Segmented Venting Valve for Cargo Tank Pressure Control
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Solution Overview
Problem
Existing venting valves for cargo tanks on oil tankers face challenges in minimizing cargo loss and environmental pollution due to large blow-down, which results in significant pressure decrease and vapor pressure re-establishment, leading to inefficiencies and high costs in maintaining pressure within narrow overpressure limits.
Innovation Solution
A venting valve design with a lifting element positioned externally on the valve body, where the circumference is largest, and a secondary valve system, which increases the venting capacity and reduces the time the valve needs to be open, thereby minimizing cargo loss and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a valve with a large blow-down is used to prevent oscillations, then valve oscillation frequency is reduced below 0.5 Hz, but cargo loss and environmental pollution increase due to significant pressure decrease and vapor pressure re-establishment
Solution Approach 1:
The valve is divided into two independent valve bodies (first and second) that can operate separately. The first valve body handles large blow-down operations to prevent oscillations, while the second valve body manages smaller pressure equalization tasks, thereby reducing unnecessary cargo venting and loss.
Solution Approach 2:
The valve system dynamically switches between two valve bodies based on operational requirements. The control mechanism activates the appropriate valve body according to the pressure conditions, enabling the system to adapt its blow-down characteristics to minimize cargo loss while maintaining oscillation stability.
2Loss of substance
If a valve with continuously increasing pressure loss is used to minimize cargo loss, then cargo loss is reduced, but the valve size becomes considerable resulting in unacceptable costs
Solution Approach 1:
Instead of designing a single large valve with continuously increasing pressure loss, the system segments the venting function into two smaller valve bodies. Each valve body is optimized for specific pressure ranges, achieving the desired pressure loss characteristics without requiring excessive valve size or complexity.
Solution Approach 2:
The system changes operational parameters by switching between two valve bodies with different characteristics rather than using a single valve with continuously varying parameters. This approach achieves efficient pressure loss management while keeping the valve dimensions and costs acceptable.
3Loss of substance
If a pilot valve controlled system is used to minimize outlet gas and avoid pressure increase, then cargo loss is minimized, but the solution becomes correspondingly costly
Solution Approach 1:
The dual valve body system operates automatically based on pressure conditions without requiring complex external pilot valve control mechanisms. The valve bodies self-regulate their operation according to the pressure differential, reducing system complexity and cost while minimizing cargo loss.
4Stress or pressure
If the valve opens for a considerable period to vent overpressure, then the narrow pressure region (20-25 kPa) is maintained, but cargo loss increases due to extended venting time
Solution Approach 1:
The venting function is segmented between two valve bodies with different opening characteristics. The first valve body provides rapid opening for large blow-down to quickly equalize pressure, while the second valve body handles finer pressure adjustments, thereby reducing the total time the valve system remains open and minimizing cargo loss.
Solution Approach 2:
The control mechanism periodically switches between the two valve bodies based on pressure conditions, enabling efficient pressure equalization through alternating operation modes. This periodic switching optimizes the venting process by using the appropriate valve body for each pressure stage, reducing overall venting time and cargo loss.
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 valve design enhances venting efficiency by 25-30% and increases capacity from 2500 m³/h to nearly 3000 m³/h, reducing the time the valve must be open to vent overpressure, thus minimizing cargo loss and environmental pollution.
Implementation Method 1
a lifting element (20) arranged on the valve body (1) such as to extend completely around an outer circumferential part of the valve body (1)... wherein the lifting element (20) is placed where the circumference or diameter of the valve body (1) is the largest
Implementation Method 2
a couple of magnets (4a, 4b) provided on the valve body (1) and in the valve housing (3) respectively in such a way that the magnetic force seeks to hold the valve body (1) against the valve seat (2)
Implementation Method 3
The gas pressure in the tank forces the lower side of the valve body 1 to open in spite of the valve body's own weight and the force exerted by a couple of magnets
Data Source
Figure 1
Figure 2~3c
Figure 4a~4b
AI summary
A venting valve for cargo tanks in, for instance, oil tankers, said valve comprising a valve housing (3) with an axially movable valve body (1) and a thereto associated valve seat (2), where the position of the valve body (1) relative to the valve seat (2) is dependent on the pressure in the cargo tank, and where the valve comprises a lifting element (20) comprising a first section (21) with an inner edge (24) and a second section (22) with an outer edge (23), the lifting element (20) being arranged such as to extend at least partially, and preferably completely, around an outer circumferential part of the valve body (1) above the valve seat (2).