Method of items preparation for leak tests

FIELD: machine building. SUBSTANCE: method is suggested for items preparation for high-sensitivity leak test, it means the item location in special tight chamber, the chamber filling by dissolving fluid, it switching to state of supercritical fluid, and holding for definite time period. After the item holding under pressure of the supercritical fluid for definite time period the liquid phase is removed from the chamber, and vapours are pumped out, then the item is held at sufficient ambient pressure also for definite time period. The dissolvent pressure in the chamber during holding is determined on the condition that: P ≥ 4,08 ⋅ 10 − 6 σ d , kgf/cm 2 , where σ is surface tension coefficient of saturate substance solution sealing the contaminant, d y n c m ; d is cross-section area of the channel for through microleakage, cm. The time of the item holding under pressure of the supercritical fluid is: τ 1 ≥ 0,5 l 2 D , s, at two-way contact of the fluid with surface of the item shells (external and internal), τ 1 ≥ 2,0 l 2 D , s, at one-way contact of the fluid with surface of the item shell (external or internal), where l is maximum wall thickness of the item in zones of possible localization of the leakage defects, cm; D is coefficient of mutual diffusion of substance molecules sealing the channels of through microleakages, and molecules of the supercritical fluid during mutual dissolution under pressure P, c m 2 s . Duration of the item holding after removal from the special tight chamber of the liquid phase and vapours of the dissolving medium is: τ 2 ≥ 4,08 ⋅ 10 − 6 η ⋅ l 2 P ⋅ d 2 , s, where η is coefficient of dynamic viscosity of saturated solution of the sealing substance in the dissolving viscous medium, g c m ⋅ s ( p o i s e ) . EFFECT: invention increases quality and reliability of works, and reduces cycle and labour intensity. 4 dwg, 5 tbl