Bulk Bags FAQs

Your Questions About Bulk Bags Answered

Here at Centurion Packaging we often get quizzed about our range of bulk bags, which is why we have put together this post answering all of your burning questions in one place.


Can Bulk Bags Be Reused?

Yes, bulk bags can be reused, which requires a multi-trip bulk bags made with a 6:1 Safety Factor. This type of bag is manufactured to be used for a specific amount of times with some users choosing to reuse bulk bags with a 5:1 safety factor.
Centurion Packaging does not recommend this practice, as you will need to take into account that bags may be worn and have a small hole in the fabric which could make the loops unstable.
We would not guarantee a certain number of uses for a 6:1 safety factor multi-trip bulk bag. You will need to inspect in between uses and retiring bags for any tears, rips and abrasions. An additional bag tag is included for tracking usage if the bulk bag is approved for further use after inspection.

What is a Bulk Bag?

Bulk bags are a large heavy-duty bag that is used for transporting free-flowing dry products, scrap metal plus various waste items that need to be transported in bulk safely. They are normally made using woven polypropylene with standard base dimensions of 90cm x 90 cm with a variable height ranging from 87cm up to 2 metres, dependant on your specifications. Bulk bags will typically hold between 500kg and 2000kg of product, which can be lifted by the 4 lifting loops attached to the bag or can be placed onto a pallet.

Can You Recycle Bulk Bags?

Yes, new bulk bags from Centurion Packaging are made from 100% virgin polypropylene.

What are the Different Parts of FIBC/Bulk Bags?

Inlets and Openings
Webbing or Lift Loops
Outlets or Discharge Spouts
Ties, Clips, and Buckles
Other Specialty Parts

What is the best way to determine what size bulk bag I need?

The size of the bulk bag you require depends on the products you have plus the method of transport and the machinery you are using and your storage method. If you are unsure which size you will need, do not hesitate to give Centurion Packaging a call and we can help you figure it out.

What Does 5:1 and 6:1 SF mean?

Many woven polypropylene sacks are manufactured for one use, with these bags rated at a 5:1 safety factor ratio. This means they can hold up to five times the amount of their rated safe working load. Centurion Packaging does not recommend filling a bag over its safe working load for safety reasons.

We can manufacture woven polypropylene bags for multiple uses, that are rated at a 6:1 safety factor ratio which means they can hold up to six times their safe working load.

How Are Bulk Bags Emptied?

Bulk bags are usually emptied using a spout that is attached to the bottom of the bag, which is also known as a discharge spout. Typically the discharge spout is tucked inside a closure on the bottom of the bag which is designed to protect the spout and prevents the product from sifting out of the discharge before its intended discharge. Talk to Centurion Packaging about having a discharge spout and closure designed for your specific needs.

Can Bulk Bags Be Stored Outside?

Bulk bags can be stored outside but they will degrade as a result of UV exposure. Standard bulk bags have a UV inhibitor added into their fabric at the manufacturing level, which aims to resist UV rays for approximately 2 months. UV rays can, however, vary in strength and degree depending on where you are based in the world.

What is an Anti-Static Bulk Bag?

An anti-static bulk bags are made with a static protective fabric, that allows static electricity to discharge safely without using a groundable tab which is commonly seen in Type C bulk bags. This is known as a Type D bulk bag.

Can You Print onto Bulk Bags?

Bulk bags can be printed on, usually on the side panels of the bag. Print colours are typically one, two or three colours, but speak to us if require specific colours to match your branding. Please note, this will affect the cost of your bags.

What is a Full Open Bottom?

A full open bottom bag will have a flap that covers the entire bottom. Once this flap is untied, the bulk bag can be discharged fast through the open bottom which allows the ability to release the product from the bottom of the bag without reaching underneath. This type of bulk bag is ideal for material that tends to cake or bridge when discharging.

What is a UV Inhibitor?

UV inhibitors are an additive that is added to the resin during the extrusion process and assists in protecting your bulk bag from the harmful effects of UV rays. Therefore, it will protect it from degrading and becoming unstable and unsafe.

Can Bulk Bags Have Liners?

Liners can be inserted loosely or attached to your bulk bag. There are a number of different types of liners for specific applications, but the main two are form-fit liners and tube liners.

What is a Fill Spout?

The standard fill spout is a spout with a 14-inch diameter opening in the centre of the bag and is typically 18 inches long. This is designed to allow the user to fill the bag, and minimise dust occurrences as the bag is being filled. The length of a standard fill spout is 18 inches long but spouts can be customised to fit your individual needs.

Is the Fabric Breathable?

Woven polypropylene is breathable. Air and water will flow through an uncoated bulk bag. We would recommend using a ventilated bulk bag for applications that need a great deal of breathability.

What Does Coating Mean?

A coating on a bulk bag is used to try and keep as much moisture out of the product as possible. Typically, the coating will be about 1 millimetre thick and will be normally heated polypropylene laminated to the inside of the bag. Please note the coating only provides a water-resistant barrier to protect the product but it is not waterproof. Using an internal liner is an alternative for many applications if you are looking for something more water-resistant.

What are Sleeves?

Sleeves are a tube of polypropylene fabric that is attached to the side of the bulk bag near the top which allows the forklift truck driver to lift the bag without having to leave the comfort of their truck. While you may pay slightly more on aggregate bags with sleeves, this will save you time on loading and unloading.

What is a Valve Top Bulk Bag?

A standard valve top is located at the top centre of the bag and is normally 15 inches in diameter and 19 inches long, which allows for a filling application minimising dust occurrences or when you need a tight fit onto an extraction mechanism.

What is a Form-Fit Liner?

A form fit liner is designed to take the exact shape of the bulk bag and allows improved filling and complete discharging of product. Unlike a basic 'tube liner', these form-fit liners offer a flat top and bottom and incorporate a spout diameter and length which complements the FIBCs fill and discharge spouts. These spouts can also be heat sealed closed for increased sanitation and protection. Form-fit liners are available in a number of standard and co-extruded polypropylene’s which include a barrier and anti-static features. Form-fit liners can be affixed permanently to the FIBC by glueing or sewn tabs or they can be designed to be easily removed from the FIBC using ties on the tabs.

How Do You Pick up a Bulk Bag?

Bulk bags are lifted by several different lifting applications that can be specific to your needs. Examples include standard 10 lift loops, lifting sleeves, single point crane lift and stevedore straps. If there is a way to lift your bulk bag, Centurion Packaging will find a suitable pickup method for you.

What is Bulk Density?

Bulk Density is the property of the product that you are adding to your bulk bag. It is the mass of product divided by the volume it occupies. The volume includes the space between particles plus the space inside the pores of individual particles.

Can Cranes Be Used to Lifted Bulk Bags?

Cranes can be used to lift bulk bags but you must use a special lifting device or loops designed specifically for a crane lift. Follow the correct manufacturer recommendations when lifting a bulk bag.

How Do I Attach My Documents to a Bulk Bag?

Typically documents are attached by use of a document pouch which is usually a 10x12 polythylene bag that is sewn to the seam of the bulk bag. Document pouches can have a ziplock opening or a standard opening and can be sowed at the exact position you require.

Why are Document Pouches Important for Rubble Bags?

Issues with bulk containers can be avoided by having the correct documentation attached to the bag of products. This could be a mandatory requirement in some instances where it is much easier than adding documentation to an area it could get lost easily. In some cases this could also have legal implications.

Cases have been reported in the past where drivers have faced legal action if their cargo wasn't properly labelled. This could be a time-consuming and costly situation for you.

Can Bulk Bags Be Lifted Over Walls and Fences?

You will need a vehicle that is parked within lifting range of the desired drop point. Where the crane will not be able to reach the desired drop point, the delivery will need to be made to the nearest point the crane can reach. We would recommend not driving on the pavement or onto property not owned by you in order to achieve this.

What is the difference between Circular and U-Panel bulk bags?

Circular bags are made from fabric which has been woven on a circular loom. The fabric is woven into a continuous tube of fabric with the bag then cut to the correct size height.

What is a duffel top?

A duffel top is usually a 30 inch 'high skirt' sewn to the top of the bulk bag. The duffel comes with a tie which allows the user to secure the duffel closed plus it gives the user full access to the product.

Are bulk bags waterproof?

No, because a bulk bag's fabric is made from a woven material. Some users specify a coating or lamination as a moisture barrier, which means it will allow a small amount of condensation or water.

Lamination is simply a moisture barrier, however, even the use of an internal poly liner works best in a lot of applications, although it is still not 100% waterproof. The difference between using a coating or a liner is in the amount of moisture that you are attempting to keep out of the product and how much that this does not occur.

Whilst standard bulk bags are not waterproof or typically designed to carry wet products, there are some products designed to hold liquid, such as liquid liners.

What Is a Conical Discharge?

A conical discharge is frequently designed to help with the flow of discharge of the product inside a bulk bag. Depending on the product being added to the bulk bag, it may not flow well when discharging which could lead to pile up in corners of the bag and lead to issues for the discharger. Sometimes the user needs to shake or tap the bag to assist in the discharge flow. The conical discharge is a design which tapers the bottom of the bag into a discharge that essentially eliminates a bottom panel of the bag. The product flows into the cone and makes it flow easily once the bulk bag is lifted.

What Does SWL Mean?

SWL stands for safe working load, which is the maximum amount of total weight the bag is rated, tested and guaranteed to carry safely.

What is Woven Polypropylene Made From?

Woven polypropylene is made using extruded polypropylene resin which is made from petroleum feedstocks.

What Is a Perimeter Band?

A perimeter band is a band that is sewn around the outside perimeter of the top of the bulk bag. It is designed to give extra strength to loops when the bag is being lifted.

How Are Bulk Bags Filled?

Bulk containers are filled through the top of the bag in a number of ways, depending on the needs of the user. Rubble bags come in several configurations designed with a specific filling method.

Spout top bags are regularly used with bag filling machines and hopper applications. Duffle top bags are commonly used when the filling method isn't controlled. This could be using a shovel or skid steer but the user is still looking to protect the product when being transported.
Open top bags are similar to duffle tops but without any product protection when being transported.

What Does Fabric Weight Mean?

Fabric weight means the actual weight of the fabric that the bulk bag is constructed from. Fabric weight units can be listed in ounces or grams per square meter (GSM). Fabric weights are closely intertwined to overall bag weight carrying capacity or Safe Working Load (SWL). Please note, higher safe working load bags will have higher fabric weights.

Why Do Bulk Bag Slings Break?

The main reason for the broken edges of bulk bags is the poor quality of the sling. Sadly, if the sling breaks it means the overall container bag cannot be used.

Got Any More Questions? Get in Touch

If you have any more questions regarding Centurion Packaging’s range of bulk bags, please do not hesitate to contact us today.

Our team of specialists have 35 years of combined experience in the industrial packaging sector, with a track record of top-quality customer service to our clients.

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