Six year internal maintenance

The pin comes out and the plastic tamper seal is cut. A broken seal on arrival says the unit has been handled since its last annual tag, so the charge gets checked whatever the gauge reads.

Hose and nozzle come off and get blown clear. The technician looks for cracking at the crimp and for packed powder in the horn, then refits and checks that air passes end to end.

The lever and carry handle come off with the valve. Both get checked for bends and for play at the pivot, because a lever that binds is the failure you find at the worst moment.

The gauge is removed and read against a test gauge. A needle sitting in the green proves nothing on its own, and a gauge that reads full on a half empty cylinder is one reason NFPA 10 asks for the internal at all.

The valve body comes off the cylinder and is stripped down. The o-rings and the valve stem seal are replaced, the threads are inspected, and the assembly goes back on to the manufacturer's torque.

A new tag goes on the neck and the month and year of this service are punched through the card stock. The punch is what the authority having jurisdiction reads first, and the six year internal is recorded on its own row.

With the valve out, the shell is inspected inside and out for corrosion, dents and gouges. Damage found inside the shell is what takes a unit out of service for good rather than sending it back to the bracket.

The siphon tube is pulled and inspected end to end for cracks, splits and blockage. A tube packed with caked powder discharges propellant and nothing else.

The powder is emptied out, checked for caking and moisture, then weighed back in to the charge printed on the nameplate. Contaminated powder is discarded instead of going back into the cylinder.

The base ring comes off so the foot of the shell can be checked where water sits. The cylinder stamp is read here: it carries the manufacture date that sets the 12 year hydrostatic test.