Browse Prior Art Database

Safety Device to Avoid Hazardous Gas Backflow

IP.com Disclosure Number: IPCOM000104412D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Agnello, PD: AUTHOR [+3]

Abstract

Disclosed is a device which will prevent the inadvertent backflow of a hazardous toxic/flammable gas in a plumbing system such as the gas supply to a chemical vapor deposition reactor. The device consists of an automatically operated valve A upstream of a pressure detecting switch B. If the pressure measured at B exceeds a certain preset value then the valve A closes automatically and prevents backflow through A. Upstream of A, for example, is a clean purge gas source at low pressure, e.g., 40 psi, and down stream of B is a toxic gas cylinder which may be opened to a line which then passes through a pressure reduction regulator and finally to a process line which goes to a deposition tool.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 64% of the total text.

Safety Device to Avoid Hazardous Gas Backflow

      Disclosed is a device which will prevent the inadvertent
backflow of a hazardous toxic/flammable gas in a plumbing system such
as the gas supply to a chemical vapor deposition reactor.  The device
consists of an automatically operated valve A upstream of a pressure
detecting switch B.  If the pressure measured at B exceeds a certain
preset value then the valve A closes automatically and prevents
backflow through A.  Upstream of A, for example, is a clean purge gas
source at low pressure, e.g., 40 psi, and down stream of B is a toxic
gas cylinder which may be opened to a line which then passes through
a pressure reduction regulator and finally to a process line which
goes to a deposition tool.  If for any reason the pressure downstream
of B increases above 40 psi such as if the toxic gas cylinder with
gas at 2000 psi opened inadvertently while the purge gas at 40 psi is
flowing, the pressure detection at B and valve closure at A will
prevent this reverse gas flow of the toxic/flammable gas into the
purge gas source which could have serious negative consequences.

      The invention can be implemented using an electrically
switching pressure gauge B, a control box C and a normally-closed
pneumatic valve A.  The gauge senses the pressure in the line at B
and if that pressure is low (about equal to the purge gas pressure
e.g., 40 psi) the gauge switch closes a contact which through the
control box C powers and op...