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  • 學位論文

呼氣閥檢測系統開發及探討

Evaluation and Development of the Leakage Testing System for Exhalation Valve

指導教授 : 陳志傑

摘要


緊密接合式的呼吸防護具裝設呼氣閥可降低呼氣時的阻抗,並且增加舒適感而延長配戴時間。呼氣閥是藉由吸氣時的負壓使閥片緊密貼合閥座而達到氣密的狀態,但實際上會因為不同閥片、閥座在生產過程中的瑕疵產生不同的洩漏,而逐一檢測是確保呼氣閥密合程度的唯一方法,因此快速檢測方法將有助於產量的提升。目前國際上通用的呼氣閥測試方規範,要求呼氣閥需在負壓 25 mmH2O的條件下,每分鐘空氣洩漏率不得超過 30 ml,而日本JIS T8151則規定在 1470 Pa之負壓條件下,回復至大氣壓力所需時間要大於 15秒以上。本研究目的為探討各式法規檢測方法操作流程及優缺點,並開發新式更快速的檢驗方法。 本研究的內容分為針對不同法規方法、原理作快速檢驗方法的改良。檢驗系統包含由排水集氣原理所設計的集泡法與雷射計數法;壓力回復法系統參數的探討;由流量檢測法所設計的電子式流量法及壓差法。集泡法及雷射計數法的系統設計包含使用不同管徑大小、洩漏率等條件來觀測氣泡產生的特性以及透過調整檢測頻率、迴圈次數來探討系統的檢測極限及穩定性。壓力回復法的實驗參數包含改變檢測腔室系統大小、檢測壓力及改變觀測結果的方式以壓差變化與時間的斜率關係來縮短反應時間。流量檢測法的評比真實洩漏率與相對洩漏率及壓差的相關性、改變系統參數大小和檢測設備對反應時間及穩定的影響。 實驗數據顯示排水集氣法所改良的集泡法及雷射計數法皆可節省水體回沖及觀測水位下降所需的操作及反應時間,而集泡法的應用因使用簡易觀測且反應時間約3-5秒,用肉眼即可得知洩漏結果;雷射計數法因氣泡產生速率快而使用光敏電阻及雷射光作為計數方法,提高偵測次數可於1秒內提供準確的呼吸閥片洩漏資訊。壓力回復法的實驗結果可得知在相同的洩漏條件,越小的腔室及壓力條件下,反應速率越快。觀測壓力回復的斜率可發現越短的觀測時間點各洩漏率的斜率差越大,檢測系統若能應用於自動程式換算即可確實的縮短反應時間並提高偵測極限。本研究所使用的電子式流量計因接於呼氣閥座後端即可節省前端開闔連接流量計(皂泡計)的操作流程,量測得到的是設定定值的負壓25 mmH2O下的相對洩漏率,與實際洩漏率取得相關性後便可得知其洩漏程度。整體反應時間可於0.16秒內得到穩定的數值。壓差法則是觀測洩漏後的壓差大小,不同的抽氣流量、壓力設定條件等皆會影響壓力變化結果,和真實洩漏率取的相關性亦可得知其洩漏情形。而反應時間約為0.7 秒。 綜合上述的檢測方法開發及探討,本研究的目標為開發”快速”的檢測方法,壓差法、電子式流量檢測法在反應時間及操作時間可在近兩秒內完成單次操作,電子式流量計檢測法在操作便利性、系統架設及反應時間等評比之下是優於各種檢測方法。

並列摘要


An ideal tight-fitting full mask with exhalation valve has features of low impedance during exhalation and comfort when worn for a long period of time. The valve normally fits tightly to the base by vacuum created during inhalation; however, leakage could occur when the valves and their bases were defective from the manufacturing process. To date, the only approach to detect leakage and ensure the effectiveness of the masks is to examine every exhalation valve, which can be time consuming. Therefore, the aim of this study was to first compare and improve across different fit testing procedures and subsequently develop a more time efficient test. This study promote the current testing methods to the instant testing system The inspection system includes the bubble collecting method and the laser counting method designed by the principle of drainage collection. The design parameters of the pressure regain method are discussed. The electronic flow method and the pressure difference method are designed by the conventional flowmeter method. The system design of the method of setting and the method of laser counting includes the use of different diameter and leakage rate to observe the characteristics of bubble generation and the detection limit, stability of the system be adjusted by the detection frequency and the loop of detection time. The experimental parameters of the pressure regain method include size of chamber, the detection pressure, and the observed slope of the pressure difference and the reaction time. The comparison of the electric flowmeter and pressure difference methods involve the correlation between the real leakage rate with the relative leakage rate and the pressure difference. Results showed that the reaction of the bubble accumulation and laser bubble method can be about 5 sec and 0.12 sec. The system would be more stable by changing higher detection rate. The experimental results of the pressure regain method shows that smaller chamber size and pressure conditions would have faster reaction time. The slope of the pressure difference and reaction time can present different leakage situation. The electronic flowmeter used in this study can save the time opening and closing the connection to the bubble meter. The measured value of the negative pressure conditions 25 mmH2O would provide the relative leakage rate, and should be adjust by the true leakage rate. The reaction time can be within 0.16 seconds to the stable value. Different leakage rate, suction flow and pressure conditions will affect the pressure difference results and the real leakage rate should correlate to the true leakage rate. The reaction time can be about 0.7 seconds. Based on the above-mentioned detection method development and discussion, the aim of this study is "rapid" detection method. Pressure difference, electronic flow rate and laser bubble count can have the operation time in nearly two seconds to complete a single operation. The electric flowmeter method is the most appropriate one for the application.

參考文獻


Bellin, P. and Hinds, W. C. (1990). Aerosol Penetration Through Respirator Exhalation Valves. American Industrial Hygiene Association Journal 51:555-560.
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Chen, C. C., Lehtimaki, M., Willeke, K. (1993). Loading And Filtration Characteristics Of Filtering Facepieces. American Industrial Hygiene Association Journal 54:51-60.

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