Title:

Double-walled Gas Tubing (Insulated pipes)

Hazard Category:

Chemical

Hazard(s):

• Chemical vapor exposure to workers due to leaks in the pipes that are used to route gases through a research facility.

Problem:

Many hazardous gases are used in research and production at the Birck Nanotechnology Center at Purdue University. There was a need to prevent and monitor leaks so that workers are not exposed to the hazardous gases used at the facility.

Risk Description:

• Hazardous gases used in research and production at the Birck Nanotechnology Center are transported throughout the facility via pipes.
• Any leak in the gas delivery system poses a threat to any individual working around that area.

PtD Strategy

Prevention through Design is the effort by design engineers to make safer workplaces through implementing safety at the project design stage. PtD strategies used with the gas delivery system at the Birck Nanotechnology Center include:

• Creating a system to prevent and monitor small gas line leaks.
• The system needs to be able to monitor a rupture in the outer line or inner line by measuring a change in pressure of the interstitial.
• A change in pressure will immediately notify appropriate staff via text message.
• In addition to this system, all hazardous gases must be monitored where they are not in double-walled tubing, such as at the source and at the point of use.

Features of the double-walled gas tubing system developed at the Birck Nanotechnology Center include:

• The inner tube transports the hazardous gas used in production and the outer tube contains nitrogen and helium (see diagram below).
• Gas in the outer tube is delivered at half the pressure of the inner tube, allowing a detection system for leaks.
• If the interstitial space increases in pressure there is a leak in the inner tube.
• If the interstitial space decreases in pressure there is a leak in the outer tube.
• A pressure of 0.0 psi is indicative of a catastrophic failure and the facility is evacuated.

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