Oil Pollution Free 'AIRGUARD' Sealing System
Hisashi Yoshida
Manager of Technical Dept., Japan Marine Technologies Ltd.
Oil Pollution Free "AIRGUARD" Sealing System
H. Yoshida/Japan Marine Technologies Ltd.
M. Nishino/Japan Marine Technologies Ltd.
1. Introduction
To prevent the sea from oil pollution, higher reliability and safety are always demanded on the stern tube seal of oil lubricating system in the world.
As for the conventional sealing system, all of the seal chambers are filled with oil. The sea water and oil contact directly through the sliding surface of seal ring. So the mixing of the sea water and oil occures in the sliding surface, the leakage of the oil or infiltration of the sea water is not avoidable in greater or lesser degree. This situation become still severer by bigger shaft vibratrion. And, if some serious failures happened on the seal rings, there is not an adequate measure to prevent the contamination. Besides, when the ship draft changes so large, manual adjustment of the oil pressure in stern tube is necessary to keep the sealing performance according to the loading.
It is obviously effective to separate the sea water and oil by the medium of compressed air for prevention from the leakage of the sea water and oil, because the air is harmless to the environment. A pollution free sealing system "AIRGUARD" was developed by installing a convenient air control unit which mounts flow controllers, an air regulator of constant flow type, for a simple seal assembly, similar to the conventional type. After the first equipment of AIRGUARD sealing system in 1988, more than 170 sets of this system have been applied to the various kinds of ships and they are satisfactorily working in every oceans.
This paper introduces the construction of stern tube seal, mechanism of pressure control, piping diagram and main features on AIRGUARD sealing system in the first place. Based on the experiment research and the performance on actual ships equipped AIRGUARD, some improvements and investigation of the used seal are briefly reported. Also, according to the ceaseless research for further development on AIRGUARD 3AS, more simplified system is proposed.
