Definition
A self-piercing valve that clamps onto a sealed refrigerant or service can, drives a sharp probe through the metal to open it, and provides a controlled outlet — typically with a threaded fitting — so the contents can be dispensed into a system without losing pressure or spilling.
Plain English
A small clamp-on tool that punches a clean hole in a sealed can and gives you a valve to control what comes out of it.
Context Anchor
Seen during aircraft air conditioning maintenance, especially when adding refrigerant from a small service can.
Derivation
Named directly from its function: it taps (pierces and draws from) a can using a built-in valve. 'Tap' here carries its old sense of opening a sealed container to draw off its contents, the same sense used when tapping a barrel.
Why Pilots Care
Pilots rarely use one directly, but understanding the term matters when reading maintenance documentation or discussing servicing procedures with a mechanic, since improper use can contaminate or depressurize a system.
Intuition Check
Do not think of this as a cockpit valve or a fuel selector. A can tap valve is a ground-servicing tool used on a refrigerant can.
Example Sentence 1
The mechanic attached a can tap valve to the refrigerant container before connecting the service hose.
Example Sentence 2
After use, the can tap valve was removed and the empty can was properly disposed of.