Steam Sterilization Chamber Pressure Pulses With Feedback Control
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Solution Overview
Problem
Existing steam sterilizers face challenges in achieving consistent temperature uniformity and steam density across the chamber, particularly due to variations in load conditions and chamber size, and rely on inaccurate ON/OFF or temperature-based PID control methods that require extensive testing and expensive equipment.
Innovation Solution
A method for pressurizing the sterilization chamber using a controlled rate of pressure change, where a steam-to-chamber valve is opened for specific durations to inject steam, with error adjustments based on pressure differences measured by sensors, allowing for precise control of pressure pulses to reach a target pressure value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If temperature-based PID control is used to control steam admission, then temperature uniformity can be improved, but control accuracy deteriorates due to slow temperature sensor feedback and requires expensive proportionally-controlled valves
Solution Approach 1:
The patent implements a feedback control system using pressure sensors to monitor chamber pressure in real-time. The controller compares measured pressure against target pressure and adjusts the steam-to-chamber valve duration accordingly, creating a closed-loop system that provides accurate, responsive control without requiring expensive proportionally-controlled valves
Solution Approach 2:
The patent replaces the mechanical/thermal control system (temperature-based PID with proportionally-controlled valves) with a pressure-based control system using electronic valve control. This substitution uses pressure sensors and electronic timing control instead of expensive mechanical valve modulation, achieving both accuracy and cost-effectiveness
2Device complexity
If ON/OFF control with fixed parameters is used, then device complexity is reduced, but reliability deteriorates due to varying performance with different loads, temperature deviations, and chamber sizes
Solution Approach 1:
The patent transitions from static fixed parameters to dynamic adaptive control. The system dynamically adjusts the steam-to-chamber valve duration based on real-time pressure feedback, allowing the control parameters to adapt to different load conditions, chamber sizes, and temperature deviations, thereby maintaining reliable performance across varying conditions
Solution Approach 2:
The patent changes the controlled parameter from temperature to pressure. By controlling pressure directly with adaptive timing adjustments based on pressure feedback, the system achieves reliable sterilization performance across different loading conditions without the complexity of temperature-based adaptive control
3Productivity
If rapid steam admission is used to reach target pressure quickly, then productivity is improved, but temperature uniformity and steam density uniformity deteriorate
Solution Approach 1:
The patent uses periodic pulsed steam admission instead of continuous rapid steam admission. By delivering steam in controlled pulses with specific durations determined by pressure feedback, the system achieves both rapid pressurization and uniform temperature/density distribution, avoiding the thermal shock and uneven distribution caused by continuous rapid steam injection
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 approach provides accurate and consistent chamber pressurization, maintaining uniform pressure irrespective of loading conditions and chamber size, without the need for additional equipment, and ensures compliance with international standards for steam sterilization.
Implementation Method 1
steam is injected into the chamber from a source of steam when the steam-to-chamber valve is in the open state
Data Source
AI summary
A method for pressurizing a sterilization chamber of a steam sterilizer with a controlled rate of pressure change. Pressure is increased in the sterilization chamber by opening a steam-to-chamber valve for a pulse duration during each of a plurality of time PERIODS needed to reach a target pressure value. During each time PERIOD, the steam-to-chamber valve is moved to an open state for the duration of the pulse. An error value indicative of the difference between a Theoretical Pressure and a Measured Pressure is determined at the end of each PERIOD. This error value is used to determine the duration of the pulse for the subsequent PERIOD, thereby maintaining a desired rate of pressure change in the sterilization chamber.