Double Mechanical Seal Pressure Control During Reverse Pump Operation
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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 and power failures, and fails to maintain effective sealing when the pump mechanism reverses direction, leading to potential leaks and temperature increases due to inadequate heat dissipation.
Innovation Solution
A sealing system with a double mechanical seal and a fluid barrier-and-cooling medium circulation line that includes a heat exchanger, shut-off valve, and a medium pressurizing pump, controlled by a system controller to manage pressure and flow, ensuring the fluid barrier-and-cooling medium maintains its pressure and cools the system effectively, even during power failures and reverse pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump mechanism is used to pressurize and circulate the fluid barrier-and-cooling medium, then the medium can be delivered from the first chamber to the second chamber to prevent leakage, but a large quantity of heat is generated around the pump mechanism which may cause thermal expansion, plastic deformation of sealing materials, and impairment of sealing function
Solution Approach 1:
The patent extracts the heat generation problem from the pump mechanism by introducing a separate heat exchanger system. The heat exchanger is positioned to receive the fluid barrier-and-cooling medium from the pump mechanism, cool it externally, and return it to the first chamber, thereby removing the thermal load from the pump mechanism vicinity and preventing thermal deformation of sealing components.
Solution Approach 2:
The heat exchanger acts as an intermediary between the pump mechanism and the fluid barrier-and-cooling medium. It provides a dedicated thermal management pathway that mediates the heat transfer process, allowing the pump mechanism to continue pressurizing the medium while the heat exchanger independently handles the cooling function, thus separating the pressurization and thermal management functions.
2Temperature
If the recirculating system is used to cool the fluid barrier-and-cooling medium through the heat exchanger, then heat dissipation is improved, but the system complexity increases due to additional circulation paths and components
Solution Approach 1:
The patent merges the cooling function with the existing fluid barrier-and-cooling medium circulation system. The heat exchanger is integrated into the circulation path such that the medium flows through the heat exchanger as part of its normal circulation cycle, combining the thermal management function with the existing pressure maintenance and sealing functions rather than adding a completely separate cooling system.
3Adaptability or versatility
If the pump mechanism operates in reverse direction, then the pressure relationship between first chamber and second chamber reverses, but the sealing effectiveness deteriorates leading to potential leakage of the fluid barrier-and-cooling medium
Solution Approach 1:
The patent applies preliminary anti-action by positioning the heat exchanger and circulation system to maintain proper pressure relationships even during reverse operation. The recirculating system is designed to ensure that the fluid barrier-and-cooling medium flows in the correct direction through the chambers regardless of pump rotation direction, preemptively counteracting the pressure reversal effect and maintaining sealing effectiveness during reverse operation.
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 integrity during normal and reverse pump operations, and ensures safe and efficient heat dissipation, preventing component damage and ensuring operational safety.
Implementation Method 1
a heat exchanger (21) which cools the fluid barrier-and-cooling medium
Implementation Method 2
The pump mechanism 119 pressurizes a fluid barrier-and-cooling medium such that the medium has a pressure Pb higher than a discharge pressure Ph of the pump impeller
Data Source
Figure 1
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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 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) attached to the first medium circulation line (30); a branch line (41) coupled to the medium circulation line (30); an accumulator (40) coupled to the branch line (41), the accumulator (40) being configured to pressurize and store a fluid barrier-and-cooling medium; an on-off valve (27) attached to the branch line (30); an optional pressure detector (52) arranged to measure pressure in the first chamber (22a); a pressure detector (51) arranged to measure pressure in the second chamber (22b); and a system controller (62) configured to open the on-off valve (27) when the pressure in the second chamber (22b) is lower than a threshold value, the threshold value being higher than discharge pressure of the centrifugal pump..