Steam Sterilization Chamber Pressure Pulsing for Uniform Heating
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Solution Overview
Problem
Existing steam sterilizers face challenges in achieving consistent temperature uniformity and steam density due to reliance on ON/OFF control and temperature-based PID control, which are inaccurate and require extensive testing, especially when dealing with varying loads and chamber sizes.
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 the difference between theoretical and measured pressures, 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 feedback and requires expensive proportionally-controlled valves
Solution Approach 1:
The patent replaces temperature-based control with pressure-based control. Instead of using temperature sensors and proportionally-controlled valves, the system uses a pressure sensor and an ON/OFF valve to control steam admission. Pressure feedback provides faster and more accurate control signals, eliminating the need for expensive proportional valves while improving control accuracy and temperature uniformity.
Solution Approach 2:
The patent changes the control parameter from temperature to pressure. By monitoring pressure changes in real-time and using pressure feedback to control steam admission, the system achieves faster response and more accurate control. This parameter substitution resolves the contradiction by providing both high measurement precision (pressure sensors are faster and more accurate) and manufacturing precision (improved temperature uniformity through better control).
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 and chamber sizes
Solution Approach 1:
The patent introduces pressure feedback control to the ON/OFF control system. The pressure sensor continuously monitors chamber pressure and provides real-time feedback to adjust the steam admission timing. This feedback mechanism allows the simple ON/OFF valve to adapt to different loading conditions and chamber sizes, maintaining reliable sterilization performance without increasing device complexity.
Solution Approach 2:
The patent makes the control system dynamic by adjusting the steam admission duration based on real-time pressure measurements. Instead of using fixed parameters, the system dynamically modifies the timing and amount of steam admission to compensate for varying loads and chamber conditions, thereby improving reliability while keeping the control system simple.
3Productivity
If rapid steam admission is used to reduce cycle time, then productivity is improved, but manufacturing precision deteriorates due to temperature deviations and poor steam density uniformity
Solution Approach 1:
The patent uses periodic pressure monitoring and controlled steam pulsing to achieve both rapid pressurization and temperature uniformity. By admitting steam in controlled pulses rather than continuously, the system maintains productivity while ensuring uniform temperature distribution and steam density throughout the chamber.
Solution Approach 2:
The pressure feedback control allows the system to rapidly pressurize the chamber while continuously monitoring pressure changes. The feedback signal adjusts steam admission to prevent overshooting and ensure uniform temperature distribution, thereby maintaining both high productivity and manufacturing precision.
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 method provides accurate and consistent chamber pressurization, ensuring compliance with international standards for steam sterilization, regardless of loading conditions or chamber size, without the need for additional equipment.
Implementation Method 1
a pressure sensor sensing a pressure level in the chamber
Implementation Method 2
moving a steam-to-chamber valve to an open state for duration of a pulse during each of a plurality of time PERIODS needed to reach a target pressure value, wherein steam is injected into the chamber from a source of steam when the steam-to-chamber valve is in the open state
Data Source
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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.