1. Definitions

Figure: Single-embossed pillow plate (left) and double-embossed (right)

What is a pillow plate?

A pillow plate is a heat exchanger made from two metal sheets welded together in a pattern and then inflated. The cavity carries a heating or cooling medium. After inflation the surface looks like a pillow. On keppelslaserwelding.com the term means a laser-welded, inflated plate.

What is a dimple jacket / dimple plate?

Dimple jacket is the older trade name. In the United States many tank shops already use dimple jacket for a laser-welded pillow-plate jacket. Pre-formed dimple is the older pressed sheet welded onto a finished tank by hand. Always ask which process is meant.

Is a pillow plate the same as a dimple jacket?

Same job — heat transfer on a tank or plate — different production routes. Laser-welded pillow plates allow free patterns, welding from one side and generally higher working pressures than classic pre-formed dimple. Sales language often mixes the names.

Laser-welded plate versus pre-formed dimple

Pre-formed dimple is pressed first, then formed and welded onto the vessel, usually by hand. Typical published limit is about 4–5 bar (60–70 psi). A laser pillow plate is welded flat as two sheets, then inflated. Laser plates give free CAD patterns, one-side welding, optional protection film on the product side, and higher pressure capability.

Single embossed versus double embossed

Single embossed: thin sheet on a thick base; only the thin sheet inflates. Common published pairs: 0.8 mm (0.031 in) on 2.0 mm (0.079 in); 1.0 mm (0.039 in) on 2.5 mm (0.098 in); 1.2 or 1.5 mm (0.047–0.059 in) on 4–15 mm (0.16–0.59 in); 2.0 mm (0.079 in) on 5–15 mm (0.20–0.59 in). Milk tanks often use 0.8 + 2.0 mm (0.031 + 0.079 in) with protection film on the base. Double embossed: two equal sheets. Common pairs: 0.8+0.8, 1.0+1.0, 1.2+1.2, 1.5+1.5, 2.0+2.0 mm (0.031–0.079 in). Working pressure published by Keppels: about −0.5 to 250 bar (vacuum to 3,630 psi), depending on pattern and thickness.

Thermo plate, laser plate, register, falling film, ice bank

Thermo plate, Laser Plate and Temp-Plate are brand names for the same physics. Register, falling-film and ice-bank plates are application names: the same pillow plate with a pattern and connections suited to that duty.

Tank jacket versus heat-exchanger pack

A jacket is usually a single-embossed plate on a tank wall or bottom. A pillow-plate heat exchanger pack is a set of double-embossed plates with product between them.