Stern Tube Seals "EVA"
Eagle Industry Co., Ltd. has developed stern tube seals, called EVA, with excellent sealing performance by fresh water purging. EVA's sealing structure and features are described below.
Two face seals are arranged on the seawater side, and a lip seal having a newly developed design on the oil side, with the two types of seals being completely separated from each other by an atmospheric chamber.
A constant small amount of fresh water is supplied between the two face seals to prevent the ingress of seawater. A trace leak of fresh water is collected inboard through a drain line. This sealing system is further provided with a net seal as a standard component, which prevents any fishing net from invading into the system.
Notable features of EVA are listed below.
(1) The seawater side and the oil side are completely separated from each other by an atmospheric chamber having a drain line, so that neither oil can leak outboard nor seawater can infiltrate into the stern tube.
(2) The face seals, which are not rubbing with the shaft like the lip seal, are hardly affected in sealing performance by any eccentricity and, coupled with the new type lip seal, are highly absorbent with eccentricity.
(3) The #1 face seal is a standby seal, which is automatically actuated if the #2 face seal is damaged or fresh water supply is stopped for any reason, so that the vessel can continue navigation without interruption.
(4) Any one of the lip seal and the face seals can be easily replaced by bonding on the shaft without pulling out the shaft.
(5) By feeding fresh water in a constant quantity from inboard through a constant flow regulating valve, the fresh water pressure can follow any fluctuation of seawater pressure and be kept about 9.8 kPa higher than the seawater pressure all the time.
(6) As the face seals slide with made of bronze casting mating rings, which are in contact with seawater and have a high degree of heat conductivity, they are made of a special kind of nitrile rubber.
(7) The low S/T L.O. pressure for bearings (about 29.4 kPa all the time irrespective of the draft) helps elongate the seal life of all the lip seals and reduce the wear of liners, both fore and aft.
(8) For the mating rings, a split type which can be reconditioned for reuse (not over #420 in seal size) and another type of which only the sliding part is replaced (#450 and above in seal size) are available.
Eagle's new products are thus attracting notes for their potential contribution to the prevention of marine pollution.
Eagle Industry Co., Ltd.
International Sales Department
Address： 12-15, Shiba-Daimon 1-chome, Minato-ku, Tokyo, 105-8587
Tel： +81-3-3436-4964 Fax： +81-3-3438-2294
