What are the main issues / areas of attention related to the operation of SOx scrubber?
Common issues noted as follows in open loop exhaust gas cleaning systems:
- Pitting on the overboard discharge pipe of wash waters. The manufacturers have introduced GRE pipe which appears to be reliable.
- Defective PT/Turbidity/Pah/PH sensors. Although there is provision of single sensor failure on MEPC.1-Circ.883, there shall be always spare sensor onboard, mainly for the outlet WMS.
- Defective membrane pumps for water monitoring system/gas monitoring system. There will need to be provision for a spare membrane pump or overhauling kit.
It is extremely important air filters and ceramic filters on the gas monitoring cabinet to be replaced as per makers’ intervals.
Do agree on above mentioned items however there are different areas that need to be close monitored / frequently inspected depending on EGCS maker / type and the peripheral components used in order to ensure proper operation of system at all times.
Some examples from personal experience on open loop scrubbers (only ) are below:
Overboard pipes are indeed suffering from corrosion due to the acidity of the discharged wash water which was known to everyone from installation day however the only counter measure to be protected from, was to apply few layers of ceramic paint at the inner surface of the O/B pipe as well as an area around the O/B on the hull prior antifouling application.
Latest applied solution with success (so far) is the installation of a 6mm thickness SMO sleeve including ceramic paint internally and epoxy putty in between the SMO sleeve and the sea tube.
Few other solutions are being used such as GRE lining, double wall O/B pipe with leak indicator etc.
GRE piping is sensitive to vibration therefore pipe supports should always be checked for proper securing on frequent internals. Vibration onboard vessels can slack bolts, loose supports, resulting in excessively stressful movement of piping and therefore potential cracks.
Repair kit for such pipes must always be available onboard. Common epoxy resin with glass cloth such as Cordobond can also be used for GRE pipe repair.
Internal condition of Scrubber tower should be checked at frequent intervals in order to ensure integrity of internal parts such as nozzles, nozzle pipes, demister or absorber section as well as tower body itself for cracks or corrosion. Sulfuric acid is a pain in the ass!
Most of vessel that were retrofitted with a Scrubber used the existing sea chests and same size of piping for supplying sea water pumps. That solution resulted in increment of the sea water flow/speed through the pipe in some occasions therefore excess cavitation on pumps and most frequent on the Scrubber sea water pumps casing/impeller.
Scrubber sea water pumps condition should be checked in order to maintain their performance as required.
Wash water monitoring systems should be checked for their sensors accuracy on frequency that each maker recommends or at every time the operator suspects loss of measurement accuracy therefore buffer solutions should always be available onboard.
PH sensor which is usually “cheap to buy” can be kept as spare onboard as well as some minor consumable for the sampling system if it is consisted of a sampling pump.
Gas analyzer’s most frequent failure is the sampling gas path or gas filter blockage. Depending on system, filters and sampling piping should be kept clean by replacement (filter) or just cleaning (sampling piping).
Various other problems related to electric/electronic components are also common failures.
In any case and in order to confirm compliance in the event of gas analyzer failure, Scrubber sea water flow should remain the same as when malfunction occurred and considering that engine’s load or fuel oil will not change otherwise should be increased to max until malfunction is restored.
Last but not least, are the water level detectors (depending on Scrubber system) installed on scrubber tower or inlet to scrubber exhaust gas piping which trip the system in order to prevent of water flowing back to the engines.
Subject detectors should be kept clean from carbon deposits and any spare available onboard will also an assistance on keeping the system in operation.
Hope i wasn’t too boring or tiring!