ETTER Engineering - Technical Tips

The Good Old Vent Valve!

The biggest concern about the vent valves of a combustion gas valve train is not only the potential of failure but, more importantly, the mode of failure when it occurs. Most gas trains on boilers and industrial gas fired equipment are indoors. The vent valve is run to a vent stack going up through the roof and venting to atmosphere above the roof. Natural gas rises due to its low specific gravity, so it floats out to atmosphere, in theory. A vent valve is a "normally open" valve, typically a solenoid. When power is not on the coil of the solenoid, the valve will be in the opened position, allowing venting. When the burner or equipment is to run, the solenoid coil is energized with the safety valves and the vent line is therefore closed. in theory!

That's the problem! Many of these vent lines are old and are not maintained. When they fail to operate, the vent line stays open or, sometimes, partially open. That results in raw gas pouring out the vent on the roof when the equipment is running. This type of failure goes unchecked all the time and usually only gets found when someone reports a "whiff of gas". Well, that whiff tells you that, due to winds and air currents, the gas does not always just "float away"! NFPA does state in the guideline that all safety and vent valves shall be tested on a regular basis. Lets be realistic, how many of us regularly check the vent lines or walk the roof checking to see that things are proper? In a recent local high profile case, a school full of children were evacuated due to a vent line failure that was leaking gas right into one of the fresh air in-takes to a Make Up Air Unit. Luckily, no one was harmed, but it sure shows the danger!

In addition, what about the money down the drain, or should I say up the vent! If that is not enough, what about the damage it is doing to the environment? This directly impacts our atmosphere as pollution. As we have stated, agencies have amended their rules and manufacturers have created new products. Today, you can put in a completely ventless system that includes pressure switches, regulators, and shut-off valves and not have to run a single line through the roof! As they say, WE HAVE THE TECHNOLOGY! If you have any questions or wish further information feel free to write to us at info@etterengineering.com or contact us 800-444-1962.