Pallet Racking FAQ’s

Each warehouse is built differently with different needs and objectives most of them to suit the builders requirements at the time. At SPAR we consider no two warehouses alike and when this difference is associated with many varieties of product lines, picking variations, product weights, product volumes etc it gets a bit complex. This brings us into the picture to impart our expertise to customers and listen to their needs. The product supplied is a natural flow of the understanding of these needs.  

What is a pallet?

A pallet or skid as its also known is small raised independent platform 1170mm W x 1170mm D x150mm H (Australian Standard) that supports goods in a stable fashion while being lifted by material handling equipment like a forklift. This unit is used to bulk stock and package goods on it so that bulk storage and transport of products is made possible making it easy to move heavy loads. The standard dimensions vary in some parts of the world.

What exactly is a Pallet Rack?

The wikipedia website describes Pallet Racking as “Pallet rack, also referred to as “pallet racking,” is a material handling storage aid system designed to store materials on pallets (or “skids”). Although there are many varieties of pallet rack, all types allow for the storage of palletized materials in horizontal rows with multiple levels. All types of pallet rack create some level of increase storage density with the least dense being the least expensive and cost increasing with storage density”. We have prepared the below table as a ready reckoner to help you understand the various aspects of a Pallet racking system used by the industry suppliers as a rule of thumb.

Racking type comparison

SELECTIVE (SR)100%Good30%
DOUBLE DEEP (DDR)50%Average60%
DRIVE IN (DIR)25%Poor65%
PUSH BACK (PBR)25%Average65%
MOBILE RACK (MR)100%Good70%
GRAVITY FLOW (GFR)25%Excellent60%

We will illustrate below using 4 Types of Pallet Racking Systems to show you why and how they are used to maximise the storage capacity of a typical 1000 square meter warehouse. 
Note: Please note that each warehouse has its own size and shape and the designs will have to be varied to suit each requirement as necessary. We request you to note the positions and widths of the aisles as well as frequency of the rack rows in the below layouts as they change with the introduction of the various systems below. 

How many kinds of pallets are there?

Basically two kinds of pallets –

  • Pallets with two sided access: The pallet allows fork lift entry bars on only two sides of the pallet.
  • Pallets with four sided access: The pallet allows fork lift entry bars from all fours sides.

What are pallets made of?

Generally pallets are made of wood but are also available in steel and plastic.

How are goods stocked?

The goods are stocked straight or in cartons / wholesale packaging side by side not to exceed the dimensions of the standard pallet and one on top of the other to a safe height depending on the weight and volume of the product used eg. tissues to steel discs.

What is a safe loading limit for pallets?

Once again depending on the product the pallet is made from its load carrying capacity varies. Wooden pallets can take about 2000kgs and up to 3000 kgs each. Steel and Plastic pallets can take more depending on the design. The wooden pallet itself weights about 50 kgs approximately.

How are pallets stored?

Pallet can be stored in an organized manner on the floor if required which is known as block stacking.

Is this safe?

Depending on the type of product, weight, volume and carton strength (if stocked in cartons) there is only a certain number of pallets you can stock over the lowest pallet on the ground before this pallet caves in with the weight of the pallets on top. This is also not safe as if the pallet gives way and collapses the avalanche effect will certainly topple the whole block of pallets. This makes it a hazard at the workplace in case people working in the area are involved.

What is a Pallet Rack?

Since we have explained what a pallet is above its easier to define a Pallet Rack now as a multi level structure made from steel components and connected in such a manner as to structurally bear the weight of pallets in an organized manner for easy access. This rack will allow handling of individual pallets as required without the need to disturb the other pallets in the system.

On what principles are Pallet racking products designed?

Pallet racking products are designed on two principles,

  • FIFO – First in First Out – The first Pallet in is also the first pallet out of the system.
  • FILO – First in Last out – The first pallet in is also the first pallet out of the system.

How many types of pallet racks exist today?

  • Selective Pallet racking
  • Double Deep
  • Drive in / Drive through
  • Narrow aisle
  • Gravity flow
  • Mobile
  • Push back
  • Automated Storage and Retrieval Systems
  • Rack Clad buildings

What is the simplest kind of pallet rack?

The simplest pallet rack is a selective pallet rack and it is the only one that can offer 100% access to any pallet in the system 100% of the time.  

How are pallets stored in a Selective rack?

Generally a Selective rack can accommodate two standard pallets in its width allowing for some space above and on both sides of each pallet for placing and removal of the pallet. The total height of the rack will depend on how many levels it is designed for.

How high can this system go?

The height of the system is limited by the height of the building itself or the maximum height the material handling equipment (like a forklift truck) can reach with the heaviest pallet in the system. If the pallets are heavier than normal (say 1500 – 2000kgs+) then the thickness and profile of the steel members can also be a limiting factor if the minimum requirements of stress on them are not met.

Does the lowest pallet always rest on the ground?

No. In case of material handling equipment like stackers that have straddles, the pallets at the lowest level cannot be stacked on the ground as they get in the way of these straddles. In this case a beam is provided at the lowest point of the rack and the lowest pallets are now kept on these beams. This allows for the straddles to move beneath the beams and pick up the pallets on the lowest beam level unhindered.

What is a Double Deep system?

This is nothing but a selective racking system that is installed one behind the other to increase the density of the storage area using a minimum of aisles. This system is generally used if you have more than one pallet of one kind of product.

Are there any drawbacks of the Double Deep system?

The only drawback is that a normal forklift cannot access the rear pallet and as such a telescopic attachment needs to be added to the Forklift to enable it to reach in and pick up the rear pallet. This also means that you cannot get to the pallet at the back till the pallet in front is removed. This effectively reduces the accessibility of pallets in the system to 50%.

What is a Push Back system?

A push back has a similar concept of a double deep in with the added advantage of more density and also the fact that a standard forklift can be used for loading and removal of the pallets. The pallets are stored on inclined telescopic roller guides such that when a pallet is initially stored the second pallet is then used to push the first pallet back and make place for the second pallet. Similarly the system can be designed for more than 2 pallets deep. In case of removal when the aisle pallet is removed the pallet behind it gently slides to the front for removal.

Are there any drawbacks of the Push back system?

The only drawback is the limited accessibility to pallets in the system.

What is a Drive in / Drive through system?

One of the densest systems of Pallet Racking is the Drive in / Drive through system. The name Drive in denotes a system where access is blocked at the end of the Drive in lane and hence a FILO system. The name Drive through system denotes a system where the access is free through at the other end of the lane and hence is FIFO system. In this system the aisle wastage is limited and pallets are stored as densely as possible along the width, depth and height almost like block stacking.

Are there any drawbacks of this system?

This system can be practically implemented if the user has many pallets of a similar product and almost useless if it’s the other way around.

What is a Narrow Aisle system?

As the name suggests a Narrow Aisle system is Selective racking designed for use with equipment that will access a pallet in the system and retrieve it in a much narrower aisle (less than 2000mm as compared to the 3000mm required for a Selective system). This obviously allows more rack rows to be installed in the same given space increasing the capacity of the system. The advantage of this system is that higher systems can be designed with guide rails for the material handling equipment thereby eliminating any errors during the handling process. The dense storage achieved offsets the cost of purchasing the desired material handling equipment.   

What is an ASRS?

Automated Storage & Retrieval Systems (ASRS) are on a broad scale Narrow and Very Narrow Aisle systems used with automated material handling equipment. In this system the warehouse database and organization ERP systems are integrated with the automated racking system for total hands free put away and picking of pallets in the system with the help of interactive consoles run on specially designed software programs.    

What is a Mobile rack?

Once again a Mobile rack is somewhat of a Selective pallet racking system achieved with minimal one or two dynamic access aisles. The racks are all placed on rails and at any given time only one aisle is open for use once again with a standard fork lift. When another aisle is needed the operator uses his electrically controlled console to issue the instruction whereby whole row of bays will move to on their guiderails to create the aisle where required. Once again this allows all the aisle spaces of the system to be used for racking and as such increases the capacity of the warehouse tremendously.        

What is a Gravity Flow system?

This is the densest system that can be used for pallet racking and is basically a Drive through system with rollers provided instead of runners. The system using the FIFO principle has heavy duty rollers installed along each pallet cell from the entry of the system (which is generally a bit higher than the exit to use gravitational force to transport the pallet towards the exit) to the exit. This system is generally suitable for use between a high volume manufacturing unit in a facility to its warehousing facility or between a storage unit and dispatch. The rollers also have speed controllers along the path to avoid stress at the exit by pallets hitting each other. So when a pallet is removed at the exit the next pallet gently takes it place.  

What is a Rack Clad building?

This unit which is popular in Europe but not so much here in Australia is nothing but a suitable pallet racking system covered on all sides as a warehouse eliminating the need to build an independent free standing warehouse. This system is designed in such a manner that it not only meets the load demands of the system it is created for but also withstands factors like wind speeds and soil movements like a conventionally civil engineered building. The unique advantage being that the building can be dismantled and moved to a new location.       

Note: For more information on any product listed above or any other associated product please email or call us on 02 96309194 at any time convenient.