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Friday, August 25, 2017

Example in setting up SOP for electrode boiler feed water de-ionization system

In the past, we normally carry out training to our subordinate with hands holding practice. But with new management style of educated management team today, a lot of SOP with standard format are requested. The amount of paperwork also increased tremendously, to the extend that wometimes there is no time to spend in production floor.

Below is an SOP prepared to train my engineering subordinate on maintenance of de-ionization system for electrode boiler. It is posted for sharing, and as a record that I so this now. 😂

To provide as training material for basic understanding on why de-ionization system is required for our electrode boiler and to provide a clear guide on how to maintain the system effectively.

To cover a brief explanation on the importance of de-ionization system with regards to electrode boiler.

To explain detail procedures in checking functionality of de-ionization column together with conductivity meter function.

3.1 Engineers/Executives

3.2 Engineering Supervisors

4.1 CONTROLLED COPY to be kept by HOD

4.2 UN-CONTROLLED COPY to be kept in [Engineering FOM Folder]

5.1 Refer to EQUIPMENT LOG AND FILING PROCEDURE for how to manage completed log sheets.

5.2 Electrode Steam Boiler Log.

5.3 ROC CCT-3300 series Conductivity Controller Operation Manual

Total Dissolved Solids (TDS) are the total amount of movable charged ions, including positively charged Cations and negatively charged Anions. These ions are originated from dissolved minerals, salts or metals in a given volume of water. It is expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm).

TDS is directly related to the purity and quality of water. Water with higher content of TDS is known as hard water. If we boil hard water, after the water being evaporated, the dissolved solids will be depositing on heating surface and form scale on the surfaces. More deposit will be formed when we boil water with higher TDS.

Water fed into boiler must be with high quality with minimum TDS. This is to ensure that no or minimum scale will be built up on the heating surfaces. Formation of scale on heating surfaces will retard heat transfer rate and if the rate of heat transfer is too low, then the heating elements will be overheated and burnt easily.

As conductivity is easier to measure, it is used in algorithms estimating salinity and TDS, both of which affect water quality. Depending on the steaming rate, the quality of water required will be different. Our electrode boiler steaming rate is comparatively low and thus only ion exchange columns are used for our de-ionization process to improve water quality.

Deionization is the process by which mineral ions in water are removed. Using specific ion-exchange resins (an insoluble matrix usually found in a bead shape), the ions in water can be drawn out and replaced. First, water flows through a certain resin that will cause the cations in the water to be drawn out, replacing the cations with hydrogen ions (cations) instead. The water, now very acidic, runs through another resin that will absorb the anions in the water, replacing these ions with hydroxide anions. The hydrogen and hydroxide will then combine to form water in a chemical reaction, leaving mineral-free water with very low TDS which will then minimize scaling of heating elements in our electrode boilers.

When the hydrogen and hydroxide ions are depleted in the resins column, the de-ionization effect will be low. In such case TDS will be increased and the conductivity measured will be higher too. This means that the de-ionization column would have to be sent for regeneration.
One important point to take note is that water flow rate passing through ion exchange column plays an important part in efficiency of ion exchange.

Parameters Setting as below:
Parameter order
Electrode Constant
Radis point setting
Measurement Unit
4mA transfer value setting
20mA transfer value setting
Alarm High Limit
Alarm Release

Note: The conductivity meter we used on the boiler feed water system is ROC CCT-3300 series conductivity controller (our unit is CCT-3200T for display only).  Refer to the CCT-3300 Series conductivity controller manual for detail on how to set the parameters.

8.1 How to carry out spot check on functionality of de-ionization system.

8.2 The engineering supervisor should go up to boiler platform and carry out the following check as a spot check to the effectiveness of technician in carry out their duty in logging boiler log.

8.3 It is advisable for the supervisor to shut the feed water supply to de-ionization system and feed water tank for 30 minutes to create some room before carrying out the following trial.

8.4 Check inlet and outlet connections to both de-ionization column and make sure that they are connected to the correct inlet and outlet holes. Take note on the IN and OUT marking on the cap.

8.5 Check all fittings in and out from the boiler, including those for the boiler gauge glass. Any deposit of white particle on the fittings indicates some minor steam leakage and the white particle that deposit after evaporation of steam or water is an indication of high TDS water.

8.6 After the water level in the feed water tank drop approximately 1 inch, the room in the tank would be good enough for the following test.

8.7 Turn on the supply valve to de-ionization system again and confirmed that water pressure drop across the system is lesser than 1.0 bar.

8.8 Partially close the valve toward the flow meter and set it to approximately 6 LPM (Litres per minute).

8.9 Check the conductivity meter and confirm that the conductivity is lower than 1µS/CM (microSimens per CM).

8.10 Set the flow rate back to approximately 6 LPM and let the system run back to normal.

8.11 During the above spot check, if the conductivity of feed water goes beyond 1µS/CM and the related technician who carry out boiler log did not report. Please guide accordingly. In case of repeated mistake, please carry out necessary disciplinary action.

8.12 Carry out the following procedures if the conductivity goes beyond 1µS/CM.

8.13 Change over to use the other column and carry out all above steps to double check that the new column is performing as expected.

8.14 Removed the exhausted column from system and replaced it with the standing by new unit.

8.15 Report to Engineer/Executive immediately for arrangement to re-generate the exhausted de-ionization column.

8.16 The duty is not end. Make sure you follow up within the week that the PR and PO are issued, old column removed to regenerate and regenerated column sent back to our plant.

8.17 The responsibility of supervisor only ends after the stand by unit of de-ionization column had been set back to stand by.

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