Safe Working Load of FIBC

SAFE WORKING LOAD (SWL)

While describing the duty condition to which the FIBC is going to get subjected to, the details given are the SWL (Safe Working Load) and SF (Safety Factor).

Normally, the SF is given as 5:1 or 6:1. Safety Factor of 5:1 indicates a single use bag and 6:1 indicates multiple use bag. We will go a bit more in details about the safety factor.

Safety factor of 5:1 means that the filled bag when subjected to hydraulic pressure should sustain a minimum of 5 times the SWL after 30 cycles of twice the SWL. If the bag breaks before 5 times the SWL pressure then it is not suitable for the required duty condition. This is called the peak load test. So if the SWL is 2200 lbs (1000 kgs) with SF of 5:1, the bag when subjected to the cyclic test and peak load test is considered passed only if it breaks after 11000 lbs (5000 kgs) pressure.

Safety factor of 6:1 means that the filled bag when subjected to hydraulic pressure should sustain a minimum of 6 times the SWL after 70 cycles of thrice the SWL. If the bag breaks before 6 times the SWL pressure then it is not suitable for the required duty condition. So if the SWL is 2200 lbs (1000 kgs) with SF of 6:1, the bag when subjected to the cyclic test and peak load test is considered passed only if it breaks after 13200 lbs (6000 kgs) pressure.

These standards were fixed by EFIBCA in 1985 to ensure maximum safety while designing the FIBC. The latest standard if ISO 21898.

As mentioned earlier, 5:1 indicates a single use of the bag. When we talk of single use FIBC it means the whole process from taking the FIBC for filling the material to the discharge of the material from the bag. Any FIBC will normally be handled as follows:

1) bag is taken up for filling the material
2) after filling it is moved to the warehouse of the producer
3) from warehouse it is moved to the truck for transportation to customer's factory
4) at the customer's factory the bag is moved from the truck to the the warehouse
5) the filled bag is then moved from warehouse to the shop floor for discharging
6) material from the bag is discharged.

This whole process is defined as "single use".

When such used FIBC are used again i.e. subjected to same process again it is called multiple use bag and the SF required is 6:1. The number of multiple uses are not specified in the standard. However, no sooner there is any damage noticed after the second use, it should be either discarded or used with utmost care.