How pressure cookers are made

A pressure cooker has a calibrated release valve and at least one emergency valve, so the steam always has an exit.

stations: 8
things upstream: 44
raw sources: 18
steps from the ground: 7

The short version

A pressure cooker body is deep-drawn from a flat metal disc into a one-piece pot, and layers of aluminum are impact-bonded to its bottom to spread heat. The lid is pressed with locking edges that grip the rim, and a gasket seals it. Valves are fitted, and each unit is pressure tested.

Cut discs from coil

Coils of stainless steel or aluminum are checked and blanked into flat round discs.

Goes in
Stainless steel
Draw the deep pot

A hydraulic press forces each disc into a die and draws it into a one-piece pot with no side seam.
Trim and bead the rim

Excess metal is trimmed from the edge and the rim is reinforced, so it can seal against the lid.
Impact-bond the base

Layers of aluminum and magnetic steel are slammed onto the bottom under enormous pressure. They fuse, so the heat spreads evenly and the base will not warp.

Goes in
Aluminum
Form the lid and lugs

The lid is pressed in several steps. The rim of the pot and the lid are shaped with matching lugs so that a quarter turn locks them.
Polish and clean

Polishing wheels give the mirror or satin finish, and an ultrasonic bath strips off oils and polishing residue.
Fit the gasket and valves

A sealing ring goes into the lid to seal the gap. A calibrated pressure valve is added, plus at least one emergency valve.

Goes in
Silicone
Pressure test each unit

Each finished cooker is pressurized to check the body and lid, and the valves are tested for the exact pressure at which they release.

End of the linePressure cooker

Worth repeating

The ancestor of the pressure cooker was the steam digester, invented in the seventeenth century by the physicist Denis Papin.
At one bar above atmospheric pressure, water inside reaches about 120 degrees Celsius.
In 1950, 37 percent of US households owned a pressure cooker, but by 2011 only 20 percent did, partly from fear of explosions.