How to decide GSM of FIBC bags?

 

Detailed Guide to Determining the GSM of FIBC Bags

Deciding the GSM (grams per square meter) for Flexible Intermediate Bulk Containers (FIBCs) involves a thorough understanding of the bag’s intended application, safety requirements, material characteristics, and industry standards. Here’s an in-depth step-by-step guide:

1. Understand the Usage Requirements

Load Capacity

• Maximum Weight: Identify the maximum weight the FIBC needs to support. FIBCs are designed to handle loads ranging from 500 kg to 2000 kg or more.
• Dynamic Load: Consider if the bag will experience dynamic loading during transportation or handling, which can affect the required strength.

Product Type

• Particle Size: The type of material being stored affects the choice of fabric. Fine powders may require coated fabric to prevent leakage, whereas coarse materials may not.
• Chemical Properties: Determine if the product is chemically reactive or abrasive, which may necessitate specific fabric treatments.

Handling Conditions

• Loading and Unloading: Assess how the bags will be loaded and unloaded. Bags handled by forklifts or cranes may require higher strength and durability.
• Transport: Consider the transport method (e.g., truck, ship, rail) and the conditions (e.g., vibrations, impacts).

2. Consider Safety Factors

Safety Factor (SF)

• Common Ratings: FIBCs typically have a safety factor of 5:1 or 6:1. This means a bag designed to hold 1000 kg should theoretically hold up to 5000 or 6000 kg in ideal conditions without failing.
• Application: Higher safety factors are needed for critical applications such as handling hazardous materials.

Regulations and Standards

• ISO 21898: This standard specifies requirements for FIBCs, including safety factors, testing procedures, and performance criteria.
• Other Standards: Be aware of other relevant standards such as ASTM, UN regulations for hazardous materials, and customer-specific requirements.

3. Determine Material Properties

Fabric Type

• Woven Polypropylene: The most common material used for FIBCs. Its strength and flexibility make it suitable for a wide range of applications.
• Fabric Weave: The weave pattern affects the strength and permeability of the fabric. Tight weaves provide more strength and are suitable for fine powders.

Coatings and Liners

• Coated vs. Uncoated: Coated fabrics provide additional protection against moisture and fine particle leakage. Typically, coatings add 10-20 GSM.
• Liners: For sensitive products, an inner liner may be required, which adds to the overall GSM.

UV Resistance

• Outdoor Storage: If bags will be stored outside, UV stabilizers are necessary to prevent degradation from sunlight. UV treatment can add to the cost and GSM.

4. Calculate the Required GSM

Base Fabric GSM

• Load-based Calculation: Start with a base fabric GSM suitable for the intended load. For instance, a 1000 kg capacity bag typically starts with a base fabric GSM of 160-220.
• Strength Requirements: Higher load capacities or more rigorous handling conditions will require higher GSM fabrics.

Layer Additions

• Coatings: Add the GSM of any coatings. For example, if a 15 GSM coating is needed, it will be added to the base fabric GSM.
• Reinforcements: Consider any additional reinforcements, such as extra fabric in critical areas like lifting loops, which can increase the GSM.

Example Calculation

For a standard FIBC bag with a 1000 kg capacity:

• Base Fabric: Choose 180 GSM fabric.
• Coating: Add 15 GSM for coating.
• Total GSM: 180 GSM + 15 GSM = 195 GSM.

5. Finalize and Test

Sample Production

• Prototype: Produce a sample FIBC based on the calculated GSM.
• Testing: Conduct rigorous testing under simulated real-world conditions, including loading, unloading, transportation, and environmental exposure.

Adjustments

• Performance Review: Evaluate the sample’s performance. If the bag doesn’t meet the required performance or safety standards, adjust the GSM accordingly.
• Iterative Process: It may take several iterations to achieve the optimal balance of strength, safety, and cost.

Summary

1. Load Capacity & Usage: Determine the weight and type of material to be stored.
2. Safety Factors: Ensure compliance with safety factor ratings and regulatory standards.
3. Material Selection: Choose appropriate fabric type, coating, and UV resistance.
4. GSM Calculation: Calculate total GSM considering base fabric and additional layers.
5. Testing: Produce, test, and refine the FIBC to ensure it meets all requirements.

By following these detailed steps, you can determine the appropriate GSM for your FIBC bags, ensuring they are safe, durable, and fit for their intended purpose.