Oil pumpjack and autoclave: what they have in common

1. Step 1. Oil pumpjack — is part of — Oil well. It drives the sucker-rod pump.
2. Step 2. Oil well — is made of — Wrought iron. The casing pipes are iron.
3. Step 3. Wrought iron — is material for — Boiler. Later — made of sheet wrought iron.
4. Step 4. Boiler — is part of — Autoclave. A steam generator.

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