Waste, especially at sea is a continuous nuisance as it is mostly solid and occasionally toxic and damaging to environment; however it is something that cannot disappear and warrants a stable disposal method: the incinerator. Incineration is used in medicine, land-based waste disposal and now on ships where easier methods of disposal are unavailable.
Incineration is a process which involves burning of physical waste in a furnace with modern iterations being upgraded to contain special features such as pollution mitigation equipment such as flue gas cleaning. Having an incinerator on-deck of a ship is required by MARPOL regulations to gain approvals for its operations in some areas. An incinerator produces residue that is mostly ash and thus easy, cost-effective and less damaging to dispose.
However, incinerators in the end of the day are machines; a category that eventually presents technical difficulties, operation errors as well as challenges to understand the workings of the overall system. Machines and their existence is based on pre-designed purposes, routines and objectives that they are created to meet, with all of them, though having alternatives recommended to integrate machines appropriately, fitting their parameters.
An example of this first error is trying to overload past normal capacity; potentially causing an explosion; leading to the first important issue of machines not being as adaptive as humans and thus not able to perform over its normal function. Another point about machines is that they require maintenance; especially in the case of incinerators where under-maintenance will wear components and cause machines to under-perform.
The machine nature of incinerators along with other equipment on ships or any working units anywhere is a recurring issue that communicates with all the lifeforms aboard the ships; with the first issue being a warning given about the machine errors. This first warning is the Flame Failure Alarm which happens when the flame sensor is stimulated. However, the flame failure alarm may go off from the flame sensor simply getting dirty which warrants more cleaning of components or replacing defectives to avoid false alarm.
If the alarm goes off after all the maintenance was done then there are 8 possibilities which may cause it.
- Dirty burner
- Ignition failure
- Blocked diesel oil nozzle
- Defective flame sensor
- Defective solenoid valve
- Incorrect opening of air damper
- Clogged fuel line filter
Dirty burner is relatively common as waste is constant on ships which appears almost daily and when it happens the engineers have to clean the burner’s flame scrod and blast tube. However, if that does not solve the problem; spark electrodes which also can be a reason for ignition failure, should be inspected; fixed by cleaning and adjusting it. Blocked diesel oil nozzles should be replaced while a defective solenoid valve, when it raises the alarm, warrants replacement of solenoid coil/valve.
Lastly, the common reason for flame failure alarm is the improper opening of air damper which prevents adequate amounts of air reaching the combustion chamber which causes ignition failure. Overall, the first batch of errors associate with the blockage and manipulation of sensors and replacement of defective parts.
Another alarm which will raise due to failure is the High Flue Gas Temperature Alarm; happening due to defective or faulty temperature sensor. Possible reasons are:
- Blocked air cooling inlet
- Faulty inverter and trasmitter
- Leaking or defective solenoid valve
- Leaking dosing pump stator
- Defective pressure control
- Clogged cooling panel slot
- Throttling brick fallen out
All these errors can be avoided with constant checks and input adjustment while pressure control and solenoid valves should be checked at regular intervals. Along with that, most of the above errors come from the incinerator parts that are again either blocked from proper environmental interactions necessary for the machine to operate. Temperature balance is always affected by the machine’s environment and the parts that link it together. An incinerator operates at high temperature (870 to 1,200 °C) which needs a proper exchange of oxygen for the reactions to maintain chemical equilibrium. Imbalance of this will cause the machine to malfunction, especially when leaks and clogs are involved where an essential component is either not reaching some parts while waste from the machine itself is not properly addressed.
So far the errors described were involved with faulty sensors and false-alarms; meaning that incinerators require constant attention as it would be more productive to avoid false alarms. Since the operating temperature is high it is also a source of error like most extremities in machine operation; leading to the next error of High Combustion Chamber Temperature Alarm. This error also occurs due to faulty sensors but alongside another factor of waste overload inside and bad refractory condition.
Another error associated with the combustion chamber is the leakage of sludge oil which escapes from base-plate corners. This error occurs due to:
- Improper opening of oil burner air damper
- Low Under-Pressure
- Closed atomising valve
- Incorrect valves in Programmable Logic Controller/PLC
- Blocked sludge nozzle atomising slot
All the above errors, especially associating with PLC occur due to improper maintenance and configuration; fixing would be to consult the manual first to configure the PLC appropriately as the machine is pre-programmed to ONLY work under preset parameters. Along with monitoring the atomising slot to be open 3/4 to 1 full turn.
Leading back to the extreme temperature in the incinerator and the rapid changes from one extreme to another/hot and cold, another error occurs; cracks in the refractory of combustion chamber. Primarily, the cracks occur when water is poured into the sludge tank during a sludge operation at high temperature; leading to a solution NOT to fill the tank when the sludge is burning. The cracks also appear due to vibration of the machinery; fixed by deck support.
Another error associates with draft failure and sounding of low pressure alarm; occurring by:
- Damaged door casket
- Broken fan belt
- Wrong rotation of fan direction
- Failure in opening of flue gas chamber
- Leakage in the sensor tube
Fan belt and door casket are important factors to observe regarding draft failure.
Leaks in mechanical seal sludge pipe can be prevented by making sure its not running dry along with changing it if required along with monitoring sludge for large debris; restarting the system by flushing and cleaning lines fixes it.
Finally, there is an issue which occurs due to blocked return in the D.O Pump Shaft End; fixed by opening the return valve or remove blocking mass. Along with this, the incinerator machine requires constant maintenance and following of proper channels and directions which should avoid all errors altogether.