Screw, cam-lever, vented and child-resistant, and how thread sizes match a can.
The closure is where a can leaks, vents or fails, so it is worth understanding as much as the body.
Quick answer: What types of jerry can cap are there?
The main closures are a screw cap, sized to the neck by designations such as DIN 51 or DIN 61; the cam-lever cap of the NATO pattern, which seals with the same force at every closing; vented caps; and child-resistant closures, required on US consumer fuel cans. The gasket does the sealing, so match its compound to the liquid.
A closure fails at its gasket far more often than at its thread, and the gasket is a material choice with the same contents-driven logic as the container. A mismatched gasket is the most common cause of a can that seals on the bench and weeps in the field.
A gasket takes a compression set over time, so a can stored sealed for years may not reseal to the same standard once opened, and gaskets are consumables. On a UN-approved can the gasket is also part of the tested design, so substituting a different material can invalidate the approval even though the container itself is unchanged.
The common closure: a threaded cap with a gasket that seals against the neck. Simple, reliable and easy to replace. Thread sizes follow designations such as DIN 45, 51 and 61, with the threads defined in DIN 6063, so a cap matches a neck by its stated size. The number approximates the neck’s outer thread diameter in millimetres and is not a quality grade, so a DIN 51 cap fits a DIN 51 neck and nothing else. Mix the standards and the pitch and diameter no longer line up. The cap cross-threads or sits proud, the gasket never loads evenly, and the joint weeps. Order the cap and the neck to the same standard and the seal repeats across a whole batch.
Application torque is the other half of a screw closure, and the half that usually goes unspecified. Under-tightened, the gasket never reaches full compression and the joint weeps under vibration. Over-tightened, the plastic neck cold-flows under the load, the thread deforms and the cap that sealed on the line will not seal again after the first opening. A capping line runs to a torque figure for exactly this reason, and a hand-tightened cap in a warehouse is a different closure from the one that was tested.
Temperature moves the same joint. Plastic caps and necks expand and contract at different rates from the gasket between them, so a can closed warm and shipped cold arrives with less compression on the seal than it left with. It is one of the reasons a load that passed a leak check at the factory can arrive weeping, and it is why the venting behaviour of the closure matters as much as its tightness. See venting and pressure.
The original military closure: a hinged lever that clamps the cap down and seals it in one motion, fast to open and close with a gloved hand. It is the classic NATO can closure.
The sealing force does not come from the thread. A screw cap converts turning into compression through the thread pitch, so how well it seals depends on how hard the last person turned it. A cam lever is an over-centre mechanism: it applies a fixed, designed load and then locks past the point of maximum force, so every closing produces the same compression whoever does it. That repeatability is why a military pattern uses one.
A cam lever has more parts than a screw cap: a pin and a spring can corrode or bend, and a damaged lever cannot be replaced by whatever is on the shelf the way a DIN 61 cap can. It also opens fast, which is a virtue with cold hands and a liability where an unauthorised opening matters. Screw caps take a tamper-evident ring more naturally, which is why decanted and resold product tends to travel under one.
A vented cap lets air in as liquid pours out, giving a smooth, glug-free pour, and it relieves pressure as temperature changes. A non-vented cap seals tighter for transport. Volatile fuels and hot climates make venting a real consideration; read venting and pressure.
The decision depends on where the can spends its time more than on what it holds. A can that is filled, transported sealed and emptied within a day never builds enough differential to matter. A can that lives on a vehicle through a temperature cycle every day for a season does, and it will either breathe through a designed path or find an undesigned one at the gasket. Ask how long the can stays shut and through what temperature swing, and the venting answer follows.
The gasket is a compatibility choice. Nitrile holds up against diesel and oils, and a fluoroelastomer of the Viton type adds ethanol petrol, aromatics and many solvents. EPDM suits water and food-grade duty. Put the wrong elastomer against the liquid and it swells or hardens, loses its grip on the neck, and the can starts to leak. Match the compound to the contents before you match anything else.
Gaskets also age on the shelf, which surprises people who treat them as hardware. Elastomers oxidise and take a compression set over time whether or not they are in service, so a box of spare seals bought five years ago is not equivalent to a box bought last month. Buy seals against a replacement schedule rather than in bulk against a discount, and store them cool, dark and uncompressed.
Portable fuel containers sold in some markets need a child-resistant closure by law, tested to a defined standard such as the US 16 CFR 1460. See EPA and CARB compliance. We supply child-resistant closures.
The US requirement traces to the Children's Gasoline Burn Prevention Act, and the closure has to pass a test. The standard measures whether a panel of young children can open it within a set time while a panel of adults can, so a closure that is only hard to turn fails on both counts. It is a performance test on a specific cap and neck combination, which means a compliant closure is not portable to a different neck without retesting.
Europe answers the same hazard by a different route. Child-resistant fastenings for consumer chemical packaging are governed under the CLP regime and tested to ISO 8317 for reclosable packaging, and the trigger is the classification of the contents rather than a container category. So a can that needs a child-resistant closure in California may not need one in Germany, and the reverse happens too. Confirm the requirement per market before tooling a closure for either.
A closure works with the dispensing fitting and the gasket. A pouring spout, a dispensing tap and the right gasket material complete the system. A misfuelling-resistant spout sized for a diesel filler neck keeps the fuel going where it belongs. A tamper-evident ring shows whether a can has been opened, which matters when product is decanted and resold. We supply caps, closures and gaskets, pouring spouts and taps and dispensing valves.
Buy them as a system, because compatibility runs between them as well as against the liquid. A spout is sized to a neck, a tap needs a matching thread and seat, and a gasket has to suit both the cap compound and the contents. Three items that each fit on their own can still make a joint nobody tested, and that joint is what leaks.
Some markets require a flame-mitigation device as part of the fuel-can system. It sits in the opening and stops an external flame from travelling back into the vapour inside the can. Where the rule applies, the device is part of what makes the can legal to sell. See flame-mitigation devices.
In the United States the device became mandatory in 2023. The Portable Fuel Container Safety Act of 2020 directed the CPSC to require flame mitigation devices. Three voluntary standards became mandatory on 12 July 2023, and the rule at 16 CFR part 1461 codified them from 9 December 2023, incorporating ASTM F3326-21, section 18 of UL 30:2022 and the ASTM F3429 series by reference. A portable fuel container for a flammable liquid sold into that market without a compliant device cannot lawfully be sold.
A part-empty fuel can holds a vapour space that can sit inside the flammable range, and an external ignition source near the opening can propagate a flame back into it. The mitigation device is a fine mesh or a perforated disc in the neck that quenches the flame front by conducting heat out of it faster than the reaction can sustain itself, the same principle as a miner's safety lamp.
It also has a cost the specification should acknowledge: a mesh in the neck slows the pour and can clog with debris or with ice in cold conditions. That is a handling consequence to plan for, not a defect, and one more reason to settle a container's market before the closure system is chosen.
The most common mistake we correct is a mismatch: a water gasket fitted to a fuel can, or a cap ordered to a different thread standard than the neck. Both pass a quick look and fail in the field. We check the closure against the liquid, the market and the neck standard, then fit the cap, gasket, spout and any required device as one set. Tell us the fluid and the destination and we specify the whole closure, not just the cap.
We fit these parts from our line.
| Your use case | Recommended can | Why this one |
|---|---|---|
| Caps, gaskets and closures |  Caps, Closures & Gaskets |
Matched to the neck standard and the liquid. |
| Pouring and misfuelling-resistant spouts |  Pouring Spouts & Nozzles |
Directs the stream into a filler neck. |
| Taps and dispensing valves |  Taps & Dispensing Valves |
Draw from a can that stays put. |
| Child-resistant closures |  Child-Resistant Closures |
To the CPSC 16 CFR 1460 pattern for US sale. |
| Flame-mitigation devices |  Flame Mitigation Devices |
Where a market requires a flame arrestor. |
A neck thread designation for plastic jerricans, where the number approximates the outer thread diameter in millimetres. DIN 45, 51, 61 and 71 are the common sizes. The neck size decides which caps, spouts and taps will fit, so it should be specified before any accessory is chosen.
A lever-operated cap that clamps down onto a gasket rather than screwing on, giving a fast, repeatable seal with no cross-threading. It is the standard closure on the NATO pattern because it can be opened and sealed reliably with gloves on and without tools.
For consumer portable fuel containers in the US, yes, alongside the self-closing spout requirement. Other markets vary and industrial containers are treated differently. Check the destination market rule, because a closure that satisfies one regime will not automatically satisfy another.
A sound steel can does not leak through its body; leaks come from the closure, or from rust once the coating has failed. The usual causes at the closure are gasket problems and cap problems. A gasket may be in the wrong compound, such as EPDM swelling in fuel, or it may have taken a compression set with age or been torn by forcing a stuck cap. A cap may be on a different thread standard from the neck, or tightened too little or too much. Replace the gasket before you replace the can.
No. A screw-on spout fits one neck size. Jerrican necks follow designations such as DIN 45, 51, 61 and 71, where the number approximates the outer thread diameter in millimetres, and DIN 61 is the most common on 20 litre UN jerricans. A DIN 51 spout fits a DIN 51 neck and nothing else: on the wrong neck it cross-threads or sits proud, and the joint weeps. Check the neck size of the can before you order a spout.
It depends on the closure. A cam-lever cap, the NATO closure, opens by swinging the lever back past its locked position, which releases the clamp. A screw cap unscrews anticlockwise. On a fuel can that has warmed up, ease the closure a little first and let the pressure settle before opening it fully, outdoors and pointed away from you. A US-market child-resistant closure is designed so adults can open it and young children cannot, so follow the maker's steps for that model.
On a screw-neck can, take the cap off and screw the spout onto the same thread with its gasket in place. The spout has to match the neck standard, such as DIN 51 or DIN 61; on the wrong size it cross-threads and weeps. Tighten until the gasket is compressed evenly: too loose and it weeps under vibration, too tight and a plastic neck deforms. Check the gasket suits the fuel. Use nitrile or FKM, never EPDM, which swells in hydrocarbons.
Clean and dry, off the can, somewhere cool and dark, with the can itself closed by its gasketed cap. The spout seals through an elastomer gasket, and elastomers oxidise and take a compression set with age whether or not they are in use. Store the gasket uncompressed and out of sunlight, and check it before refitting. Replace one that has hardened, cracked or swollen, because a gasket in that state weeps at the neck.
On a cam-lever can, check the gasket sits clean in the cap, swing the hinged cap onto the neck and press the lever down until it goes over centre and locks. The over-centre cam applies the same sealing force at every closing, whoever closes it. On a screw-cap steel can, turn the cap until the gasket compresses evenly. If the lever will not lock or the cap weeps, look at the gasket first: a swollen, hardened or missing seal is the usual cause.
The standards and regulations this page relies on, at their issuing body. Where a market rule is named here, check the current revision before you specify against it.
Last reviewed by David Guru, Co-Founder & Business Development Director.
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