Warehouse Racking (Storage Racks)
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Introduction:
This article presents complete information for selecting a
suitable warehouse racking system. Read further to learn
more about.
- Warehouse Racking Overview
- Benefits of Using a Racking System
- Factors for Consideration
- Different Types of Warehouse Racking
- And much more…
Chapter One – What is a Warehouse Racking System?
Warehouse racking, also known as storage or pallet racking, is a
material handling system suitable for mass storage of goods
unitized on skids or pallets. It allows efficient utilization of
space while providing easy access to stockpiled items for better
inventory control. Racks are used by manufacturers for mass
storage of mostly non-perishable products when storage space is
not enough. Palletized products are usually stacked up to not
more than three layers before it becomes unsafe and prone to
collapse. A racking system enables manufacturers to store
palletized products five to seven stacks high, depending on the
height of the facility.
Aside from finished goods handling, racking systems are also
used for raw material and parts storage. Selective racking can
be designed so that the greatest number of items can be
accessed, permitting high variety. Also, some distribution
systems favor the use of FIFO or the first-in, first-out method
of inventory control. Having a racking system provides access to
the oldest items in the warehouse inventory, allowing them to be
off-loaded first.
Chapter Two – Benefits of a Racking System
Aside from maximizing storage space, there are other benefits
that make warehouse racking feasible. These benefits can be
quantified in terms of economic value or savings from leasing
additional storage space, less workforce effort, and higher
throughput. On the other hand, compliance with safety standards
and quality management are other value-adding factors that do
not directly translate to savings. Enumerated below are the
benefits of a warehouse racking system.
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Efficient storage space utilization: As mentioned
earlier, racking takes advantage of the available vertical
space that is otherwise unused. Warehouses that are built to
contain racks are made with high ceilings to allow racks with
higher bays.
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Easy inventory organization: Racks can be addressed
easily in comparison to stockpiling. Storing goods with many
distinct varieties is virtually impossible with stockpiling
without consuming large floor spaces. A type of racking system
known as selective racking allows storing different types of
goods while keeping the consumed space to a minimum.
Fewer damaged goods:
The implementation of racking systems was necessary to avoid
damage to goods and products. Initially made of wood, racking
systems have gradually developed into exceptionally stable metal
structures capable of stacking goods several feet into the air
with the only limitation being the height of the facility.
The implementation of racking systems was necessary to avoid damage to goods and products. Initially made of wood, racking systems have gradually developed into exceptionally stable metal structures capable of stacking goods several feet into the air with the only limitation being the height of the facility.
Palletization of materials offers an easy and convenient method
for organization shipments and receiving supplies. A racking
system is a way to place palletized materials in a safe and
secure location such that they will not be damaged by
mishandling, miscellaneous contact, or falling. Essentially, the
metal frame of the racks keeps pallets from shifting and
provides a protective barrier. The various designs of racking
from two deep designs to excessively tall racking systems makes
access to goods easy without disturbing surrounding pallets.
Increased employee productivity:
In a racking system, the location of an empty pallet can easily
be found and accessed. This eliminates small unnecessary
movements that, in time, stack up to significant losses.
Storage automation:
Adapting a racking system is the first step to warehouse
automation. This is achieved by integrating smart conveyor
systems and guided forklifts and cranes. This can lead to
significant savings in terms of manpower costs and can
streamline the business process especially for large
distribution centers.
Increased safety:
Warehouse racking is designed to take advantage of storage
space, arrange products efficiently, and provide a cataloging
system making it easier to pick required items. Safety measures
are a necessary part of the efficiency of a warehouse and are an
integral part of racking system design. Included as safety
measures are sensors and alarms, guard rails, rack end
protectors, rack guards, and column guards.
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Guard Rail Systems - Guard rail systems are made of heavy duty
rails strategically placed in potentially dangerous areas. The
sturdy durable materials of guard rails are designed as
protection to avoid accidents and damage to materials.
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Sensors - Sensors are a method of alerting warehouse personnel
of dangerous situations. They have a flashing light and
audible signal that alerts people in the area regarding
forklifts, location of shelving, and the position of stackers.
-
Warehouse Software - Warehouse software is used to calculate
safety risks and the most productive method for moving
products. Its main function is to reduce the number of manual
actions by personnel. Additionally, warehousing software
determines the most picked items and products and produces a
report with proper placement of those goods and the best route
to their location.
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Rack End Guards - Rack end guards are designed to protect the
bottom of racks. They are bolted to the floor to absorb
impacts. Rack end guards are painted safety yellow and have a
low contour shape to separate them from column guards.
-
Column guards - Warehouse column guards come in a wide
assortment of sizes, shapes, and dimensions to be able to meet
the needs of different sized racking. As with rack end guards,
column guards are floor mounted and painted safety yellow.
They erap around three sides of the bottom of the column to
protect damage from the pallets, forklifts, and pallet jacks.
Clean and contaminant-free handling:
By having better access, it is easy to clean goods and storage
spaces. Better segregation can be achieved to separate goods
that can possibly deteriorate or damage adjacent items.
Leading Manufacturers and Suppliers
Chapter Three – Selection Factors in Designing a Racking System
Before investing in a racking system, it is important to note
several factors to determine the viability of the project. Keep
in mind that racks can also cause a space to be less utilized
since the frame and its appurtenances take up space. The biggest
drawback of a racking system is its difficulty in being modified
and reconfigured. To make the most out of the investment, the
following are some points to consider.
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Available Storage Space: The first step is to assess
how much space is available for constructing storage racks and
if the warehouse layout permits such construction. It is
important to note that for an existing warehouse, the whole
floor area may not be utilized. Racking systems available in
the market usually come in standard sizes. Also, the structure
of the racking itself takes up storage space. Thus, the
desired storage density may not be as expected. In some cases,
warehouse features such as walls, partitions, and doors must
be modified to accommodate a racking system.
-
Vertical Clearance: Aside from the available horizontal
space, also assess how much vertical space can be utilized.
Available vertical clearance directly influences the storage
racking density. Adding one or two layers to an existing
three-layer pallet stack can even decrease the storage density
due to less utilization of the floor area. Racking systems
that take advantage of vertical slopes, such as gravity flow
systems, can further decrease the storage density by removing
a layer to accommodate the required slope. Moreover, it is
important to take note of the required clearances for fire
suppression systems and obstructions for airflow. Elevating
the stack height may defeat the design features of these
systems and may call for modifications that further add to the
initial cost of the project.
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Unitized Load Dimensions: After taking into account the
available space and its restrictions, next comes the
consideration of the shape and size of the pallets to be
stored. The racking system must be designed specifically
according to the form of the palletized load. For production
lines that produce unitized loads with varying sizes, one may
consider the pallet with the largest dimensions. This allows
greater flexibility once there is a need to store more of that
particular product.
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Load: The frame must be able to support the pallet load
by selecting the appropriate material. Most racking systems
are made of steel but are created through different
manufacturing methods. For lighter loads, cold-rolled steel is
sufficient. On the other hand, heavy-duty applications require
structural steel that is formed through hot rolling or
extrusion.
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Target Capacity: Knowing the target capacity means
determining the target warehouse capacity utilization.
Warehouse capacity utilization is an important key performance
indicator (KPI) in a business process, especially for
logistics and distribution centers. Having too high a capacity
has its drawbacks of higher investment and operating costs.
Having too low means less room in case of distribution
difficulties or overproduction. Also, consider storage space
taken by seasonal inventory. Warehouse capacity utilization
can substantially increase during the off-seasons.
-
Volume of Incoming and Outgoing Goods: This is linked
to the target capacity of a storage system. It is important to
know the throughput of the manufacturing plant and the rate at
which the goods are sold or off-loaded. Aside from these,
determine the average duration of seasons with low demand.
Usually, manufacturing plants have a minimum throughput or
breakeven point. Low storage space can result in halting or
lowering the rate of production, which in turn impacts
profitability.
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Number of SKUs: A stock keeping unit, or SKU, the
number of distinct types of goods. It can also refer to the
code or designation given to a specific item for inventory
management. Determining the number of SKUs to be stored will
help balance between selectivity and storage density of a
warehouse racking system. Prioritizing either selectivity or
storage density will determine which type of racking system is
required.
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Type of Inventory Accounting Method: Regarding storage
racking systems, this can be FIFO (first-in, first-out) or
LIFO (last-in, first-out). Inventory cost accounting might not
be representative of the physical off-loading of goods.
Intuition suggests that the oldest item stored must be taken
out first so that there will be no stagnant items that can
lose value. However, some businesses use LIFO, which off-loads
the most recent goods first. Off-loading from a stockpile of
material will usually draw the most recent item added to the
pile.
-
Investment and Operating Costs: This is perhaps the
most important factor for determining the feasibility of using
warehouse racking systems. Costs per pallet position typically
have range from $50 to $100 for low-density, high-selectivity
racking systems and $100 to $250 for high-density,
low-selectivity racking systems. For existing warehousing
systems that have other options of acquiring additional
storage space, such as warehouse extension or leasing storage
spaces, it is best to determine the economic benefit of
adapting racking systems. The high investment can be offset by
savings in operating costs such as decreased manpower, savings
from space rentals, etc. Also account for intrinsic benefits
such as safety, ergonomics, and compliance with regulatory
requirements, which can ultimately affect profitability.
Chapter Four – Different Types of Warehouse Racking Systems
There are several racking designs and configurations suited for
a particular application. Storage racks are generally divided
into either high-selectivity, low-density or low-selectivity,
high-density applications. Racking with high selectivity and low
density are selective, double deep, and very narrow aisle
racking systems. High-density applications are push-back,
drive-in, and pallet flow. Special systems are also possible,
which are basically modifications of the previous
configurations.
Selective Racking:
Selective pallet racking has a high SKU count but offers the
lowest storage density. Conventional selective pallet racking
can be visualized as large shelves that have storage space for a
single row of items. The racks can be arranged back-to-back to
improve storage density, although they have low storage density
because of the space consumed by the aisles. This type is mostly
seen in raw materials warehouses, parts storage spaces, and
distribution centers where there are many distinct types of
products with low volume. Selective pallet racking can be
combined with other types to accommodate SKUs with high volumes.
Other properties of selective racking are its flexibility
between FIFO and LIFO inventory management, the operability of
standard forklifts, accessibility for cleaning and inventory
accounting, and simple construction that allows for easy
reconfiguration. Selective racking has different frame and beam
connection designs that are divided into teardrop and slotted
racks.
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Teardrop Racks: Teardrop racking is a type of selective
racking with modified frame and beam attachments that can be
reconfigured and expanded easily without the use of machine
tools. Upside down teardrop-shaped holes are punched along the
upright frames, where pins attached to the beams are inserted.
As the pin falls into the tapered opening, friction secures it
in place without requiring additional fasteners. This
connection has enough strength to be comparable with permanent
joints. Adding heavier loads causes more friction to fix the
beam in place. Wire decks are placed above the beams that
become shelves for the pallets. Appurtenances such as pallet
supports, crossbars, ties, and anchors are added to further
strengthen the structure. Teardrop pallet racks are usually
produced by roll forming in which metal sheets are cold-rolled
into rectangular frames and beams.
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Slotted Racks: These are sometimes referred to as
structural racks. Instead of using upside-down teardrop-shaped
holes, slotted racks have a pair of rectangular openings
milled along with the upright frame. The frame and beam can be
attached by hooks protruding from the beam or by bolts. The
main advantage of using slotted racks over teardrop racks are
their higher durability and strength. Slotted racks are
produced from hot-rolled structural steel, making them more
robust than teardrop racks. Higher gauges of sheet metal are
used to allow a higher load-bearing capacity. The downside of
using slotted racks is their higher cost and weight.
Double Deep Pallet Racking:
This is a modification of the standard selective racking where
instead of using single pallet rows, two rows are used per
pallet shelf. This increases the storage capacity of selective
racking by 40-60%. This also preserves the advantages seen from
the standard selective racking. To operate under FIFO inventory
management, the adjacent rows must have the same SKU. This
increases the storage density, but selectivity is lowered. The
main disadvantage of using this system is the need for
specialized forklifts or standard forklifts with double deep
handling attachments. This leads to higher operating costs and
requires well-trained operators.
Very Narrow Aisle (VNA) Racking:
The concept of this pallet racking is to further improve space
utilization of a standard selective while maintaining 100%
selectivity. This is done by loading pallets using a fork truck
capable of side loading. This eliminates additional space
intended for maneuvering the forklift. The aisle space can be
minimized by up to 40%. A downside of this type is the need for
two sets of equipment for loading and unloading. One is a
side-loading fork truck, and the other is a standard forklift
for moving products from the palletizing station to the staging
area.
Push-back Racking:
This type of racking involves loading the pallet on carts
resting on a pair of rails that are available on each push-back
lane. These carts are designed to be nested at the front of the
aisle. To load a pallet, the forklift pushes against the other
pallet, which moves it deeper into the lane. This dynamic
racking system allows higher storage density than single or
double deep racking. Each lane is one SKU that can be configured
three to six pallets deep. Specialized forklifts with deep
handling attachments are not needed since the pallet is readily
accessible at the front of the lane. The lanes are inclined so
that the carts roll towards the aisle. Each lane is a LIFO
management since only the most recent pallet is accessible.
Drive-in and Drive-through Racking:
In this type, the pallets rest on a pair of rails that are
specifically designed for the pallet dimensions to be loaded.
The rails are designed to support the pallet while providing
access to the forklift mast and fork as the forklift moves along
the bay. Loading is done by driving a forklift into the last
open position. Once in position, the pallet is slowly lowered
into the rails. After loading, the mast is retracted, and the
forklift backs out of the bay. Each bay is dedicated to a single
SKU that can be several units deep, making it suitable for
high-density storage but with low selectivity. This system is
available in two configurations, drive-in and drive-through. In
drive-in, the bay has only one access for entrance and exit,
allowing for LIFO inventory management. The drive-through, on
the other hand, has two access points, one for loading and the
other for off-loading. This is used for FIFO inventory
management.
Pallet Flow (Gravity Flow) Storage:
This design employs roller beds that move the pallets into the
last open position. The lane has two openings similar to a
drive-through racking, one at the front and one at the rear. The
pallet is loaded at the rear side. After loading, the pallet
rolls along the lane towards the front side. This is achieved by
having the lane inclined at the rear. Off-loading is done on the
front side of the racks. Pallet flow, like drive-in and
drive-through racking, is suitable for high volume, low SKU
number applications. In terms of inventory management, this
system is suitable for FIFO. It has the same storage density as
a drive-through but not as much as drive-in racking since it
uses two lanes. This dynamic system is better than drive-in and
drive-through since it is not prone to damage from forklifts
that can lead to collapse.
Cantilever Racking:
This type is ideal for storing long products such as roofing
materials, pipes, tubes, and lumber. It is composed of upright
columns with cantilever arms on one or both sides. Vertical
clearances between the arms can be adjusted depending on the
bulkiness of the product. The angles can also be adjusted to
help with load retention. Unlike standard selective racking,
cantilever racks do not have upright frames at the front that
obstruct loading. Aside from storing long products, it can also
store irregularly shaped items such as appliances and furniture.
Carton Flow:
The principle is similar to pallet flow racking. This type also
has two access points, one for loading and the other for
off-loading. Manual loading and off-loading can be done without
the need for forklifts. This is ideal for high volume piece-pick
applications such as in cold storages and food racks. Carton
flow lanes can accommodate non-standard size items.
Mobile Racking:
This type involves moving a whole rack assembly laterally to
create an aisle space. Moving the rack is usually accomplished
by driving it using electric motors. Smaller racks can also be
mechanically or manually operated through pushing or pulling or
by rotating handwheels with a high ratio. This type is a
high-density storage system with high selectivity. However,
access is not readily available as the racks need to be moved
first for access. This is suitable for warehouses with low
traffic.
High-Bay Racking:
As the name suggests, this type takes advantage of having high
bays. They are most suitable for automated distribution centers
for high density, high selectivity, and high throughput storage.
The racks can be single, double, or in some instances,
multi-deep rows. Automatic cranes with telescopic forks or
order-picking trucks stabilized by rails and supports move along
the aisle. The crane picks up a pallet from the conveyor system
and places it on its designated rack. Due to the complexity and
high cost of this system, it is only viable for warehousing that
hedges profits on efficient storage.
Chrome Wire Racking:
Chrome wire shelving is highly versatile and inexpensive with
the same strength as stainless steel. It has a clean finished
look and can be used to store a wide assortment of items with a
durability capable of holding trays, cartons, boxes, and storage
containers.
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Strength - Chrome plated wire shelves can hold up to
800 LBS when the shelves are under four feet tall. A standard
four shelf unit can hold up to 3,200 lbs of products while
shelves over four feet can hold 600 lbs.
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Light Reflection and Penetration - Unlike standard gray
metal shelving, chrome plated wire reflects light, which can
brighten a storage area. Since the shelves are made of wire
and not solid, light passes through the shelves to make it
easier to identify stored items.
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Sprinkler Effectiveness - In the case of a fire, the
chrome plated wire shelving allows water penetration to the
floor, a feature that is positively viewed by fire marshals.
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Mobility - Chrome plated wire shelving can be turned
into mobile shelving by adding casters.
Special Shelving:
Epoxy coated shelving, which can be gray, black, or green, is
ideal for humid and wet environments. Some types of epoxy
shelving can have an antimicrobial agent to prevent the buildup
of bacteria, which is important for shelving used in the food
industry and healthcare.
Automated Storage and Retrieval Systems (ASRS):
ASRS systems use software, computers, and robotics to make
handling, storage, and picking smoother and more efficient. They
can be adjusted and customized to fit any size warehousing
system and are dependent on various technologies to
automatically complete warehousing tasks.
There are several different types of ASRS systems that are
capable of being configured to meet every type of warehousing
need. The most common systems are:
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Unit Load ASRS - are used for large cases or pallets
including loads that weigh several thousand pounds. They have
fixed and movable aisle cranes.
-
Mini-load ASRS - are smaller versions of unit load
ASRSs and are used for lighter loads. They have shuttles and
cranes designed for narrow aisles.
-
Horizontal Carousels - Horizontal carousels are a form
of sorting device used with small parts and products. They can
be activated by a computer program or an electronic switch.
-
Vertical Carousels - Vertical carousels operate like
horizontal carousels and have the same activation mechanisms
but complete their function vertically rather than
horizontally.
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Vertical Lift Modules (VLM) - VLMs place or pick items from
trays. They are the most flexible of the automated inventory
methods and adjust when the inventory changes. Each tray is
capable of holding a ton of parts. VLMs have two columns of
trays for picking and placing.
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Cube Based storage - Cube based storage is the newest of the
automated inventory methods. Items are placed in cubes that
have robots that shuffle, sort, and pick bins to be delivered
to workstations. Every cube on the cube grid works
independently and is connected by a wireless system. Cube
based systems are modular, which makes it easier for insertion
and replacement of cubes.
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Shuttles - Robotic shuttles move independently riding on
narrow rails to different storage levels. They operate quickly
and efficiently handling totes weighing 35 lbs. To 110 lbs.
Their speed can be adjusted higher or lower to fit the needs
of the warehousing system.
Instead of using carts or roller beds, the system uses remotely
controlled shuttles to lift and lower pallets and to move
pallets. Since the length of a lane is not limited by the
incline, shuttles have a large number of pallet positions per
lane. This type can be utilized for FIFO and LIFO inventory
management.
Conclusion
-
Warehouse racking, also known as storage or pallet racking, is
a material handling system suitable for mass storage of goods
unitized on skids or pallets. This allows for efficient
utilization of space while providing easy access to stockpiled
items for better inventory control.
-
Some of the benefits of racking systems are efficient space
utilization, easy inventory organization, fewer damaged goods,
increased employee productivity, automation, safety, and
cleanliness.
-
Important factors to consider before investing in a racking
system are the available floor area and vertical space, pallet
load weight and dimensions, target capacity, throughput,
number of SKUs, type of inventory management, and cost.
-
Racking with high selectivity and low density are selective,
double deep, and very narrow aisle racking systems.
High-density applications are push-back, drive-in, and pallet
flow.
Leading Manufacturers and Suppliers