Low pressure steam boiler with 25psi on the steam gage

I usually install most of the time but I'm between installs now so I am helping out on service until the schools get out next week.

So, at 2pm yesterday I go on a call a Burnham steel boiler 2,500,000 btu low pressure steam with a Webster modulating gas burner. The customer complained of a lockout on MFF. First time at this account.The burner was running when I got their maintaining 10psi steam and modulating the flame.

So I put my analyzer on which had a low battery and some other issues (probably because I haven't used it in a while), checking gas pressures and adjusting the burner (low fire too small and unstable). High fire is fine, low fire still not happy with that and checking the flame signal when I came out to the front of the boiler and see their is now 25psi on the pressure gage. Now I quickly become less concerned with the burner issue.

Kind of stunned me for a second as I reached for the off switch.

No discharge from the safety valve, I checked the L404A operating pressure control and The L404E manual reset high limit (on separate pigtails) and the mercury in both controls was no ware near tripping.

I decided the steam gage must be bad so I went out and got a gage on my truck. A pet cock on the steam trim wouldn't open (didn't want to snap it) but their was a petcock on the gage glass blow down so I opened it to make sure it was clear and put the gage on.

It read 20 psi within 1 psi of the boiler gage. The steam pressure had dropped 5psi since I shut it off.

Stood their for a few not believing what I was seeing. 20 psi on the boiler, 2 gages agreeing, no safety valve discharge and 2 pressure controls on 2 pigtails not moving??

I notice the pressure controls were mounted out of level a fair amount so I fixed that thinking that would solve the pressure control issue.....nope.

Customer didn't want to shut down, process load but I insisted so I had to baby sit it a while then shut it down at 3;30 when most of their employees leave and proceded to dump some steam.

I took off both pressure controls and they were very clean on the inside. Took off both pigtails (steel) both plugged up solid couldn't blow any air through. I took the safety valve off and found the seat frozen to the disk, no sign of any corrosion or gunk. All boiler connections to the pressure controls and safety valve were clear.

No way to get to the supply house before they closed so I got the safety valve to open with a hammer and a screwdriver. I reinstalled the pressure controls with 1/4" nipples and started the burner. Watched the burner cycle on pressure 3 times. The safety valve was free and was leaking some steam at 10 psi and I could manually open it so I let it run.

I returned first thing this morning and put new brass pigtails under the pressure controls and checked their operation. I also replaced the safety valve. The boiler is due for it's summer shutdown and inspection so we will see what it looks like then. Maybe a water treatment issue??

Just a few more gray hairs that I don't need. I think that boiler would have made the local news this morning after it exited through the roof. I still find it hard to believe.