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[MOG8]

THIS IS IT

[Bernhard]

hi...i did one time see one like this,,,,,,,,,i think it whas from Regner
look to very simpel to make,,,,,,,,,,,.



Bernhard

[SteamboatPhil]

Hey Mog8, that would make a great flash steam coil 

[MOG8]

Hello Bernhard,
you are probably referring to this:
http://www.dampfmodellbau-keifler.de/

[Bernhard]

hi..ohh yes thats the one ,,,Thanks

[oiler]

This is the one I bought from Regner Germany.

[oiler]

This is a tank with a passive heat exchanger from work that illistrates what I was talking about earlier.

[oiler]

another picture

[Circlip]

Some of the heatpipe assemblys on LAPTOP cpu coolers look ripe for scavenging, fancy pipes and rads.

  Regards  Ian

[Bunkerbarge]

This is a tank with a passive heat exchanger from work that illistrates what I was talking about earlier.

You'll need a big hull to get that in though Oiler!!

[oiler]

You'll need a big hull to get that in though Oiler!!

nah.. just a large shoehorn   

[Brooks]

Oiler mentioned G-scale loco engineers exploding gas tanks by heating them with hot water. He may be referring to my experience. I've never seen another like it, at least on the active US G-gauge live steamer forum. I posted the details over on mylargescale.com, this was several years ago:
http://www.mylargescale.com/forum/topic.asp?TOPIC_ID=35013

What Happened, and the Solution:

1) the loco's tank did not explode, it bulged and split a seam. There was just a hissing, no explosion or flame, etc.
2) the tank was filled with propane/butane mix sold for campstoves (the tank was designed for butane only, though this mix is used by many US steamers in cold climates, and even indoors at the famous annual Diamond Head steamup in Louisanna).
3) the calculated tank pressure (given the measured temperature of the hot water + gas pressure tables) was at all times less than the tank's test pressure certificate,...so why the problem?
4) answer - the problem was not excessive *Gas* pressure, but excessive *Hydraulic* pressure. The tank had been filled plum full of the liquid mixture before I closed the valve (and then added hot water to the loco tender to keep the tank warm; I run in freezing temps here in Montana). The tender was made, by the manufacturer, watertight just for this purpose, namely warming the tender mounted butane tank. But, and this is the problem, if you warm liquid it expands, generating hydraulic pressures in the 1000+psi range (my farm tractor for instance, runs it's hydraulic system at 2000psi). No model tank can withstand 1000psi, so naturally my tank bulged and split a seam.
5) the solution - don't fill tanks plum full of liquid. Propane dealers say you should not fill an outdoor propane tank (home heating) more than 80% full.  Always leave a space in the tank for the gas phase. If the gas phase is present, then pressure can never exceed the pressures found in gas/temp tables (which are what the tanks are designed to bear). But if the gas phase is eliminated by filling the entire tank, then pressures rise precipitously with heat, and no tank can sustain them.
6)after the incident, I examined my other loco's butane tanks. Even though I never heated them, a couple mounted on the footplate near the boiler (by the manufacturer) had bulges. It is common to mount loco butane tanks near the boiler so that they stay warm enough to maintain butane gas pressure. For small locos with small tanks it is common to fill them plum full. And apparently, the residual boiler temperature during refueling servicing was enough to make these tanks experience hydraulic-level pressures w/o my realizing it (and w/o causing a leak).
==========
After the incident, I switched to pure propane firing of my locos. I could run in freezing temperatures with no problem, the tank entirely unheated (it rode in a gondola car, no where near the heat of the boiler). The only time I ever had a problem was when the propane gas regulator froze due to frozen condensed moisture from the air, the symptom was lack of gas regulation, leading to the fire going out. Normally Montana winters are so dry this is not a problem, but this particular, high relative humidity, sub-freezing temp day was anomolous. If you shift to propane firing, you will never have a butane sag in your fire. You can't use your original butane tank for propane (propane produces 3x the pressure of butane), so the system must be re-engineered. I can give details if desired.

[Bunkerbarge]

Many thanks for sharing this incident with us, it clearly demonstrates a very serious potential issue with model gas tanks that we must be aware of and avoid at all costs.  I'd just like to add a couple of other points if I may to expand on this situation.

Firstly another method I use to ensure that the gas tank is not overfilled with liquid is an arrangement of valves.  I have fitted an additional valve that has a 'dip' tube, extending into the tank to about 20% of it's height.  As I fill the tank with liquid through another valve the first valve is cracked open allowing the tank to vent off outside the boat hull.  When I see liquid spitting out of this vent I know the liquid level has reached the bottom of the dip tube and I know to stop filling.  I haven't yet seen this method used anywhere else but it works surprisingly well and, of course, ensures that I don't completely fill the tank with liquid.

The second point to think of is that hydraulic lock is equally a concern in the boiler and it should never be filled to a level over the top of the sight glass.  The consequences of a boiler rupture in operation could be quite disastrous.

The final thought has to be the fact that although the incident above didn't develop into a major incident the potential for an extreemly serious issue, leading to an explosion was very real.  Gas releasing at the rate it would do from a pressurised state to atmosphere in very close proximity to the boiler flame has all the potential for a very real explosion and possible injury to anyone close.  This didn't happen in this case as a result of nothing more than good luck for which everyone concerned should be very relieved but also very aware of the fact that this was a very close call.

[Brooks]

Yes, never refill the gas tank while the fire is burning, or there are nearby fires. It's tempting to do so to avoid loss of steam pressure during a service stop, and I've done so. But no more... it's ok as long as nothing unexpected happens, but that's why they call them accidents . The loco tank on this occasion was filled in the house (outdoor RR track) since it was very cold outside. Thus, the split seam (actually, you could not see the damage, just hear the hiss) was not near flame. But it could have been very exciting, I was lucky.

The manufacturer, Accucraft, used to put safety valves on it's large loco gas tanks. This would have saved the tank from hydraulic damage. Unfortunately, they quit doing so (I only knew because the 1st large loco I purchased had the safety valve, but the 2nd did not). The reason offered was that the escaping gas was a danger....but a split tank is just as dangerous, so I think it was a cheapening-of-the-product motive, not "safety." Likewise, the safety valve on a boiler should protect against hydraulic damage, albeit at the cost of overflow water discharged into the boat. I've run into that "solution" when servicing a loco w/o a sight glass (via Goodall valve). Hot water spurts all over, and that can be a hazard when onlookers are crowding around. Besides the hot water,  the surprize factor may make someone jump and cause a problem.

An operational trick, with a dual purpose: crack the gas valve on the tank a tiny bit while you are refilling (outdoor ops only). This has 2 benefits:1) faster fill since the liquid is shot into the tank under near full refill bottle pressure (otherwise, the liquid dribbles in, after an initial spurt). 2) You can't inadvertantly hydrolock while filling since there is an exit for the overflow. Also, it shows you when you are topped up completely by spurting droplets of liquid out the burner jet, which you can detect by the sputtering sound. In the loco world, at least at that time, it was common to fill the tank until liquid spurted out the refill valve. Thus, it's a wonder more tanks have not bulged, etc. Or maybe they have, just never developed a leak?

Your overfill pipe is the best way to avoid hydraulic problems, not available to those who don't make their own tanks. I wish the manufacturerers were listening, sigh.

[oiler]

Well I live here in Great Falls Montana as well. This week as you know it was 35 degrees below zero F.  I used to have a number of Accucraft locos back in the day when Charlie just started to make them. I spoke to him and Cliff at the Queen Mary Garden Railway show in LA about safeties and other topics regarding their Live steam locos. One reason they didn't offer safeties anymore was the fact the burner is so close to the tank and a fire could be a problem if the safety popped off, which made sense. The horrible burner design was cleaned up a little thanks to Dave Hotmann but not designed like Dave and the rest of us would've liked because of manufacturing costs.

I did submit an article a long time ago to Steam in the garden magazine about how I was running Propane safely and posted it on Shad's site; Mylargescale.com. Basically I bought one of Don Winter's refer cars and put a plumbers torch propane cylinder in it I got from Ace hardware or Homedepot. The Regulator was from Home Depot as well from a torch kit. Also tried using a camping stove regulator to use with isobutane but it froze up as well so don't try it.

Anyway glad nobody got hurt. Any time liquid is filled into a cylinder it's always filled to 80% to allow for expansion. The only time a cylinder is all the way 100% is when they are hydro tested.

[mrsgoggins]

I've just seen how long it is since I said I was to try out a gas vapouriser. Well I've done it and here is an update.

The vapouriser is a 1/16" copper coil wound onto a shouldered brass bobbin all silver soldered up as one lump. A bolt through the centre of the bobbin clamps it to a blanking plug at one end of the boiler - all should be clear from the pics below. Diameter over the coil is 1/2".

The "Tower" at the outlet end was added to improve burner stability (by trapping liquid droplets).

Bench and sailing tests have proved totally satisfactory with gas pressure being maintained and no risk of overheating the tank.

The gas system comprises;
    200g refillable tank with gas and liquid outlet valves feeding one manifold
    R/C non-resetable emergency shut off valve
    Combined gas regulator/attenuator to a design by Malcom Beak
    Fine mesh filter adjacent to burner
    No 16 gas jet running at 10/15 psi inlet pressure (c. 170g/hr)
    2" diameter ceramic burner
    Butane/propane mix

I start up on gas and change to liquid with 30psi on the boiler pressure gauge - with no noticeable effect on burner pressure or noise.

If started on liquid, by mistake, all seems well until the burner pressure falls to zero. It then takes the regulator a few minutes to sort itself out after switching back to gas.

I hope this is of interest. It does require a spare blanking plug on the boiler but so far has proved to be a simple and safe solution to the problem of falling gas pressure.

[gondolier88]

A very tidy and compact plant, well done. Your gas vapouriser is a very practical and elegant solution to the problem. What LPG are you vapourising out of curiosity?

I'm also admiring your side venting safety valve- is this something you have made or is it bought?

Greg

[mrsgoggins]

Hi Greg,
Gas is generally a 30/70 propane/butane mix.
I made the safety valve. It is more or less a conventional design with a side outlet to the "bonnet" and the normal top exhaust holes deleted. The splindle protrudes through th top of the bonnet and is sealed by a lightly fitting "O" ring.

Keith

[Bunkerbarge]

That's a very neat little device and well worth considering for a future project.  I like the idea of using liquid from the tank but I'm still on the lookout for a device that will then control it according to boiler pressure.

Interestingly enough, as your device flashes the gas off before it gets to the burner, you have the opportunity to control the gas before it gets to the burner with an attenuator.

Very neat plant by the way, it certainly looks the business!

[mrsgoggins]

Hi Bunkerbarge,
The gas is fed to the burner via the pressure regulator/attenuator. This allows me to choose the initial burner pressure and set the boiler pressure at which the gas supply is reduced.
Currently I set the gas pressure at 10/15 psi and the attenuator is adjusted to kick in at about 55 psi bolier pressure- this holds the boiler between 50 and 60 psi regardless of the load. The other benefit is that I don't waste steam via the safety valve when I "heave to".
I can thoroughly reccomend Malcom Beak's design of regulator/attenuator.

I am also using the Model Boats design of water level control which has proved equally successful.

Regards,

Keith.

[steamboatmodel]

'I am also using the Model Boats design of water level control which has proved equally successful."
Which one? There has been a number of them published over the years.
Regards,
Gerald.

[mrsgoggins]

Hi Gerald
Apologies for my c**p memory. The circuit was published in Model Engineer in Jan 2007 and can be configured to either power an electric pump or operate a servo to bypass the flow from a crankshaft driven pump - I chose the latter option. until I realised the boiler was running dry and cut the gas supply
Only quirk I have found is that when the unit is demanding water any spashing around the probe resets the timer for the warning LED. I had a pump failure and the red LED did not start flashing. I need to do some more work on shrouding the probe.

Keith

[benjaml1]

A totally enclosed ( shrouded) probe, open at the bottom with a small vent at the top will dampen down boiler oscillations...

[mrsgoggins]

Benjaml1
Yes, I've been thiking along those lines.
The probe is fitted through the steam offtake dome which is probably a fairly lively area and why my initial attempts at shrouding failed - but I shall persevere!

[TAG]

As the author of the Model Engineer article of 2007 on electronic boiler control I was interested in mrsgoggins comments that the alarm timer is reset by water momentarily contacting the electrode in the boiler. This was not originally intended but the flow chart used for the PIC programming shows that the alarm timer resets under these conditions. Also tests in my workshop show the same. Further thought indicates that the alarm timer should be reset by the time out of the detector timer.
Obviously the PIC needs a spot of reprogramming.
Unfortunately my friend who did the programming for me died this February so presently I have no one to make this change, the programme died with him.
As a quick fix can I suggest fitting an external timer energised from the pump connection blocks so as to monitor the total pumping time. I have a timer which will do the job on a purpose build pcb measuring about 23x30mm. Any one interested please PM me.

As regards gas tanks, in my latest project, a steam driven TID tug I am experimenting with a gas tank movable heat shunt. To monitor it's performance the only way I can measure the gas pressure was to make an adaptor to fit the pressure gauge to screw into the Schroeder valve after filling the tank. The adaptor is designed to depress the valve enough to feed gas to the gauge. There is an o-ring seal to prevent leakage.
Last year I experimented with a 50mm round ceramic burner preheating it by gas then changing over to liquid which was vapourised in a coil soldered to the back of the burner. This system was generally successful but a couple of times the flame appeared to move back to the wrong side of the ceramic and the burner got extremely hot! Any ideas or comments?