25 October 1999 Preventing molecular and particulate infiltration in a confined volume
Author Affiliations +
Contaminants form an instrument's self-generated sources or from sources external to the instrument may degrade its critical surfaces and/or create an environment which limits the instrument's intended performance. Analyses have been carried out on a method to investigate the required purging flow of clean, dry gas to prevent the ingestion of external contaminants into the instrument container volume. The pressure to be maintained and the required flow are examined in terms of their effectiveness in preventing gaseous and particulate contaminant ingestion and abatement of self- generated contaminants in the volume. The required venting area or the existing volume venting area is correlated to the volume to be purged, the allowable pressure differential across the volume, the external contaminant partial pressure, and the sizes of the ambient particulates. The diffusion of external water vapor into the volume while it was being purged was experimentally obtained in terms of an infiltration time constant. That data and the acceptable fraction of the outside pressure into the volume indicate the required flow of purge gas expressed in terms of volume change per unit time. The exclusion of particulates is based on the incoming velocity of the particles and the exit flow speed and density of the purge gas. The purging flow pressures needed to maintain the required flows through the vent passages are indicated. The purge gas must prevent or limit the entrance of the external contaminants to the critical locations of the instrument. It should also prevent self-contamination from surfaces, reduce material outgassing, and sweep out the outgassed products. Systems and facilities that can benefit from purging may be optical equipment, clinical facilities, manufacturing facilities, clean rooms, and other systems requiring clean environments.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John J. Scialdone, John J. Scialdone, } "Preventing molecular and particulate infiltration in a confined volume", Proc. SPIE 3784, Rough Surface Scattering and Contamination, (25 October 1999); doi: 10.1117/12.366723; https://doi.org/10.1117/12.366723


Assessment Of Contamination In The Shuttle Bay
Proceedings of SPIE (February 18 1982)
Contamination Control Plan For Prelaunch Operations
Proceedings of SPIE (April 11 1983)
Managing contamination-enhanced Laser Induced Damage (CLID)
Proceedings of SPIE (September 01 2008)
Chemical concentrator for rapid vapor detection
Proceedings of SPIE (August 01 1999)
Observations on one-dimensional counterflow diffusion problem
Proceedings of SPIE (September 10 2002)
Hubble Space Telescope Contamination Analysis
Proceedings of SPIE (December 31 1986)

Back to Top