Piening Propeller provides its first PCP-type pitch propeller to Danish company Rohde Nielsen with its hopper dredger »Thor R«. The new design brings several advantages
A hopper dredger is a pure work boat whose variable pitch propellers are subject to extreme loads due to the[ds_preview] digging in the sand. »Thor R« has been operational for many years. During this time pitch propellers by different producers Wärtsilä and Berg were installed.
As the bearing clearance in the propellers is rapidly increased by invading sand, the hubs constantly have to be provided with new bearing shells which results in a complete disassembly of the hub for postprocessing in addition to the docking. The ship has a double shaft system with two four-bladed controllable pitch propellers (CPP). But the vessel features a total of four full CPP units including blades to react quickly without having to wait for repairs. Thus, the customer has a lot of experience with the use of bearing shells in the blade bearings of the propeller. This experience is not all positive.
Since Piening successfully provided repairs for the shipping company at propeller blades or fixed pitch propellers of the fleet over years, the customer approached Piening early in 2016 and asked for a better solution for »Thor R«.
Piening suggested to adapt their new variable pitch propeller design to fit the arrangement aboard »Thor R« which is a challenge in itself since the existing shafting is not to be changed for cost and time reasons. The proposal included to increase the hub but to install a five-bladed PCP with the option to keep existing blades.
Piening has developed a special seal design which both prevents hydraulic oil from leaking out of the hub, and the penetration of dirt into the control hub. For this task, further adjustment to the existing Piening design was made and a second barrier to penetrating sand was established.
The shipping company welcomed the proposal to work with composite material as bearing elements. Composite elements will be used in all highly stressed bearings of the adjusting mechanism. The abrasion on the adjacent metallic parts is demonstrably minimal and hardly measurable, Piening says. During service, the composite elements can be replaced with very little effort – machining of the adjacent components is not necessary. Furthermore, the composite materials are characterized by the fact that no lubrication is needed by hydraulic oil and the PCP can also be operated with water hydraulics (see report in HANSA 08/2016).
The delivery by Piening according to this contract consists of four complete pitch propeller hubs »PCP 5-705« (custom made) and ten blades.
RD
