Disturbances of the operation
On 19 January 1983 the engine stopped and thereafter it was not possible to operate the starter motor. The motor was replaced and the engine then started easily.
It is not clear whether this problem stemmed from a defective engine ring gear (which may have been faulty from the beginning) or whether the problem has to do with the use of producer gas, which often calls for somewhat prolonged use of the engine’s starter motor.
The gasifier operated normally during January and February 1983. However, on several occasions the gasifier outlet temperature rose above 475°C, a phenomena which was not accompanied by higher pressure drops over the gasifier and the filter section. Rotating the ash grate did not result in a reduction of the outlet temperature. The engine was stopped for one to two hours on these occasions.
Later (see below), it was possible to attribute the fault to air leakage into the gasifier.
On 4 February, it was noticed that the frequency of refilling with shells had increased from the normal 15 minutes to 5-10 minutes. Since the weather had been exceptionally hot and dry from late January onwards, the shells were wetted before loading into the gasifier. Thereafter the frequency of filling returned to the original 15 min.
On 11 February, the engine started misfiring (speed equivalent to 47-50 Hz). Upon replacement of the spark plugs with new ones the misfiring of the engine stopped.
On 21 February the temperature of the gasifier outlet rose to 500 C. It was noted that tar was leaking out of the gasifier safety hatch door. Because it wars suspected that air was being sucked in through this safety hatch, thus causing the temperature rise, the door was tightly closed. This brought down the gasifier outlet temperature to the normal value of 430°C.
It was planned to replace the spring-loaded safety hatch door by a metal explosion disc, as in the bag house filter.
On 25 February it was noticed that the inside of the inspection hatch (at the gasifier hearth zone) had deteriorated. Therefore an air leak was suspected through this door. A repair was carried out with mild steel plates as there was a danger of the refractory lining cracking and falling down. The sealing on the door of the inspection hatch was cleaned. Inspection a week later showed that the mild steel plates were holding out.
On 1 March it was noticed that the refractory lining had flaked off at the top and bottom edges. This may have been caused by the frequent cooling/heating cycles. No measures were taken and the situation seemed to remain stable.
Inspection of the ash pit on 23 March showed a semisolid slag as if the ash had burned in the ash pit. Air must therefore have been leaking into the gasifier ash-space either through the ash outlet or through the grate seal. The grate seal was suspected as it could not be tightened. The Giriulla mills-engineer fitted an additional sleeve after which there were no further problems.
In February the average engine inlet temperature rose to 50°C, as compared to 42°C in January. Probably this was due to the high ambient temperature in February (on 11 February it was 37° C in the shade and 39°C inside the gasifier shed).
In May 1983 the engine started misfiring again. A change of spark-plugs had no effect. Upon dismantling of the engine it was found that the pistons were covered with carbon 1 mm thick. Also it was noted that the engine inlet manifold was covered with a 2 mm thick semi-solid layer of either tar or dust/water slurry. The engine’s valves appeared to be clean. The misfiring of the engine was attributed to pre-ignition caused by carbon build-up in-the cylinders.
It is not clear whether the tar production results from the rather low loads at which the engine is now and then operated or stems from an incorrect installation of-the glass fibre cloth filter.