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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sat Nov 11, 2017 4:54 pm 
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Sometimes I have gotten frustrated with this forum, I maintain that at some level many steamers are grumpy, and it can come off worse on forums.

Thing is, it's way too educational and mostly civilized for me to stop reading/participating here.

I will tell you that I have talked to enough steam "experts" who claim up and down that they know what they are talking about but have just sort of memorized and repeat partially correct information that does not hold up to tough scrutiny.

Fred I grant an exemption for because he's worked in the industry, been on ASME boards, is a PE, and most importantly in my book he has actually built and operated a steam launch.

Ron and I bang heads sometimes, but I respect his steamboating and steamcar experience.

I readily admit that I am crazy, but I've been a practitioner of handfired steam for 5 years as a hobby. I looked at the steamboating world and saw a number of what appeared to be abandoned or abadoned due to age/health steam launches spending years 5-10+ years on a beautiful hull only to see no functioning fruit of their labors. To me that is sad, and I although I respect and admire a hull like that - I wanted to get on the water as quickly as possible and be doing the acual steamboating instead of focusing on building a pretty hull. I find Modern Steam Launches from the 1960s to actually have more interesting, from a technical point of view, steam launches then I see nowdays.

I am more of a build a little/test a little/repeat type of an engineer, and I've purposely built Nyitra to be able to grow and change and try things. I say that Nyitra has enough finickiness to allow for years of tinkering. I don't claim to be an expert, but I have become a practitioner of handfired steam.

And certainly Nyitra has benefited from the contributions from those who answer my questions. If you go back you can see barts helping me calculate that I needed an extra pontoon, my first and current rudder is based on Freds instructions, etc.

-CB


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sat Nov 11, 2017 5:06 pm 
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Quote: " It's much easier to get from 150 to 200psi then 100 to 150psi right now."

I've noticed that too. Down in the sub 100 psi of steam generation, it's just tough to get out of - using it and making it. I think what it is, high temperature steam expands more and you simply get more work out of it - don't use as much and it's easier for the boiler outrun the demand.

I've fired the tug for many hours and I taught my brother to fire it one morning, and by afternoon, he showed me how to do it, after I asked how he was keeping the pressure higher than I normally do. He said, pick a low point on the gauge, throttle back until the pressure was up in operating range above the low point and he wouldn't let it fall below that with the throttle. When it started falling to the low point, he would add fuel, throttle back, pull in some cut-off, play the feedpump bypass etc. whatever it took to get it back up. Eventually he was maintaining it at the operating point all the time and with not very good wood.

-Ron


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sun Nov 12, 2017 1:47 am 
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So if you(anyone reading this) don't have a set (or at least this volume), it's a very good reference.

Image

Regarding Lubrication...

I find my 1945 copy has this to say, "The present day manufacture of scientifically designed mechanical equipment, together with highly perfected lubricant quality, permits a certain standardization in recommendations and applications both, that was not possible a few years ago."

There are some recommendations on steam cylinder oil use that may be helpful below.

Mr. Lopez just slipped under the 140psi door of wet steam with his foggy 135psi :)

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Image
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-CB


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sun Nov 12, 2017 4:36 am 
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Please allow me to change my position with regard to my statement that I have yet to find any professionals here. I have spoken out of turn and without a reasonable knowledge of the people making comment, or of the relations between some of those people who perhaps understand better the intent of what is said rather than the way it is perceived by the uninitiated who are simply reading the words as they are written.

My remarks were made, as I pointed out, from the perspective of somebody that registers on this forum and then proceeds to read through many of the posts. I am certain that I am not the only person to be left with the feeling that many of the replies are overly argumentative.

I agree wholeheartedly that if a person is misinformed about an issue where safety is involved, then correction in stronger terms can be warranted. I would simply like to leave you with the suggestion that although you may be writing in reply to a particular known individual, the way in which you reply is left to the perception of many who cannot read the look on your face as you say/write it.

I will edit my previous post to remove the section that I now wish I has written differently.

Cheers

Lionel


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sun Nov 12, 2017 5:27 am 
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DetroiTug wrote:
I've noticed that too. Down in the sub 100 psi of steam generation, it's just tough to get out of - using it and making it. I think what it is, high temperature steam expands more and you simply get more work out of it - don't use as much and it's easier for the boiler outrun the demand.

I've fired the tug for many hours and I taught my brother to fire it one morning, and by afternoon, he showed me how to do it, after I asked how he was keeping the pressure higher than I normally do. He said, pick a low point on the gauge, throttle back until the pressure was up in operating range above the low point and he wouldn't let it fall below that with the throttle. When it started falling to the low point, he would add fuel, throttle back, pull in some cut-off, play the feedpump bypass etc. whatever it took to get it back up. Eventually he was maintaining it at the operating point all the time and with not very good wood.

-Ron

So I noticed twice with Nyitra before I got a grasp on how to repeat it. The one time was by the Chautauqua Institute, the Belle and I had been tagging along across the northern part of the Lake. They had to stop for a while to offload passengers and I told my fireman (Steam Mentor Tom D.) that I was going to come to a stop and he should fill the firebox so we could build pressure. Up shot is we got to 200 and then I had to start doing something so I just went back and forth under full power. Nyitra was snorting like an eager colt in a horse pull popping off her relief valve from all the positive feedback. But eventually she fell off because our fuel was only tight grain maple.

When we had the long 14 mile roundtrip on well seasoned mixed hardwood we found that the new nozzel really sucks - and that's a good thing...

Very similar thing to what you are describing, we have these injector batches that we run every 5minutes or so and add a few gallons back. We found if we kept the throttle a little down and hold that we can increase how much it swings in psi. I got a digital count down timer as an option for my fireman to keep a pace and change the pace. I thought my fireman would find the beeping annoying - but it's a very good training tool and well received. I tell them that as fireman they are responsible for the water level, and that every time it beeps they need to check the sight glass and make a decision whether they need to add water and how much.
By closing that interval to 3minutes we found that we could get up to MAWP of 200 easily, and stay there - actually my buddy had to start backing off on the fire.

Imagine when I decide to try coal again.. :lol:

We did similar to what you are describing - he picked a psi within these feedwater psi swings and would add fuel, and then at the peaks add water.

-CB


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sun Nov 12, 2017 12:48 pm 
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A couple of technical facts that are relevant to the raising of steam pressure.

When raising steam, the temperature climb of the boiler and all of its contained water is relevant here. For example, with a fixed heat input (fire), raising steam pressure from 40 PSIG to 50 PSIG takes a temperature rise of 11F, while raising the pressure from 140 PSIG to 150 PSIG requires a temperature rise of only 5F, so on that basic property of H2O, pressure tends to climb much more rapidly at higher pressures.

That temperature rise applies to all the water inside the boiler, as well as all the metal forming the pressure vessel of the boiler.

With oil or gas firing, the fire is generally fairly constant, so the saturation pressure / temperature curve for steam dominates the result.

With hand firing some other issues are often at play here:

Early in the process the fire is in its infancy, probably more sluggish when going from 40 to 50 psi, the stack temperature is lower, so less chimney draft, also promoting a sluggish fire, so even slower pressure climb.

Also, early in the process, the furnace, refractory brick (if used) and other parts of the boile have not fully warmed up, so these parts take away heat, reducing what gets to the boiler proper.


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Sun Nov 12, 2017 8:54 pm 
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fredrosse wrote:
Also, early in the process, the furnace, refractory brick (if used) and other parts of the boile have not fully warmed up, so these parts take away heat, reducing what gets to the boiler proper.


This was definitely noticed on Nyitra's somewhat large VFT. It really takes 2-3 hours of being underway before it is fully warned up. The difference is a pleasant surprise, after fully being warmed up the pressure dips much less or not at all on the gauge when water is added.

-CB


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Mon Nov 13, 2017 3:32 pm 
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Quote: " For example, with a fixed heat input (fire), raising steam pressure from 40 PSIG to 50 PSIG takes a temperature rise of 11F, while raising the pressure from 140 PSIG to 150 PSIG requires a temperature rise of only 5F, so on that basic property of H2O, pressure tends to climb much more rapidly at higher pressures. "

That explains it quite well. I was referring to the car with the "sub 100 psi" level, with the Kerosene fire, up around 150-180, it's just a few seconds away from 250 and blowing off. In a crowd of people :), I've had them jump as high as 3 feet when I killed the burner too late. It is really loud, and what makes it worse is the car is dead quiet at low speed, I can hear people remark "oh no, that's not steam, that's gotta be electric powered" I built a muffler with a feedwater pre-heater coil in it which works very well. There are two feedwater heaters, one in the muffler and 50' of economizer. Was reading Hiram Maxims book on his steam powered airplane and he claimed heat transfer with water on the outside of a feedwater pipe was 2400 times more efficient than air on the outside of a feedwater pipe. Submerged or condensing coil versus an economizer in the smokespace. After I installed the muffler, I could tell a big difference taking on feedwater, the economizer works, but it very short duration, it chills down very quickly. Economizer works better either metering the feedwater through (lowering the velocity) or very short cycling.

-Ron


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Tue Nov 14, 2017 7:05 pm 
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DetroiTug wrote:
Economizer works better either metering the feedwater through (lowering the velocity) or very short cycling.

Does anyone know if an Economizer coil or feedwater exchanger can be used with an injector?

My understanding of an injector is the suction intake water is supposed to be cool, but also the water->to_boiler piping is supposed to be as short and direct as possible. (Which if completely true precludes their use)

-CB


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 Post subject: Re: Pros/Cons Piston Valve and Balanced Slide Valve
PostPosted: Tue Nov 14, 2017 9:00 pm 
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I think the only way to know that is, try it. An economizer can be a bit erratic with pressure, when not taking on feedwater it's basically a monotube generator connected to the feedwater inlet. It can have pressure spikes, this doesn't bother an engine driven feedpump as the pressure they generate far exceeds anything the economizer will, and a steampump that can double the steam pressure deals with it ok as well. But, an injector is sort of a magical thing to begin with, so for someone to know whether or not it will work without trying it, is not very likely.

My guess is, it will work. I think the issue you may run in to, under long periods of not taking on feedwater, the economizer can boil dry, the sudden in rush of cold water on the hot tubing will flash boil, and you'd get a pressure spike right when the injector is trying get the magic going. Maybe put a bleeder/bypass on it right before the economizer to get the flow going, then cut it in gently.

A piston pump, if it has a restriction ahead of it, it just builds enough pressure to overcome it, and keeps trying with every stroke until it does and if it can't and there is no relief valve on the piping, bad things happen to the pump.

-Ron


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