Outside Mechanical Seal for High-Temperature Pump Sealing
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Solution Overview
Problem
Existing shaft seal units for high-temperature sealed liquids in hot water or hot oil pumps in thermal power plants face issues with inconsistent sealing due to thermal deformation, require extensive cooling systems, and have large sizes that increase power consumption and maintenance needs.
Innovation Solution
A shaft seal unit with an 'outside type' mechanical seal where the sealing elements are positioned outside the stuffing box, and an annular cooling jacket is placed between the housing and rotating shaft, allowing for forced air cooling without the need for flushing lines or coolers, reducing size and maintenance requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact mechanical seal of inside type is used for high temperature sealed liquids, then sealing function is provided, but thermal deformation and material deterioration occur due to high temperature and pressure
Solution Approach 1:
The patent extracts the sealing function from the high-temperature environment by positioning the mechanical seal outside the stuffing box, where it operates in cooler atmospheric conditions while still providing effective sealing for high-temperature fluids through the extracted sealing mechanism
Solution Approach 2:
The patent introduces an intermediary cooling system that mediates between the high-temperature sealed fluid and the mechanical seal, using cooling water passages to maintain the seal at acceptable temperatures while allowing it to function in the high-temperature sealing application
2Temperature
If flushing lines and a cooler are added to cool the mechanical seal, then cooling function is improved, but device complexity and installation space increase
Solution Approach 1:
The patent merges the cooling function directly into the housing structure by integrating cooling water passages within the housing itself, eliminating the need for separate external coolers and flushing lines while maintaining effective cooling of the mechanical seal
Solution Approach 2:
The housing serves multiple functions: it contains the sealed fluid, provides structural support, and acts as a heat sink with integrated cooling passages, thereby eliminating the need for dedicated separate cooling components
3Reliability
If the mechanical seal is positioned inside the stuffing box, then sealing is provided, but the sliding face cannot be cooled by outside air and heat accumulates
Solution Approach 1:
The patent extracts the mechanical seal from the hot stuffing box environment and positions it outside where atmospheric cooling is available, while maintaining the sealing function through the extracted seal configuration that operates in cooler conditions
4Reliability
If the seal end face width exceeds 2.5 mm, then sealing capacity is improved, but high heat is produced by sliding requiring large flushing flow
Solution Approach 1:
The patent replaces the mechanical flushing system with a thermal management approach, using the housing's thermal mass and integrated cooling passages to dissipate heat from the seal faces, thereby eliminating the need for high-volume flushing flows
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
This design achieves efficient cooling without additional cooling systems, reduces initial and operational costs, and enhances thermal efficiency by minimizing the need for coolant and pumping components, while maintaining effective sealing and heat dissipation.
Implementation Method 1
an annular cooling jacket is disposed within a stuffing box which is formed in the shaft bore, such that the cooling jacket is disposed between an inside periphery of the housing and an outside periphery of the rotating shaft
Implementation Method 2
a rotating-side sealing element and a stationary-side sealing element are placed in intimate contact sliding at their mutually opposed end faces
Data Source
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AI summary
[Problem] An object of the present invention is to provide a mechanical seal of no-flushing and no-cooler design. [Solution] The invention is characterized in that the mechanical seal is of an "outside type" for sealing a sealed fluid that may leak from an inside periphery of a sliding face towards an outside periphery; a rotating-side sealing element and a stationary-side sealing element are disposed so as to be situated externally with respect to a stuffing box; the stationary-side sealing element, which accommodates a spring, is installed on a seal cover that is secured to the housing; the rotating-side sealing element is installed on a collar that is installed directly on the rotating shaft; the rotating side, which comprises the rotating-side sealing element and the collar, is positioned such that rotation takes place in the atmosphere on a machine-exterior side; a balance ratio A2/A1 is 1 or less, A1 being an axial-direction projection area of the sliding face of the stationary-side sealing element and A2 being an axial-direction projection area that is subjected to a seal fluid pressure acting as a motive force in the axial direction relative to the stationary-side sealing element; and an annular cooling jacket is disposed between an inside periphery of the housing and an outside periphery of the rotating shaft.