In the previous article we saw the safety issues related to IG systems on board ships. In this article we will proceed to learn something about the maintenance and upkeep of Inert Gas systems and routine checks associated with the same.
Maintenance of the IG System
In order for the Inert Gas plant to be running satisfactorily there must be routine checks and overhauls carried out of various parts of the system on the plant side as well as the distribution side and some of these have been listed as follows.
- The IG scrubber is one of the most important components and it should be regularly inspected for signs of fouling, corrosion damage and any other damage. This inspection can be done through the manholes provided for the purpose and the parts to be inspected should include nozzles, cooling pipes, floats, sensors, demisters and so forth.
- The inert gas blowers should be checked for similar signs of damage or soot deposit. Apart from this visual inspection the blower should also be observed when actually running to observe any signs of imbalance or abnormal vibration which could be due to loose parts.
- The deck seal performs a vital role in the overall system and hence needs to be checked regularly for corrosion, blockage and so forth.
- Periodic checks should be carried out of the various alarms in order to find out whether they are functioning at the correct level of parameters for which they are set. Similarly valves which are supposed to open and close automatically or which are operable from a remote location should be verified to work correctly as required.
- Certain parts and sections of the IG system such as the scrubber effluent line can only be inspected during periods of dry dock and hence every dry dock should be used to inspect these parts.
- There are other components which are not directly a part of the IG system on board the ship but are used for important functions such as the oxygen analyzers and gauges used to measure hydrocarbon vapour levels. These instruments should be checked for their accuracy and calibrated so that they do not give false readings which could really be dangerous in most cases.
Time Frame of Inspection/Maintenance
I have frequently mentioned that the parts need to be inspected at regular intervals but it remains to be seen how often does this need to be carried out. The time interval can be decided based on manufacturers instructions, frequency of use and previous experience of shipboard engineers and the period of inspection could vary widely based on the component or section under consideration and the type of activity to be carried out. Inspection can be frequent by overhauling needs to be given a time gap to prevent unnecessary wastage of time. For example in case of flue gas isolating valve it can be checked for operation once in a week while the deck water seal can be opened for overhaul twice a year.