The ULTIMATE steam skimming tool....

Mark Eatherton

http://heating.danfoss.com/PCMPDF/AVTB-RA_DS_VDBJD222.pdf

Connect to cold make up water. Fill and start fire side of boiler and open make up water. Sensor well would be immersed in discharge water and will maintain 190 degrees F., and maintain it throughout firing cycle, opening as temperature exceeds 190 and closing as temperature drops below 190 F.

This is a reverse acting non electric thermostatic control valve used in light commercial cooling (different temperature range) applications and industrial applications like mold injection cooling, compressor controls etc.

Remember me in your will Frank Wilsey

ME

EBEBRATT-Ed

In the "old days" when ac started water cooled package ac units were popular, very popular, York, Carrier, Trane all made them. Wheel one into a building locate it in the space or in a closet. No ductwork, wire, it condensate drain, city water and a place to dump the city water.

Used these valves to regulate the water flow. Johnson Controls (Penn) was the most popular. used refrigerant to operate the valve usually instead of temperature. City water was colder than tower water, 1.5gpm/ton would do the job 80deg discharge water

people would pipe the water outside to water there garden etc

Of course it was a big water waste and later outlawed in most locations

what my comments have to do with boiler skimming I have no Idea!!!!

Harvey Ramer

Looks like Hatterasguy (Brian) may be back under a new name again.

Mark Eatherton

Qing said:

The device might be able to maintain 190F feed water temperature for about 60 seconds.

Since the skim requirement is approximately five gallons per hour, the required energy is 5600 BTUH.

A typical steam boiler with 100K output would be 20X too large and would have to shutdown within one minute to prevent climbing over 212F at that flow rate.

This makes the device useless for the purpose intended.

Well, you are entitled to your mistaken opinion. These valves are proportional in their operation. It WILL maintain 190 degrees F so long as the boiler is firing and water is available for flow. It is trying to "cool" the heat source down to 190 degrees F. Extremely accurate flow control to maintain a given output temperature. It is a REVERSE acting TRV. Regardless of burner/vessel size, set up properly, it will maintain and control the discharge temperature of the boiler.

Brian.

ME

Mark Eatherton

OK, I have a minute and will do the math for you.

Let's assume a 100K btuH input, @ 80% efficient would be a net output of 80,000 btuH.

Let's assume the incoming ground water is 40 degrees F. We need to create a 150 degree F rise to get our discharge to 190 degrees F.

So 80,000 divided by 150 degree rise at 8.33 pounds per gallon and 60 minutes in an hour would equate to a flow rate of 1.06 GPM. The valve will modulate flow to maintain 190 degree F discharge, which should equal 1.06 GPM once it has stabilized its operation (minutes). To be clear, this device would have its capilliary sensing bulb immersed in the effluent coming out of the skim tap, meaning the vessel is open, and no where near generating the PRESSURE required to shut the boiler down.

My other assumption is that you understand that the steam boiler operates on pressure, and if there is no back pressure being built, the burner will not cycle off until it either generates pressure, or boils off the water to the point that the LWCO shuts the burner down.

On the water side, my assumption is that the boiler is completely full of water before firing, and as the water is heated, it expands.

A person would need to connect the inlet of the valve to a water source (drain cock on the DHW heater) and then its outlet would be connected to the boilers drain cock. We are not restricting the outlet, we are restricting the incoming water. As the heated water flows out of the boiler, the bulb senses the temperature and opens to cool the effluent down to 190 degrees F. No pressure to shut the boiler down. Proportional water flow to maintain 190 degrees F. Open vessel. Free flowing hot water, no steam pressure... No pressure shut down.

I should have been more clear in my initial comment.

Make sense Brian?

ME

Steamhead

And that, ladies and gentlemen, is why we think so highly of @Mark Eatherton . Also @Erin Holohan Haskell - she rules!

ChrisJ

Can you skim at a gallon per minute?

That may be a silly question, but everyone is always talking about skimming really slow etc.

Mark Eatherton

To my understanding, skimming is not about velocity, but is about causing oils, fluxes and other hydrocarbon products to float to the top of the water and to be washed out with the flow, with extremely hot water. This device would automatically compensate its flow based on the firing rate.

Until you leave the residential sector boiler size wise, it should work fine. And I am certain that Danfoss can make these valves in whatever size a person would need them for a given application.

ME

ChrisJ

@Steamhead
@gerry gill
When I first came on the forum, the big push was for slow skimming, the slower, the better. I believe, it was said this was to allow things to float on the surface of the water and to not cause any turbulence or stirring motion of the water.

A nice.......slow trickle into a bucket with as little movement as possible.




Am I remembering wrong?

RomanGK_26986764589

I remember @Hatterasguy offered a nice skimming tool. But I haven't heard from him in awhile. Is he still on HeatingHelp?

EBEBRATT-Ed

Cant picture this. 40 degree city water is pretty cold for a lot of places.

I am thinking a city water line feeding water to the boiler with a valve to control the water makeup to the boiler and thus the skimming speed.

City water also feeds the Danfoss valve who's sensor is in the skim water outlet. The outlet from the danfoss valve tees into the skim water downstream of the sensor to cool the skim water.

Is that what this is or am I screwed up??

Mark Eatherton

EBEBRATT-Ed said:

Cant picture this. 40 degree city water is pretty cold for a lot of places.

I am thinking a city water line feeding water to the boiler with a valve to control the water makeup to the boiler and thus the skimming speed.

City water also feeds the Danfoss valve who's sensor is in the skim water outlet. The outlet from the danfoss valve tees into the skim water downstream of the sensor to cool the skim water.

Is that what this is or am I screwed up??

You're close to correct Ed. And FWIW, the incoming water temperature really doesn't matter. I used 40 for worst case scenario. Water here in Denver common drops to 40 degrees F in the winter, and rises to around 60 in the summer. The valve will modulate to maintain the 190 (or whatever it is set for) discharge temperature. Remember, it is acting in the exact reverse function that we are used to. It is trying to cool the discharge by bringing water into the bottom of the boiler through the drain cock of the boiler, and will open up flow as the discharge exceeds 190 degrees F. It WON'T cool the water below its set point (190 F) because as the discharge temperature drops, the valve slows flow.

ME

Mark Eatherton

EBEBRATT-Ed said:

Cant picture this. 40 degree city water is pretty cold for a lot of places.

I am thinking a city water line feeding water to the boiler with a valve to control the water makeup to the boiler and thus the skimming speed.

City water also feeds the Danfoss valve who's sensor is in the skim water outlet. The outlet from the danfoss valve tees into the skim water downstream of the sensor to cool the skim water.

Is that what this is or am I screwed up??

Chris, it's all basic thermal mechanics. With a given BTUH output, if you flow the water fast enough, you can make the boiler really cold, in fact condensing. If you slow the flow down, the water discharge temperature will rise, and if it is too low, it will hit vaporization point, and you don't want that (rising steam bubbles) when you are floating oil. You want to keep the surface on top as smooth as possible to avoid mixing the oils back into the water, hence slow flow.

Essentially, this takes the human interface out of the equation. As a mechanic on the job, this will allow you to do other work (insulating pipes, etc) while the boiler is self skimming. I can't tell you how many hours I've spent sitting on a bucket, adjusting a ball valve in an attempt to keep the water as hot as possible, but avoiding the production of steam. Literally DAYS...

ME

gerry gill

ChrisJ said:

@Steamhead
@gerry gill
When I first came on the forum, the big push was for slow skimming, the slower, the better. I believe, it was said this was to allow things to float on the surface of the water and to not cause any turbulence or stirring motion of the water.

A nice.......slow trickle into a bucket with as little movement as possible.




Am I remembering wrong?

Really, it depends on the boiler upper nipple port passage..ECR small package steamers have to be skimmed at a high flow cause the end section opening is lower than the middle. Of course you could skim slow with a slotted plug like the one gentleman on the site came up with. I cant remember his name, sorry. But point i'm getting at is that 'it depends'.

Steamhead

RomanGK_26986764589 said:

I remember @Hatterasguy offered a nice skimming tool. But I haven't heard from him in awhile. Is he still on HeatingHelp?

Nope- Erin banned him for cause. He tried to come back as "Qing" and got banned again.