Archive for the ‘Dunnage Bags’ Category

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

March 5, 2014

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.

DP p7 Dunnage bag at the top pic 2

Oxo biodegradable polywoven dunnage bags?

July 16, 2012

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.

Loading Plans Using Dunnage Bags

April 1, 2011

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:
       

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:
      
     

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

February 10, 2011

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?

January 21, 2010

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

October 26, 2009

Dunnage Bag Training

Dunnage Bag Terms

April 24, 2009

Common Terms Used In Dunnage Bags
AAR                                                           American Association of Railroads
Air Bladder                                            The inner plastic bag holding the air . Also called liner.

Burst pressure                                      The pressure beyond which the bag may burst

Crosswise bracing                               The dunnage bag is installed with the length parallel to the floor

Deflate                                                      Air is released from the inflated bag

Effective contact area                       The area of the bag directly in contact with the cargo loads or walls. The inflated bag

                                                                    is rounded at the top and bottom so only the central portion is in contact with the

                                                                    cargo load 

Force                                                        The force generated by the inflated dunnage bag. It is proportional to the effective
                                                                     contact area and the inflation pressure.

Gap                                                            See void

GSM                                                          Refers to the weight in gram per square metre of the kraft paper or polywoven fabric

Inflate                                                      Fill the bag with compressed air

Install                                                      Place and inflate a bag in a void

Kraft paper                                            Special paper used to make the outer bag

Laminated paper                                Refers to kraft paper laminated with layer of polywoven fabric

Layer                                                       The number of separate layers of material making up the bag

Leak                                                         The inflated bag losing air over time

Lengthwise bracing                           The dunnage bag is placed with the length perpendicular to the floor

Level 1                                                    AAR classification of dunnage bag with working pressure of 2.5psi and burst pressure

                                                                   of 8psi 

Level 2                                                   AAR classification for dunnage bag with working pressure of 5psi and bust pressure of 

                                                                  17psi

Level 3                                                   AAR classification of dunnage bag with working pressure of 8psi and burst pressure of

                                                                 25psi

Level 4                                                 AAR classification of dunnage bag with working pressure of 10psi and burst pressure of

                                                               30psi

Liner                                                     See air bladder

One-way valve                                 The valve only allows compressed air to enter the bag but not out of it.As such, the bag

                                                                can only be inflated once.

Paper dunnage bag                        A dunnage bag with a paper outer bag

Ply                                                        Refers to the number of separate layers of paper in the outer bag

Polywoven dunnage bag             A dunnage bag made with a polywoven outer bag

Recyclable                                        The material making up the bag can be recyled into raw material for reuse.

Reusable                                           The bag can be used 2 or more times

RoHS                                                  This refers to the European Union directive on Restriction on use of Heavy Metal

                                                              substances

Size of bag                                         Refers to the length and width of the uninflated bag

Two-way valve                               The valve allows compressed air to be pumped into the bag and also allows the air

                                                               inside the bag to be released . This means the bag is reusable.

Void                                                     The empty space between cargo loads or between the cargo load and the wall where the

                                                               dunnage bag is installed.

Working pressure                          The  pressure that the bag can be safely inflated to.

WPP fabric                                         Woven propylene fabric is woven from polypropylene yarn

RoHS in Dunnage Bags

March 30, 2009

heavy-metals-in-plastic-dunnage-bags-60309

How Many Dunnage Bags To Use?

March 18, 2009

no-of-dunnage-bags-needed-for-standard-container1

Dunnage Bag Forces

March 13, 2009

Dunnage Bag Forces

The forces that can be generated by a dunnage bag is determined by the bag size, working pressure and the void size . Charts of the forces for some common sizes and working pressures are listed below.

dunnage-bag-forces2