Pop-off
Pop-off turns up in 2 fields: adhesives, boilers. Here is what it means to the people in each one.
Pop-off in adhesives
A part that lets go with a snap, leaving the adhesive cleanly on one side and nothing on the other.
A pop-off is how adhesive failure looks on the line: a bracket, label or trim piece that comes away whole with a crack, often under light load or after a temperature swing. Glossy plastics, plated metal, mold release and paint with poor intercoat adhesion are frequent culprits. Pop-offs send engineers back to surface energy and cleaning procedures.
"Third pop-off this week on the chrome trim, the CA just won't stay on that plating."
Pop-off in boilers
Shop slang for the safety valve on a steam boiler or the relief valve on a hot water boiler.
Service techs, plumbers and homeowners alike call the relief valve the pop-off, after the sound and action of a steam safety lifting. The word covers both the 30 psi relief on a hot water boiler and the 15 psi safety on a steam boiler. Saying the pop-off is weeping is common shorthand for a valve that drips because of system pressure problems or debris on the seat.
"Customer says the pop-off is spraying water all over the basement, bring a tank and an air pump."