Dual-Piston Pilot Valve Assembly for Hydraulic Shock Mitigation
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Solution Overview
Problem
In the refrigeration industry, existing dual position pilot operated valve assemblies are prone to hydraulic shock during power failures, as they lack effective mechanisms to control the rate of response to high pressure gas changes, leading to potential liquid hammer and piping stress issues.
Innovation Solution
A dual position pilot operated valve assembly with independently controlled main and secondary pistons, featuring an adjustment mechanism that varies the degree of partial opening and closing, utilizing high pressure gas forces to manage the valve's operation and mitigate hydraulic shock by controlling leakage rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a standard pilot operated valve assembly is used, then the valve can open or close quickly, but hydraulic shock and liquid hammer occur during power failures
Solution Approach 1:
The valve assembly is segmented into a main piston and a secondary piston, each controlled by separate conduits. The secondary piston acts as a pilot to control the main piston's movement, allowing the valve to open or close in stages rather than instantly, thereby mitigating hydraulic shock while maintaining operational speed.
Solution Approach 2:
The secondary piston performs a preliminary action by partially opening or closing the valve before the main piston completes the full stroke. This preliminary movement reduces pressure differentials gradually, preventing sudden liquid hammer effects while still achieving full valve opening/closing when needed.
2Productivity
If the valve opens or closes completely, then flow control is maximized, but liquid hammer and piping stress increase
Solution Approach 1:
The valve assembly dynamically adjusts its opening degree through coordinated action of the secondary piston (controlling partial opening) and the main piston (controlling full opening). This dynamic control allows the system to optimize flow capability while avoiding the harmful effects of sudden complete opening or closing, reducing piping stress.
Solution Approach 2:
The system changes the valve opening parameter in stages rather than in a single abrupt movement. The secondary piston first adjusts the opening degree to a partial position, then the main piston completes the stroke. This parameter change strategy maintains flow control effectiveness while preventing liquid hammer and excessive piping stress.
3Device complexity
If a single piston is used, then the device complexity is low, but the ability to control partial opening and mitigate hydraulic shock is insufficient
Solution Approach 1:
The piston function is segmented into two independent pistons: a secondary piston for pilot control and partial opening, and a main piston for full opening/closing. This segmentation enables sophisticated hydraulic shock mitigation while maintaining relatively simple individual piston structures, balancing complexity and reliability.
Solution Approach 2:
The secondary piston serves as an intermediary between the control system and the main piston. It receives control pressure first and partially opens the valve, creating a buffer that prevents sudden pressure changes from directly impacting the main piston and valve seat, thereby mitigating hydraulic shock.
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 solution effectively minimizes liquid hammer and vapor propelled liquid at the termination of a hot gas defrost cycle, reducing the risk of hydraulic shock and piping stress by allowing the valve to open or close partially, thereby controlling the response to high pressure gas changes.
Implementation Method 1
independently controllable, via high pressure gas forces, main and secondary pistons
Implementation Method 2
a valve member forming a lower portion thereof and being adapted to sealingly mate with the valve seat
Implementation Method 3
a biasing member for normally biasing the valve member away from the valve seat
Implementation Method 4
a central axial stem depending from a bottom surface of the second piston and extending into and through the adapter cylindrical bore portion to the first piston bore cavity for contracting the first piston
Data Source
AI summary
A dual position pilot operated valve assembly having a main piston, with a valve member, reciprocable within a valve body, wherein the valve body is adapted for sealingly mating with a valve seat and passage located intermediate the valve body inlet and outlet ports, the valve body having a cylindrical adapter secured to an open end thereof and housing a secondary piston, reciprocable therein, with an axial stem depending from the second piston bottom surface and extending through the adaptor to the first piston cavity for intermittent contact therewith; and an end cap secured to and closing the adapter and having an inlet port interconnected with a source of high pressure control gas and respective first and second conduits leading to the main and secondary piston bore cavities, with an adjustment mechanism controlling the degree of opening/closing of the valve assembly. Several methods of operation are also set forth.