Backflow Preventer Pressure Loss Reduction via Segmented Flow Path
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Solution Overview
Problem
Conventional backflow preventers experience significant pressure losses due to the large differential pressure required to keep the relief valve closed, leading to increased load on pumps and potential premature opening of the relief valve during water supply, which results in inefficient water supply systems.
Innovation Solution
The backflow preventer design incorporates a first check valve with a back-pressure chamber and a narrow flow path portion, along with a differential pressure applying mechanism, which reduces pressure losses by utilizing the differential pressure between the upstream fluid pressure and the fluid pressure in the back-pressure chamber to facilitate larger valve openings, and ensures the relief valve remains closed by using the differential pressure between the upstream pressure and the narrow flow path pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fairly strong spring is used in the first check valve to prevent immediate opening when water supply starts, then the relief valve can be kept closed before first check valve opens, but considerably large pressure losses are produced in the conventional pressure-reducing backflow preventer
Solution Approach 1:
The first check valve is segmented into two functional parts: a main flow path for water supply and a separate pressure control path through the back-pressure chamber. This segmentation allows the valve to simultaneously maintain reliable relief valve closure and reduce pressure losses by controlling pressure distribution in different zones.
Solution Approach 2:
The back-pressure chamber acts as an intermediary mechanism between the upstream pressure source and the relief valve. It mediates the pressure relationship by creating a controlled pressure differential that keeps the relief valve closed without requiring excessive spring force in the first check valve, thereby reducing overall pressure losses.
2Reliability
If a large differential pressure is generated by the first check valve to keep the relief valve closed during water supply, then the relief valve remains closed, but the load on the booster pump increases considerably
Solution Approach 1:
The back-pressure chamber serves as an intermediary that redistributes pressure in the system. It maintains the necessary differential pressure to keep the relief valve closed during water supply, but does so in a controlled manner that reduces the overall load on the booster pump compared to conventional designs.
Solution Approach 2:
The invention applies local quality by creating a specific pressure condition only in the back-pressure chamber area rather than throughout the entire system. The narrow flow path portion generates localized low pressure that acts on the relief valve diaphragm, allowing the relief valve to remain closed during supply without requiring high differential pressure across the entire system, thus reducing pump load.
3Loss of energy
If the pressure loss in the first check valve is reduced, then the overall pressure losses decrease, but the differential pressure between upstream and downstream may become smaller than the specified pressure difference, causing the relief valve to open undesirably
Solution Approach 1:
The pressure control function is segmented from the main flow path and placed in the back-pressure chamber. This allows the first check valve to operate with lower pressure loss in the main flow while the back-pressure chamber independently maintains the necessary differential pressure for relief valve stability through its separate pressure control mechanism.
Solution Approach 2:
The back-pressure chamber acts as an intermediary that decouples the relationship between pressure loss reduction and relief valve stability. It mediates by maintaining the required pressure differential for relief valve closure even when the main flow path pressure loss is reduced, ensuring reliable operation without undesired relief valve opening.
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 significantly reduces overall pressure losses in the backflow preventer, improving fluid supply performance and reducing the load on booster pumps, while maintaining the relief valve closed during water supply, even with decreased differential pressure.
Implementation Method 1
utilizing the differential pressure between the upstream fluid pressure and the fluid pressure in the back-pressure chamber to facilitate larger valve openings
Implementation Method 2
a narrow flow path portion having a small flow path area and formed downstream of a position at which the valving element abuts against the valve seat
Implementation Method 3
ensures the relief valve remains closed by using the differential pressure between the upstream pressure and the narrow flow path pressure
Data Source
Figure 1
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Figure 3
AI summary
A first check valve has a narrow flow path portion (68) formed between an arcuate portion (46) of the outer periphery (45) of a support member and a second enlarged-diameter portion (11) of a casing. The narrow flow path portion (first portion of an intermediate flow path) is in fluidic communication with a back-pressure chamber (50) defined in the support member at the rear of the top of a valving element through a communicating passage (67) including a gap (66) between the outer periphery of the valving element and the inner periphery of a large-diameter portion (38) and grooves (27) on the rear surface of the top of the valving element. Thus, a low static pressure of fluid flowing through the narrow flow path portion is introduced into the back-pressure chamber to move the valving element by a large differential pressure during the supply of fluid, thereby allowing the valve opening to become larger than in the conventional apparatus and enabling a reduction of pressure losses. An intermediate chamber has a pressure chamber (130) defined therein by using a rigid partition (see figure 6). A high-pressure chamber (131) of the pressure chamber is in communication with the upstream side of the first check valve, and a low-pressure chamber (132) thereof is in communication with the narrow flow path portion. Thus, a valving element (136) is acted upon by a force larger than the differential pressure between the upstream side and an internal flow path (106) of the intermediate chamber, thereby allowing a relief valve (135) to be surely kept closed.