Detailed explanation of what causes the "Plunger Down" Error and possible solutions.
Overview
The “PLUNGER DOWN DETECTED” error is displayed when the infer red light from the LED is no longer received by the detector array. This can be caused if the manual clean wiper (plunger) is stuck in the down position or there is a high quantity of air, oil or solids etc in the sample that can obstruct the light. Staining or debris on the inside of the glass tube can also cause plunger down.
Troubleshooting
The first check should be to see if the sample is heavily soiled or bubbly. To eliminate the possibility of a poor sample, bottled water should be poured into the measuring cell by isolating all flow, removing all pipe work and plugging all holes.
The manual clean wiper should be removed and clean bottled water should be poured into the measuring cell via the manual clean wiper hole. You should place your hand over the hole to stop any external light entering the measuring cell and interfering with the detectors. If the monitor doesn’t read between 0NTU and 4NTUppm then the measuring cell should be cleaned in accordance with the following cleaning procedure.
Cleaning the cell is a simple process that requires only a bottle brush and a mild acid such as orange juice, vinegar or cola. These acids are preferred as they are safe to both the operator and the equipment.
Step 1 – Isolate all power to the system.
Step 2 – Isolate all flow to the Measuring cell.
Step 3 – Drain the measuring cell.
Step 4 – Remove the Autoclean / Manual clean.
Step 5 – Plug the inlet and outlet of the Measuring cell.
Step 6 – Fill the cell tube with a mild acid via the Autoclean / Manual clean hole. Orange juice, vinegar and cola give the best results and are also safe for the operator and equipment.
Step 7 – Leave this acid to soak for a minimum of 12 hours
Step 8 – use a clean, soft bottle brush to clean the inside of the glass tube.
Step 9 – Drain the measuring cell
Step 10 – flush with plenty of clean water.
Step 11 – refit the Autoclean / Manual clean. Reconnect all pipework, power and flow.
If the error still persists, then the measuring cell should be replaced.