Propeller Shaft Seal Pressure Control
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Solution Overview
Problem
Existing shaft sealing systems for propeller shafts in ships face challenges in maintaining optimal pressure differential and temperature conditions, especially in limited spaces, which affects the service life and reliability of the seals, particularly when using biodegradable oils and in varying operational environments.
Innovation Solution
A shaft sealing system that optimizes pressure differential across lip seals by regulating the pressure in internal chambers using a control unit with sensors and a PI controller, combined with a cooling system that utilizes circulating oil to keep the seal interfaces at an optimal temperature, allowing for efficient use of biodegradable oils and accommodating varying environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional pressure regulation devices are added to the shaft sealing system, then the pressure differential over lip seals can be optimized, but the available space in electric rudder propeller systems is substantially reduced
Solution Approach 1:
The patent combines the pressure regulation function with the existing seal chamber structure by introducing a controllable volume space that can be integrated into the seal assembly. This merging approach allows pressure control without adding separate external devices, thus optimizing space utilization while maintaining reliable seal performance through active pressure differential management.
Solution Approach 2:
The patent implements a dynamic pressure regulation system where the volume of the seal chamber can be actively adjusted during operation. This dynamic adjustment allows the system to adapt to varying operating conditions (such as different water depths and speeds) to maintain optimal pressure differential across the lip seals, improving reliability without requiring multiple fixed-volume chambers.
2Reliability
If the pressure in seal chambers is adjusted by feeding air or connecting to an oil tank, then the seal chamber pressure can be maintained at the desired level, but the system complexity and space requirements increase substantially
Solution Approach 1:
The patent implements a self-regulating pressure control mechanism where the controllable volume space automatically adjusts its pressure in response to operating conditions. The system uses the inherent compressibility of the contained medium (oil or air) and the mechanical coupling with the propeller shaft rotation to self-regulate pressure without requiring external control systems, tanks, or complex valve arrangements.
Solution Approach 2:
The patent introduces a controllable volume space as an intermediary element between the seal lip and the external environment. This intermediary volume acts as a buffer that absorbs pressure variations and allows indirect pressure control through volume adjustment rather than direct pressure application, simplifying the overall system architecture.
3Object-affected harmful factors
If biodegradable oils are used in the bearing lubrication system, then environmental friendliness is improved, but the oils become more sensitive to temperature variations affecting seal performance
Solution Approach 1:
The patent actively manages the temperature parameter in the seal chamber by controlling the volume and pressure of the contained medium. This allows the system to compensate for the increased temperature sensitivity of biodegradable oils, maintaining optimal viscosity and sealing characteristics even when using environmentally friendly lubricants that are more susceptible to temperature variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system extends the service life of the seals, maintains optimal conditions in limited spaces, and supports the use of biodegradable oils by keeping pressure and temperature within optimal ranges, reducing maintenance costs and facilitating condition monitoring.
Implementation Method 1
The control unit is configured to regulate a volume of the seal chamber to control a pressure differential over the lip seals
Implementation Method 2
The heat output created at the seal is transferred by the circulating oil into the frame of the rudder propeller device and further into the sea water
Implementation Method 3
The heat output created at the seal is transferred by the circulating oil into the frame of the rudder propeller device
Implementation Method 4
A shaft sealing system that optimizes pressure differential across lip seals by regulating the pressure in internal chambers using a control unit with sensors and a PI controller
Data Source
Figure 1
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AI summary
The invention relates to an arrangement and method for sealing the propeller shaft (10) of a ship using sealing (26), which sealing (26) comprises a group of lip seals (30, 32, 34, 36), arranged consecutively in the direction of the propeller shaft (10) so that a seal chamber (38, 40, 42) is created between adjacent lip seals. The pressure of the first seal chamber (38) on the propeller (6) side is close to the pressure of the surrounding water at the propeller shaft (19) level and the pressure of the second seal chamber (42) furthest from the propeller (6) is adjusted to a fixed value that is lower than the pressure of the first seal chamber (38). The pressure of the third chamber (40) located between the first chamber (38) and the second chamber (42) is adjustable by pressure regulation devices to a value between the pressure values of the first (38) and the second chamber (42) by adjusting the pressure loss caused by the flow of the liquid medium.