Wet Steam

PhilKulkarni · January 2

As suggested by @ethicalpaul, I have started this thread to steer the discussion from boiler pipe sizes and carryover to water quality induced wet steam.

Several standards are used to measure wet steam, among them IAPS Industrial Formulation that measures the dryness fraction of steam as a %. The ISO 5167 standard is used to correct steam flow rates by plugging in wetness correction ratios from a pressure table. Then there are inline instruments used to monitor steam dryness, a common one is a mass flow meter for that sets off an alarm when the liquid water content of steam drops below 80%.

I have attached a pic of the water level in the sight glass shortly after my main vents close. It falls another 1/2” towards the end of the heating cycle-typically 20-25mins. I have also shown my pressure reading and my 3” takeoff for my 63-03. I have one pipe steam with two headers.

Sorry but I am presently jet lagged; I will be glad to address any questions I might have missed.

How do I know I have wet steam? When steam reaches the end of my mains, my Bigmouth lets out two puffs of steam,3-5 secs each, before it closes shut. No water droplets fall out, but if I hold a sheet of paper close to this vent, I see several drops of water that are in the form of a mist. At the remotest rads. my #5 Moms will spit out water just before they shut off and a small amount after they shut off, meaning they open intermittently and will spit some water but for the most part remain closed. On my largest rad I have a #C Mom that seldom shuts off because the stat is satisfied before heating entirely, but the vent, not the rad, makes a gurgling sound.

I have a small rad in a bath that makes a gurgling sound which unfortunately has a 1/2” riser. It’s feed valve has a screw, not a knob, but is wide open. It is pitched but has a lot of water condensing in it. I am attributing this to wet steam.

Finally, I should comment about water quality. I drain the boiler to remove the crud because my vents get frequently clogged by rust particles and stop working. I get most of them to work by washing with vinegar but lose 1-2 each season. This is my 4th heating season with this boiler and I have skimmed it 6 times; 2x with washing soda. I had to skim it myself as my installer simply drained it once and added Surgex to it. When I drain the boiler for rust, I don’t see any oil on the rusty water in the pan or in the sight glass. @ethicalpauls video shows that when you have carryover the water level in the sightglass drops. In my case the drop is substantial despite the oversized takeoff.

By method of deduction/ elimination, if the water is leaving the boiler in such copious amounts, with no leaks,

where is it going? Wet steam?

ethicalpaul · January 2

is your water level at the designated mark when your boiler is at rest?

If so, you are experiencing carryover.

“Wet steam” isn’t a thing you can control in a residential boiler because all the steam created is by definition wet steam.

Your main vent behavior is just normal behavior. A small amount of condensed steam will escape just before it closes.

It is pitched but has a lot of water condensing in it. I am attributing this to wet steam.

all radiators condense a lot of water. If you hear gurgling it is due to something like a mid-pitched pipe or a partially closed or bad valve.

mattmia2 · January 3

or a takeoff that is too small or someone trying to use baseboard on 1 pipe steam.

unless your house is 212f+ eventually the steam is going to turn in to water somewhere

if your system is parallel flow, do the returns get hot before the runnounts and mains really start heating?

Eastman · January 3

To reiterate @ethicalpaul 's question slightly modified: does the water level eventually go back to where it was before the cycle? Or are you missing more and more water every cycle due to a leak?

PhilKulkarni · January 5

After draining the boiler to remove rust each month, I have to add 4-5 quarts of water. With each cycle I do lose some water but it only becomes evident after2-3 days of operation. I am estimating that I am drawing down 1+ quarts of rusty water and the rest is water loss from opening and closing of the main and rad vents. I have checked for leaks at the usual places but have yet to find one. During the installation of the boiler three years ago I had the installer check for leaks along the two mains and the wet returns.

I try to keep the boiler level 1” below the factory mark to minimize the carryover. This season, I have one Ventrite that is closed shut and I am using a #4 Mom in its place. I prefer the Ventrites because they have no problem closing with wet steam while the MOMs spit water even at 0.5 PSI when installed on small rads. They are ok on big rads since they seldom have to close.

@mattmia2, I have a combination of counterflow and parallel flow mains. I may not have entirely understood your question, but my wet returns are insulated and stay hot between cycles.

@ethicalpaul, you are right on point with the small rad that makes a gurgling sound. It has the steam inlet about a 1/4 distance from one end with a 4” horizontal runout towards the middle of the boiler. I had it pitched like all other rads, yesterday, however, I made it level to see if the water would drain back faster. I want to observe for a couple of days to see if it does. What is the right way to pitch it?

jesmed1 · January 5

I am not a steam expert, but the question of how much water a steam system should lose has been discussed before. You might find this thread helpful. Although the original question was about 2-pipe systems, some people gave answers about water loss in their 1-pipe systems.

https://forum.heatinghelp.com/discussion/160671/percent-of-water-lost-in-steam-boiler

ethicalpaul · January 5

Don't bother trying to pitch radiators, it doesn't matter. Just have them close to level. If interested, see my experiment where I pitched radiators the wrong way.

Here is the one pipe video, but I also did 2-pipe which you can find:

https://youtu.be/yFvba237kvQ

dabrakeman · January 5

@ethicalpaul I agree from your good experiment that the radiator doesn't have to pitch back to the inlet to avoid hammer, but, if it slightly pitches the other way would you have any concern over long term corrosion at the bottom of the radiator, much like a sag in a return pipe leads to through corrosion over time?

ethicalpaul · January 5

No because regardless of radiator pitch, radiators hold water at the bottom. The radiator castings have low spots at the bottom that are lower than the supply port, and additionally almost all supply ports have a reducing bushing on them resulting in more captured water.

Have you ever had a radiator not spill water out of it when you disconnect it?

Wet Steam

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