The first choice whenever mixing of the two media must be ruled out by design - for system separation in domestic hot water or in food and pharmaceutical applications. Pressure and temperature range are tighter than for the welded design.
Monitorable without opening the unit: a leak shows at the gap before it can reach the system. Advice on materials and approvals directly from Düsseldorf.
Design and limits
Each heat transfer surface consists of two separately pressed plates in contact, welded at the port openings. A leakage gap between the plates vents to the outside: a leaking plate drips visibly instead of mixing the media.
| Max. operating pressure | 25 bar |
|---|---|
| Temperature range | -20 to 180 °C |
| Plate materials | 1.4404 (316L), Titan |
| Gaskets | EPDM, FKM |
Preliminary guide values. You will receive the binding sizing with your individual quote.
Strengths
- mixing of media ruled out by design
- leakage visible from outside without opening the unit
- meets system separation requirements for drinking water
Limits
- lower heat transfer than a single-wall plate, therefore larger area
- tighter pressure and temperature limits than the welded design
Pressure ratings and temperature limits
The operating envelope of a double-wall plate is not set by the plate material alone but by the mechanical construction: the two plate layers sit together in press contact and are held in place by the gasketed frame. For that contact to hold across the full operating range, the permissible pressure and temperature span is narrower than for the fully welded design.
As with the gasketed design, the elastomer gasket in the frame adds a further limit: EPDM and FKM each cover a different temperature range depending on the medium, and the selection follows the same criteria as for a gasketed unit.
The currently approved values for pressure rating and temperature range are listed in the table above on this page. As with any pressure equipment, classification under the Pressure Equipment Directive 2014/68/EU depends on maximum allowable pressure, volume and the fluid group of the plant.
Materials and gaskets
Both plate layers of a double-wall plate are made of the same material, typically stainless steel 1.4404 (316L); titanium is available for chloride-bearing media or higher corrosion demands. The two layers are welded together only at the port openings, while the rest of the press contact stays unjoined - that is exactly where a leak becomes visible through the open gap.
The frame itself is sealed the same way as in the gasketed design, typically with EPDM or FKM depending on medium and temperature. Here the gasket does not separate the two media circuits from each other - the double plate layer does that - it seals the frame against the environment.
The design therefore combines two layers of protection: mechanical separation of the media by two independent plates, and the classic frame seal. That explains the higher manufacturing effort compared with a single-wall plate.
Typical applications
The classic application is domestic hot water heating: DIN EN 1717 requires a system separation there that rules out mixing of the heating and potable water circuits by design - a single dividing wall is not enough, because an undetected leak would otherwise connect both circuits.
For the same reason, double-wall units are used in the food and beverage industry and in pharmaceutical production, wherever product contact with the heat transfer fluid must be excluded and a leak needs to be visible immediately without opening the unit.
Where this kind of system separation is not required, the double-wall design is rarely the most economical choice, owing to its larger area and higher manufacturing effort - gasketed or welded units remain the standard solution there.
Selection and sizing in practice
Selection turns first on whether mixing of the media must be ruled out by design, alongside the usual heat duty, temperatures and flow rates. If it must, the double-wall design is set; the remaining sizing steps follow those of a gasketed unit.
Because the extra plate layer and the contact resistance between the layers lower the heat transfer coefficient compared with a single-wall plate, the transfer area has to be sized larger to deliver the same output - which shows up in plate count and unit size.
For maintenance planning, the leakage gap is worth a look: it makes a leaking plate visible from outside, so a visual check during operation is enough to catch an emerging leak early.
The Platecore configurator captures these key figures online and checks them for plausibility right away. The thermal design itself is done by our engineering team - the binding quote follows within one business day.