Chrome steel liners
Chrome steel liners and Distance rings
Chrome steel liners
Our AFT and FWD chrome steel liners are OD-finished machined (standard design). Other machining works are to be carried out by the customer.
Our chrome steel liners are:
- Compatible with Simplex® Compact SC-1 and Compact SC-2 types.
- Compatible with Kobelco® C, CX and DX types.
- Compatible with Kemel® CX, DX stern tube systems.
- Compatible with Wärtsilä® MK-1 and MK-2 types.
- Compatible with Lips®MK-1 and MK-2 types.
- Compatible with John Crane®MK-1 and MK-2 types.
- Compatible with Waukesha® MK-2 types.
- Compatible with Chuetsu® MK-2 types.
- Compatible with Dover Japan® MK-2 types.
- Compatible with JMT (Japan Marine Technology)® MK-2 types.
- Compatible with Deep Sea Seals® MK-2 types.
- Compatible with IHC Lagersmit® Supreme types.
Distance-/ spacer ring:
A distance or spacer ring can be installed between the stern tube and the AFT seal housing. The ring improves the durability of the liner and ensures a new, clean running surface for the stern tube seals.
Distance-/ spacer rings can be installed without removing the propeller.
Chrome steel liner life span
Stern tube seals from oil-lubricated lip-type systems run on a bush or liner. The seals, quite often, create grooves in these liners. When we replace seals during overhaul, you want the new seals to run on a fresh liner surface.
On the AFT system, this can be achieved by removing or placing a distance ring between the actual stern tube and the seal housing. This way the whole seal box moves its position on the liner (that is attached in a fixed position on the propeller).
After you have two sets of grooves on a liner, it’s time to take the liner off the propeller shaft and have it machined in a workshop. Once machined, the liner is good for two more seal overhaul periods.
5-year dry docking
In general, if a distance ring is installed during new build. With the first seal overhaul during the first, 5-year dry docking the distance ring will be removed.
10-year dry docking
With the 10-year dry-docking, the liner should then be removed from the shaft and machined in the workshop. After that, with the installation of a distance ring, the liner is good for 10 more years.
Please feel free to contact us about liner tolerances, whether or not your system has a distance ring installed, or any other questions regarding oil lubricated stern tube systems.
Issues with Ceramic coated liners
Over the last few years, we encountered some issues with ceramic coated liners (chipped off the coating, which can damage the seals) and with severe wear (and signs of overheating) on stern tube seals.
After discussing these issues and analyzing these situations with our supplier, we concluded that in general, the stern tube liner needs a certain surface roughness to distribute oil under the lip of the seal to prevent it from overheating and provide lubrication in order for the seal to work properly and keep its 5-year lifespan.
The general consensus between RM Propulsion and our supplier is also based on experience from our supplier with seals in other applications.
Based on this consensus we are putting out a guideline for surface roughness of the stern tube liners that has to be met in order to guarantee the proper functioning of our stern tube seals (assuming the stern tube oil is in good condition).
If the surface roughness is not met, we are not able to give a full warranty on the functioning of our seals.
The roughness of a ceramic coated
The initial roughness of a ceramic-coated liner will probably meet these roughness criteria. But after 5 or 10 years of operating, there will be a polished track on the liner. The roughness will not meet the required parameters anymore. On stainless steel liners the polishing will also happen, but also there will be a groove in the liner. This will make it more feasible to move the seal to a fresh running surface either by removing or adding a distance ring to the system.
However, in case of a ceramic coated liner, a groove will normally not occur because of the hardness of the material, and most of the systems are sold without a distance ring. Although, the roughness of the ceramic coating will still be affected. If a polish mark is visible on the ceramic coated surface, the roughness is most likely under 0,4Ra.
We will provide a roughness meter to our service engineers in case we know in advance that an overhaul needs to be done on a system with a ceramic coated liner.
Chrome steel liner more cost- efficient.
In case stern tube seal overhaul is performed on a system with a ceramic coated liner, the customer should be made aware that we recommend bonding the seals on a fresh running surface (for an AFT system this means installing or removing a distance ring).
If that is not possible, RM Propulsion recommends to replace the coated liner with a new chrome steel liner. We don’t see the advantage of a ceramic coated liner and we are convinced that the use of a regular chrome steel liner is more cost-efficient.
If a customer insists on bonding new stern tube seals on a ceramic coated liner with visual polish marks, the surface roughness needs to be measured and found between 0,4 and 0,8 Ra.
If this is not the case or if no measurement can be taken (only visual proof of polishing) RM Propulsion will only grant a limited warranty on the stern tube seal overhaul on that system.
Issues related to severe wear or overheating of the sealing rings will not be covered by our service warranty.