Cryogenic Excess Flow Valve With Isolated Spring Return
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Solution Overview
Problem
Existing excess flow valves for cryogenic fluids, such as liquid hydrogen, become less effective over time due to deformation from high flow rates, leading to potential spillage and damage during fuel transfer operations.
Innovation Solution
The design includes a valve body with a piston plug and spring configuration that isolates the spring from direct exposure to high flow rates, using a spring slot outside the fluid flow path and a bleed hole to equalize pressure, allowing the piston plug to return to the open position once flow rates decrease below a threshold, thus extending the valve's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spring is positioned inside the fluid flow path to respond to flow rate changes, then the valve can effectively limit excessive flow rates, but the spring becomes deformed by high flow rates over time, reducing valve effectiveness
Solution Approach 1:
The spring is extracted from the fluid flow path and positioned in a chamber formed by the piston plug and valve body. This allows the spring to remain outside the direct path of cryogenic fluid flow, preventing deformation from high flow rates while maintaining its ability to bias the piston plug for flow rate limiting functionality
Solution Approach 2:
A piston plug acts as an intermediary between the spring and the fluid flow path. The piston plug transmits the spring's biasing force to control valve opening while being directly exposed to fluid pressure, thereby protecting the spring from direct exposure to high flow rates and their deforming effects
2Reliability
If the piston plug is biased toward the closed position to prevent spillage, then safety is improved, but the valve may fail to return to the open position when flow rates decrease, reducing operational life
Solution Approach 1:
The system incorporates feedback through pressure equalization. When flow rates decrease, fluid pressure differential changes, and combined with spring bias, this feedback mechanism ensures the piston plug returns to the open position, allowing the valve to repeatedly cycle between open and closed states throughout its operational life
Solution Approach 2:
The valve utilizes changes in fluid pressure parameters to control piston plug position. When flow rates decrease, the pressure differential across the piston plug changes, working in conjunction with spring bias to return the valve to the open position, enabling repeated operational cycles
3Speed
If the spring is exposed to direct fluid flow to sense flow rate changes, then responsiveness is improved, but the spring deformation from high flow rates reduces valve effectiveness over time
Solution Approach 1:
The piston plug serves as an intermediary that transmits fluid pressure changes to the spring without exposing the spring directly to high velocity flow. The spring responds to pressure changes transmitted through the piston plug, maintaining responsiveness while avoiding direct exposure to deforming flow conditions
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 configuration effectively prevents excessive flow rates from deforming the spring, maintaining the valve's functionality and preventing spillage, while ensuring the valve returns to the open position when flow rates are safe, thereby extending its operational life and preventing damage.
Implementation Method 1
a spring disposed in the spring slot. The spring includes a first end that engages the flange surface to bias the piston plug toward the open position
Implementation Method 2
The piston plug also includes a bleed hole that fluidly connects the inlet to the outlet when the piston plug is in the closed position to facilitate the piston plug returning to the open position by equalizing pressure
Data Source
AI summary
An excess flow valve for cryogenic fluid is disclosed. An example excess flow valve includes a body, a piston plug, and a spring. The body includes a valve seat and an inner body surface that defines an inlet, an outlet, and a chamber. The piston plug is disposed within the chamber. The piston plug includes a plug that is configured to engage the valve seat in a closed position and be disengaged from the valve seat in an open position. The piston plug includes an inner piston surface, an outer piston surface, and an flange that extends from the outer piston surface and defines a flange surface. The flange, the outer piston surface, and the inner body surface at least partially define a spring slot outside of the fluid flow path. The spring is disposed in the spring slot to bias the piston plug toward the open position.