery time. As a result, many times, when the express call arrives, the customer is not nearby, which means that the customer has to arrange someone to pick up the goods and the courier has to wait a little longer, which is inconvenient for both parties. At this time, the service of express stations came into being. Generally, express stations cover an area of several square meters or more than ten square meters. They are responsible for sending and receiving all kinds of express delivery in their radiation areas for free, and have the storage function, so that customers can pick up their own express delivery at any time when they have time.

This also means the problem of storage, so a large number of shelves are needed. Long span shelves are usually manually stored and stored. They are assembled structures with even and adjustable layer spacing. Goods are also often loose pieces or not very heavy packaged goods. The shelf height is usually less than 2.5m, otherwise it is difficult to reach manually. The length of unit shelf should not be too long, and the width of unit shelf should not be too deep. According to the load capacity of each layer of unit shelf, it can be divided into light, medium and heavy duty shelves. The deckings are mainly steel deckings and wooden deckings.

(1) Light duty long span shelf: the load capacity of each layer of unit shelf is not more than 200kg, and the total load capacity is generally not more than 2000kg. The length of unit shelf is generally not more than 2m, the width is not more than 1m (mostly within 0.6m), and the height is generally within 3m. The common rack structure is angle steel column rack structure, which is light and beautiful in appearance, and is mainly suitable for storing small items with light weight. Less capital investment, widely used in electronics, light industry, culture and education and other industries.

(2) Medium duty long span shelf : the load capacity of each layer of unit rack is generally 200~800kg, and the total load is generally not more than 5000kg. The length of unit shelf is generally not more than 2.6m, the width is not more than 1m, and the height is generally within 3m. If the unit shelf length is less than 2m and the floor load is less than 500kg, it is generally appropriate to choose the beam less medium shelf shelf; If the unit shelf span is more than 2m, generally only the beam type medium shelf type shelf can be selected. Compared with the beam type medium shelf, the shelf type medium shelf has a larger adjustable space, more stable and beautiful, better coordination with the environment, and is more suitable for some warehouses with higher cleanliness requirements; The industrial characteristics of the beam type medium-sized shelf are stronger than those of the long span shelf, which is more suitable for storing metal structure products. The medium-sized shelf is widely used in all walks of life.

(3) Heavy duty long span shelf: the load of each layer of unit shelf is generally 500~1500kg, the length of unit shelf is generally within 3m, the width is within 1.2m, and the height is unlimited. It is usually combined with and coexists with heavy pallet shelf, which is more common in large warehouse supermarkets and logistics centers.