Moka pot and oil well: what they have in common

1. Step 1. Moka pot — has part — Safety valve. A valve.
2. Step 2. Safety valve — is part of — Boiler. A mandatory safeguard for boilers.
3. Step 3. Boiler — is made of — Wrought iron. Later — made of sheet wrought iron.
4. Step 4. Wrought iron — is material for — Oil well. The casing pipes are iron.

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