Slow Openning Gas Valves

[Amechanical]

Whats the difference between a regular gas valve and a slow opening gas valve, advantage vs. disadvantage, operation, etc.. thanks

[crab master]

This would likely be better answered in the technical or commercial section but I'll give it a shot.

If you have a fast opening gas valve and a regulator after/downstream of the valve you could potentially blow out the diaphram of the regulator. This would be the same reasoning that they tell you to slowly open the gas valve at the meter.

So to better answer your question - it depends on the application - if there is a regulator after the valve then the slow opening would be preferred.

On a pilot light on a boiler you would typically want a fast opening valve, less concern on delayed ignition, also warms up the flame sensor faster to prevent nuisance lockouts.

[jogas]

Never thought about that....
Could it have something to do with the light-off characteristics of the burner?
Or just the way it was done back then (technical/budget capabilities of the era).
I haven't seen a slow-opening gas valve on any new equipment. Has anyone else?

[crab master]

Good points - also some burners, mainly atmospheric, a slow opening gas valve could/would help prevent the heavy, hard "whoof" on light off on a burner. It would be a much "softer" fire off.

[dapper]

Yea Crab, I agree with your second point. It seems that most that I remember seeing were on large upshot burners or good size unit heaters or furnaces. I know that when you have your face in there you much prefer the slow opening feature.
There might be other reasons as well such as preventing the pilot from snuffing out on light off.

[Chris_Worthington]

Gas Valves have many different timings when you get into the larger burners, from the opening to the speed of closing the valve.........

As a boiler specialist on boilers up to 5000 HP and having seen many a bad things happen over the years (prior to pushing the easy buttons :rolleyes:) I recommend not deviating from what the manufacturer has given you, without their approval or a "very" senior and "very experienced" boiler guru, period...

Boiler/Bomb same damn thing, don't fool with it :D

[asdf;ljk]

Slow opening valves are typically applied to direct ignition systems (systems where the igniter lights the main burner directly, as opposed to lighting a pilot burner first and then the main burner). Because there is such a large amount of gas flowing in a direct ignition system, a slow opening gas valve provides a more controlled ignition.

[jogas]

Slow opening valves are typically applied to direct ignition systems (systems where the igniter lights the main burner directly, as opposed to lighting a pilot burner first and then the main burner). Because there is such a large amount of gas flowing in a direct ignition system, a slow opening gas valve provides a more controlled ignition.

That makes sense.
I remember seeing them on older unit heaters that had standing pilots/thermocouples.
Remember the Bryants with the electric time delay fan switch with the lever to adjust "fan on" timing?

[x-wrenchturner]

That makes sense.
I remember seeing them on older unit heaters that had standing pilots/thermocouples.
Remember the Bryants with the electric time delay fan switch with the lever to adjust "fan on" timing?

Or their standing pilot with the 3 wire warp switch.







ut oh....potential hijack (and/or flashback) ALLERT!



.

[jogas]

Or their standing pilot with the 3 wire warp switch.
.

I had nightmares about those pic and hold gas valves with the warp switch pilots.