This page is the working brief for one kind of enclosure: a large-format transit case that has to move equipment, carry medical supplies, or sit outside a fire or border post until it is needed. It sets out what the case has to prove in each of those roles, how the composite shell and the seal are specified against it, what the interior load plan looks like, and how a finished case is accepted. None of it is a catalogue: every number below is fixed per project, in writing, before the first panel is cut.
On this pageApplicationsEnclosureSealingInteriorsProcessVerificationOptionsContact
What changes between these roles is not the size of the shell. It is what the case has to prove, and therefore which decision has to be made first.
Repeated short moves · mixed loads
Instruments, tools and spares moving between buildings, vans and sites. The case is opened and re-packed by different people under time pressure, so the load plan has to work without the person who designed it. It must prove stacking strength on a van deck, latch life over hundreds of cycles, and an interior that still locates its contents after somebody has packed it in a hurry.
Fixes the buildHow many different items share one case, and how much that list is expected to change.
Clean interior · moisture control
Consumables, instruments or field medical stock that has to arrive sealed and clean. Nothing inside may shed fibres, hold moisture, or leave a seam that cannot be wiped. It must prove gasket integrity every time the lid is closed on a busy shift, humidity control during sealed storage, and an interior with no crevice a disinfectant cannot reach.
Fixes the buildThe cleaning regime, and whether contents are expiry-controlled and counted at every opening.
Outdoor dwell · gloved operation
Protective equipment, tools and spares held at a post until an incident. The case sits in sun, frost and dust for months, then has to open and close in the dark, in gloves, under load. It must prove UV and thermal cycling without the gasket taking a set, dust ingress at the rated level, and hardware — latches, handles, vent — that works with a gloved hand.
Fixes the buildDwell time and the temperature range at the post, not the weight of the contents.
A transit case is three things at once: a load path, a pressure boundary, and an inventory. Design it as one of them and the other two fail in service.
First rule of enclosure specificationThe body is a composite: closed-moulded glass-fibre skins over a structural core, or a ribbed polymer shell where weight and unit cost matter more than stiffness. Two numbers choose between them — the stacking load the case has to survive and the packed weight one or two people have to lift — and then the quantity: a single case can be built around a moulded shell, while a fleet rarely justifies one mould for a short run.
Reinforcement is local, not uniform. The rim, the four corners, the latch strike plates, the castor mounts and the top surface that carries the stack are where force enters and leaves the case. A uniformly thick wall spends weight everywhere else and still flexes at the corners.
UV-stable, impact-resistant face — the surface that meets a tail-lift edge and a concrete floor.
Ribs and plates behind handles, latches, castors and the stacking surface, so hardware lands on structure.
Stiffness without mass. Thickness follows the stacking load, not the drop test.
Wipeable and non-shedding where medical stock shares the case; smooth and bondable where a foam cradle is fixed.
Machined into the rim rather than bonded onto it, so the seal sits in a groove that cannot wander.
A sealed case is a pressure boundary with hardware on it. Four things decide whether it stays one.
The interior decides whether the case is re-packed correctly by someone who has never seen it. Choose by how much the contents change, not by how the case looks when it is opened for a photograph.
Cut to the load · positive location
Best for: a fixed equipment set that is moved repeatedly, where the same person is not always packing it.
Reconfigurable cells · mixed loads
Best for: consumables, spares and loose kit in mixed sizes, where counts change more than shapes do.
Layered access · partial loads
Best for: small parts, instruments and consumables in quantity, at sites where the full kit is never needed at once.
Each step needs one decision from your side. A missing decision does not stop the project; it moves the change later, where it costs more.
Name the worst route the case will travel, the dwell it has to survive, and how it is handled: by hand, tail-lift, van, air or sea. This is the statement the enclosure is designed against, not a summary written afterwards.
Output: one written duty statement, agreed.
Measured envelope for every item in its packed state — handles, cables and valve stems included — plus the accessory list and the count of each. Measure the outermost point, never the body shell.
Output: dimension sheet and counted load list.
A 1:1 layout: a pocket or cell for every item, finger reliefs, layer heights, which items share a zone, and where desiccant, documents and the humidity indicator sit.
Output: signed layout drawing — the machining reference from here on.
Shell size from the envelope plus liner allowance, wall build-up from the stacking load, hardware from the handling method. Seal profile, vent, latching, mobility and marking are all fixed here — this is the last cheap point to change any of them.
Output: the specification sheet for signature.
One case is built and put through the checks in §06 with the intended load inside it. Seal seating, latch effort and interior fit are corrected on the prototype, not on the batch.
Output: test record and marked-up prototype.
Batch build to the released specification, then acceptance unit by unit: latch operation, seal seating under a closed lid, interior fit, marking, and the documents that travel with the case.
Output: released cases, spare liner set, archived specification.
No case is released on a rating alone. Each check is run on the assembled case with its intended load, and the pass criteria are written into the specification sheet at sign-off.
MethodSpray and dust exposure to IEC 60529, on the latched case with the vent closed.
Released whenNo water inside, no dust on the load face, channel clean.
MethodCorner, then face, at the packed weight, onto a hard floor.
Released whenLid stays latched, no load shift, interior intact.
MethodLoaded cases stacked to the specified height for a set time at the route temperature.
Released whenDeflection within the agreed limit and the lid still operates.
MethodDistribution-cycle profile to ISO 4180 / ASTM D4169 for the intended route.
Released whenNo abrasion through the liner; fasteners still at torque.
MethodRepeated cycles across the post's range with the case sealed.
Released whenThe gasket returns to profile; no condensation on the load.
MethodOpen and close to the specified count — gloves on for field roles.
Released whenCompression still in range, latch effort within the agreed limit.
MethodWipe-down with the site's own disinfectant, then interior inspection.
Released whenNo lifted liner edge, no fibre shedding, no trapped residue.
MethodOne case on the real route for the agreed period, packed by the crew who will use it.
Released whenThe crew reports no damage and no load shift.
Standards are named so the conversation starts from a method rather than an adjective. Which of these apply, and the numeric pass limits, are set per project on the duty brief.
The configurable items, the common options, and the question each one has to answer at sign-off. Final values come from measurement and confirmation, never from a default.