Hach CL17 Measuring Dechlorinated Water
This document outlines a standardized procedure for the Hach Technical Support and Field Service personnel to follow when Hach CL17 analyser is used to monitoring water containing no oxidant (RO or WW dechlorination applications) and is suspected to be malfunctioning. This procedure is also aimed to provide educational background for Hach personnel as well as users.
In case a Hach process analyser is suspected of providing false positive readings for zero chlorine water, the Hach Technical Support and Service personnel must first make sure the analyser in question is well maintained at the customer site. To address customer’s concerns follow these steps:
1. Evaluate the CL17 readings and if they are consistently below 0.04 ppm (Limit of Detection – LOD 1 ) try to convince the customer that no action should be taken. If the customers still wants the instrument to read zero, perform the following procedure: a. Verify the chlorine concentration in the sample of question with a reference instrument/method (e.g. a suitable handheld meter).
b. Compare the readings between two instruments. If both instruments are reading within 10% from each other 2 or within the LOD 3 , no repair should be warranted.
2. If the readings are in agreement, conduct thorough cleaning of the process analyser as outlined in the user manual, make sure the reagents, tubing, etc. are in good shape, default calibration values, and then verify performance of both instruments on relevant standard (chlorine free water) 4 . For CL17 calibration/verification follow the procedure provided with the kit ((Catalog Number/ Order Code 5449089).
3. If the readings of the process analyser on the provided zero chlorine standard are below specified LOD (e.g. 0.04 ppm for CL17) – conduct offset calibration as outlined in the user manual.
4. In case the CL17 displays readings above the LOD, conduct thorough maintenance of the analyser as specified in the user manual (e.g. replace tubing, stir bar, reagents, and thoroughly clean the colorimeter, etc.) and then repeat the steps 1 through 3 above. If the analyser still fails the chlorine-free standard test – arrange for repair service and replace the unit with a working CL17 instrument.