Guide to Selecting Safe Working Load (SWL) for Ton Bags

Safe Working Load (SWL) is the core parameter for ton bag selection. This article details the selection methods and precautions for SWL.

Definition of SWL

Safe Working Load (Safe Working Load, SWL) refers to the maximum weight that a ton bag can safely carry under normal operating conditions.

Standard Specifications of SWL

Common SWL Specifications

SWL	Application Scenario
500kg	Light load materials, small batches
750kg	Medium density materials
1000kg	Standard specification, most common
1250kg	High density materials
1500kg	Heavy load materials
2000kg	Extra heavy load materials

Special Specifications

SWL	Application Scenario
300kg	Laboratory, small packaging
2500kg	Special heavy load
3000kg	Extra extra heavy load (customized)

SWL Selection Methods

Method 1: Based on Material Weight

Direct Selection:

SWL ≥ Material Weight × Safety Factor (1.1–1.2)

Example:

• Material Weight: 850kg
• Safety Factor: 1.1
• Calculation: 850 × 1.1 = 935kg
• Selection: 1000kg SWL

Method 2: Based on Material Density and Volume

Formula:

SWL = Material Density × Ton Bag Volume × Fill Factor

Example:

• Material Density: 1200kg/m³
• Ton Bag Volume: 0.9m³
• Fill Factor: 0.9
• Calculation: 1200 × 0.9 × 0.9 = 972kg
• Selection: 1000kg SWL

Method 3: Based on Transport Tool Limitations

Transport Tool	Single Item Weight Limit	Recommended SWL
Manual Handling	<50kg	Not Applicable
Manual Forklift	500–1000kg	500–1000kg
Electric Forklift	1000–2000kg	1000–2000kg
Container	28000kg	1000–2000kg

Considerations for SWL Selection

Material Factors

Factor	Impact
Material Density	Determines volume requirements
Material Characteristics	Affects safety factor
Material Value	High value requires higher safety margin

Usage Factors

Factor	Impact
Usage Frequency	High frequency usage requires higher Safety Factor
Loading/Unloading Method	Degree of mechanization affects selection
Stacking Layers	Higher stacking requires consideration of bottom load

Environmental Factors

Factor	Impact
Temperature	High or low temperature affects material strength
Humidity	Humid environment requires consideration of material performance
Outdoor Use	UV aging effects need to be considered

Relationship Between SWL and Volume

SWL Selection for Materials of Different Densities

Material Density (kg/m³)	0.5m³	0.75m³	1.0m³	1.25m³
500	250kg	375kg	500kg	625kg
700	350kg	525kg	700kg	875kg
900	450kg	675kg	900kg	1125kg
1100	550kg	825kg	1100kg	1375kg
1300	650kg	975kg	1300kg	1625kg
1500	750kg	1125kg	1500kg	1875kg

Recommended SWL Specifications

Calculated Load	Recommended SWL
<600kg	500kg or 750kg
600–900kg	750kg or 1000kg
900–1200kg	1000kg or 1250kg
1200–1500kg	1250kg or 1500kg
1500–2000kg	1500kg or 2000kg

SWL Selection Examples

Example 1: Fertilizer Packaging

Material Info:

• Material: Compound fertilizer granules
• Density: 900kg/m³
• Target Load: 1000kg

Selection Process:

1. Calculate required volume: 1000 / 900 = 1.11m³
2. Consider fill factor 0.9: Actual volume = 1.11 / 0.9 = 1.23m³
3. Select ton bag spec: 90×90×110cm, volume 0.89m³ (insufficient)
4. Select larger spec: 100×100×130cm, volume 1.3m³
5. Determine SWL: 1000kg

Example 2: Flour Packaging

Material Info:

• Material: Flour
• Density: 600kg/m³
• Target Load: 750kg

Selection Process:

1. Calculate required volume: 750 / 600 = 1.25m³
2. Consider fill factor 0.85: Actual volume = 1.25 / 0.85 = 1.47m³
3. Select ton bag spec: 100×100×150cm, volume 1.5m³
4. Determine SWL: 750kg or 1000kg (Recommended 1000kg, leave margin)

Precautions for SWL Selection

Safety Margin

It is recommended to reserve a safety margin of 10–20%:

Application Scenario	Safety Margin
Standard Application	10%
Heavy Load Application	15%
Hazardous Materials	20%

Avoid Overloading

Hazards of Overloading:

• Risk of ton bag rupture
• Loss from material leakage
• Potential safety accident hazards
• Legal liability

Consider Future Needs

When selecting SWL, appropriately consider future demand changes:

• Material density may change
• Load amount may increase
• Safety requirements may improve

Relationship Between SWL and Cost

Cost Comparison

SWL	Relative Cost	Description
500kg	Baseline	Standard cost
1000kg	+20%	Most common specification
1500kg	+40%	Heavy load specification
2000kg	+60%	Extra heavy specification

Cost-Benefit Analysis

Consider when selecting SWL:

1. Ton Bag Cost: Higher SWL means higher cost
2. Transport Cost: Single item weight affects transport efficiency
3. Loading/Unloading Cost: Weight affects loading/unloading difficulty
4. Safety Cost: Potential loss from accidents

Frequently Asked Questions

Q: Can SWL be overloaded?
A: Absolutely not. Overloaded use brings serious safety hazards.

Q: What is the relationship between SWL and actual carrying capacity?
A: Actual carrying capacity = SWL × Safety Factor (5–8 times).

Q: How to verify the SWL of a ton bag?
A: Check product labels and test reports.

Conclusion

Correctly selecting SWL is the foundation for safe use of ton bags. If you have any questions, welcome to contact our technical team!