How to detect dry (or wet) steam

Jeff_44

Hello -



What are the indicators of wet steam in a one pipe system?



Conversely, what are the indicators of dry steam?

JStar

Steam

Wet steam will cause high fuel bills, spitting vents, uneven heat distribution, water hammer, and wild pressure fluctuations between cycles.



Dry steam will cost less to heat thge raiators and keep them hotter longer. Run times will be shorter, and pressures will hold for longer.

nicholas bonham-carter

Wet steam test

If you can unscrew the plug in the lower gauge cock on the sight glass, replace it with a small ball valve. When the boiler is steaming, close the lower gauge cock, and open the ball valve with a bucket underneath it. Only steam should come out. If water sprays out, the boiler is producing wet steam, and needs to be skimmed. Doing this also will keep the sight glass clean.

Even when the boiler is clean, a certain amount of water is going to jump up into the riser, and the purpose of a properly built header is to return those droplets back through the equalizer to the boiler at low velocity.--NBC

Jeff_44

Thanks

Will do as suggested with the ball valve. Our system runs quiet, no hammer, no spitting vents, and our bills are reasonable. But we do have some uneven heating from time to time in the rads. Have posted questions here about venting and have implemented suggestions about main vents, rad vents, etc. and all those were very helpful and improved the performance of the system. Also, the boiler runs on very low pressure. I installed a 0 - 3 lbs. gauge and the needle hovers around the 0 mark and never moves upward. The pressuretrol has never kicked in.

Rod

SightGlass Blowdown Fitting

Hi Jeff-

    The best setup I’ve seen for a Sight Glass blowdown is one that Gordo & Steamhead use. Gordo very kindly provided the information on where one can get this rather unique fitting.

    Also note the attached hose- This is a regular washing machine hose - (The one you use to hook up the water taps to the machine).  You cut the hose in half and you have a blow off hose and a spare;



Nh Yates & Co Inc

117 Church Ln Ste 3

Cockeysville, MD 21030

(410) 667-6300                                 

(800) 878-8181

Website:  http://www.nhyates.com/home.html

STEAM DOCTOR

Top valve

You also need to open the top valve. The idea behind this testing method is to see whats happening in the top of the boiler(i.e. where the steam is exiting). This test only tells you if there is wet steam in the boiler. If for example, the boiler is making dry steam but the near piping is bad(risers too short, bad pitch in header etc) then you can see dry steam from the valve and still have wet steam in the system.

Hap_Hazzard

Fluctuating Water Line

When you push a lot of water into a system, it can take a long time for it to return. If your water level gets unusually low during each heating cycle, then takes a long time to return to normal, that's a pretty good indicator of wet steam. The water level will normally dip during the heating cycle, but for every gallon of water that leaves as steam, you get 1,600 gallons, or about 214 cubic feet of steam. If it's carrying its own weight in water, it takes twice as much water out of the boiler. Depending on the size of your boiler and system, you might see the water line dip as much as an inch under normal operation, but usually less than a half an inch. It certainly shouldn't get anywhere near the bottom of the gauge glass or trip the low water cut-off to shut down the burners. If anything like that is happening--assuming your wet return isn't clogged--then you've got wet steam.

Jeff_44

OK -

This is all very helpful. As always, thanks to all of you who spend time and energy helping us out. From all that's been described, I think we're in good shape. On a heat cycle, the water in the glass may dip about an inch but that's it. I just don't ever see the pressure gage indicate any pressure. Once, I shut off all the rads and watch as the system built up a nice head of steam - I knew then that the gauge was working fine. For a long time the rads had too much venting and the main vents would almost never shut. Once I trimmed the rads back, the main vents worked fine. The only issue I have is that on occasion, a random rad won't get heat (or less heat) than the rest - the trouble is it's not always the same one so I feel like I'm chasing a ghost.



Thanks again for all your help.

nicholas bonham-carter

Venting conundrum

Can you elaborate on how the radiator venting prevented the main vents from closing?

It could have been a symptom of over pressure, in spite of what the gauge shows.--NBC

ChrisJ

Wet vs Dry

The way I started testing is a little different than the ways mentioned above and I'm not even sure if it works, but I think it does.



I take a small sample from my wet return after the system has been running for a bit and measure it using a TDS meter.  By measuring the total dissolved solids in the return water you should be able to tell if you have wet steam.  What I have found on my own system is a typical TDS level of around 1 or 2 PPM.  This is practically distilled water which suggests very little if any carry over from the boiler as my boiler water is usually around 300-500PPM.

Like I said, this is what I came up with and I really don't know if its an accurate test or not but it makes sense to me. 

Jeff_44

I had too much

venting on the rads. They were all filling full of steam before the mains. As I look back, what would happen is that the rads would fill with steam and once those air vents shut off, then the mains would fill with steam and then the main vents would shut off. I don't remember the exact details but it seems that it would take 20 - 30 minutes for the mains vents to get hot enough to close.



I changed from Vent Rite rad vents to Maid - o-Mist and got a variety of orifice sizes and then sized them accordingly and things came much better into balance. As stated before the odd thing is that there will be a rogue rad on occasion without heat. It's not always the same one but it's usually one of three or four. My quest is to bring ALL the rads into balance.

Techman

Wet Dry

If the steam at the sight glass was wet , would that be a bad thing? Due to the riser, header, drop header ?