Question on pressure drop for 1 pipe vs 2 pipe system

vapor1

Reading TLAOSH - Revisited, and on page 25, I learned to estimate steam pressure drop at 1 oz per 100 ft of pipe run for a 1 pipe system, and 2 oz / 100 ft for 2 pipe. Is this difference a result of pipe sizing, or is there something else? I read later in the book that in the 1 pipe system, steam would be sharing space with counterflow condensate, and I would expect more resistance, not less.

Also, on page 27 using a Pressuretrol the system in the example is set to operate between 1/2 psig and 1 1/2 psig. Yet with a Vaporstat, the same system is set to 4 oz to 10 oz. Why the difference?

This newbie homeowner thanks you for any help. Stay safe.

Jamie Hall

Those are design guidelines, and they don't necessarily show what's actually happening.

The restriction to flow in a counterflow one pipe system should be minimal, assuming that the pipe has enough slope to allow the condensate to drain freely (otherwise it's likely to hammer). There is remarkably little condensate in terms of volume -- the ratio of volume of steam to volume of condensate is about 1700 to 1!

Vapour systems were and are designed to operate at much lower pressures than more conventional two pipe systems. In general, the idea was that only enough steam would reach the radiators to condense there, and no steam would pass -- the traps are there, and necessary, to make this works the way it should. But in order to do that, they need to be controlled at the low pressures -- typically less than 7 to 8 ounces per square inch. Therefore, in modern systems, the need for a vapourstat which works at those pressures, rather than a pressuretrol which becomes unreliable below a pound or so.

One can run a more ordinary system on the low pressures; if anything, it will probably run better. But is it enough better to justify the more expensive vapourstat? Good question. On the other hand, a system designed as a vapour system must run on the low pressures.

Don't know if this helps...

vapor1

Yes, and thank you for the reply, Jamie Hall. I still don't see why the 2 pipe pressure drop to the radiator would be twice the 1 pipe.

DanHolohan

As I recall, the 2 oz/100 feet of run was meant for the much larger buildings. It allowed for a smaller pipe, which saved money on the installation. The vapor systems did just the opposite. Those pipes are larger than what you'd see in a typical 1-pipe system. The goal there was to get the pressure drop even lower. I hope that helps.

PMJ

I can verify that vapor systems were designed to work at very low pressures. My 1000EDR system never sees over 2 inches of water pressure at the header, well below vaporstat territory. The only thing I know of that could produce pressures higher than that in these systems is to fill the radiation all the way up with steam or pretty close to it. My question is why on earth would anyone ever want to do that?

vapor1

Thank you for your reply, DanHolohan. And thank you for your book - count me a fan.

I think our system is, or at least was, a vapor system because of the Webster 0023 Vent Trap (with the stainless ball removed) installed at the ends of the return mains. Does your reply mean that 1 oz/100 feet might be OK to use instead of 2 oz/100 feet in figuring the pressure drop at the furthest convector?

DanHolohan

Yes. And thanks!

vapor1

Wow, PMJ. That's only a little over 1 oz/square inch. Do you know the net BTU/hr for your boiler? Do you control it by pressure, or does it normally just shut off when the thermostat is satisfied? Does it draw a vacuum? Does it heat evenly?

Our boiler is set up on a Pressuretrol (.5 PSIG cut in and 1.5 PSIG cut out), but that normally does not come into play. Its 182,300 BTU/hr net cannot generate more than about 1/2 PSIG for the 947 square ft. EDR. But eventually it does heat the house. Detroit climate.

ChrisJ

@vapor1
I have a single pipe system with 392sqft of radiation.

I can heat all of the radiators all the way across at around 0.75 - 1"WC. This only happens if I'm doing a recovery though, normally the radiators would never heat for that long.

The radiation and venting is what limits my pressure. The boiler just produces everything it can and the radiators keep up with production.

jumper

Controversy between undersized boiler steaming non-stop all winter versus conventionally sized on-off operation? Certainly some operators believed that they saved fuel after replacing boiler with multiple small ones. I speculate that strategy especially applies to one pipe steam because it is wasteful to raise steam to pump air.

ChrisJ said:

@vapor1
I have a single pipe system with 392sqft of radiation.

I can heat all of the radiators all the way across at around 0.75 - 1"WC. This only happens if I'm doing a recovery though, normally the radiators would never heat for that long.

The radiation and venting is what limits my pressure. The boiler just produces everything it can and the radiators keep up with production.

PMJ

ChrisJ said:

@vapor1
I have a single pipe system with 392sqft of radiation.

I can heat all of the radiators all the way across at around 0.75 - 1"WC. This only happens if I'm doing a recovery though, normally the radiators would never heat for that long.

The radiation and venting is what limits my pressure. The boiler just produces everything it can and the radiators keep up with production.

Your Ecosteam does control run time doesn't it? Based on an ongoing calculation of what is needed for the conditions I think. That would prevent running long enough to generate any pressure for sure as filled radiation is never needed to satisfy the demand.

All that is required for no pressure operation is not filled radiators. A boiler too small to ever do that under any circumstances is one way to get there. Ecosteam doesn't care how big the boiler is and would provide ultra low pressure operation anyway.

ChrisJ

PMJ said:

ChrisJ said:

@vapor1
I have a single pipe system with 392sqft of radiation.

I can heat all of the radiators all the way across at around 0.75 - 1"WC. This only happens if I'm doing a recovery though, normally the radiators would never heat for that long.

The radiation and venting is what limits my pressure. The boiler just produces everything it can and the radiators keep up with production.

Your Ecosteam does control run time doesn't it? Based on an ongoing calculation of what is needed for the conditions I think. That would prevent running long enough to generate any pressure for sure as filled radiation is never needed to satisfy the demand.

All that is required for no pressure operation is not filled radiators. A boiler too small to ever do that under any circumstances is one way to get there. Ecosteam doesn't care how big the boiler is and would provide ultra low pressure operation anyway.

I can do a very large recovery without stopping, fill my radiators completely and not exceed 1" WC.

The Ecosteam is used in my case for comfort, not to limit pressure. It would however, in my case force a 10 minute rest if I hit 8"WC due to the TRV's being shut allowing things to stabilize and radiators to dissipate some heat. This hasn't happened yet but things are in place for it.

I suppose in normal use it could limit pressure by forcing shorter cycles, but that can only go so far in my opinion especially when it's really cold out. Also, it in theory reduces efficiency.

PMJ

ChrisJ said:

PMJ said:

ChrisJ said:

@vapor1
I have a single pipe system with 392sqft of radiation.

I can heat all of the radiators all the way across at around 0.75 - 1"WC. This only happens if I'm doing a recovery though, normally the radiators would never heat for that long.

The radiation and venting is what limits my pressure. The boiler just produces everything it can and the radiators keep up with production.

Your Ecosteam does control run time doesn't it? Based on an ongoing calculation of what is needed for the conditions I think. That would prevent running long enough to generate any pressure for sure as filled radiation is never needed to satisfy the demand.

All that is required for no pressure operation is not filled radiators. A boiler too small to ever do that under any circumstances is one way to get there. Ecosteam doesn't care how big the boiler is and would provide ultra low pressure operation anyway.

I can do a very large recovery without stopping, fill my radiators completely and not exceed 1" WC.

The Ecosteam is used in my case for comfort, not to limit pressure. It would however, in my case force a 10 minute rest if I hit 8"WC due to the TRV's being shut allowing things to stabilize and radiators to dissipate some heat. This hasn't happened yet but things are in place for it.

I suppose in normal use it could limit pressure by forcing shorter cycles, but that can only go so far in my opinion especially when it's really cold out. Also, it in theory reduces efficiency.

I said that one way to run without pressure is to size a boiler small enough to be incapable of filling enough to pressurize. I think that is what is usually described as "perfectly sized" around here. I want one much bigger than that or I couldn't make as good use of vacuum.
I bring up Ecosteam because in doing what it does it also limits run time based on demand. Better comfort comes from not putting more steam out there than is needed for the conditions. No matter how big the boiler is an Ecosteam control ( or one that limits the duration of straight run times) will effectively eliminate pressure while still heating the building. It won't ever put enough steam out there to fill and pressurize because that much steam is never needed.

Your boiler is apparently small enough that it won't make pressure anyway. Great. I'm just pointing out that if someone had your system with a much bigger boiler and the Ecosteam there wouldn't be any pressure either.

PMJ

vapor1 said:

Wow, PMJ. That's only a little over 1 oz/square inch. Do you know the net BTU/hr for your boiler? Do you control it by pressure, or does it normally just shut off when the thermostat is satisfied? Does it draw a vacuum? Does it heat evenly?

Our boiler is set up on a Pressuretrol (.5 PSIG cut in and 1.5 PSIG cut out), but that normally does not come into play. Its 182,300 BTU/hr net cannot generate more than about 1/2 PSIG for the 947 square ft. EDR. But eventually it does heat the house. Detroit climate.

Right @vapor1 , that's all it is. Yes the heat is very even. How even the heat is is directly related to how wide a temperature range the rads themselves swing through. Obviously in the original design radiator temperatures were pretty steady because nothing could change quickly! Since you couldn't just turn the boiler off like we do now, the rads had to be warm all the time but most of the time not very full at all.

Partially filled radiators condensing steam are actually themselves slightly below atmospheric and pulling steam from the mains, so very little pressure at the header is required to move enough steam to heat. Beyond that, these systems when run continuously as in the original design could never have had filled radiators, or the occupants would have been roasted. When I realized this( that there was tons of extra installed radiation by design), I set about finding a control scheme using intermittent fire that would keep radiators partially filled and continuously warm, more like the original setup. Yes, I do let the system go into vacuum between burns which has tremendous positive effects on overall performance and eveness of the heat; but even when I am pushing out air no more than the 2 inches water is required for that. And all the air from the whole system goes out through one 1/2"NPT port in my garage.

I too am a big fan of Dan's books (I think I have them all). But the standard vaporstat conrol system never made any sense to me. I never understood why the change from coal to intermittent fire required leaving the ultra low pressure zone these systems were designed for and going to a cut in/cut out pressure zone dramatically higher. I mean after all everyone does seem to agree that pressure is bad!

So unfortunately running always at much lower pressures and much more even radiator conditions requires a custom control. It isn't all that complicated but this market has never supported anything beyond the standard vaporstat control. It is assumed to be, well, "good enough". Yes, if you install a small enough boiler it will heat most of the time not tripping the vaporstat at all. But in my view that alone is not nearly as good as steam can be.

I've posted a lot about it on this site if you search around. I'm always available for further discussion too either online here or PM if you wish.

motoguy128

With one pipe, you can stall a small enough boiler and control the balance with smaller air vents such that it will heat evenly, even if it lacks the output to fully heat the radiators.

This is good an bad. By not fully heating radiators and cycling, You have less stored heat in the radiators between cycles And less radiated surface. However, it heats slower, so more time is spent actively heating and it doesn’t overshoot. Plus the boiler is smaller, so less standby losses since it runs longer and flue and jacket are smaller.

That being said, my system runs at 0oz. Nothing. No needle movement on a 10oz gauge. About 100’ of header.

ChrisJ

> @motoguy128 said:
> With one pipe, you can stall a small enough boiler and control the balance with smaller air vents such that it will heat evenly, even if it lacks the output to fully heat the radiators.
>
> This is good an bad. By not fully heating radiators and cycling, You have less stored heat in the radiators between cycles And less radiated surface. However, it heats slower, so more time is spent actively heating and it doesn’t overshoot. Plus the boiler is smaller, so less standby losses since it runs longer and flue and jacket are smaller.
>
> That being said, my system runs at 0oz. Nothing. No needle movement on a 10oz gauge. About 100’ of header.

Mine doesn't show anything with a gauge on a pigtail either. But there's certainly pressure there.

Jamie Hall

There are several of us who run very low pressure vapour systems -- with varying control strategies, and varying relationships of boiler size to radiation. So long as the pressure is kept down, however you want to do it, things work stunningly well.

A couple of points. First, remember that the pipe sizing guide we started out here is for design and installation purposes -- and is not meant to be a guide to what pressure you should target to run your system at. For that one wants to run as low as will get the job done.

Second, if one is using a pressure control as your control (not the safety control -- that's a different device), there is a very simple way to decide what it should be set at -- and at the same time to ensure that your main venting is adequate. Using a low pressure gauge (essential) start from a cold start. When the boiler comes up to steam, you should see a very slight rise in pressure -- say to an ounce or so (some will be less, some slightly more) and then it should stabilize at that pressure or at worst increase only slightly and slowly for a long time. In fact, until most of the radiation is accepting as much steam as it can condense (you may have to set your thermostat really high to make it do this). At that point, you will note the pressure will start to rise significantly faster -- and that is the point where you want to shut off the burner (plus perhaps an ounce or two for lack of consistency). The only caution is to also make sure the shut off pressure is low enough to not activate some of the other overpressure safeguards which are found on some vapour systems, such as a Hoffman Differential Loop (typically less than 7 ounces). Some boiler and radiation combinations may never get to that point, which is OK so long as the building heats satisfactorily.

It is also worth noting that in all of this we are actually talking about differential pressure in the system, not either gauge nor absolute. Since in general in a vapour system the main vent is always wide open, this usually is distinction without a difference, but if the system is operating under vacuum, it does make a difference: the header pressure to return differential should never be allowed to exceed that 6 to 8 ounces.

motoguy128

ChrisJ said:

> @motoguy128 said:

> With one pipe, you can stall a small enough boiler and control the balance with smaller air vents such that it will heat evenly, even if it lacks the output to fully heat the radiators.

>

> This is good an bad. By not fully heating radiators and cycling, You have less stored heat in the radiators between cycles And less radiated surface. However, it heats slower, so more time is spent actively heating and it doesn’t overshoot. Plus the boiler is smaller, so less standby losses since it runs longer and flue and jacket are smaller.

>

> That being said, my system runs at 0oz. Nothing. No needle movement on a 10oz gauge. About 100’ of header.



Mine doesn't show anything with a gauge on a pigtail either. But there's certainly pressure there.

Keep in mind I have a 10oz range gauge with 0.2” increments. MY last boiler would run at 1-2oz when firing. But this new/salvaged boiler is much smaller and with a proper drop header and equalizer. 200k input on a system with about 500-700EDR depending on TRV’s opening.

PMJ

I hope we can all accept that these vapor systems were all built with excess radiation by design; and if so we must then accept that the radiation never needs to be full to heat the structure. Therefore there never needs to be any pressure - certainly not enough to do any control with. Ultra low pressure operation can be achieved by installing a boiler that simply doesn't have the capacity to fill the system, yet will still have the capacity to do the job. That is a pretty expensive solution for someone that already owns a bigger boiler. It can also be achieved with a boiler of any size simply by controlling the burns and spreading them out in smaller more even pieces. There is no efficiency cost to doing this. In fact I will argue that coupled with natural vacuum the bigger boiler cycling more often is more efficient than the small boiler pushing air every cycle it runs. The heat with vacuum is surely a lot more even, this I do know for sure. I imagine I will get an argument about all this, but sadly very few have actually experienced life in vacuum. And why more has not been done with this second control approach over all these years remains a mystery to me. Much of the angst I read on these pages about pressure and short cycling could very easily be eliminated.



.

Jamie Hall

Ah... perhaps Cedric is unique. Wouldn't surprise me. But... on a really cold, windy day, he runs almost continuously (the thermostat never stops calling) and all the radiation is operating at full temperature all the way across.

So... be just a little careful with the assumption that "these vapor systems were all built with excess radiation by design" as it may not be true. It probably is true for a structure which was originally built and intended for four season use. It may not be true for a structure which was not intended for four season use initially, but has been repurposed, if you will, for that.

PMJ

Jamie Hall said:

Ah... perhaps Cedric is unique. Wouldn't surprise me. But... on a really cold, windy day, he runs almost continuously (the thermostat never stops calling) and all the radiation is operating at full temperature all the way across.

So... be just a little careful with the assumption that "these vapor systems were all built with excess radiation by design" as it may not be true. It probably is true for a structure which was originally built and intended for four season use. It may not be true for a structure which was not intended for four season use initially, but has been repurposed, if you will, for that.

I think they were designed that way. I don't see how the ultra low pressure damper control devices could possibly work with the rapidly changing pressures associated with radiators hitting full. I think the coal boilers were huge and expected to operate in the middle of the range. Likewise the radiators. Nothing else makes sense from a control standpoint.

My house was built in the 20's. High end system in a high end neighborhood. I'm guessing engineered as recommended. The house is basically original still with no insulation and the radiation clearly way more than needed. You say hot all the way across and boiler maxed out. Radiators aren't full until serious pressure starts. Mine approach hot all the way across at the top in very cold weather, but they are not nearly full all the way down - no where near enough to make pressure. I'd guess half - just like the capacity of my boiler that is needed for days like that.

Jamie Hall

Drop by some day on a -10 day with a 20 mph wind and I'll show you maxed out...

PMJ

Jamie Hall said:

Drop by some day on a -10 day with a 20 mph wind and I'll show you maxed out...

That would be great...seeing Cedric in full stride!

Jamie Hall

You'd be welcome to come! Place has an interesting history -- Cedric's predecessor (an H. B. Smith which would have done justice to the Titanic) and the radiators and all were installed in 1930, when the place was not open in the winter at all -- and the whole show sized for, I would guess, no lower than perhaps 25. Storm windows have been added, and some insulation, and now it's open year round. Kind of gives one the idea -- from the heating standpoint -- of how oversize some of the original installations were, which is, of course, exactly your point, @PMJ !

ChrisJ

> @Jamie Hall said:
> You'd be welcome to come! Place has an interesting history -- Cedric's predecessor (an H. B. Smith which would have done justice to the Titanic) and the radiators and all were installed in 1930, when the place was not open in the winter at all -- and the whole show sized for, I would guess, no lower than perhaps 25. Storm windows have been added, and some insulation, and now it's open year round. Kind of gives one the idea -- from the heating standpoint -- of how oversize some of the original installations were, which is, of course, exactly your point, @PMJ !

I mean,
To be fair the Titanic had boilers that were 15 1/2 feet in diameter and 20 feet long.

I'm thinking you're exaggerating.

Jamie Hall

What? Me exaggerate? Well... yeah. But the thing was … large. The steam drum (separate) hangs from the ceiling about 7 feet off the floor, and the boiler base was in a shallow pit. About 4 feet wide, and perhaps 6 feet long. Charles piped Cedric to use the old steam drum as a second header -- so super dry steam.

The thing was fired by a Quiet May running at 5 gallons per hour... efficiency was not a real big thing back then.

ChrisJ

> @Jamie Hall said:
> What? Me exaggerate? Well... yeah. But the thing was … large. The steam drum (separate) hangs from the ceiling about 7 feet off the floor, and the boiler base was in a shallow pit. About 4 feet wide, and perhaps 6 feet long. Charles piped Cedric to use the old steam drum as a second header -- so super dry steam.
>
> The thing was fired by a Quiet May running at 5 gallons per hour... efficiency was not a real big thing back then.

I honestly don't believe that.
If you look at any decent steam boiler even drum 100+ years ago they appear to be designed entirely around efficiency.

Look at the Titanics boilers and it's Quadruple expansion setup running below atmosphere.

I believe efficiency was a very big thing.

Jamie Hall

At least for marine engines, quite right -- they were amazingly good. Not that much worse, if any, than later steam turbines (which is why many if not all Liberty ships used them). Plus, they ran at speeds well suited to ship's propellers -- which turbines don't. Hence the reduction gears or turbo-electric drives (a surprising number of capital ships). And thanks to the seawater condensers, the low pressure cylinders (or, in the case of turbines, low pressure turbines) exhausted at quite high vacuums (although a curious side note -- perhaps trivial! -- since they were seawater, the available power dropped in warmer water!).

PMJ

Jamie Hall said:

You'd be welcome to come! Place has an interesting history -- Cedric's predecessor (an H. B. Smith which would have done justice to the Titanic) and the radiators and all were installed in 1930, when the place was not open in the winter at all -- and the whole show sized for, I would guess, no lower than perhaps 25. Storm windows have been added, and some insulation, and now it's open year round. Kind of gives one the idea -- from the heating standpoint -- of how oversize some of the original installations were, which is, of course, exactly your point, @PMJ !

Expect that I won't let you wiggle out of this invitation @Jamie Hall - no matter what I might write in these pages between now and when I come calling. I am sure I would enjoy a visit indeed. Still working full time with no interest in stopping, but I do get East occasionally.

Anything expected to last needs to be built with extra and lope along sufficiently below its max capacity. Call it comfortably oversized. The expectation that anything needs to last very long seems to have been removed without much(any) protest in a short time. No one even mentions the ongoing cost of the equipment itself anymore which has skyrocketed in annual terms.

Ah well, I plan to finish out my days surrounded by as much of the good stuff as I can. Slate, copper, and steam....life is pretty good.

jumper

Jamie Hall said:

At least for marine engines, quite right -- they were amazingly good. Not that much worse, if any, than later steam turbines (which is why many if not all Liberty ships used them). Plus, they ran at speeds well suited to ship's propellers -- which turbines don't. Hence the reduction gears or turbo-electric drives (a surprising number of capital ships). And thanks to the seawater condensers, the low pressure cylinders (or, in the case of turbines, low pressure turbines) exhausted at quite high vacuums (although a curious side note -- perhaps trivial! -- since they were seawater, the available power dropped in warmer water!).

Marine propulsion history is a fascinating subject. Before WW II some steam boats were converted to Diesel. You had to cut up the boiler and disassemble the engine to remove them. Then the Diesel was assembled in place. Those Diesels were direct drive like the steam engines they replaced. You could go farther with Diesel but it was far more difficult to repair in the middle of nowhere.

I think that the last marine steam engines were unaflows installed in WW II baby aircraft carriers.Were any of those hundred engines salvaged when the boats were scrapped? If you don't need to vary speed or power unaflows are supposed to be at least as efficient as complicated multiple expansion steam engines. Opposed piston unaflow is claimed to be even more efficient.

PerryHolzman

Concerning Marine Propulsion... and the "reuse" of its equipment.

I was a steam propulsion Machinist Mate for 5 years (MM2) on a 1979 auxiliary supply ship USS Savannah AOR-4. We had Three 600 PSI Marine Type D boilers, 2 steam turbine 16,000 Shaft horsepower engines, and four 2000 KW SSTGs (Ships Service Turbo Generators - a steam turbine driven electrical generator with its own condenser, circ water and condensate pump set).

I have been in a lot of other ships (including old commercial) as well on tours.

The Tripple Expansion engines were highly efficient for their day, and we have a local example on display in the Manitowoc Wisconsin Maritime Museum.

The SS Badger - A car ferry that still operates between Manitowoc Wisconsin and Ludington Michigan spring to fall has Two Skinner Unaflow four-cylinder steam engines rated 3,500 horsepower at 125 RPM (total 7,000 horsepower). The ship has Marine Type D boilers.

While in the US Navy and during times on both East and West Coast I heard of and actually toured a factory where at the end of WW II they used the surplus Marine Type M boilers of the day and the SSTG set to build their factory. It was new equipment that had never been installed on a ship... and they could get the entier boiler and its support fans and pumps and SSTG sets and their support pumps and air ejectors as a package for about $1/3 of the cost of new.

They could run pressure reducing stations for the main plant steam flow - and were pleased as punch about this equipment (even 40 years later).

I have never heard of any equipment being reused from a scrapped ship.

Have a great day,

Perry

jumper

@Perry
If you're going to destroy the ship anyhow why not remove valuable equipment? I've seen marine turbines for sale but don't know if they were used or new. Those pocket aircraft carriers used five cylinder Skinner unaflow.

PerryHolzman

@jumper

Boiler are not worth the cost to remove from the ship at the scrapping yard and transport elsewhere. It's cheaper to just cut them into pieces in the boiler room and remove in small pieces.

Most commercial boilers of equivalent steam flow ratings used to be field assembled for the same reason (and still are above a certain size).

Those surplus WW II Navy Boilers for ships that were never built were also likely field assembled. The plants that purchased them only bought several rail-carloads of the parts, and had an erector put them up.

Smaller pumps and other equipment often is worth transporting and much more likely to find a service match in industry.

Keep in mind that most commercial boilers are only 100 or 150 PSI (at the most). They don't need 400 PSI or higher pressure boilers - and there are disadvantages in using them. But if you can get the parts at about 33% of a normal boiler... it works.

Turbines sometimes are resold (and there are also used power plant turbines that are sold as well). A ships HP turbine would likely work for a 3600 RPM generator if you manufactured the matching coupling. The LP turbine likely for a 1200 or 1800 RPM generator. More likely that someone buys a old small power plant turbine generator set and reconditions it though...

I've never heard of a reduction gear sold that was not part of a SSTG.

Perry

Jamie Hall

Problem with removing equipment from a bigger ship -- as opposed to say a yacht -- is that it often really is part of the ship, rather than something more or less detachable as a unit. This is less true now than it was in the days of steam -- marine gas turbines, for instance, are pretty much self contained. But the big marine diesels really aren't, and steam (even something as compact as a Unaflow!) isn't at all.

But as you have said, the field of marine propulsion is really fascinating.

PerryHolzman

@Jamie Hall

You are correct about the structure of a modern large marine diesel. They are now part of the structure of the ship.

Interesting thing, You can shut down a cylinder and rebuild it (complete with replacing the push rod) while the engine is running.

They have this really neat "quick disconnect/reconnect" push rod bearing cap.

That's how they solved the reliability of modern large marine diesel engines - which often only have one engine per ship.

Where you have smaller diesels that are supported on a foundation; there are usually 2 of them with 2 propellers.

Perry

vapor1

Thank you all for your help and discussions.

vapor1

@Jamie Hall , Your suggestions for freeing stuck radiator valve worked. Thank you.
and @PMJ , I have found what is probably an original ball for the Webster Vent Trap 0023, and it works in the system! The units of measurement are not specified on the old Marsh compound gauge (from another house years ago), but I believe the vacuum units are inches Hg and the pressure units are PSI. It reads a fraction of 1 PSI while the system vents for about 15 min during startup, and afterwards while the burner is still firing, close to zero. Then the fun begins on shutdown - Over the next 38 min, the gauge drops to -14 (in. Hg I think). Two hours later, it still reads -8. If the units are in. Hg, that would be about -7 PSI and -4 PSI. Now that warmer weather is here, we finally have a vacuum system. Thank you to all who have contributed.

PMJ

vapor1 said:

@Jamie Hall , Your suggestions for freeing stuck radiator valve worked. Thank you.
and @PMJ , I have found what is probably an original ball for the Webster Vent Trap 0023, and it works in the system! The units of measurement are not specified on the old Marsh compound gauge (from another house years ago), but I believe the vacuum units are inches Hg and the pressure units are PSI. It reads a fraction of 1 PSI while the system vents for about 15 min during startup, and afterwards while the burner is still firing, close to zero. Then the fun begins on shutdown - Over the next 38 min, the gauge drops to -14 (in. Hg I think). Two hours later, it still reads -8. If the units are in. Hg, that would be about -7 PSI and -4 PSI. Now that warmer weather is here, we finally have a vacuum system. Thank you to all who have contributed.

Great news @vapor1. If the gauge is accurate and in hg that is a lot of natural vacuum. If you stand next to the boiler you will notice how much longer it continues to make steam with the burner off than before as the vacuum sets in and then also how much faster it gets to a full boil on refire. These aren't small differences. Then notice how much longer your radiator feed pipes stay warm during boiler off periods. Great stuff. You are on your way. Too bad the season is over.

motoguy128

Jamie Hall said:

Ah... perhaps Cedric is unique. Wouldn't surprise me. But... on a really cold, windy day, he runs almost continuously (the thermostat never stops calling) and all the radiation is operating at full temperature all the way across.

So... be just a little careful with the assumption that "these vapor systems were all built with excess radiation by design" as it may not be true. It probably is true for a structure which was originally built and intended for four season use. It may not be true for a structure which was not intended for four season use initially, but has been repurposed, if you will, for that.

Late to respond. I suspect there is excess radiation installed for two reasons. One main reason is that coal fired systems require manual fueling, so they would be allowed to almost die down To just a small hot bed overnight and then the oversized system allowed it to recover faster.

Second excess radiation allowed more surface area And mass for a vacuum system as it downfires to continue to heat the home adequately without refueling.

Third, I doubt detailed load calculations were performed. There were rules of thumb applied based on window area, building orientation and room purpose and size.

For example, the rooms I have with 2 outside wall have more radiation than those interior. Rooms on the north side have larger radiators than similar ones on the South. The header intentionality runs clockwise starting norther east and running to the south west which follows sun exposure. So on shorter cycles, the north rooms get a little more heat than south rooms. Lately upstairs radiators are much smaller than downstairs.


Having had Botha grossly oversized boiler and now a slightly undersized boiler. I can attest than the later is much more efficient. Despite now making DHW as well, the boiler room is far cooler. I’m not losing nearly as much heat In off cycles. SOme of that is the draft hood design difference between boilers, and the fact than the new boiler is a low mass modern design At about 550lbs and the previous was a Smith G300 monster weighing probably 1500lbs. SO maybe an unfair comparison. But every time the draft damper opens for pre and post purge there is wasted heat and far, far less overshoot in all weather as since it heats up slower the thermostat lag is better managed.

vapor1

Thanks, @motoguy128 . Your header discussion is really interesting and matches our system here. Maybe we're better off undersized, but steam now takes nearly 1/2 hr longer to reach the further convectors - located in the SE corner.

motoguy128

> @vapor1 said:
> Thanks, @motoguy128 . Your header discussion is really interesting and matches our system here. Maybe we're better off undersized, but steam now takes nearly 1/2 hr longer to reach the further convectors - located in the SE corner.

Id guess that your radiator vents are too big and main venting isn’t adequate. My main fully heats prior to heat getting past the first section on my first north corner radiator in my dining room.... which is almost all windows on the 2 outside walls.

I have the equal of 5 big mounts venting my approx 100’ 3” main but Gorton 4-5 on everything else. At very low pressures, larger radiators heat faster as they pull a larger local vacuum as they are heating. It’s a push/pull system. The leading edge of steam is collapsing into a vacuum. A bigger radiator heats faster as it cools steam faster than a small radiator.

I literally had a 5 section and a 12 section radiator both with a vent rite set to 5 or a Hoffman 40 (sane vent rate) and the big one only heats about 20-25% slower not 50% slower.

Undersized boiler also allows the liberal use of TRVs.

However with slow main vents and thermostatic big mouths you need a vacuum breakEr or you get horrific whistling in shutdown as it pulls a deep vacuum.

Finally, be sure radiator valves are not leaking or that will cause balance issues. You can test by flipping a float type radiator vent upside down and if the riser pipe going to the radiator still gets hot then you have leaking packing.