When bulk shippers hear the term “container liner,” they usually picture a large fabric bag inside a 20ft or 40ft container. But there is an important split: dry bulk container liners for flowable solids, and liquid container liners — more accurately called flexitanks — for non-hazardous liquids. Both fit inside standard ISO containers. Both replace traditional packaging. But after that, the similarities largely end.
Choosing the wrong system can lead to cargo loss, container contamination, regulatory issues, and insurance claims. This guide compares the two technologies so you can decide which packaging approach fits your cargo, route, and supply chain.
What Is a Dry Bulk Container Liner?
A dry bulk container liner is a large sealed liner installed inside a standard shipping container to carry free-flowing solid cargo. Typical cargoes include grains, flour, sugar, cocoa beans, plastic pellets, cement, minerals, chemical powders, and resins.
Most dry bulk liners have:
- A top loading spout for auger, conveyor, or pneumatic filling
- A bottom discharge spout for gravity or pneumatic unloading
- Lifting loops and securing straps to anchor the liner inside the container
- Sealed or sift-proof seams for fine or powdery products
- Moisture barrier layers for food and moisture-sensitive commodities
Common dry bulk liner material formats include woven PP or HDPE fabric, often PE-coated for moisture resistance, and pure PE blown film for smoothness and food contact. Thermally insulated dry liner versions add reflective foil, foam, or bubble layers for temperature-sensitive solids.
At Giant Flexpack, the dry bulk liner range includes:
- DBL-W01 — 140 gsm HDPE woven liner for general agricultural, chemical, and mineral cargo
- DBL-W06 — sift-proof woven liner with PU-taped seams for cement, talc, pigments, and fine powders
- DBL-F01 — 140-micron PE film liner for food ingredients, chemical pellets, and smooth-surface discharge
- DBL-W02 — malt-grade liner with food-grade double-sided LDPE lamination for malt, grains, and food powders
Depending on product density and container size, dry bulk liners typically hold 10–30 tonnes per container.
What Is a Liquid Container Liner / Flexitank?
A liquid container liner, commonly called a flexitank, is a sealed flexible bladder that carries non-hazardous liquids inside a standard 20ft dry container. It is not simply a large plastic bag. It is an engineered single-use system designed to replace ISO tank containers for certain liquid shipments.
Flexitanks are built from multi-layer polyethylene, sometimes combined with PET, PA, or EVOH barrier films. They include high-volume filling and discharge valves, reinforced seams, and hull protection accessories.
Common flexitank cargoes include:
- Edible oils
- Wine and grape must
- Juice concentrates
- Non-hazardous base oils
- Latex
- Some water-based industrial liquids
A standard 20ft flexitank can carry up to about 24,000 litres, depending on the system, liquid density, and route. Flexitanks require proper wall protection, bulkhead bracing, and trained loading personnel.
Key Differences at a Glance
| Feature | Dry Bulk Container Liner | Liquid Container Liner / Flexitank |
|---|---|---|
| Cargo type | Dry flowable solids | Non-hazardous liquids |
| Load capacity | 10–30 tonnes | Up to 24,000+ litres in 20ft |
| Core materials | Woven PP/HDPE, PE film | Multi-layer PE/PET/EVOH bladder |
| Filling method | Auger, conveyor, pneumatic top loading | Pump through hoses and valves |
| Discharge method | Gravity, pneumatic, manual bottom spout | Pump or gravity through lower valve |
| Seam requirement | Sift-proof for powders, moisture barrier | Liquid-tight under dynamic pressure |
| Main failure risk | Tearing, sifting, moisture ingress | Valve leaks, seam rupture, liquid surge |
| Reusability | Mostly single-use; some thermal liners reusable | Single-use |
| Typical container size | 20ft, 30ft, 40ft, 40HQ | Almost always 20ft |
| Regulatory focus | Dry food contact, ISO 9001, REACH/RoHS | Liquid food contact, migration testing, flexitank standards |
Cargo Compatibility Is the Hard Limit
The most important difference is physical state. Dry bulk liners are designed for granular, powdered, or pelletised materials. Flexitanks are designed for liquids.
Trying to ship liquid in a dry bulk liner is dangerous. A dry liner’s seams and spout connections are not built to hold hydrostatic pressure. Liquid will find the weakest point and leak. Conversely, filling a flexitank with dry solids damages the bladder, blocks discharge, and makes loading impractical.
Use the right system for the right cargo:
- PVC resin pellets → dry bulk liner
- Sunflower oil → flexitank
- Cocoa beans → dry bulk liner, often with thermal protection
- Wine → flexitank or ISO tank
- Cement or titanium dioxide powder → dry bulk liner with sift-proof seams
- Latex → flexitank
Material, Seams and Failure Modes
Dry bulk liners rely on tensile strength and tear resistance. Woven HDPE fabrics provide high strength and are frequently coated for moisture resistance. PE blown film liners offer a smooth food-contact surface and excellent barrier performance, but may be less puncture-resistant than woven options in abrasive conditions.
Flexitanks, by comparison, must manage continuous liquid pressure during transit. They use thick multi-layer films with controlled elongation, high weld strength, and barrier layers to prevent oxygen ingress or chemical interaction. The failure modes are different: a dry liner may tear or sift, while a flexitank may burst at a valve, split at a seam, or leak due to film delamination.
That is why dry bulk liner buyers should focus on seam type, fabric weight, and sift-proofing. Liquid shippers must evaluate weld integrity, valve design, and film compatibility with the specific liquid.
Filling and Discharge
Dry bulk loading usually happens at a silo, hopper, or bulk terminal using an auger, conveyor, or pneumatic system. The product enters through the top spout. Unloading may be gravity-assisted through the bottom spout or accelerated with pneumatic air. No specialist liquid pump is required.
Flexitank filling and discharge use food-grade hoses and pumps. The process requires clean connections, controlled flow rates, and careful pressure monitoring. Discharge is typically by pump, although some lower-viscosity liquids can be gravity-discharged.
This infrastructure difference matters commercially. If your operation already handles bulk solids with conveyors and silos, a dry bulk liner fits naturally. If you have liquid pumping capacity and want to avoid ISO tank repositioning, a flexitank may be the better fit.
Food Safety and Regulatory Considerations
Food-grade dry bulk liners focus on dry food contact compliance. Buyers should expect certifications such as FDA, LFGB, EU food-contact compliance, ISO 9001, and where relevant REACH and RoHS. For fine powders, sift-proofness and contamination control are central requirements.
Liquid food-grade flexitanks face stricter migration and hygiene demands. Because liquid stays in continuous contact with the film for weeks, tests for overall migration, specific migration of additives, and organoleptic impact are critical. Flexitank suppliers must provide documentation for the exact liquid being shipped.
At Giant Flexpack, dry bulk container liners are produced under ISO 9001 quality management and are available with FDA, LFGB, REACH, and RoHS compliance. For food-grade dry cargo, we support lot traceability and can provide relevant certification documentation before shipment.
Cost and Total Logistics Economics
Dry bulk container liners are generally the lower-cost packaging option per container. They eliminate most bag handling, allow container loading directly from bulk equipment, and reduce manual labour. In many food and agricultural supply chains, they replace hundreds or thousands of small bags.
Flexitanks are more expensive as a packaging system, but they compete against ISO tanks and drums. A flexitank can dramatically reduce repositioning, cleaning, and tank management costs while allowing one-way liquid shipment in a standard dry container.
The right choice is not the cheapest liner. It is the system that protects cargo, matches available loading equipment, clears compliance requirements, and reduces total landed cost per tonne or per litre.
Reusability and End-of-Life
Most dry bulk container liners are single-use because of contamination risk. However, certain heavy-duty thermal container liners can be reused 3–5 times by responsible shippers. Woven PP and HDPE liners can often be recycled where local collection programmes exist.
Standard flexitanks are single-use by design. Cross-contamination concerns, cleaning complexity, and structural fatigue make reuse impractical. End-of-life handling for both systems should be part of the buying decision, especially for companies with sustainability targets.
Container Suitability and Installation
Dry bulk liners are available for 20ft, 30ft, 40ft, and 40HQ containers. Installation is comparatively direct: place the liner, attach straps and loops, fit corrugated protection if needed, and secure the loading spout.
Flexitanks are almost exclusively used in 20ft containers. Liquid surge and dynamic forces make 40ft flexitank applications riskier and less common. Properly bracing the container doors and reinforcing side walls is essential, and installation should follow the flexitank manufacturer’s training checklists.
Common Misunderstandings
Several assumptions create problems in bulk shipping:
- “Any container liner can handle liquid.” False. Dry liners are not liquid-tight under pressure.
- “A flexitank is just a big plastic bag.” False. Flexitanks are engineered pressure-containment systems with specific valve, film, and seam requirements.
- “Dry liners work for slurry or semi-liquid cargo.” No. They are designed for dry, free-flowing solids.
- “Food-grade dry liner documentation works for liquids.” No. Liquid food-contact approval is a separate regulatory pathway.
How to Choose Between the Two
Start with the physical state of your cargo.
Choose a dry bulk container liner when your product is granular, powdered, pelletised, or flaked. It should be free-flowing enough to load through an auger, conveyor, or pneumatic system and to discharge through a bottom spout. Common commodities include grains, flours, pellets, minerals, cement, cocoa beans, and chemical powders.
Choose a flexitank when your product is a non-hazardous liquid, a liquid food product, or a pumpable industrial fluid. Flexitanks make sense when ISO tank supply is unavailable, too expensive, or operationally inconvenient for one-way shipments.
If your dry cargo is also temperature-sensitive — such as cocoa beans, sugar, or food powders — a thermal dry bulk liner or insulated container liner may be required in addition to the moisture and contamination barrier.
What a Dry Bulk Liner Supplier Should Ask
Before specifying a dry bulk liner, a serious manufacturer should ask:
- What is the commodity and its particle size?
- What is the bulk density and moisture content?
- Is the cargo food-grade or industrial?
- What is the loading method — top fill, pneumatic, auger?
- What is the discharge method — gravity, pneumatic, manual?
- What container size will you use?
- What route and climate will the shipment face?
The answers determine fabric type, liner thickness, seam construction, spout placement, anti-static treatment, sift-proof requirements, and food-grade certification.
Giant Flexpack manufactures dry bulk container liners in woven PP/HDPE and PE film constructions. We also offer thermal container liners and thermal pallet covers for temperature-sensitive solid cargo. Our team helps buyers match liner design to the specific cargo, route, and unloading method.
FAQ
Can I use a dry bulk container liner for liquid cargo?
No. Dry liners are moisture barriers, not hydrostatic liquid barriers. The seams, spouts, and connections are not designed to hold liquid under pressure. Use a flexitank or ISO tank.
What is the difference between a dry bulk liner and a flexitank?
A dry bulk liner handles flowable solids and uses top filling plus bottom discharge. A flexitank handles liquids and is a sealed bladder with pump or valve connections.
Are liquid container liners reusable?
No. Standard flexitanks are single-use due to contamination risk and structural stress. Most dry bulk liners are also single-use, although some thermal liners can be reused.
Can one liner handle both dry and liquid cargo?
No. Liners are engineered for one physical state. Mixing them creates a high risk of leakage, contamination, or liner failure.
What certifications should I check for food-grade dry bulk liners?
Look for FDA, LFGB, EU food-contact compliance, ISO 9001, and the relevant migration documentation for your commodity. Industrial cargo may require REACH and RoHS.
Does Giant Flexpack manufacture flexitanks?
No. Giant Flexpack specialises in dry bulk container liners, PE film liners, and thermal container liners. We help dry bulk shippers choose the right liner for their cargo.
Get the Right Dry Bulk Liner for Your Cargo
If your shipment is a dry, flowable commodity, choosing the correct liner protects against sifting, moisture ingress, contamination, and unloading delays. Giant Flexpack supplies FDA and LFGB compliant dry bulk container liners, PE film liners, sift-proof woven liners, and thermal insulation liners for global bulk supply chains.
Contact our technical team at [email protected] or call +86 523 87683880 to discuss your cargo, route, and unloading method. We will recommend the most reliable, compliant dry bulk liner for your specific application.
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