Mechanical Seal Assembly with Low-Pressure Double Sealing
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Solution Overview
Problem
Mechanical seals in cartridge type suffer from wear and corrosion due to high pressure, leading to reduced operational life and frequent maintenance or replacement, with the need for seal pots and flushing devices to mitigate these issues.
Innovation Solution
A mechanical seal design featuring a rotary subassembly with a sleeve and a stationary subassembly with a gland, incorporating a lip seal as a secondary lubricant and a scroll with a notched surface to create a low-pressure area, thereby reducing pressure-induced wear and eliminating the need for seal pots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical seals operate under high pressure conditions, then sealing capability is improved, but wear and corrosion increase leading to reduced operational life
Solution Approach 1:
The seal cavity is divided into high-pressure and low-pressure zones using a pressure equalization channel and seal pot, allowing the sealing face to operate in a low-pressure environment while the pump operates under high pressure, thus reducing wear and extending operational life
Solution Approach 2:
A lip seal acts as an intermediary barrier between the high-pressure process fluid and the sealing face, preventing high-pressure fluid from directly contacting the seal faces and reducing pressure-induced wear
2Duration of action of moving object
If seal pots and flushing devices are used to mitigate wear, then operational life is extended, but device complexity and water consumption increase
Solution Approach 1:
The lip seal integrates multiple functions into a single component: it acts as a barrier to high-pressure fluid, a lubricant delivery mechanism, and a pressure equalization element, eliminating the need for separate seal pots and flushing devices
Solution Approach 2:
The lip seal automatically delivers lubricant to the sealing face through its inherent design, and the pressure equalization channel self-regulates fluid flow to maintain optimal pressure conditions without requiring external flushing systems
3Reliability
If high pressure is applied to maintain sealing, then sealing effectiveness is improved, but friction and heat generation increase causing accelerated wear
Solution Approach 1:
The seal system separates the high-pressure sealing environment from the low-friction lubrication zone, allowing effective sealing under pressure while minimizing friction and heat generation at the sealing interface
Solution Approach 2:
The lip seal and pressure equalization channel act as intermediaries that regulate fluid pressure and lubricant flow, reducing direct high-pressure contact between sealing faces and thereby minimizing friction and heat generation
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 design extends the wear life of mechanical seals by creating a low-pressure area, reducing friction and heat generation, and eliminating the need for seal pots, thus conserving water and minimizing operation failure modes.
Implementation Method 1
a scroll crimped onto the sleeve of the rotary subassembly at the downshaft end thereof has a notched surface spirally-arranged on its outer diameter to draw fluid away from the seal faces, thereby drawing a vacuum and creating a low pressure area
Implementation Method 2
a lip seal disposed within the gland at the back face below the gland lip, wherein the lip seal concurrently seals and acts as a secondary lubricant within the seal
Data Source
AI summary
A mechanical seal of the cartridge type. A rotary subassembly includes a sleeve, the sleeve packed against and adapted to be in sealing disposition with a pump shaft of a pump. A stationary subassembly is for attachment to a stuffing box of the pump, the stationary subassembly including a gland, the gland having a front face and a back face and a gland lip extending from the back face. A lip seal is disposed within the gland at the back face below the gland lip, wherein the lip seal concurrently seals and acts as a secondary lubricant within the seal. In addition, a scroll is crimped onto the sleeve of the rotary subassembly at the downshaft end thereof, wherein the scroll includes a spirally-arranged, ridged outer surface.