Pilot Operated Parallel Valve for Wide Turndown Flow Control
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Solution Overview
Problem
Proportional pneumatic flow control valves lack precision at lower flow rates, leading to significant errors and imprecision, which is problematic for applications requiring accurate control across a wide range of flow rates.
Innovation Solution
A unique electropneumatic proportional flow control device with two internal valves in parallel: a small, electronically controlled miniature valve for precise low-end control and a larger mechanical pilot-operated valve for high-end output, integrated within a valve assembly including a manifold, diaphragm, electronic control circuitry, and a flow restrictor, allowing for a flow output turndown ratio of 100,000:1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single proportional pneumatic flow control valve is used, then the valve can control a wide range of flow rates, but the precision at lower flow rates deteriorates
Solution Approach 1:
The flow control valve is divided into two separate valve bodies (first valve body and second valve body) that operate in parallel. The first valve body handles lower flow rates with higher precision, while the second valve body handles higher flow rates. This segmentation allows each valve to be optimized for its specific flow range, resolving the contradiction between precision and flow range coverage.
2Measurement precision
If two independent valves are used in parallel or sequence, then accuracy over particular segments of the full flow range is increased, but device complexity increases
Solution Approach 1:
Two separate valve assemblies are merged into a single integrated valve body with common inlet and outlet ports. The first and second valve bodies are combined such that they share the same fluid pathway, eliminating the need for separate connections and reducing overall system complexity while maintaining the accuracy benefits of dual-valve operation.
3Productivity
If a larger valve is used to compensate for higher flow rates, then high flow capability is achieved, but low flow precision deteriorates
Solution Approach 1:
The valve system is segmented into two distinct valve bodies with different sizing characteristics. The first valve body is optimized for precision at lower flow rates, while the second valve body provides high flow capability. By operating these valves in parallel and selecting appropriate valve sizes for each segment, the system achieves both high flow capability and low flow precision simultaneously.
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 device provides improved precision and accuracy in controlling pneumatic flow rates, enabling both low-end precision and high-end volume flow capabilities, while being compact, lightweight, and resistant to position and vibration, with both internal and external feedback for reliable operation.
Implementation Method 1
a pilot response member (diaphragm) which responds to a pressure differential across the pilot response member to actuate the valve
Implementation Method 2
a flow restrictor positioned downstream of the valve
Data Source
AI summary
An electropneumatic proportional flow control device improves flow control because it incorporates two internal valves in parallel: a first electronically controlled, miniature proportional valve manipulated in parallel with a second and larger pilot -operated valve. The miniature valve allows for precision control of the low-end of the full scale output; the larger mechanical valve allows for the high-end of the full scale output. These valves are encompassed within a valve assembly comprising a valve manifold, a pilot-operated diaphragm, electronic control circuitry, and a flow restrictor.