first thing the service tech has to complete is take the fire extinguisher out of the way. Instead of spraying the extinguisher and creating a mess, the hose is removed from the handle and another hose that’s leads to a collection container is attached. After clamping the trigger, it is then the job of the technician to drain the extinguisher.
Next, the service tech makes use of a rubber hammer dislodge and twist off the trigger mechanism as well as the pressure meter. It is now possible to observe the insides that extinguisher. For a visual inspection to find cracks and corrosion, he employs the flashlight and a dental mirror. The cylinder can be refilled for refill if it passes the inspection visually.
The technician then disassemble and rebuild this valve. Compressed air cleans out dust and new o-rings and stems are added. The whole cylinder then gets cleansed and then the valve is reinstated and tagged with a service mark to show the extinguisher was thoroughly inspected.
The full details can be found in the video below.