Convertible Trim Cage Assembly for Stable Low-Flow Regulators
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Solution Overview
Problem
Fluid regulators, particularly 'boot style' regulators, exhibit instability at low fluid flow conditions due to minor fluctuations causing the diaphragm to shut off and overcorrect, leading to frequent cycling between closing and opening.
Innovation Solution
The implementation of convertible nested cages, where a second cylindrical cage is nested within a first slotted cage, requiring the sealing member to travel further before allowing fluid flow, thereby stabilizing the regulator and reducing noise, and allowing the same regulator to be used for both low and high flow applications by adjusting the position of the second cage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diaphragm is used to engage and seal and move away from a sealing surface to prevent/allow the flow of fluid, then the regulator can control fluid flow, but during low flow conditions the travel is so small that any minor fluctuation in the fluid flow results in the regulator shutting off and then overcorrecting by opening too much, causing instability
Solution Approach 1:
The trim assembly is segmented into multiple components: a first cage with a first opening, a second cage with a second opening, and a diaphragm. The second cage is positioned downstream of the first cage and divides the first opening into a first portion and a second portion. This segmentation allows different regions of the fluid flow to be controlled independently, with the second cage providing additional flow path control that stabilizes low flow conditions by preventing complete shut-off and overcorrection cycles.
2Reliability
If attempts are made to reduce instability by using stiffer springs, lower gain, smaller control lines, or adding friction, then some stabilization may be achieved, but these attempts have had limited success and often require several return trips, trial and error, and parts kits
Solution Approach 1:
The second cage is made movable relative to the first cage, allowing dynamic adjustment of the flow control configuration. The second cage can be positioned in different locations within the first opening to optimize performance for different flow conditions. This dynamic adjustability provides a straightforward method to stabilize low flow conditions without requiring trial and error with springs or friction modifications.
Data Source
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AI summary
A regulator (10) includes a body (15), a first cage (100) positioned in the body, a diaphragm (45) positioned within the body, and a second cage (200) operatively connected to the diaphragm. The body has an inlet (20), an outlet (25), and a passage (30) formed between the inlet and the outlet and the first cage is positioned adjacent the passage. The second cage moves with the diaphragm and is positionable on a first side of the diaphragm, opposite the first cage, or on a second side of the diaphragm such that the second cage is positioned within the first cage and is movable relative to the first cage.