Then it will be estimated that the temperature of #2 seal ring is also changed in accordance with the alternation of differential pressure.
The experimental results on the simplified AIRGUARD 3AS is shown in Fig.14. For comparison, two kinds of differential pressures for #2 seal ring were set up as the test conditions, one is 100 kPa for the sea water pressures of 40 kPa and the other is usual 40 kPa for the sea water of 100 kPa and 130 kPa. This means the differntial pressure of #2 seal ring for shallow draft is compelled to be bigger than that for deep draft.
Although the temperature of #2 seal ring becomes to higher than the original system in case of bigger differential pressure (100 kPa), the temperature is enough to low on the material property of seal ring. The temperatures of #3 seal ring are always a little higher than that of original 3AS system because of no L.O. cooling in the experiment.
5. Summary
The mechanism that the air and oil pressures follow up automatically to the change of the sea water pressure is attained by the combination of the principle of the constant air flow rate and the function of the aftermost seal ring. Applying this mechanism to the simple aft seal and stem tube lubrication, the pollution free sealing system is realized to practical use as AIRGUARD.
By improvement of the system, experience on actual ships and investigation of the used seal, higher reliability and safety have been confirmed in AIRGUARD sealing system.
This system has been installed also in CRP (Centra-Rotating Propeller) shafiing system and the series of the biggest container ships, so it is actually corroborating to achieve the excellent performances.
Furthermore, the simplified AIRGUARD 3AS system has been developed for the ships which have the small draft changing, and in order to maintain marine environment, we, as one of the seal manufacturers, are looking forward to spreading pollution free sealing systems to every kind of ships.
