Plug
Plug turns up in 2 fields: concrete, railroad. Here is what it means to the people in each one.
Plug in concrete
A blockage that jams a concrete pump line or hose, stopping placement until it is cleared.
Happens when a harsh, under-sanded, segregated or stiffening load packs off in a reducer, elbow or hose, or when the line was not primed with slurry before the first concrete went in. The crew stops, relieves the pressure, finds the plug by tapping along the line and listening, and breaks the coupling to clean it out. Opening a line that is still under pressure is one of the most dangerous moves on a pump job.
"Got a plug at the reducer, shut it down, relieve the pressure and nobody touches a clamp until I say."
Plug in railroad
A short piece of rail cut into the track to replace a section with a defect or a break.
When a detector car finds an internal rail flaw or a rail breaks, the track crew cuts out the bad piece and installs a plug, a replacement length of rail joined with joint bars or field welds. The plug must match the existing rail's section and wear, and in welded track the crew adjusts for temperature so the rail stress stays right. A fresh plug often carries a slow order until it is welded and inspected.
"Detector car found a transverse defect at MP 118, the section crew's putting in a plug this afternoon."