Drilling & tapping a "too big" vent hole on a steam radiator

ethicalpaul

That was a freak, once in 500 years kind of event caused by several failures, not just one and really shouldn't be used to make any decisions.

tim smith

gonner, next!

branimal

mattmia2 said:

If you wanted to save it you would have to drill at the end of the crack, grind it wider, then fill it with brazing material, then braze a bung over the remnants of the tapping.

I ended up buying an oxy-acetylene torch and tanks for another project. I am getting ready to make an order from Supplyhouse. What kind of brazing rods would I need to fix the crack in the cast iron radiator.

I have #2 and #3 brazing tips.

Thanks.

pecmsg

J W Harris
Low Fuming Bronze
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ScottSecor

My recommendation is to replace radiator, vent and complete radiator valve.  Unless, you have unlimited time and some money for tools you may never use again.  

About that once in a lifetime event that the radiator vent let go...About thirty years ago we proposed to replace an ancient coal fired snowman (cast iron sections, stacked like pancakes).  The family was going away for Christmas and we were scheduled to install new boiler soon afterwards.   Heat was on when they left town.  When they got home three or four of the ten radiator vents were embedded I'm the plaster walls.   Apparently the pressure built pretty high and the threads let loose.  I can only imagine what it looked and sounded like.  My  guess is ninety year old pressure control hung and relief valve no longer functioned.   Thankfully the family was away at the time.

ethicalpaul

That story sounds apocryphal and I'll tell you the main reason why I think so. There is no way a runaway boiler will blow 3-4 vents simultaneously. One of the vents is going to be the weakest one, and it will go first, relieving the pressure.

If you saw the vents stuck in the wall I will defer to you, but is it possible this was a story you heard about and didn't actually see?

OK, now let's say 3-4 vents really did blow at once and go back to how common this event would be.

• Apparently the thermostat failed closed because otherwise the boiler would not get to high enough pressure to blow vents off of the radiators (especially 3-4 of them at once).
  
• The pressure control failed
  
• The pressure relief valve failed
  
• The hartford loop failed (just kidding, LOL, as we know the hartford loop doesn't do anything)
  

Now that is what I would call a very unlikely failure of multiple safeties and not really valid as part of any kind of decision making--if it really did happen, Scott himself says it is at most a one in 30 year career event.

But the weirdest part of this story is actually how LUCKY the family must have been. Because after all those failures, somehow the boiler decided to shut down and not burn down the house. How did that happen? What safety decided to kick in and shut down the burner before it lit the house on fire?

EBEBRATT-Ed

1 vent blowing out is not going to relive enough pressure to keep the pressure down, 1 radiator vent is 1/8" IPS. What is the smallest steam safety valve used on residential boilers? 1". 1 1/4" 1 1/2"??


I had a job the last year I was working a 15PSI Burnham Commercial steam boiler. The customer complained about the gas burner didn't sound right and was rumbling wanted a combustion test. They used the boiler for process so they ran at 12psi.

I get in the boiler room and the burner is firing 11psi on the gauge. I hook up the analyzer and am behind the boiler for a while checking the flame through the rear sight port and using the Testo combustion analyzer. The burner had a modulating pressure control and 1 high limit and an operating control

I walked out front by the burner to get some tools and the steam gauge is now reading 35psi. I just laughed and told myself the gauge must be bad. I shut the burner off and went to the truck for a gauge. Stuck it in a spare tapping 35 psi the gauge on the boiler was right!!

Safety valve not opening, rusted closed.

Shut the boiler down (they were not happy with me) got rid of the steam , pried the safety valve open so it would work,

Removed all the pressure controls and the pigtails on the high limit and operating controls were completely plugged (black pigtails)

Made sure the piping that was going into the boiler for the controls was clean. Could not clean the old pigtails. All the supply houses were closed by now. Put the Pressure controls back on with 1/4 " nipples and 90s to make a water seal. Made sure the safety valve was opening. It was leaking some steam now.

Left the job was back there at 7:00am the next day with a new safety valve and brass pigtails and fittings.

Murphy's law if it can happen it will happen.

In 46 years it was the only time a boiler scared me.


The original call for the burner rumbling was given to me late in the day like 2:30 pm (we worked 7-3:30) and my boss was going to send me the next day.

Good thing he didn't because there could have easily been loss of life and a big hole in the roof.

Who knows maybe the safety would have opened at 50 or 75 psi.

Multiple failures are rare but do happen especially with neglected equipment.

realliveplumber

Residential relief valves are usually 3/4" tappings.

I had one, (hot water ) the relief valve was discharging. So the homeowner (engineer) tried to stop it by placing a 12" cinder block on the pin in the center of the relief valve, with hopes that it would not lift.

The more experience you have in the trade, the more stuff you see. And you learn not to discount too much. Because just when you say. "That cant happen) is when it does, and it will bite you right in the you know what.

ChrisJ

@realliveplumber

What kind of engineer was he?

realliveplumber

Im not sure. He worked for a Dept of Defense contractor. He was a regular customer of the shop I was working for, and he made sure you knew it.

He was the type that wouldnt leave you alone and talked your ear off the whole time you were working.

ScottSecor

@ethicalpaul I neglected to mention a few of the details that I still remember. I suspect the thermostat wiring was about seventy or eighty years old at the time. I'm guessing the rest of the original wiring, controls and the natural gas burner were at least that old.

ethicalpaul

Thanks Scott, I bet it was a beast