Double Mechanical Seal Circulation for Reverse-Rotation Leak Prevention
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Solution Overview
Problem
The existing sealing system for centrifugal pumps is inadequate in preventing leakage of toxic or flammable fluids into the atmosphere, especially during normal operation, power failures, and reverse rotation of the pump mechanism, and it fails to effectively cool and replenish the sealing system without compromising sealing performance.
Innovation Solution
A sealing system with a double mechanical seal, a pump mechanism driven by a rotational shaft, and a fluid barrier-and-cooling medium circulation line that includes a heat exchanger, shut-off valve, and a medium pressurizing pump, along with a system controller to manage fluid flow and pressure, ensuring the sealing system remains effective during normal operation and power failures, and prevents leakage even during reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump mechanism pressurizes the fluid barrier-and-cooling medium to prevent leakage, then sealing reliability is improved, but heat generation increases causing thermal expansion and deformation of components
Solution Approach 1:
A cooling medium circulation system is introduced as an intermediary between the pump mechanism and the environment. The cooling medium absorbs heat from the pump mechanism and seal components, circulating through a cooling jacket to maintain safe operating temperatures while the pump mechanism continues to provide sealing pressure
Solution Approach 2:
The system changes the thermal state of the seal components by introducing a separate cooling medium with different thermal properties. The cooling medium flows through channels in the seal housing and pump mechanism, actively removing heat and maintaining component temperatures within safe limits despite continuous pressurization operations
2Temperature
If the recirculating system cools the fluid barrier-and-cooling medium, then thermal management is improved, but system complexity increases due to additional external components
Solution Approach 1:
The cooling system is merged with the seal housing structure itself. Cooling channels and jackets are integrated into the seal housing and pump mechanism components, eliminating the need for separate external cooling systems. The seal housing serves dual purposes: containing the sealing mechanism and providing cooling pathways
Solution Approach 2:
The fluid barrier-and-cooling medium serves multiple functions simultaneously: it acts as the sealing medium between the pump and atmosphere, provides cooling for the pump mechanism, and maintains pressure balance in the sealing chambers. This multi-functionality reduces the need for separate dedicated cooling systems
3Reliability
If the pump mechanism is positioned between the pump-side and atmospheric-side sealing mechanisms, then sealing reliability is improved, but heat generation causes interference and deformation of surrounding components
Solution Approach 1:
The seal housing is segmented into distinct thermal zones with separate cooling channels positioned around the pump mechanism. This segmentation allows targeted cooling of heat-generating areas while isolating temperature-sensitive sealing components, preventing thermal interference through strategic thermal zoning
Solution Approach 2:
Cooling channels filled with cooling medium are positioned as intermediary pathways between the pump mechanism and surrounding seal components. These channels act as thermal barriers, absorbing heat from the pump mechanism before it can affect adjacent sealing components, thus preventing thermal deformation
4Device complexity
If the fluid barrier-and-cooling medium is supplied from the pump discharge, then system simplicity is improved, but leakage risk increases when the pump handles toxic or flammable fluids
Solution Approach 1:
The cooling medium supply is extracted from the pump discharge line and instead sourced from a separate, safe fluid supply. This extraction eliminates the pathway through which toxic or flammable pumped fluids could leak into the cooling system and subsequently into the atmosphere, while maintaining the simplicity of using a dedicated fluid supply for cooling
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 effectively prevents leakage of toxic or flammable fluids into the atmosphere, maintains sealing performance, and cools the double mechanical seal and pump mechanism, ensuring safety and reliability during both normal operation and power failures, including scenarios where the pump mechanism rotates in reverse.
Implementation Method 1
a heat exchanger and a shut-off valve attached to the first medium circulation line
Implementation Method 2
a pump mechanism driven by the rotational shaft, the pump mechanism being located between the pump-side sealing mechanism and the atmospheric-side sealing mechanism
Data Source
AI summary
A sealing system includes: a double mechanical seal having a pump-side sealing mechanism (10, 12) and an atmospheric-side sealing mechanism (11, 13); a pump mechanism (19) driven by a rotational shaft (1); a first medium circulation line (30) for circulating a fluid barrier-and-cooling medium between a first chamber (22a) and a second chamber (22b), the first medium circulation line (30) being coupled to the first chamber (22a) and the second chamber (22b), the fluid barrier-and-cooling medium being different from a fluid handled by the centrifugal pump; a heat exchanger (21) and a shut-off valve (28) attached to the first medium circulation line (30); a second medium circulation line (31) bypassing the shut-off valve (28); and a medium pressurizing pump (45) and an on-off valve (23) attached to the second medium circulation line (31).