[ RadSafe ] Gamma Radiation and Fire Eyes

[Rob O'Donel]

Please read the situation below and comment if you have any information on
the subject.  Specifically, what level of radiation is required to trip the
fire eyes?

 

 

Fire Eyes Inadvertently Activated By X-rays Releasing Halon

 

 

A Hawaii Refinery recently sent the following lesson learned regarding fire
eyes on a turbine / compressor / generator being inadvertently tripped by
x-rays. Here's their report:

 

 

"Last Monday, welding was being inspected by X-ray immediately adjacent to
the turbine, about 10 feet from the section containing two fire eyes. The
welding inspectors were on the north side of the Unit 3 package, with the
fire eyes inside and on the south side of the package. While pointing the
X-Ray device at a piping weld, Unit 3 tripped on fire detection, and Halon
was released."

 

 

"The Solar reps were still here for their last day of the new controller
installation. The Solar Regional Field Engineer stated he had seen this
happen before, and the Solar Field Service Representative was aware of it
happening. Since there was still doubt that the X-raying had set off the
fire eyes, Solar conducted a test. While Unit 3 was down, Solar reset the
fire eyes and had the inspectors X-ray the nearby weld again. Immediately
upon X-raying the weld, the fire eyes tripped and issued an alarm (the Halon
was completely released from the previous trip)."

 

 

"Solar then disabled the fire eyes for Unit 1 and Unit 2 through the Fire
Eye Lockout switches located on the unit control cabinets. Even though the
fire eyes were locked out, Solar still recommended removing the fire eyes
before inspecting nearby welds via X-ray to ensure that no further Halon was
released inadvertently.  It takes about 1 minute to remove the fires eyes
from each package - the cap unscrews like a light bulb, and then you simply
pull the fire eye detector out." THIS PRECAUTION SHOULD BE CONSIDERED FOR
ALL X-RAY PROCEDURES.

 

 

The lesson here is that fire eyes can indeed be triggered by x-rays. So
anytime x-raying is to be conducted within 25 feet of fire eyes, the
consequences of a false trip of the fire eyes needs to be evaluated. If the
consequences are serious, the fire eyes need to be disconnected from the
emergency system before x-raying commences. Note that x-rays penetrate steel
walls and equipment so even if the fire eyes are not in direct visual path
of the x-rays they can still be activated.

 

 

 

Rob O'Donel 
Radiation Safety Consultant 
Suntrac Services, Inc. 
281-338-2133 
Fax: 281-338-2136 
www.SUNTRAC.com