Measurement of cryogenic valve straightness without accessing valve exterior

•Cryogenic control valves are characterized by low mechanical stability•Straightness of cryogenic valves needs to be verified with a quick, reliable method•The work presents simple noninvasive measurement of cryogenic valve straightness•Valve’s deflection is measured using computer vision (Hough transform for circles) The work presents a method of noninvasive measurement of long-stem cryogenic valve straightness, using simple and generally available means. The method does not require an access to valve exterior, what is a common requirement in practice, where such access is impossible in case of helium cryogenic valves confined in all-welded valve boxes. Valve’s deflection is computed using computer vision algorithms (Hough transform for circles), based on photographs of valve interior. Results obtained by the method have been validated using reference data from a validation test stand with a ruler for deflection measurement. The method may be applied for a more general case, namely to measure deflections of pipes ended with sleeves with diameters smaller than the pipe’s diameter.