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A flexible intermediate bulk container (FIBC), also known as a bulk bag, is a highly versatile packaging solution for businesses that need to store and transport large quantities of material. These durable, lightweight and flexible containers come in a variety of shapes and sizes.

Custom Bulk Bags is a leading manufacturer and supplier of FIBCs in South Africa. We have an annual production capacity of 3.5-million bags, which can hold between 500kg and two tonnes each. All of our bulk bags have a minimum 5:1 safety factor rating, which means that they can hold at least five times their intended load without breaking.

Due to the wide variety of styles and optional extras available, customers should consult with one of our experts before placing an order. One of these variables is the bottom closure – the method by which the bottom of a FIBC is sealed or opened. This choice depends on the materials stored within the bag, as well as the peripheral equipment used on site. Here are the different types of bottom closures available to our customers.

Spout bottom closure

The spout bottom is a funnel-like opening that allows the bag to be discharged easily. The spout is neatly tucked into the bottom of the bag and remains tightly closed until you want to release the material. Spout bottoms are ideal for powdered products or materials with a small-to-medium grain, such as sand, gravel, seeds and plastic pellets.

Spout bottom with safety valve

This attachment, also known as an iris valve, is combined with a regular spout bottom. It allows you to control the rate of discharge from a FIBC by adjusting the size of the spout with some strings – much like the iris of an eye controls the diameter of the pupil. The safety valve also minimises dust and other particles during discharge, which is very important when working with hazardous substances and flammable materials.

Spout bottom with cover

This is another adaptation of the regular spout bottom closure, commonly called a star closure or petal cover. It utilises a piece of fabric sewn between the spout and the closure to hold the spout in place during transport. Another square piece of fabric is sewn over the entire spout to secure it, which keeps the FIBC tightly sealed and prevents leakage or contamination of fine-grained materials and powders.

Discharge spout with flap

This is a large flap that protects the entire bottom of the bulk bag, including the spout. The flap minimises wear and tear on the spout and can make discharging easier. It also helps to keep the surrounding area clean during discharge.

Cord lock

A cord lock is also known as a B-Lock closure. It is simply a cord threaded around the spout that is pulled tight to create a better seal – much like a drawstring bag. Cord locks help to prevent any loss of fine material and they also act as a tamper-proof seal. These bottom closures are available in a variety of sizes and offer a quick and easy sealing method

Conical bottom

Some materials do not flow very easily, such as rubble, mining ore and wood. In t6hese cases, the FIBC should be fitted with a conical bottom; instead of the normal flat bottom, the fabric is cone-shaped. This allows bulky, sticky and dense materials to funnel towards the bottom of the bag more easily.

Full bottom discharge

This type of FIBC bottom is the fastest and most simple method of discharging. The entire bottom of the bulk bag opens to allow the stored material to fall away. It is necessary for large-grain products or for those that may clump together and harden over time. 

When working with a full bottom discharge FIBC, be sure to keep well away from the bag while the material discharges. It’s also important to be accurate with the placement of the bag and to ensure that the material falls exactly where it is supposed to.

These are the main types of bottom closure for bulk bags. Each one will have distinct advantages and drawbacks, so make sure that you speak to a consultant when placing an order. For more information about our bulk bags and optional extras, please contact us today. 


Custom Bulk Bags is a leading South African manufacturer of woven polypropylene bags for various industries, such as mining, chemicals and food. We are able to produce over 3.5-million bulk bags per year, keeping our customers in-stock at all times. Our bags adhere to the highest levels of quality as a result of our stringent in-house testing and quality control programmes.

Custom Bulk Bags holds ISO 9001 certification and we currently have a number of UN-certified designs. We are a Level 3 B-BBEE manufacturer and supplier and fall under the ownership structure of Deneb Investments Limited. For more information on our products, contact Follow us on Facebook for our latest news and industry insights.