2014 in review

The WordPress.com stats helper monkeys prepared a 2014 annual report for this blog.

Here’s an excerpt:

A San Francisco cable car holds 60 people. This blog was viewed about 1,500 times in 2014. If it were a cable car, it would take about 25 trips to carry that many people.

Click here to see the complete report.

Can the plastic (wpp) dunnage bag be made to perform like a paper dunnage bag?

The short answer is yes.

The uninflated wpp dunnage bag can be sandwiched between two pieces of cardboard ( new or used)  before being placed between the cargo loads .The cardboard also serves to protect the inflated  dunange bag from being punctured by any sharp object or edges. Ensure that the dunnage bag is inflated till it tightly pushes the cargo loads against the walls or roof.

2013 in review

The WordPress.com stats helper monkeys prepared a 2013 annual report for this blog.

Here’s an excerpt:

A San Francisco cable car holds 60 people. This blog was viewed about 1,200 times in 2013. If it were a cable car, it would take about 20 trips to carry that many people.

Click here to see the complete report.

Oxo biodegradable polywoven dunnage bags?

In layman’s terms, oxo biodegradable plastic is plastic that will degrade into micro fragments in the environment in years and/or months instead of the normal hundreds of years.This is made possible by adding some metal salt additive into the plastic resin which will help to speed up the degradation process.
Many countries have introduced requirements for throw-away and single-use plastic articles to be made from oxo degradable plastic.Examples of such articles are shopping bags, rubbish bags, plastic wraps, shrink wraps , cling wraps, cutlery etc. There are some grey areas where the authorities,users and manufacturers are in disagreement on the scope. More studies and discussion will be necessary to sort out the contentious issues involved.
As a general guideline, all inflatable plastic products should be outside the scope of this oxo biodegradable requirement.Inflatable products are normally filled with air and there must not be any holes( no matter how small) in the plastic liner.Otherwise, the air will leak out and render the product unusable. The risk of a puncture when oxo biodegradable plastic is used is very high as the degradation will take place in the presence of air and moisture immediately after the product is made. As such dunnage bags should be placed outside the scope of the oxo biodegradable plastic requirement.

Comparison of composite strapping with woven polyester cord strapping

Comparison of Woven And Composite Polyester Strapping

Loading Plans Using Dunnage Bags

1) Loading Plans
It is recommended that a loading plan be drawn up before loading the container and installing the dunnage bags.This will ensure that the cargo loads are correctly placed and the dunnage bags installed in the right locations.Any potential problem would have been highlighted and resolved at the planning stage resulting in smooth container loading operation.The same loading plan can be re-used for similar cargo loads.
It is also recommended that a few photographs be taken of the container stuffing at the half-way stage and final stage.One of the photograph should be with one of the container doors closed displaying the container no. These should be filed with the loading plan together with relevant information such as date, time, cargo type ,lot no. and loading staff involved. These pictures and information are available for review in case of any problem at the destination and also for study and future improvement .

2) Typical Loading Plans

2.1)Loose Carton Boxes And Tins

       Example 1 – Loose Carton Boxes

Loading Plan for Loose Cartons 220311

Dunnage Bag Holding The Carton Boxes Inside The Container

Securing Loose Cartons In Container With Dunnage Bags

                                                                                                                                                                                                                                                            

          Example 2 – Securing Loose Tins Inside the Container Using Dunnage Bags

          Loading Plan for Tins 220311

         

Securing Loose Tins Inside The Container Using Dunnage Bags

        

Securing Loose Tins Inside A Container

                                                                                                                                                                                                                                           2.2)Palletised Cargo Load

       Example 1

       Cargo Securement Plan For Palletized Cargo Load 230311          

       Example 2

       Cargo Securement Plan For Palletized Cargo Option 2 230311

       Example 3

       Cargo Securement Plan For Palletized Cargo Option 3 230311

       

Securing palletised cargo loads with dunnage bags

 

Securing palletised cargo loads with dunnage bags

                                                                                                                                                                                                                                            

2.3) Cargo Loads In Crates

         This is similar to palletised cargo except that the cargo load is very heavy or fragile and so need extra protection from the crates.

        

 

Securing crated cargp loads with dunnage bags

                                                                                               

Heavy crates secured with dunnage bags

                                                                                                                                                                                                                                           2.4) Big Bags

        Normally these are palletised before loading into the container .

        Example:

        Loading Plan for Big Bags 240311

       

Securing big bags with dunnage bags

                                                                                                                                                                                                                                                        2.5) 25-kg Bags

       If these are palletised , then this category of cargo load can be treated like palletised cargo. Sometimes , these bags are manually stuffed into the 20-footer container. In this case, the stacking method is also important .It pays to make full use of the alternating stacking pattern together with dunnage bags to ensure the cargo loads are safely secured inside the container.

      Example:

      Loading And Securement Plan For 25kg bags 280311 

      

     

Securing 25-kg bags with dunnage bags

     

     

       

     

    

                                                                                                                                                                                                                                           2.6) Cargo in roll form

         Example:

       

Securing rolls of plastic waterproofing sheets with dunnage bags

     2.7)  Jerrycans

                Example:

               

Securing jerrycans with dunnage bags

3.0) Conclusion

          There is no one best method to secure the cargo loads inside the container.It depends on the weight, shape, quantity and how the cargo loads are bundled together.  Just remember that the dunnage bags can be installed: a)between cargo loads  b)at the sides between the cargo loads and the sides of the container and c)at the top between the cargo loads and the roof of the container. The only forbidden place to install the dunnage bag is between the cargo loads and the doors . Installing a dunnage bag here is difficult and dangerous to the person opening the door at the destination.

Paper Dunnage Bags Versus Woven Polypropylene Dunnage Bags

There has always been an ongoing debate as to which is better. To answer this, we need to look at the background of the development of the dunnage bags.
The paper dunnage bag was introduced in the 1950’s and was a big advancement over the 1st generation rubber dunnage bag. It is lighter,easier to use, and much cheaper so it can be discarded after each use. There is no need to collect back the dunnage bags at the  destination for re-use.
In step with the advancement of plastic technology , plastic has quickly replaced paper in most areas . So in the 1990’s the 3 rd generation woven polypropylene (WPP) dunnage bag was introduced. The WPP dunnage bag quickly gain acceptance and has since grabbed the lion’s share of the dunnage bag market.It’s  advantages over the paper dunnage bag are lighter, stronger, waterproof and cheaper .

The paper dunnage bag supporters have put up the following major arguments :

1)We have used paper dunnage bags for decades and have no problem with them.

2)The paper dunnage bag is thicker and heavier so it can resist puncture better.

3)The surface of the wpp dunnage bag is smoother so it can easily slip out during transportation .

4)The paper dunnage bag is more resistant to chemicals.

Nothing can be done about Argument #1 so we move on to the other 3 arguments.

Paper Dunnage Bags Are More Puncture Resistant

All types of dunnage bags are filled with compressed air and so can be punctured by sharp objects . To minimise the risk , it is recommended that the user take the following precautions :

1. Remove or cover any sharp edges that may come into contact with the inflated dunnage bag during container stuffing.

2. Sandwich the dunnage bag between 2 sheets of cardboard , plywood or chipboard ( new or recycled) before installing it between the cargo loads. The boards also serve to distribute the pressure evenly onto the cargo loads.

The Surface Of The WPP Dunnage Bag Is Smoother So It Can Easily Slip Out

There are 2 possible scenario where the dunnage bag,whether paper or wpp, can slip out during transportation:

1. Installing 2 dunnage bags side-by-side as the void between the cargo loads is too big. This is a no-no in installing the dunnage bags as during transportation the rocking and vibrations will cause one of the dunnage bags to slip out. If the void is too big, user may need to install one dunnage bag on either side of the cargo load(s). Or use solid void fillers to reduce the void size before installing the dunnage bags.

2. Underinflation.If the dunnage bag is under-inflated , then it will slip out during transportation . It needs to be inflated until the cargo loads on both sides are pressing hard against it thus holding it in place even during transportation.

The Paper Dunnage Bag Is More Resistant To Chemicals

Both the paper and wpp dunnage bag contain an inner PE liner bag which holds the compressed air during inflation. This liner bag is about 1 micron thick.If the chemical is corrosive , both types of bag will be damaged .Anyway, there are special guidelines governing transportation of hazardous chemicals as there are great risk to the people handling them .

The WPP dunnage bag is the market leader by a wide margin and growing . So, the majority of the users must be onto something . It pays for us to take note of the trend. The end user has to look at his situation objectively and evaluate which  bag is most cost effective for him. Dunnage bags are added overhead cost and need to be managed as well.

Is lamination necessary for polywoven dunnage air bags?

Historical Background
The lamination process is a carry-over from the FIBCs and big bags which came into being in the 1960s.These bags were used to hold flowable materials like food grains, plastic resins, animal food pellets and powder like cement .The lamination helps to prevent the contents from leaking out and dirt & mosture from seeping in. In the process, a plastic film (PP or PE)of thickness from 0.02 – 0.06mm is laminated onto the surface ( inner, outer or both) of the bag using heat.

What does the lamination do to the dunnage bag?
It does not contribute anything to enhance the performance of the dunnage bag. On the contrary , it adds about 3-5% to the cost of the bag.
Some quarters claim that with lamination the polywoven dunnage bag is stiffer and therefore easier to hold in place during inflation .We have always recommended that the uninflated bag (both polywoven and paper types) be ‘sandwiched” between two pieces of cardboard ( used or new) before inflation . This will make it easier to hold the bag in place during inflation and also prevent the inflated bag from being punctured by any sharp edge or point from the pallet or cargo load.

Training On Using The Dunnage Bag

Dunnage Bag Training

Using Plastic Slip Sheets To Replace Pallets

1) What is a slip sheet?

 The slip sheet is used as a portable material handling base for storage and transportation of unitized goods. It is actually a thin sheet ( from 0.5mm to 2.5mm) made from solid fibre , corrugated board or plastic materials.

Typical solid fibre slip sheet

  Typical Plastic Slip Sheet

2) Background

After World War II , the wooden pallet has become the primary portable platform/base  for the movement and storage of goods  in the advent of containerization.

However , shippers are always looking for innovative ways to reduce cost and receivers are searching for ways to reduce trash disposal costs.The large US food processors were the first industry group to adopt slip sheets during the 1970’s .The slip sheet was developed by such companies as General Foods and Quaker Oats for shipment of their goods.

The first slip sheets were made from solid fibre and later corrugated kraft liner medium . A little later the plastic slip sheet made its appearance.

The “green” movement to reduce usage of wood and the implementation of the ISPM15 (Regulation of Wood Pacakaging Material in International Trade) has led to exporters shifting to other portable bases such as slip sheets, paper pallets, pressed wood pallets and plastic  pallets.

3) Construction of the plastic slip sheet

This can be made from any kind of combination of polmerized material , including but not limited to polyethylene or polypropylene that provide adequate tensile strength . Most of the plastic material used are recycled. The most common method of production is by extrusion.

4) Specifications

4.1 Tensile Strength

This is the strength per unit cross-sectional area.It will determine how thick a slip sheet need to be in order to support a given payload. For practical purposes, it is given as thickness versus load capacity  . For example , a typical PE slip sheet will have the following load capacities versus thickness:

          Thickness (mm)                            Load Capacity (tonne)

                 0.7                                                    1.0

                 0.9                                                    1.2

                  1.1                                                   1.5

                  1.6                                                   2.0

                  2.2                                                   3.0

4.2 Coefficient Of  Friction

The side of the slip sheet where the goods sit on must have high slip resistance so that the goods will not slide off during loading, unloading or movement.However, the reverse side has to be smooth so that the loaded slip sheet can slide on the floor /pallet smoothly during loading and unloading . The standard measure of slip resistance is known as the coefficient of friction where the higher value signifies a higher slip resistance.

In practice ,one side of the slip sheet is embossed with a criss-cross pattern to increase the friction while the opposite side is smooth. Typical coefficient of riction values for plastic slip sheets are :

Side                                           Coefficient of friction

Embossed face(rough)                           0.5+

Smooth face                                       0.2 – 0.3

5.0) Pull Tabs 

Pull tabs are areas at the edges of  the slip sheet where the gripper clamps on during loading and unloading . More tabs will allow the handling equipment to approach the loaded slip sheet  from more sides (very much like the 1-way,2-way 4-way entry pallet concept).

Typical tabs & scoring for solid fibre slip sheets

        Typical Plastic Slip Sheet Dwg 140709

5.1 No. of tabs

There are 4 possible configuration :

i)   Single tab

ii)  Two opposite tabs

iii) Two adjacent tabs

iv) Four tabs

The typical tab width can range from 75 – 100mm .Unlike the solid fibre slip sheet, the tabs are not clearly defined as no scoring or cutting are necessary to form the tabs for the plastic slip sheet.

5.2 Scoring

Scoring is only necessary for solid fibre and corrugated slip sheets. As the solid fibre is stiff, scoring and cutting at the corners are necessary to allow the tab to bend upto 90 degrees. Otherwise , the stiff fibre will crack and the tab will tear when the gripper clamps on it and pull on it .

As the plastic slip sheet is very flexible , scoring or cutting at the corners to from the tabs are not necessary. A typical plastic slip sheet therefore appears as a rectangular sheet with no clear demarcation of the tabs. The user has the flexibility to assign the pull tab(s) during use when loading the goods onto it.

6.0 Unitizing

The common feature of using  pallet and slip sheet is that the goods need to be unitized.

Individual products are combined and shipped in larger unitized loads . These unitized loads can then be handled using mechanical handling equipment saving cost of manual labour and turn-around time . There is also less pilferage and less handling  damage so less costly protective packaging is needed. The load is unitized using the following methods or combination of methods :

i) Strapping

The goods are strapped together to form a single load.

Strapped Load

                        

Unitizing the drums using strappings

ii) Shrink wrapping

The plastic shrink film /bag is put over the goods and heat shrinked to form a unitized load.

Shrink wrapping

                                                     
 

                                             

iii) Stretch Wrapping

The stretch film is wrapped around the goods to form a unitized load.This can be done manually or by using a machine.

Stretch Wrapping

iv) Net Wrapping

The goods are wrapped with netting or  perforated film . Normally , done for goods that need to “breathe ” like fruits and vegetables.

Net Wrapping

                                                                            

Net wrapping of vegetable

v) Using adhesives

Each layer of products are glued onto the next so that they form a unitized load .

Load unitized by using adhesive Using adhesive to unitize the load

                         

Using adhesive to unitize the cartons

vi) Using hot-melts

This is similar to using adhesive except that hot-melt adhesives are used.

Hot melt guns used to apply the glue for unitizing the load.

viii) Rubber banding

Big rubber bands are used to tie the products together to form a unitized load.

Pallet banding

  

Unitized load using pallet band

7.0) Handling the Slip Sheets

It should be noted that the slip sheet handling equipment must be available at both the shipping and receiving stations for loading and unloading the goods shipped on slip sheets.

7.1 Push-and- Pull Attachment

This is an attachment for the forklift so that it can handle the loaded slip sheet . It basically has  a gripper which grips the pull tab and pull the loaded slip sheet onto its 2 platform arms for transportation. In unloading, it pushes the loaded slip sheet onto the pallet or floor.The attachment just fits onto the normal forklift (without need to remove the original forks) and it  takes only  a few minutes.  

Typical push pull attachment

 

Forklift with the push pull attachment

7.2 Rollerforks

This is also an attachment for the forklift . It has 2 sets of rollers on each arm which can roll the loaded slip sheet onto the arms for transportation. A specially designed pallet with extra slats(RF pallet) will greatly improve efficiency of handling the slip sheets when used with the rollerforks . The rollerforks can also be used with the normal pallets.

Rollerforks attachment

8.0) Using the slip sheets

8.1 Inside the factory or warehouse, the slip sheet is placed on top of the pallet and the goods are loaded on top of it. The slip sheet is arranged on the pallet so that the desired pull tab(s) extend out from the edge(s) of the pallet . With this arrangement , the push pull attachment can easily grip the tab later on.

8.2 The goods are normally moved about within the premises using these captive pallets ( these pallets never leave the premises). Some organizations invest in high quality plastic captive  pallets .All movement of the goods within the premises is  done using the forklift and pallet just like normal.However, this movement can also be done using the slip sheet if so desired.

8.3 The goods on the pallet are unitized  ,either before storage or just before loading  into tthe container/truck for shipment. 

8.4 When loading the loaded slip sheet into the container or truck, the push pull or rollerforks attachment will be needed.

8.5 It is possible to retrieve   and save the slip sheet  when loading the goods into the container or truck  using a specially designed push pull attachment.In which case, the goods will have to be unloaded manually at the discharge destination.

Sheet Save push pull

9.0) References

9.1 http://en.wikipedia.org/wiki/slip_sheet

9.2 http://www.scotland.gov.uk/Topics/agriculture/plant/18273/potatoexpconds/ISPM15

9.3 http://rollerforks.com/pushpull.aspx

9.4 http://www.cascorp.com

9.5 ISO 12776:2008, Pallets-Slip sheets