dead man 2 pipe design question

STEAM DOCTOR

Why would the dead men ever install a 2 pipe steam system with traps instead of orifices? With the orifice there are no moving parts and don't need to be repaired every 5 years? In addition if there are issues(such as maybe sludge blocking the orifice) you are able to do the work during the winter without concern of damage from other defective traps or orifices.

Pumpguy

I'm not

an expert in steam piping design for space heating, but I do have a theory. 



Orifices are dumb.  By that I mean they have just one setting and can't modulate.  In theory, you wouldn't need a trap if the steam supply equaled the condensing rate of the load.  But of course the load is constantly changing.  Sometimes you need more heat, sometimes less.  Traps are modulating valves that cope with this ever changing load.

MTC

I can't really answer why the dead men didn't use them...

but I do have similar feelings in general. I like the orifice system a lot.



But Pumpguy is right... the orifices are limited in some ways. This is where I think the beauty of those old orifice valves comes in... adjustable orifices - turn the valve to the next setting and you have the next size orifice, in effect. I'm not sure why this system wasn't more popular.



I would note, though, that steam traps aren't really any more "adjustable" than orifices. They let ALL the air out until steam hits them, then the close. They reopen briefly for condensate to exit, and close again when steam hits them. Their job is to keep the radiator FULL of steam, and empty of air and condensate. This does vary a bit, as the condensation rate of steam varies with the temperature differential of the room, how cold the iron is, etc. But for the most part in a properly operating system, this effect will be minor once the system is up and running for the year. Orifices let most of the air and all of the condensate out, keeping the radiator about 80% full of steam typically once the metal has heated up. It would, theoretically, take a little longer for a cold radiator to get heated up with the orifice system, but once hot, it should produce a more even, consistent heat throughout the building with less fluctuations.



If you assume some important things - pressure will remain low and constant (no knuckleheads turning it up) being the key one, an orifice system IS moderately adjustable. You don't have to adjust the orifices, you can size them to about 80% of EDR (so that it will always condense fast enough and never blow much through to the return), and then from there you can use the valve to throttle it down lower. This also, in theory, allows you to replace your boiler with the next smaller size, but that's another discussion... Problems with orifices clogging up are easily solved, and you know exactly where the problem is, unlike traps that cause the problems elsewhere in the system, not at the failure.



I think a big part of it, at least today, is that there's no money to be made in selling orifices. That's why Tunstall is the only one out there selling them. Steam traps are big, repeating business. Couple that with the "this is how its always been done" mentality (which is good to a degree... you should always question WHY you're doing something different than history, but that doesn't mean you don't question it), and orifices have a very small following.



The simplicity of a gravity return 2 pipe system with orifices and water seal loops instead of F&T traps is definitely appealing, as long as you keep the knuckleheads away from the boiler controls...



Unfortunately, most of the systems I work on in the buildings I manage are all muddled up with moving parts - condensate and boiler feed pumps, rad traps, F&T traps everywhere. I'm in the process of replacing all of the rad traps and the guts of all the F&T traps in one large building now. I tried to sell the owner on orifices, but b/c all the sales reps didn't know what they were, or had cryptic "bad feelings about them," he wouldn't go for it. Instead he's spending a fortune on traps.



Thinking about trying to sell him on the orifices after the fact, as a way to balance the system better, and greatly prolong the life of his huge investment in new trap elements. If they do wear out primarily based on open/close cycles, the orifices should make them last nearly forever. Of course they'll probably get dirt buildup and stuff in there that will make them not seal properly after a while, since they'll never actually do anything...

Pumpguy

Thanks

for your excellent write up.  Helps me understand a little better. 



Another orifice type steam trap is STEAMGARD.  They are based in Vernon Hills, Illinois.

Jamie Hall

A couple of thoughts...

Perhaps there were reasons to use simple thermostatic traps, such as the Hoffman No. 8 -- of which I have quite a number.



First, they were used as the crossover traps from the mains to the dry returns, which accomplished venting the mains in a terrific hurry (they pass a lot of air!).  It was (and remains) a dead simple way to vent the mains.  Condensate in such a system was taken care of by drips to wet returns.  Again, dead simple.



Second, such traps are astonishingly reliable and long-lived, provided they are not abused (that is, either over pressured or subjected to back pressure).  I have heard that they have an expected life on the order of a decade -- but the ones in my system, with two exceptions (see below), have lasted 80 years so far.



Third, the anaysis of the big benefit of the orifice system -- simplicity -- is certainly valid, but the same objective can be accomplished in a properly set up system using throttling valves (which mine has -- and which is why the two failed traps aren't a problem).  But there is a big benefit to the throttling valves: They are easier to specifiy and instal.  Believe it or not, the dead men needed to work to a budget, too, and if a valve was going to be used anyway, why not one which could be adjusted to fit the supply to the radiator?



A related benefit to the valves is that if it turns out that there is a cold room, and the radiator is demanding relatively more steam (or, conversely, a warm room and less steam) it is easy to tweak.



Again, with traps if the system does run over pressure, the little seals won't get blown out.



And last -- some systems used a variety of ingenious contraptions to protect the boiler from excess pressure by pressurizing the returns with steam if the pressure got too high, thus returning the condensate to the boiler.  But that system needed the traps.



Just a few thoughts...

SWEI

throttling valves

does anyone still make these?

Jamie Hall

Haven't a clue...

Mine are the original Hoffman valves.  Actually a rather complex, but very elegant design -- there are actually two sleeves, one within the other.  One of them you sort of take the valve partly apart to set -- that one sets the absolute maximum.  Then the other turns from off to on.  Neat.  Beautifully made, like so much of the old stuff.

vaporvac

Trane similar

My original Trane valves are similar. too bad all my rads don't have them...I'd love to find something similar.

gerry gill

yes, SWEI

http://www.mepcollc.com/steamspec/regv.htm



The two on the right side. I would answer this threads question but i type with the one finger search and destroy method, and i'm just to tired.

Steamhead

The reason orifices weren't as popular

is that Frederic Tudor had patented the Orifice system, and no one wanted to pay him royalties.



However, Mr. Tudor did not control this patent in Europe, so his system became popular there:



http://www.heatinghelp.com/article/163/Older-Steam-Heating-Systems/1302/European-Heating-Systems-circa-1907

SWEI

Thanks, Gerry

Looks like the SWRF B has an adjustable limiting screw/orifice which the SWRF C lacks?

Dave in QCA

A Much Older Throttling Valve from Dunham,

Here is a much older version from Dunham.



Also, early on they used standard valves.  On partial steam cycles, even distrubution was an inherent problem.  They solved this with regulator plates that were simply orifices.  They still used traps, so I would assume that the orifices were sized at somewhere from 4-8 oz., but I have not been able to find any information regarding their sizing.

Jamie Hall

That'll do it,

every time!

jumper

flexitaulic ?

I think some company, maybe Flexitaulic, promoted orifice traps in the seventies. They called them diaphragm traps according to my recollection. There had more than one disc so perhaps labyrinth is a better term. I agree with MTC that there's no profit in supporting a simple device that probably lasts too long.

This site shows terminals with dampers to control convection. Seems to me a cheaper way to control heat output. A labyrinth can let water drain but restrict steam to a small amount. You still must get the air out somewhere some way. In my experience common radiator traps are not maintained and that gives steam a bad reputation.

PMJ

My experience is

that if the two pipe pressure is low enough (basically atmospheric vapor) then nothing is needed at all at the return pipe of the radiator. Isn't the only time you might need something to keep steam out of the return is if the radiator is completely full of steam? And when is that? Almost never. It would have to be on a day when it is so cold you have reached the max demand the system was designed for and everything was maxed out. Especially with big older systems designed for "open window" operation in the house when originally there was no insulation you shouldn't ever be getting close to filling them today - I don't.

Most of my rads never get past 3/4 full. There are a few first floor really small ones in a lavatory and front foyer that will fill - I throttle those way down and even have put a trap on one, but in 75% of my rads I don't think anything is really needed at all.

Dave in QCA

Thoughts on the subject

First, thank you Jamie and MTC for some very thoughtful comments on this subject.  I think you pretty much covered the topic, but after grinding on this for a few days I have some comments too.



Back to the original question, It seems to me that there were two main camps in the vapor heating business.  One with traps and the other without.  Keep in mind this was the great era of inventions.  Within a very short span of time the world was introduced to electric lights, radio, cars, skyscrapers, washing machines, indoor bathrooms, flush toilets, automatic vapor heating... the list is almost endless.   So, one line of vapor system inventors decided to work with the steam trap.  Remember, the thermostatic trap was invented by Mapes in 1903 and first produced and marketed by C.A. Dunham around 1907.  This enabled steam heat to function in a new an desirable way.  Not having a hissing spitting radiator vent was an AMAZING advantage according to the companies selling vapor systems.   On the orifice side of the competition, there were not too many (if any) that used plate orifices like we think of today, but rather they used various types of orifice or regulating devices that were incorporated into the design of the valve.  The Moline system, for example, used a cylinder within the valve with a series of very narrow slits.



It seems to me that major differences between the orifice and trapped systems lies in the other system requirements or parameters of the system.  In a trapped system, steam is kept out of the returns by the trap.  It works just as well at 2 psi as it does at 4 oz.   However, because of issues with the B dimension, 2 psi will usually cause all kinds of problem because of water backing up in the returns, so that had to be dealt with.  Dunham used the air eliminator on vapor systems and included the return trap for systems running over 8 oz.  Hoffman developed the differential loop and also a return trap.  There was the alternating receiver as well.  These dealt with the problem that was caused by the flexibility of the traps that worked just as well at 2 psi or higher as they did at 8 oz vapor. 



On the orifice side of the game, pressure control was of paramount importance!  The beauty of the orifice systems was described quite well by Moline in the marketing brochure.  They claimed that there were ZERO moving parts and nothing to ever wear out.  Well, it was a pretty slick system, but zero moving parts was an exaggeration.  The air exhauster was a check valve device that did have a moving part or two in it. Its proper function was to keep air from reentering the system as the boiler cooled.  There were also valve packings to tend to, which are pretty important on a system that requires absolute air tightness.   But, all of that aside, the most important issue in all orificed systems was that of controlling the pressure at no more than 6-8 oz.  At this pressure, the amount of vapor entering the radiator was slightly less than what the radiator was capable of condensing.  As a result, steam was prevented from entering the return lines.  The various systems developed all sorts of very sensitive devices to control the draft on a coal boiler.   Think of how we struggle today to find an accurate vaporstat ---  if such a thing even exists.  Back in the day, they were building devices capable of moving large iron draft doors and check dampers, and doing it accurately within an ounce.  Pretty incredible I think!  



And then... Dunham, perhaps the other trap folks too, began to realize that they had some problems with distribution.  Dunham, at a very early date had started to offer an electric room thermostat wired in series with a very accurate vaporstat.  They controlled an electric damper motor that opened and closed the draft and check dampers.  This provided an on/off type operation of a coal boiler.  The problem that they encountered, which I also encountered in my 1909 Dunham system, was that of very uneven distribution on a partial steam cycle.  Given the fact that most, (90% of all cycles through the season,) are partial steam cycles, the operation of the system would result in some radiators being 50% heated while others heated about 5%.  In a one pipe system, balancing is established by sizing the vents and we all know the problems caused by overly aggressive radiator vents.  Well, now consider the fact that the Dunham traps have an seat opening in them of about 5/16".  That's way too much venting and explains the problems in balance.   Dunham dealt with this by introducing "regulating plates" for the valves.   I have installed Tunstall orifices in my Dunham system and the result is perfect distribution.  Of course, Dunham also introduced regulating valves similar to Hoffman and Trane's. 



But my system also has traps, why?  Well, it was mostly a result of tackling one problem at a time.  The traps were service and repaired first.  Oh, and that makes me think.  I had a few traps that had not been touched since 1909.  They needed new disks, needless to say.  But, there were many other traps, 1E models, that I would guess were installed 50 years ago that still worked just fine.  The current buzz is that traps will probably last about 5 years.  I think that is a gross under-exaggeration.  Even in a large institutional setting where steam is up 24/7, traps last much longer than that!  When you look at a vapor heating system, you have to remember that steam actually hits those traps on a very rare occasion.  Most of the time, the traps are just sitting there wide open. 



So, traps or orifices?  It depended on the company and the patents they held.  Everyone was trying to build a better mousetrap and then to market it as the very best available.  I think the variety is amazing and it attests to human ingenuity.

MTC

Thanks Dave!

Great write-up of the history of this whole phenomenon. I don't know much of that stuff, just a good bit of theory and a little practice on the buildings I manage. Its always good to hear how things got to be the way they are now.



I am particularly interested in all of this right now, as I spent the day replacing the guts of every F&T trap and every radiator trap in a 7 unit building today. Was quite the project, and hoping that this will help balance out the building better, and allow us to turn down the timer setting a little bit more on the heat timer. Insulating the mains already allowed for a 1.5 letters reduction (I figure this works out to 15-20% by itself). Less tenant complaints and service calls where you basically can't do anything b/c who knows which trap failure is causing the problem - priceless.



Anyway, I remain a fan of the orifice system, whether it be plates in the radiator unions, or valves that incorporate an orifice type setup. I imagine that with this setup in a properly balanced system, even today's much less robustly built traps would last nearly forever, should you choose to have both. This alone justifies the cost/work of the orifices, even without considering the ability to balance the system perfectly, etc.