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[MichaelK]

Hi,
Just another question, all the other answers I've had are helping a newby into a steam boat.
My boiler runs at 60psi, but the engine (TVR1A) is only rated to 30psi.

I am assuming that the regulator (steam controller,  accelerator?) will have 60psi on the inlet side, and will vary from 60psi down to zero psi on the outlet side, and so controll the revs of the engine. Is ths correct???
So, I can either change the blowoff\safety valve, so the boiler output is regulated down to 30psi, and so probably use less gas,   OR,  I can run the boiler at 60psi,  and put a fixed "throat" (something like a washer with a small apperture, or maybe a length of small id pipe)  between the boiler outlet and the lubricator. (Or maybe after the lubricator, between the "steam controller\accelerator" and the inlet manifold of the steam engine?), and have 30psi at the engine.
I'm asking this because it seems a really simple way of having a controlled 30psi at the engine, and surely, the "steam controller\accelerator" is just a variable "throat" affair.

Or is my theory just too simple, and am I missing out on something much bigger and more sinister?
Thank you for input
Mick.

[Circlip]

Your boiler is designed to run at a certain safe pressure Mick. The Safety Valve is just that, it's designed to release when the pressure exceeds the safe working pressure of the Boiler. So once set and calibrated for that pressure, don't mess with it and have it verified at regular intervals.

  Steam supply to the engine is regulated via one or another forms of Throttle be it a tapered valve plate or needle valve type or whatever you can control with a servo, your hole in a washer would only allow a fixed amount of propulsive gas (Steam) through.

  Work on a maximum speed for the engine with full bore of the feed pipe and turn the burner wick down to maintain the engine pressure without the safety blowing. The speed of the engine is then controlled by a throttle, OR VP prop if you want to go that way.

  Regards   Ian.

[TAG]

Why not use a gas control linked to steam pressure, there are a number on the market. Stuart Models have an electronic one and Forrest Classics have a diaphram type regulator to name but two. I am sure there must be others. They should save you a fair bit of gas and achieve your objective.
Tim

[derekwarner]

Hi Mick.....a few misconceptions here that I also stumbled upon 

1. the boiler steam discharge valve is simply that = an isolation valve
2. the steam regulator valve is only a sophisticated metering valve....however it is not pressure compensated [on the input or output side]
3. if you are happy with the 2 Bar requirement of the engine....you could consider a gas regulator that maintains boiler pressure @ an adjustable range +/- 0.1 Bar on your chosen set point.........
4. I am sure Mr Burneonli would have agreed with your (something like a washer with a small aperture, or maybe a length of small id pipe).... ....however regulation is required as we add the variables of engine load demand together with the boiler capacity to supply this demand 

Derek   

[flashtwo]

Hi Mick,

I run a Stuart D10 engine from a highly controlled monotube (flash) boiler without any throttle or regulating valve between the boiler and engine - it is just a straight through pipe. The steam pressure is varied by controlling the feed water flow and the gas burner, and the engine ticks over at 7psi and at 30psi does about 650RPM with a 5inch prop.

The steam pressure is also a function of the load on the engine and also the position of the engine's valve gear.

If any engine is restricted from turning (perhaps some weed has got tangled in the prop), then the engine steam pressure, even with a throttle valve restriction, will become that of the boiler. If your engine is rated for 30psi then the boiler should be run at 30psi maximum.

For the best efficiency the throttle valve should always be fully opened to avoid what is called "throttling losses". The downside is that you can't increase the engine speed without increasing the boiler pressure.

Ian.

[gondolier88]

I am assuming that the regulator (steam controller,  accelerator?) will have 60psi on the inlet side, and will vary from 60psi down to zero psi on the outlet side, and so controll the revs of the engine. Is ths correct???
So, I can either change the blowoff\safety valve, so the boiler output is regulated down to 30psi, and so probably use less gas,   OR,  I can run the boiler at 60psi,  and put a fixed "throat" (something like a washer with a small apperture, or maybe a length of small id pipe)  between the boiler outlet and the lubricator. (Or maybe after the lubricator, between the "steam controller\accelerator" and the inlet manifold of the steam engine?), and have 30psi at the engine.
I'm asking this because it seems a really simple way of having a controlled 30psi at the engine, and surely, the "steam controller\accelerator" is just a variable "throat" affair.
Mick.

Your assumption is correct- your regulator will have boiler pressure on the inlet side minus pipe restriction pressure losses and condensation you will be looking about 45-50psi on the inlet side of the regulator when open.

You can de-rate a safety valve if you know how to do it and are conifdent it will de-rate it and not up-rate the pressure blow-off. If it were me I'd set it to 40psi. If you don't know  what you are doing with it see if anyone on here that is experienced with steam lives nearby and can change it for you- or supply a new gauge. Someone like Mike at Macc Steam may be able to supply a SV rated at 40psi for you.

Under NO circumstances should you restrict a steam supply after the boiler outlet- it will cause massive condensation and stop your engine working properly and would make you use more gas- you could restrict it at the boiler outlet- do you have a main steam stop valve on the top of the boiler that you could solder a blank into the inlet side and re-drill with a smaller hole and use a smaller steam supply pipe (say 1/8" if the normal size is 5/32") which would be an unrestrictedsupply in the sense the steam has a smooth and unhindered path to the engine, but it is restricted in the amount of steam that can get through the pipe, and even with 50psi at the inlet of the regulator it would not be able to supply more than 30-35 psi to the engine at full throttle.

Greg

[south steyne]

Hi all, Derek is spot on and just to hopefully simplify things no matter what test you do on the bench it will have little bearing on the water as you will use more of everything so a gas control valve or a water feed system or both in my view is the way to go
Merry Christmas
John

[MichaelK]

Thank you all.
Thinking about the problem, and the replies, I think I'll either adjust the saftey valve, or if necessary, replace it with a suitable one,  to blow off at a pressure that gives me 30psi at the engine inlet manifold.
A gas regulator and all the attendant bits and pieces can wait untill the boat has actually putt-putted around the creek a few times.
And just to save my workshop, club members, general public, and most importantly, ME!, I will enlist someone who knows exactly what they are doing, and has the right tools.
  Thank you all again
Mick

[Circlip]

Hmmm, DON'T throttle the engine and ALWAYS run at full bore?

  Soooo, if you want yer boat to go backards, you're going to have to fit a reduction gearbox or a VP propeller. OR make it pointy at both ends.

  Sound advise.

  Regards   Ian.

[ooyah/2]

Hi Mick,

Don't be put of by all the advice given particularly this about pressure regulators, you don't need one.
If you have a site glass on your boiler and a pressure gauge you can gain valuable experience by working with the burner  the gauge and the water level.
All you have to be aware of is watching that the pressure doesn't go above the 30 psi that you want your engine to run at, this can be controlled as has already been said by turning down the burner, if you are not confident in adjusting the safety valve leave it at 60 psi and by turning down the burner you can keep it running at 30 psi. and with your throttle control you can shut off the steam and revers your engine although with the Hackworth gear you can revers without shutting off the steam.
Keep your steam feed straight without restrictions as has been said and don't block the pipe.
By tuning the burner to the boiler you will save yourself approx £100, and gain valuable experience and use less gas, it's expensive enough running  a steam boat without all the add on GIZMOS that ain't needed.

Go to it and enjoy your steam boat, hope that there is water in the Creek.
George. 

[Underpressure]

Hi Mick,

Don't be put of by all the advice given particularly this about pressure regulators, you don't need one.
If you have a site glass on your boiler and a pressure gauge you can gain valuable experience by working with the burner  the gauge and the water level.
All you have to be aware of is watching that the pressure doesn't go above the 30 psi that you want your engine to run at, this can be controlled as has already been said by turning down the burner, if you are not confident in adjusting the safety valve leave it at 60 psi and by turning down the burner you can keep it running at 30 psi. and with your throttle control you can shut off the steam and revers your engine although with the Hackworth gear you can revers without shutting off the steam.
Keep your steam feed straight without restrictions as has been said and don't block the pipe.
By tuning the burner to the boiler you will save yourself approx £100, and gain valuable experience and use less gas, it's expensive enough running  a steam boat without all the add on GIZMOS that ain't needed.

Go to it and enjoy your steam boat, hope that there is water in the Creek.
George. 

Thanks George that's music to my ears.

I thought I was the only one here who didn't have regulators, attenuators and electronics all over my steam plants.

Neil

[HS93 (RIP)]

I must be a Luddite as well Neil

Peter

[Underpressure]

Ohhhh yes!

I prefer the approach that best suits my brain....simple.

Neil