Double Check Valve Venting for Automatic Drain-Back Freeze Protection
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Solution Overview
Problem
Existing back flow preventors for exterior fluid delivery systems are cumbersome, prone to malfunctions, and lack effective drainage features, leading to potential contamination and damage from freezing, especially when used in exterior applications where pressure differentials can cause backflow and freezing issues.
Innovation Solution
A double check valve system with a valve body containing an inlet and outlet check valve, a hose plunger, and a vent system that allows for self-draining and freeze protection without additional components, reducing size, weight, and complexity, while meeting ASSE regulations for backflow prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a manually draining valve is used, then drainage function is provided, but reliability deteriorates because it relies on operator action
Solution Approach 1:
The valve automatically drains when hose pressure exceeds supply pressure, eliminating the need for manual operation. The differential pressure mechanism self-activates the drainage function based on pressure conditions, making the system self-servicing and reliable without operator intervention.
2Reliability
If a spool and internal valve system are used, then backflow prevention is achieved, but device complexity increases
Solution Approach 1:
The valve is divided into two independent check valves (inlet and outlet) rather than a complex spool mechanism. Each check valve independently prevents backflow in its respective direction, simplifying the overall mechanism while maintaining reliable backflow prevention through modular, segmented design.
Solution Approach 2:
The inlet check valve and outlet check valve are combined in a single valve body, integrating multiple functions into one compact device. This merging eliminates the need for separate components and reduces overall system complexity while achieving comprehensive backflow prevention.
3Reliability
If check valves are installed in exterior fluid delivery systems, then backflow prevention is improved, but freezing damage risk increases due to trapped liquid
Solution Approach 1:
The valve automatically drains trapped liquid before freezing conditions can cause damage. When hose pressure exceeds supply pressure (indicating hose removal or freezing risk), the drainage mechanism activates in advance to clear liquid from the valve body, preventing freeze damage before it occurs.
Solution Approach 2:
The drainage mechanism extracts and removes trapped liquid from the valve body through a drainage passage. This extraction function eliminates the harmful liquid that would otherwise remain trapped and cause freezing damage, directly addressing the freezing risk by removing the problematic substance.
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 double check valve system effectively prevents backflow, provides automatic self-draining, and protects against freezing, resulting in a more reliable, cost-effective, and compact solution for exterior fluid delivery systems, significantly reducing the risk of contamination and damage.
Implementation Method 1
an outlet check spring positioned about the outlet check body that contacts a portion of the outlet check body and a hub of the plunger
Implementation Method 2
the hose plunger and outlet check body are forced upward when the hose pressure exceeds the supply pressure
Implementation Method 3
allowing drainage of any trapped liquid within the sill cock and/or check valve
Data Source
AI summary
A double check valve is provided that includes an in-line inlet check valve and an outlet check valve that cooperate to prevent back flow of fluid through the valve. The check valve also includes at least one vent that allows for fluid trapped within the check valve to drain, thereby preventing freezing of the check valve and hydrant to which it is interconnected. The check valve provided omits many superfluous components and thus is smaller and easier to install than check valves of the prior art.