FIBC Types Explained: Type A, B, C and D

What are FIBC types A, B, C and D?

FIBC types A, B, C and D are the four material classes that describe how a bulk bag handles static electricity. FIBC stands for Flexible Intermediate Bulk Container, the woven bag that moves powders and granules in loads commonly running between 500 kg and 2,000 kg. The International Electrotechnical Commission defines the four classes in IEC 61340-4-4. Type A is standard woven fabric with no added electrostatic treatment. Type B, Type C and Type D each answer the same behaviour through a different fabric construction.

Class selection is a specification task before it is a plant task. The class moves from a site risk assessment into the drawing, the purchase order, the label and the incoming inspection record. A bag ordered without a stated class arrives as Type A, because no treatment was specified.

Why does woven polypropylene behave as an insulating material?

Woven polypropylene behaves as an insulating material because the polymer holds a very high surface resistance. Charge that forms on the fabric has no conductive path and stays in place. Filling and discharging generate that charge through contact and separation between product and fabric, an effect called triboelectric charging. Fabric, sewing thread, coating and the liner all take part in the same process.

What does IEC 61340-4-4 cover?

IEC 61340-4-4 is the classification and test standard for the electrostatic behaviour of FIBCs. The standard sets the type definitions, the laboratory test methods behind them and the marking rules that put the class on the bag. Type B is defined through breakdown voltage, meaning the voltage at which fabric lets charge pass, with a limit below 6 kV. Type C is defined through measured resistance from the conductive threads to the groundable point, below 10 megohm.

IEC 61340-4-4 classifies material behaviour and does not perform the hazard assessment for a site. Matching a class to a powder, an atmosphere and a filling process stays with the user's own risk assessment. Purchase documents therefore name the standard, the edition and the class, and keep the risk assessment as a separate record. Electrostatic class and load rating are separate lines. Safety Factor is commonly 5:1 for single trip bags and 6:1 for multi trip bags. Neither figure describes charge behaviour.

Type A, B, C and D side by side

Type A, B, C and D differ across four areas a specification can check: fabric construction, grounding requirement, documentation and typical specification use. The table sets those areas against each class in wording a purchase document can reuse.

Type C and Type D sit together in the antistatic FIBC range of most producer catalogues, which is why the two are confused at the ordering stage. The difference that matters commercially is the grounding line, not the price line.

How is each class written into a purchase specification?

A purchase specification records the class as a testable statement, not as a product name. Wording such as "antistatic bag" carries no test method and no acceptance criterion. The line that survives an audit names the class, the standard, the edition and the test the supplier must document.

• Electrostatic class with its standard reference, for example Type C to IEC 61340-4-4
• Grounding requirement stated explicitly as required or not required
• Liner class and how the liner connects, or does not connect, to the body
• Safe Working Load (SWL), safety factor and single or multi trip status
• Dimensions, lifting loop configuration, inlet and outlet type
• Test reports required at delivery and the laboratory accreditation behind them
• Label content, batch code format and traceability period

Which test reports and laboratory accreditation should a supplier provide?

Test reports carry weight only when the issuing laboratory is accredited to ISO/IEC 17025, the standard for testing laboratory competence. An accredited report names the method, the sample, the test date and the measured values. A certificate that states a class without measured values proves nothing about the delivered batch. Procurement teams separate the type test, which qualifies a design, from batch documentation, which ties a delivery to that design.

Dangerous goods add a second document layer above the electrostatic class. A UN certified FIBC carries a design type approval issued under the United Nations recommendations. ADR and comparable regulations adopt those recommendations, and the approval code is printed on the bag. Non-dangerous applications reference ISO 21898 instead.

What do label and incoming inspection checks cover?

Label checks confirm that the bag in the warehouse matches the bag in the specification. Class marking, safety factor, SWL, batch code and production date all appear on the label, and each has a counterpart in the order. A mismatch caught at goods receipt costs a rejection note, while the same mismatch caught at the filling station costs a line stoppage.

1. Class marking on the label matches the class on the purchase order
2. Batch code matches the code on the delivered test documentation
3. SWL, safety factor and trip status match the specification
4. Grounding tabs are present and identifiable on Type C deliveries
5. Liner type and liner class match the body class recorded in the order

How do batch traceability and multi trip records work?

Batch traceability links a delivered bag back to its fabric lot, production date and test documentation. A batch code on the label keeps that link auditable years later, when a claim or a recall reaches back through the supply chain. Cesur began FIBC production in 1985 and added a 100,000 class clean room in 2003 for hygienic and food grade lines.

Multi trip products need a record system that single trip products do not. The specification defines who owns the bag history, how many trips the design allows and which condition ends service life. Storage, cleaning and inspection between trips belong to the user's own procedure, not to the manufacturer's type test. The class was verified on a new bag under laboratory conditions.

Matching the liner class to the bag body

Liner class is a separate decision that the body class does not cover. An inliner, the inner film bag that protects the product or seals against moisture, has its own charge behaviour and its own documentation. A treated body paired with an untreated film changes how the assembled package performs. Specifications name liner material, thickness, class and connection method as a distinct block, and treat any substitution as a specification change.

Sample evaluation before a production order

Sample evaluation turns a written specification into a physical reference before volume commitment. A first article sample, tested and retained by both parties, becomes the benchmark for later deliveries, recorded with its batch code, test reports and date. Trial fills then expose mismatches a document review cannot show. Outlet diameter against a discharge station, loop height against a lifting frame and liner fit against a filling head appear only in a real handling cycle.

Which class belongs in your specification?

Class choice follows the risk assessment, and the risk assessment follows the product and the atmosphere. Type A describes untreated fabric and fits only where no flammable atmosphere and no flammable product are recorded. Type B answers a combustible dust case through breakdown voltage, with no grounding line. Type C depends on grounding being available and verified at every point, while Type D removes that dependency and shifts attention to surface condition and permitted use limits.

Documentation, not terminology, decides whether a delivered bag matches the order. Accredited test reports, batch codes, label content and a retained sample turn a class name into something an auditor can verify. Liner class, UN approval and food contact evidence stay separate files, each with its own line in the specification.

This content is informational and does not replace a site specific risk assessment or the full text of the relevant standard. Electrostatic class selection for flammable atmospheres is a safety decision for a competent person. That decision rests on IEC 61340-4-4, the applicable dangerous goods regulation and reports from an accredited laboratory. Verify current standard editions and product documentation with the manufacturer and the testing laboratory before finalising a specification.

Frequently Asked Questions

What is the difference between Type C and Type D FIBCs?

Type C fabric contains interconnected conductive threads, and its specification calls for a grounding connection during filling and discharge. Type D uses specially treated fabric that limits charge without that connection, so its specification does not call for grounding. The practical difference is whether a verified ground exists at every handling point in the chain.

Is a Type A bulk bag ever the correct specification?

Type A is standard woven polypropylene with no electrostatic treatment, and it fits where a risk assessment records no flammable atmosphere and no flammable product. Many mineral, feed and construction material applications fall into that category. Type A becomes a problem only when it arrives by default, because the order left the class field blank.

Which standard defines FIBC electrostatic types?

IEC 61340-4-4, published by the International Electrotechnical Commission, defines the four FIBC electrostatic types and the test methods behind them. The standard also sets the marking rules that put the class on the bag. ISO 21898 covers FIBCs for non-dangerous goods, while UN design type approval applies where dangerous goods regulations govern the shipment.

What documents should a procurement team request from an FIBC supplier?

Procurement teams request the electrostatic type test report from an ISO/IEC 17025 accredited laboratory. Batch documentation linking the delivery to that design, load test results and the label specification complete the file. Dangerous goods applications add the UN design type approval code. Food or pharmaceutical applications add hygienic production evidence such as clean room and certification records.

Does the liner need the same class as the bag body?

Liner class is specified separately from the body class, because the inner film carries its own charge behaviour and its own documentation. Pairing a treated body with an untreated film changes how the assembled package performs. Specifications name liner material, thickness, class and connection method as a distinct block, and treat a liner substitution as a specification change.