밸브 누설방지를 위한 메탈시트 접촉면의 접촉압력 해석 = Assessment of Contact Pressure Occurred on Metal Seat to Ensure Valve Seat Tightness

국문 초록 (Abstract)

극저온 환경에서 작동하는 볼 밸브는 -253 ~ -73°C에서 유체를 조절하고 저장하는 장비에 사용된다. 이러한 환경에서 메탈시트 접촉면의 표면 거칠기에 따라 기밀을 위하여 요구되는 접촉압력이 저하하고 누설이 발생할 우려가 있다. 따라서 표면 거칠기를 고려하여 정확한 접촉압력 평가를 기반으로 한 누설방지 설계가 요구된다. 본 연구에서는 트러니언 방식의 볼 밸브를 대상으로 표면 거칠기를 고려하여 볼과 시트 사이의 접촉압력 분포를 이론적으로 계산하였고, 이를 수치해석 기법으로 얻어진 결과와 비교하였다. 접촉부의 지배방정식이 도출되었으며, 접촉 면의 표면 거칠기를 통계적으로 모델링하기 위해 확률밀도함수와 자기상관함수를 사용하였다. 상기 과정을 통해 얻어진 압력분포 결과는 PYTHON 스크립트 언어를 이용한 반복연산으로 얻어진 값과 비교하여 수치해석의 특이해를 제외하고 약 15% 이내로 일치함을 확인하였다.

다국어 초록 (Multilingual Abstract)

A cryogenic ball valve is used to control and store working fluids in the temperature range from -253 to -73°C. In such conditions, contact pressure is reduced, leading to leakage owing to change of the surface roughness on the metal seat. Therefore, the assessment of contact pressure occurred on the metal seat should be carried out to ensure valve seat tightness. In the present study, the distribution of contact pressure between ball and metal seat of a trunnion-mounted ball valve was calculated theoretically and numerically, considering the surface roughness. The surface roughness was evaluated statistically from probability density and auto-correlation functions, and the governing equations in the contact region were derived. Then, the contact pressure was assessed theoretically by an iterative calculation via PYTHON script language. The obtained contact pressure was compared with that estimated by numerical analysis. Both of contact pressures agreed well within an error range of 15% except singular solutions from the numerical analysis.

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