Rijkswaterstaat (RWS) recently decided to retrofit their multifunctional ship Kennemer from an open water lubricated to a closed oil-lubricated stern tube system. The Kennemer used to sail in relatively deep waters, until RWS decided to deploy the ship in the West Frisian Islands area. Even though the current system functioned quite well in deep waters, it failed in the new unpredictable area.
As Henk Bos (RWS) explains: “The sea around the West Frisian Islands tends to turn in to tide-land quite unpredictably. If possible, we try to sail through, even in very shallow waters. In this situation a lot of sand and debris enters the stern tube. This is disastrous for open water lubricated systems.”
While sailing in shallow waters, the filters, membranes and retaining ring got heavily polluted or even clogged. As a result, the ship had to dock more than once a year to replace the bearings resulting in high maintenance cost. At that point RWS decided to retrofit to the alternative durable SUPREME closed oil-lubricated system. RWS chose IHC Lagersmit to deliver fully compatible SUPREME lip seals and bearings. Diametrically opposed to the water lubricated system, the oil-lubricated system is closed to ensure oil stays inside and water keeps out of the stern tube. To protect the system against sand and debris the aft seal is equipped with multiple lip seals and an extra dirt barrier.
“We find that problems with sand and debris are the number one reason to switch from open water to closed oil-lubricated systems” , Jan Boomsma (Application Engineer with IHC Lagersmit) explains.
Ship details
Ship name: MS Kennemer
Type of ship: Multifunctional, flat bottom
Shaft diameter: 80mm
Operation area: West Frisian Islands (Waddengebied)
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Source: IHC Lagersmit, May 4, 2011.