On an armoured vehicle or a warship, radios, radar, navigation equipment and electronic control units share one hull, and each of them has to go on working while the others transmit. That is why defence equipment is specified, then tested, for what it emits and for what it withstands: its electromagnetic compatibility (EMC).
At the enclosure, the weak points are the joints. Two mating surfaces that look flat still leave gaps, and a gap is a slot that can radiate like an antenna. ElectroDome supplies the EMI gaskets that close those slots and the thermal pads that give the heat of the electronics a path to the housing. This page starts from the constraints a defence specification puts on a joint, and gives the gasket that answers each one.
⚔️ Defence equipment concerned
- Land vehicles: electronic control units and communication systems, and the hatches and panels that give access to them.
- Naval shipboard systems: communication and navigation electronics behind doors, hatches and access panels exposed to salt air.
- Radar systems: shielding keeps signal reception and transmission clear.
- Military radios: housings sealed and shielded by the same gasket or O-ring.
- Shelters, racks and electronics cabinets: doors, drawers and access panels.
- Embedded computers and power modules: heat to remove from closed boxes.
🔧 What the specification asks, and the gasket that answers
Flanges that are not flat, covers bolted down for good
No housing is perfectly flat once it has been welded or machined. Where its cover is screwed down and left closed, knitted wire gaskets follow the irregularities and give over 100 dB depending on the alloy and the frequency. Knitted wire mesh is one of the materials used on military ground vehicles, around control units and communication systems. The wire (Monel, tin-plated copper-clad steel, stainless steel) is matched to the housing metal. An all-metal gasket needs a firm closing force; knitted over a silicone core it is softer and works from −50 °C to +200 °C. On its own the mesh keeps out dust at most, while the combined version, mesh beside a sponge seal, gives sealing up to IP65.
Rain, salt spray, fuel
On deck or on the outside of a vehicle, the joint has to seal as well as shield. A conductive elastomer seal does both in one part: 40 to 110 dB depending on the filler, −55 °C up to +125 °C or +200 °C, and sealing to IP65, IP66 or IP67 when the groove and the compression are right. In salt air, filler and flange metal can corrode each other, so the filler is chosen with the flange alloy and its finish in mind. Where fuels or solvents are present, a fluorosilicone base brings chemical resistance. On the product page, the silver-filled compounds are listed with their MIL-DTL-83528 material type.
Hatches, shelter doors and drawers
Some joints are made to be opened: a hatch, the door of a shelter, a drawer in a rack. Every time they close, contact has to be restored round the whole frame, with little force. Beryllium copper finger strips do that and reach up to 100 dB at 25 % compression; each closing wipes the contact surfaces. They are mounted by clip, rivet, solder or adhesive. The adhesive version covers −55 °C to +121 °C; beyond that, clip, solder or rivet mounting applies, with the range confirmed on the quote. Fingers do not seal, so on an outside door they sit behind the weather seal.
Sealed boxes with no airflow
Where a unit is closed against dust and water, no air passes through it, and the heat of its processors and power stages has to leave through the walls. Silicone gap filler pads bridge the space between a component and the housing or a heat sink at 3 or 5 W/m·K, from 0.3 mm thick up to 15 mm in the 3 W/m·K grade. They are soft, electrically insulating, rated UL 94 V-0 and work from −40 °C to +220 °C.
Thin panels in a protected space
Where a front panel, a display bezel or a connector plate is too light to compress a solid gasket, a fabric-wrapped foam gasket closes it with very little force. It is rated UL94-V0, comes with an adhesive backing and can be cut to connector shapes (I/O, D-SUB). It is a gasket for dry, protected spaces, inside a shelter or a rack: −10 °C to +110 °C, down to −40 °C depending on the reference.
📐 MIL-STD-461, MIL-STD-464, MIL-STD-810: which covers what
Defence EMC is written at two levels. MIL-STD-461 is the level of the box: it sets the requirements for the emissions and the susceptibility of equipment and subsystems, and describes itself as best suited to electronic enclosures no larger than an equipment rack, linked by wiring harnesses. MIL-STD-464 is the level of the platform: it sets electromagnetic environmental effects (E3) requirements for complete airborne, sea, space and ground systems. Both are United States documents. The United Kingdom has its own, DEF STAN 59-411, and NATO has AECTP-500, under STANAG 4370, whose emission and susceptibility tests are largely derived from MIL-STD-461 and DEF STAN 59-411. For airborne equipment, RTCA DO-160 is presented on our page on EMI shielding for avionics.
MIL-STD-810 is about the environment, not about EMC. Its title is Environmental Engineering Considerations and Laboratory Tests: it describes how tests are tailored to the environmental stresses that materiel meets throughout its service life, and states that it does not itself impose design or test specifications. All of these documents apply to the finished equipment or platform. A gasket matched to the joint contributes to the compliance of the equipment; with the quote we send the material data (shielding effectiveness, temperature range, filler or alloy, flammability rating) so that you can choose it and confirm it in your own tests.
🛠️ To your drawing and your specification
If your part comes with a drawing and a specification instead of a catalogue number, send them. We need the section of the flange or the groove, the metal and its finish, the environment (temperature range, salt fog, fuels), how often the joint is opened, the attenuation you are looking for and over which frequencies, and any material specification named in your contract. We reply with the reference that matches, as extruded profile, cut gasket, strip or pad, and its datasheet comes with the quote. We handle prototypes, small series and series.
🤝 Dealing with ElectroDome
- One contact for shielding gaskets and thermal pads, in Paris, replying in English or French.
- A sample of three pieces to try on the real hatch or housing.
- Batches identified and traceable, each delivery checked before it leaves.
- Data stated as indicative, then confirmed on the quote for the reference proposed.
❓ Frequently asked questions
What is the difference between MIL-STD-461 and MIL-STD-464?
MIL-STD-461 deals with one piece of equipment or a subsystem: what it emits and what it withstands. MIL-STD-464 deals with the complete system or platform in its electromagnetic environment.
What is the MIL standard for environmental testing?
MIL-STD-810, Environmental Engineering Considerations and Laboratory Tests. It describes how laboratory tests are tailored to the conditions the materiel will meet in service.
Can your gaskets go into equipment tested to MIL-STD-461 or DEF STAN 59-411?
Yes: they are designed for EMC and can contribute to the compliance of the equipment. The tests are passed by the finished equipment, so you confirm the result in your own tests, with the material data we send.
Which EMI gasket for a hatch or a shelter door?
Beryllium copper finger strips where the door is opened often, behind a weather seal if it is outdoors. For a cover that stays bolted, knitted wire mesh or a conductive elastomer.
Which gasket for equipment exposed to salt spray?
A conductive elastomer seal in a groove, with a filler chosen for the flange metal to limit galvanic corrosion.
Can I test a sample before ordering?
Yes: 3 pieces of the reference proposed. Availability and lead time depend on the reference and are given on the quote.
Characteristics and values are given for guidance only. See our terms of sale for details. For any critical application, please contact us.