4 Standing pilots on 960,000 BTUH boiler......is there a safer shutdown method?..Guard Dog Asleep

JUGHNE

Have a 1960 Bryant boiler in a nursing home. Was shut down for one year. System holds pressure OK. So no freeze up as electric heaters were on for empty building. New owners want to use this place for maybe 2 years before building new facility.
Boiler certainly needed cleaning. This design has front removable plates for cleaning, pretty handy as there are 17 sections and each section is of a serpentine design that will not let a brush go down from the top.

Before starting to clean, I lite the 4 pilots to check the safety. The MGSV was off. 3 of the 4 pilots have a Baso safety T-couple that keep the next pilot fed with gas. The last pilot proves for the main single safety switch. With a ohmmeter on the Baso L62GB-3 (100% shut off) safety switch it was closed with the 4 pilots on. When the pilot gas valve was shut off and the pilots dropped out, it was a Long 50 seconds for the safety to open. The thought of having 960,000 worth of gas flowing for that long is a scary thought. But this is the way it used to be! And to think this was originally fired on propane!......it is now on NG.

Is there a simple fix for quicker shut down on flame failure? The gas usage of the 4 pilots in not a concern.
Just a flame sensor....perhaps even redundant to existing safety T-couples......that would shut down main gas valve for flame failure?

aircooled81

Flame failure within 50 seconds, woudn't any ignited gas continue to burn until the MGV shut off? Basically, isn't the theroy that even if it takes 50 seconds, wouldn't that gas be ignited from the other burners/pilots?
Well I imagine you are not looking to retrofit the ignition system to direct ignition.... If you are I have a few ideas.
But, these guys make ignition controls and Flame scanners and flame safeguards. Maybe they can provide a solution that allows you to keep the standing pilot?
http://www.fireye.com/Products/Pages/Products.aspx

JUGHNE

If any of the 4 pilots flame out its own T-couple would shut down the pilot gas to the next pilot. True there would probably be some standing flame to burn off flowing gas.

The one situation I could see is if pilots are burning, T-couples proving, MGV opens and has delayed ignition for what ever reason and snuffs out the pilots. Then the count to 50 starts.
I have seen this happen to smaller burners of 100,000 or less, however those burners/heat exchangers needed cleaning etc.

My concern may be unwarranted as these burners were very dirty (covered with soot/rust) and now are cleaned. I have talked to previous maintenance persons and delayed ignition or rollout was never mentioned. (These are usually memorable events to those people) Plus there was no evidence of flame rollout and very little of flashback at the 16 burners.

Thanks, any other input on this is appreciated.

Tim McElwain

As one who is 100 years old I have seen hundreds of these from back in the day. Keep in mind a typical thermocouple can have as much as three minutes before the system drops out.

Your system should work fine as is and should not keep you awake at night. There are still a lot of these used here in RI in a lot of the old homes with the same boiler you have and the same set up.

To retrofit to intermittent pilot (you can not legally go to direct spark ignition or hot surface as that is not allowed) is going to cost a lot of money I would say for parts plus labor more than they want to know.

Leave it as is and as long as it shuts off on safety it should be okay, In 50 seconds only about 19,200 btus would escape.

If you think about it you have multiple safeties. Many more than some systems on gas that fire that much with one pilot safety.

JUGHNE

Tim, thank you very much, that makes me feel better. Now with the burners & exchanger clean the chances of roll out/flame out will be even less.

I approach this start up with caution as things such as this Guard Dog was wired as shown. It is the PS-851-m-120, (new model).
The 120 VAC was done by an electrician.....the control wiring by who knows?

Knowing the history of this place, the LWCO would not have been installed without the insistence of the Insurance Inspector.
There would have been an external annual inspection of controls. Pushing the test button would have shown shut down, needing reset. But obviously the burner would not shut down operation.