Note: CEC’s Combustion Safety Team has found that 5-10% of gas train vents contain some type of obstruction
CEC’s Combustion Safety Team has found that many facilities do not have insect screening installed on their gas train regulator vent terminations. Our teams found that 5 – 10% of the gas trains inspected were obstructed or severely clogged with insect nests (typically wasps or spider colonies).
The danger is that in the case of a ruptured diaphragm or leaking SSOV (safety shut of valve), the vents can not perform their intended function and let the gas pass to a safe place. Clogged regulator screens also make for ineffective pressure regulation. If no air movement is possible on one side of the diaphragm the regulator can’t do its job properly. This can also be very dangerous and make for nuisance equipment shut downs.
National Fuel Gas Code, NFPA 54 requires the following:
The vent shall be designed to prevent the entry of water, insects or other foreign materials that could cause blockage.
CEC’s inspectors have found the vast majority of vent terminations have nothing installed at all. Another 10 -15% have some sort of insect screening. In most of the cases where insect screening is installed, it is highly ineffective. In many cases hardware cloth is pushed up into the ends of the pipe. This makes for an obstruction and may fall out anyway. In other cases vent screens of a very fine meshed are installed that are clogged with dirt. These are typically of the same pipe size as that of the terminating elbow. This again makes for an obstruction.
Vent termination fittings should be designed in such a manner that they are able to be cleaned, are none corrosive, and provide adequate free area to properly vent all the gas necessary in the event of a diaphragm rupture.
Honeywell Combustion Safety, formerly CEC Combustion Safety, LLC, has been in business since 1984. With engineers and staff members that sit on Code committees such as ASME CSD-1, NFPA 56, NFPA 85, NFPA 86, and NFPA 87, our inside expertise is integrated within all of our practices and our global reach ensures that customers around the world are kept safe. Contact us at +1 216.749.2992 or visit www.combustionsafety.com for additional information.