What Is Bitumen Flexitank
Last updated: 2026-10-17
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What Is a Bitumen Flexitank
A bitumen flexitank is a single-use, food-grade or industrial-grade polymer bladder (typically 16–24 KL capacity) that fits inside a standard 20-ft ISO container to transport bulk bitumen, usually at 140–170°C. It replaces the traditional 200-litre steel drum and the ISO tank, cutting packaging, heating, and freight costs by roughly 20–40% per tonne. One 20-ft flexitank holds around 20–22 tonnes of bitumen, versus 4–5 tonnes in a drummed container or 20–24 tonnes in a heated ISO tank.
How a Bitumen Flexitank Works
A bitumen flexitank is engineered for hot, viscous, high-density cargo — a very different duty cycle from standard water-based flexitanks used for wine, juice, or palm oil. The core principle is simple: the bitumen never touches the container floor. It stays sealed inside a multi-layer polymer bag, supported by the container walls and a reinforced bulkhead/door-frame system.
The working sequence is:
- Positioning: The empty flexitank is unfolded inside the container on a corrugated liner/floor mat.
- Filling: Hot bitumen at 140–170°C is pumped through the top valve at 15–25 tonnes/hour via a 3-inch or 4-inch camlock connection.
- Transport: The filled unit is sealed, the container doors closed, and the load shipped as a standard dry container (no heating during ocean transit for short routes).
- Discharge: At destination the bottom valve is connected, the bitumen is re-heated if needed, and pumped out at temperatures again around 150–170°C. Residual heel is typically 0.3–1.0%, depending on grade and drainage time.
Because the bitumen solidifies at ambient temperature, discharge must be planned around reheating capacity — either at the port, at a heated tank farm, or at the customer's asphalt plant. This is the single most important operational constraint in bitumen flexitank logistics.
| Stage | Bitumen Flexitank | ISO Tank | Drummed Cargo |
|---|---|---|---|
| Fill temperature | 140–170°C | 140–170°C | 150–180°C |
| Fill rate | 15–25 t/hr | 20–30 t/hr | 4–8 t/hr |
| Discharge rate (heated) | 10–20 t/hr | 20–30 t/hr | 3–6 t/hr |
| Residual heel | 0.3–1.0% | 0.1–0.5% | 0.5–2.0% |
Bitumen Flexitank vs ISO Tank vs Drums: Cost and Logistics Comparison
The commercial case for flexitanks is driven by freight cost per tonne, not by equipment cost alone. The table below compares the three main export methods on a per-container and per-tonne basis for a typical 20-ft shipment.
| Metric | Bitumen Flexitank (20-ft) | ISO Tank (20-ft) | Drums (20-ft) |
|---|---|---|---|
| Payload | 20–22 t | 20–24 t | 4–5 t |
| Equipment cost (one-way) | $150–$450 per unit | $2,500–$4,500 per trip | $25–$40 per drum |
| Flexitank/liner cost | Included above | N/A | N/A |
| Heating requirement in transit | None (short routes) | Optional/steam | None |
| Return freight | Not required | Often required | Not required |
| Loading labour | Low (2–4 hrs) | Medium | High (8–16 hrs) |
| Discharge labour | Low–medium | Low | Very high |
| Cost per tonne (indicative) | $18–$35 | $40–$70 | $90–$160 |
| Container turnaround | Single-use | Reusable (100–200 trips) | Single-use |
Indicative figures; actual costs vary by route, grade, and season.
Key takeaways from the comparison:
- Per-tonne freight advantage: Flexitanks cut packaging and handling cost to roughly one-third to one-half of drummed cargo.
- No return logistics: Unlike ISO tanks, flexitanks are not returned, eliminating empty-container repositioning costs that can add $1,000–$2,500 per trip on imbalanced routes.
- Payload penalty vs ISO tank: Flexitanks carry 1–2 tonnes less than a full ISO tank, but the equipment saving usually outweighs this.
- Handling speed: A flexitank can be filled and sealed in 2–4 hours, versus 8–16 hours for a drummed container.
For exporters shipping under 5,000 tonnes per year per destination, flexitanks frequently deliver the lowest landed cost. For high-volume, dedicated routes with return-leg cargo, ISO tanks can close the gap.
Data Table: Traditional vs. Flexitank Bitumen Export Costs
To make the commercial case concrete, here is a route-level cost model for a 20-ft container moving 21 tonnes of penetration-grade bitumen from an Asian refinery to a Southeast Asian port.
| Cost Component | Flexitank | ISO Tank | Drums |
|---|---|---|---|
| Ocean freight | $1,200 | $1,400 | $1,200 |
| Equipment/liner | $300 | $600 (amortised) | $650 (drum cost) |
| Filling cost | $120 | $100 | $400 |
| Heating (transit) | $0 | $150 | $0 |
| Discharge cost | $150 | $80 | $500 |
| Documentation/handling | $60 | $60 | $120 |
| Total per container | $1,830 | $2,390 | $2,870 |
| Cost per tonne | $87 | $114 | $137 |
Illustrative model. Actual rates depend on route, season, fuel surcharges, and contract terms.
The model shows a flexitank saving of approximately $27–$50 per tonne, or $570–$1,040 per container, versus the alternatives. On a 10,000-tonne annual programme, that is $270,000–$500,000 in logistics savings — before considering reduced drum disposal and demurrage exposure.
What Types of Bitumen Can Be Shipped in a Flexitank?
Not all bitumen grades are suited to flexitank transport. The determining factors are viscosity at discharge temperature, penetration grade, and reheating tolerance.
| Bitumen Type | Typical Grade | Flexitank Suitability | Notes |
|---|---|---|---|
| Penetration grade | 40/50, 60/70, 80/100 | Excellent | Most common flexitank cargo |
| Cutback bitumen | MC-30, RC-250 | Limited | Solvent attack risk on liner |
| Bitumen emulsion | CSS-1, SS-1 | Good (with liner check) | Lower temp, 50–80°C |
| Polymer-modified (PMB) | PG 64-22, PG 76-22 | Good | Higher discharge temp |
| Oxidised/blown | 85/25, 90/15, 95/25 | Moderate | Very high viscosity |
| Hard grade | 10/20, 20/30 | Moderate | Reheating critical |
| Industrial/roofing | Various | Varies | Check liner compatibility |
Practical selection rules:
- Best fit: Penetration grades 40/50 to 80/100, where viscosity at 150–160°C allows clean pumping.
- Workable: PMB and oxidised grades, provided the destination has reheating capability above 160°C.
- Avoid: Cutbacks containing high aromatic solvent content, which can degrade low-density polyethylene (LDPE) liners over long transit.
- Always verify: The flexitank supplier's temperature and chemical compatibility chart before booking.
Typical load factors by grade:
- 60/70 penetration: 21–22 tonnes per 20-ft flexitank
- PMB: 20–21 tonnes
- Oxidised 85/25: 19–21 tonnes
Benefits, Risks, and Best Practices for Bitumen Flexitank Shipping
- Lower cost per tonne: 20–40% saving versus drums and ISO tanks on many routes.
- No return logistics: Single-use design removes empty repositioning.
- Faster loading: Fill in 2–4 hours versus 8–16 hours for drums.
- Better cargo protection: Sealed, single-use liner eliminates contamination and drum leakage.
- Scalable: Book one container or a hundred; no equipment pool constraints.
| Risk | Impact | Mitigation |
|---|---|---|
| Valve blockage on cooling | Delayed discharge, demurrage | Reheat to 160–170°C before discharge; use large-bore valves |
| Liner puncture | Product loss, contamination | Use reinforced bulkhead and floor mat; inspect before fill |
| Residual heel | 0.3–1.0% product loss | Drain hot; tilt container during discharge |
| Over-temperature fill | Liner deformation | Cap fill temp at supplier limit (usually 170°C) |
| Destination reheating gap | Solidified cargo, delays | Confirm reheating capacity before booking |
| Documentation/regulatory | Port rejection | Verify destination acceptance of flexitank bitumen |
- Confirm destination reheating capacity is ≥160°C before booking.
- Use a high-temperature-rated liner rated for 170°C+ continuous contact.
- Fill at 15–25 t/hr and never exceed the supplier's maximum temperature.
- Fit a reinforced bulkhead and door-frame brace on every unit.
- Drain hot and tilt the container to minimise residual heel.
- Pre-clear customs and port documentation for bulk bitumen in flexitanks.
FAQ: Bitumen Flexitank
Q1: How many tonnes does a bitumen flexitank hold?
A standard 20-ft bitumen flexitank holds 20–22 tonnes of bitumen, depending on grade and density. Higher-density grades such as oxidised bitumen may load 19–21 tonnes, while penetration grades like 60/70 typically reach 21–22 tonnes.
Q2: What temperature is bitumen loaded into a flexitank?
Bitumen is loaded at 140–170°C, with most operators targeting 150–160°C for penetration grades. The flexitank liner must be rated for continuous contact at that temperature, typically verified to 170°C+ by the manufacturer.
Q3: Is a bitumen flexitank cheaper than an ISO tank?
On most routes, yes. Flexitanks cost approximately $87 per tonne versus $114 per tonne for ISO tanks in a typical 21-tonne shipment, a saving of about $27 per tonne. However, ISO tanks can be competitive on high-volume routes with return-leg cargo.
Q4: Can all bitumen grades be shipped in a flexitank?
No. Penetration grades 40/50 to 80/100 are the best fit, along with PMB and most oxidised grades. Cutback bitumen with high aromatic solvent content should generally be avoided because it can degrade standard LDPE liners.
Q5: How long does it take to load and discharge a bitumen flexitank?
Loading takes 2–4 hours at a fill rate of 15–25 tonnes/hour. Heated discharge takes roughly 1–2 hours for pumping, plus reheating time if the cargo has solidified, and typically leaves a residual heel of 0.3–1.0%.
Calculate Your Bitumen Flexitank Cost with 6Tar
Ready to see whether a bitumen flexitank beats your current export method? Use the 6Tar cost calculator to model landed cost per tonne across flexitank, ISO tank, and drum options for your specific route, grade, and volume. Enter your destination port, annual tonnage, and bitumen grade — 6Tar returns a full cost breakdown in seconds, so you can quote faster and ship smarter.