# Warehouse capacity

Russian: Вместимость склада

In the design process of automated and mechanized warehouses there is performed a large number of calculations that allow us to determine all the parameters of the warehouse, the size of plots, area, the required amount of equipment, technical and economic performance storage and so on. This group does not include the calculations related to the design of the equipment warehouses: racking and pallets strength calculations, metal conveyor belts, drive belts calculations, reloading equipment, stackers and other mechanisms. In designing warehouses one of the first and main issue is the proved choice value of warehouse, storage capacity because it affects all the other technical solutions for the storage, namely the processing capacity of the warehouse, warehouse size, width and height of the stacks (stacked in storage), the number of cells in racks (with rack storage method), capital costs, operating costs, reduced costs, at least that is the most objective criterion of optimality of the warehouse.

capacity of storage (E) is the amount of cargo (measured in tons, units, m3, etc., depending on the type of cargo), which can be placed at one time in a warehouse in the area of ​​the main storage for a given method of storage. Total storage space - is constant and is determined by its size, methods and parameters of warehousing.

Stocks (I) - is the total amount of goods that may be in stock at any given time. Number of stored goods, or stocks - is a variable and depends on the nature, attributes and combinations of incoming and outgoing cargo from the warehouse. Rail stocks of goods can range from 0 to Imax, that is the maximum number of stocks is equal to the capacity of the warehouse E

Storage capacity should be the minimum necessary to ensure that the costs at the warehouse facilities were the least. The most "effective" should be regarded as a warehouse, which has a minimum capacity and at the same time be able to receive all incoming cargo and a consistent supply of consumer goods are stored in it at the right time and in the right quantities or efficient cargo transfer from one to the other modes of transport.

The capacity calculations relate only to storage areas and can be done differently for the two main cases of the design.

1. Designing a new warehouse. Stocks of goods to be stored in a storage area are set. It's needed to determine the required parameters of all storage areas (dimensions, size, number of cells).
2. There is existing warehouse with known dimensions. It's needed to determine capacity with using of modern stock and to calculate all parameters of this issue of stock (the number of tiers in racks, the number of cells, shelving etc)

Currently, the most frequently used method of calculation, based on standard periods of storage of goods. But even in this method, different authors show a significant difference, in particular - accounting or not accounting irregularity factor.

• Based on the normative terms of storage of goods, taking into account the uneven fluctuations in inventory storage capacity can be determined by the method given in:[1]

$\mbox{E}=\frac{k_z}{360}\sum_{i=1}^{n}{Q_i [t_{xp}]}$ , tons

Where:

• $\!\mbox {Q}_ \mbox {i}$ = annual cargo traffic for i's nomenclature, tons per year;
• $\!\mbox {t}_\mbox {xp}$ = standard period of storage in a warehouse for i's cargo group, days;
• $\!\mbox {k}_\mbox {z}$ = 1.05 … 1.3 – variation factor of stocks, taking into account the random fluctuations of stocks, resulting from combinations of daily arrival and departure of cargo from the warehouse;
• $\!\mbox{n}$ = amount of cargo groups with different periods of storage.

This method of calculating the capacity of the warehouse is not accurate enough because it only takes into account the estimated random processes of the formation of stocks by the coefficient kz. There are no recommendations for determining this factor. Using the coefficient of irregularity knowingly overstates the capacity of the warehouse E.

1. Based on the normative terms of storage of goods, excluding non-uniformity coefficient storage capacity is determined by the formula from:[2]

$\mbox{E}={Q_{np}^{cym} t_{xp}}$ , tons

Where:

• $\!\mbox {Q}_\mbox {np}^\mbox {cym}$ = average daily cargo traffic on the arrival, tons per day;
• $\!\mbox {t}_\mbox {xp}$ = normative term storage of goods in stock, days.

The difference between these methods is that in the first method uses the annual cargo traffic, while the second - use the average daily flow. This method assumes that the average daily flow is the ratio of annual freight traffic to the number of days per year. Thus not taken into account the unevenness of arrival and departure of goods. The possibility exists that the supply of goods in stock by this method of calculation may be smaller than that for sending goods to recipients, resulting in unproductive downtime rolling stock and industrial processes for consumers.

1. Taking into account reserve ratio, it is proposed to determine storage capacity in tons by the method outlined in:[3]

$\mbox{E}=\sum_{i=1}^{n}{K_{cki}Q_{cpi} [T_{xpi}]}$

Where:

• $\!\mbox {K}_\mbox {cki}$ = reserve ratio for every group of the cargoes.
• $\!\mbox {T}_\mbox {xpi}$ = storage terms of every cargo's group, days.
• $\!\mbox {Q}_\mbox {cpi}$ = calculated daily cargo traffic of i's cargo; is the average daily flow of materials in a warehouse, multiplied by a factor of irregularity.

The textbook, which refers to this method, the concept of reserve ratio is not explained. Do not completely clear the meaning of this factor, and how to identify different types of stores. Unlike previous methods for calculation of the required capacity of the warehouse, in the formula used by the estimated daily cargo traffic. It is most accurately takes into account the traffic on the days during the year, but does not provide methods for determining the coefficient of irregularity of different conditions and types of storage and transport.

1. Storage capacity E can be calculated by the number of packages in stock, like in:[4]

$\!\mbox{E}={R G}$ , tons

Where:

• G = weight of the overpack, tons;
• R = the total number of transport packets to be placed in the warehouse, items.

$\!\mbox{R}=\mbox {x y z}$ , tons

Where:

• $\!\mbox {x, y, z}$ = the number of packets that are placed on the width, length and height of the racks respectively.

This method is not universal, since it can be applied only to existing warehouse with a certain size and a certain way of storage. Also, this method not only takes into account the uneven traffic arriving and departing from the warehouse, but does not include freight traffic volumes in general. It only gives information about how many tons of cargo could be accommodated with the existing layout of transport packets.

## References

1. Маликов О. Б., Малкович А. Р. Склады промышленных предприятий: Справочник. - Л.: Машиностроение. Ленинградское отделение, 1989. – 672 с.
2. Маликов О. Б. Определение параметров механизированных складов штучных грузов. Метод. указ. по курсовому и дипломному проектированию. – Л.: ЛИИЖТ, 1989. – 37 с.
3. Гриневич Г. П. Комплексная механизация и автоматизация погрузочно-разгрузочных работ на железнодорожном транспорте: Учебник для Вузов ж.-д. транспорта 4-е изд., перераб. и доп. - М.: Транспорт, 1981. – 343 с.
4. Маликов О. Б., Семеркин А. А. Обоснования технических решений по грузовым терминалам. Метод. указ. по практич. занятиям, курсовому и дипломному проектированию. – СПб.: ПГУПС, 2002. – 42 с.