Model Engine Maker

Engines => Your Own Design => Topic started by: gary.a.ayres on September 09, 2019, 10:37:18 PM

Title: Developing a Small Steam Plant
Post by: gary.a.ayres on September 09, 2019, 10:37:18 PM
Hi.

With my 3 inch boiler and 12 mm oscillator now finished, the next step is to incorporate them into a properly finished little steam plant. The boiler is loosely based on a design by Stan Bray, and the engine on a design by Steve's Workshop, but I have taken plenty of liberties with both.

Here are all the components of the plant that I currently have:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/838589.jpg)

Three interchangeable burners (pressurized kerosene, pressurized alcohol, gas), hand pump for boiler feed, boiler stand, engine and boiler.

My plan is to bring together all of the components of the plant and experiment with layout before looking for a base board, so that I get the size of the board right.

In addition to the above, I will need a water reservoir (currently in progress) and I'm also considering a steam separator for the exhaust (perhaps combined with a feedwater pre-heater, and possibly route the exhaust up the boiler chimney), an inline lubricator of some kind for the engine, and maybe even a very small generator and lamp post.

However, I don't want to go over the top, so I'd welcome your feedback on whether you think that's excessive for a plant this size. Equally, if you have any suggestions for anything else that I might add in that isn't mentioned above, please feel free to say so, as it's all part of the fun.  :cartwheel:

Cheers,

gary
Title: Re: Developing a Small Steam Plant
Post by: Ye-Ole Steam Dude on September 10, 2019, 01:41:48 AM
Hello Gary,

Fantastic job that you have done with this entire project and some beautiful machine work on the parts.

Have a great day,
Thomas

PS, enjoyed your last video
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 10, 2019, 09:12:43 AM
Thanks Thomas - very kind of you.

All the Best,

gary
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on September 10, 2019, 12:43:41 PM
Hi Gary, definitely not over the top.  I believe in always including a lubricator, a displacement type for steam, and an exhaust separator to keep the bench cleaner and dry.  And the generator and light will be a great and appropriate conclusion.  I have completed three plants like this, only one with a purchased boiler.

I have yet to build a feed pump.  I would like to say it is on the list, but definitely a ďone dayĒ.

Itís looking great so far.  Your artistic input shows in all your items and I look forward to seeing the progress on the complete plant.

MJM460



Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 10, 2019, 06:10:46 PM
Thank you MJM!

I'm pleased you think my scheme is reasonable.

I have a feeling that I'll probably be looking for some advice from you (and others) along the way.   :)

gary
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 11, 2019, 12:33:44 AM
I'm thinking of incorporating a combined steam separator and feedwater preheater into the plant.

I'm sure that I saw some plans for one somewhere online once upon a time, but a search isn't bringing much up.

Keith Appleton has a short youtube series about building one, but I have a feeling it could be done more simply and cheaply than his (nice as it is with its cast end caps). I'd also prefer an upright one (his is horizontal).

Does anyone know of any plans for one? If not, I suppose I could just scratch build it using KA's as a guideline...

As with many things, the principle is simple enough but the devil is in the detail.

Thanks.
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on September 12, 2019, 08:37:52 AM
Hi Gary, so long as you do not put a valve or other stopper in the stack or chimney the separator is always open to atmosphere and not a pressure vessel, so does not have to be designed for pressure.  You only have to design for function, along with your artistic input.

I have made them vertical with success.  The idea is that the engine exhaust enters high in the cylindrical side, preferably tangentially so the steam is forced to travel around the wall.  The heavier water droplets hit the vessel wall and tend to coalesce and run down to the bottom.  The stack protrudes inside below the inlet, so the steam flowing around the wall has to change direction again to go up the stack.  It needs a bit of vertical height below the end of the outlet to accumulate a bit of water and force it out the drain.

Ideally, the lower section should be conical.  As the steam moves down while whirling around the wall, it goes faster (conservation of angular momentum, like a skater spinning and changing posture).  Commercial ones sometimes use parallel corrugated plated to cause the changes of direction so the drops impinge on the walls and run down.

I have attached a picture of one, assembled in the steam plant, and another with the stack removed so you can see the part hidden inside.  (It started out shiny, but tarnishes incredibly quickly.)  And it works quite well.  The next one will have the stack vertical, something obviously slipped there.  I catch a bit of water from the drain outlet at first, then when it is all hot, the water ceases.  I get nearly no droplets out the top unless I have excessive carryover due to over-filling the boiler.  You can see that in my case, it is all about function with no artistic input!

I tried a horizontal one for a lower profile, also in the pictures.  The tube I had was too small for the body and it did not work.  I suspect not enough height to separate out the drops when the tube was horizontal, and I had even more hot rain than without the separator.  I have now obtained a larger diameter tube to try again.

If you want to incorporate feed water heating, I would suggest a coil for the feedwater water inside the vessel.  This would require a larger vessel than I have used.  But quite doable with say 38 mm or 50 mm or larger tube for the vessel.  And as many turns as you can fit, which is more easily accommodated in a larger diameter vessel.  The coil should be on the discharge side of the pump, as the pump will not like hot water.  I tend to use 3/16 tube for the water and steam lines, but 5/32 might be ok.  Of course if you want more heat transfer area, you can make a full on heat exchanger with many tubes, just like another boiler.

The heat lost to feed water will cause more condensation so you might need a bit more disengaging space above the coil.

MJM460

Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 12, 2019, 06:39:26 PM
MJM460 -

As always, very clear and comprehensive.

It's a bit like the steam version of the cyclonic funnel on a dust extraction system.

Your post offers a great resource which I shall use as my guidline when I come to build the separator / preheater - it's a text in its own right.

The only change I plan to make is to route the exhaust from the separator up the boiler chimney, so I guess that rather than have a chimney on the separator there would just be a steam out pipe.

Re your point about your work being functional rather than artistic - I really like the look of your work. The robust functionality has an aesthetic of its own, and to me it has a real beauty to it.

As always, thank you for your input and the time you spend in offering it.

 :cheers:

gary
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on September 13, 2019, 12:42:52 PM
Hi Gary, thank you, you are most welcome.

Yes exactly like a dust extraction cyclone.

You might need two sets of nut and tail connectors or pairs do flanges to connect the steam out pipe to the boiler stack connection, but yes, thatís the idea.

Hard to know how many turns to make the water coil, the water outlet can only approach but never equal the engine exhaust temperature which will probably be very close to 100C.  Making the coil will be good practice for that flash steam plant.  What ever you do will help your boiler steam output, but I expect the surface area of the coil will be the practical limit to how much you can achieve.  Five to seven percent might be achievable.

Looking forward to seeing how you go.

Thank you for your comments about my engines.  I enjoy making them, which is of course the whole idea.

MJM460



Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 14, 2019, 01:28:49 AM
I look forward to interpreting your suggestions and applying them in practice.

They certainly give me a direction but no doubt there will be further discussion ahead...

 :) :ThumbsUp: 
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 15, 2019, 04:59:37 PM
Next up is the water reservoir. The body is cut from a bottle which was filled with Waitrose German Reisling which I had to get rid of before I could use the bottle  :wine1:.

I chose it because of its deep turquoise green. I have never seen another wine bottle of this colour, and I thought it would suit the feel of the plant. The top cover is a nice cast brass ceiling rose from an old electric chandelier courtesy of the charity shop. I enlarged one of the two screw holes to accommodate the pipe to the pump. The other can... er... serve as an air vent   :).

The underside of the rim had to be turned to fit the rim of the glass and there is still a bit more work to do on this to get a good fit. The stopper for what was the cable opening is made from an old brass drawer door knob plus a spigot which I turned from brass so that it sits nicely in the hole. The stopper assembly lifts out easily so that the reservoir can be refilled in situ using a funnel. I'll look out for a nice brass or copper funnel rather than keep lowering the tone with one of my blue plastic ones   :)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/838998.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/838999.jpg)
Title: Re: Developing a Small Steam Plant
Post by: Jo on September 15, 2019, 05:06:45 PM
Looks nice  :)

Next up is the water reservoir. The body is cut from a bottle which was filled with Waitrose German Reisling which I had to get rid of before I could use the bottle  :wine1:.

Pleased to see you managed to cut the bottle on the first attempt. I am sure you would have hated to have to repeat the experience   :paranoia:

Jo
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on September 15, 2019, 05:58:35 PM
Thanks Jo.

Truth to tell, it is particularly brittle glass and I did break one. Or was it two? I can't remember...

And there were also the other ones that I bought in case of future breakages. My shop looks like the glass recycling depot at the moment...
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 01, 2019, 10:04:48 PM
Well, I'm back from my travels and getting back into the shop, so will continue with the topic of the thread soon.

For now, though: one of the things I did when I was away was pay a visit to our forum friend Peter, aka Gas_mantle. We spent an enjoyable (and for me educational) couple of days coal firing his 5 inch vertical boiler and running a few of his engines on it.

Here he is with his newest - a vertical Stuart-like beastie (which I have just learned he calls 'Kermit'  :) ). In the background is my trusty home from home - my Ford Transit camper van conversion:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840205.jpg)

And here is a detail shot of his elegant Potty Grasshopper beam engine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840204.jpg)

A good time was had, including the obligatory beers of an evening!
Title: Re: Developing a Small Steam Plant
Post by: Gas_mantle on October 01, 2019, 10:16:54 PM
Cheers Gary  :)

A good bit of steaming during the day and later in the evening getting myself steamed with a few pints of the dark stuff  ;)
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 01, 2019, 10:19:08 PM
 :cheers:
Title: Re: Developing a Small Steam Plant
Post by: steam guy willy on October 02, 2019, 02:19:47 AM
Hi, A really interesting project .. :popcorn: :popcorn: :popcorn:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 02, 2019, 10:22:17 AM
Thank you  :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 04, 2019, 09:26:55 PM
A little bit of progress. Mounting block for pump - aluminium slab sawn and milled square enough and drilled and tapped M3 for the pump base:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840461.jpg)

And the underside drilled and tapped M6 for screws which will come up through the mounting board:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840460.jpg)

Steam separator/feedwater heater next...
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 05, 2019, 11:52:33 PM
So... below is my CAD ('Clunky And Dodgy') diagram for the steam separator / feedwater preheater.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840538.jpg)

I hope it is more or less self-explanatory. Gratitude to MJM 460 for his technical advice, and to other sources found online. This is a bit of a synthesis, with hopefully a few touches of my own as it pans out.

Here are the some of the basic materials (based on 2" diameter copper pipe and fittings) which I acquired today:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840539.jpg)

All advice welcome. Please feel free to offer any ideas and changes you may have in mind - it's all part of the process...

 :)

Title: Re: Developing a Small Steam Plant
Post by: MJM460 on October 06, 2019, 10:54:07 AM
Hi Gary, good to see that the good old back of the envelope still has itís place in modern CAD.

I would suggest that the steam outlet is moved to the top in the centre, with an internal projection down below the inlet.  The idea is that the wet exhaust steam has to start moving downwards, then has to turn back 180 degrees to the outlet.  This change of flow direction helps the separation of the more dense water droplets. 

It is also worth thinking about the detail of the lid.  If those bushes, plus the third one for the outlet are made longer and set in holes in the lid, it is easy to locate them when soldering.  The parts on the inside can be drilled for the ends of the internal tubes, and the outside can be threaded for your pipe connections.  Might need some nut and tail connections or flanges to make it possible to assemble.  You could even make it a flanged lid for maintainability.

How much heat you recover in the feedwater is limited by the exhaust temperature, probably very close to 100 C, and the area of tube in the coil, so wind as much as you can into the coil for more heat transfer area.  I suspect the smallest radius you can bend the tube to will determine how many coils you can fit.

Looking forward to see your interpretation and how it works in practice.

MJM460



Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 06, 2019, 10:22:07 PM
Hi MJM -

Once again, thanks for your input.

Back-of-the-envelope is the future of design, you know.

Decent progress this evening.

I will move the steam outlet to the centre of the lid, as you suggest. I made the basic forms tonight, and had to drill a hole in the centre anyway in order to turn the form I had roughed out by chain drilling:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840669.jpg)

The hole will do nicely as the basis for the steam outlet. The bushes in my sketch above weren't really a complete idea. I still have to think the connections through, and I'm sure your thoughts above will help.

The main forms are shown here:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840668.jpg)

The stand will be carved from the aluminium tube, and there will be a layer of insulation between the cylindrical part of the copper vessel and the inside of the stand. The bottom of the stand will be cut away to reveal the cone, and a drain cock of some kind will be inserted into the blanking cap at the end of the right angle. The stand is taller than the separator so the bottom pipe and drain cock will be held above the 'ground'.

The cap has a circular locating groove which was milled into the underside on the rotary table. This will hold the top part of the separator in the correct position when I solder the cap on. The first joint down from the cap will be left as a tight push fit so that it can be taken apart for cleaning, etc. The cap is wider than both the separator and the stand so it will support the separator by sitting on the top of the stand. I reckon a nice little pitch circle of tiny screws fixing the cap to the thick wall of the stand will finish it off nicely at that point   :)

When I get to the preheater coil I'll bear your advice in mind.

So, a bit more drilling and some soldering next...

Cheers   :ThumbsUp:

gary
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 07, 2019, 11:07:58 PM
Now, the cap, hand-fitted together at this point. Following MJM's suggestion, the steam outlet is now via a connector in the centre of the cap with a 1//4 " pipe, the end of which will be inside the separator lower down than the steam inlet, with the other end of the pipe going up the boiler chimney. The two outer connectors will bring water via 3/16" pipe from the pump into the coil and out to the boiler respectively.

The brass of the cap was thick enough to take a thread so I don't think any of these connectors will need to be soldered into the cap. I drilled the middle hole (for a turning mandrel - too big) before I knew I would be putting a pipe connector through it, hence the o-ring. Originally I was thinking of putting some kind of finial or knob on it to close the hole. Given the vessel is open to atmosphere I think the o-ring will be fine. If I get any steam leakage from the other two connectors I'm sure a twist of PTFE tape will fix it.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840741.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840740.jpg)

I can only avoid the torch for so long now...  :Mad:
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on October 08, 2019, 12:30:29 AM
Hi Gary, looking really good.

Remember, the vessel will be at atmospheric pressure, so sealing is no too difficult.  The only pressure is in the feedwater pipe, so the tube connections to the coil have to be sealed against the full feed water pressure.

MJM460

Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 08, 2019, 08:55:42 AM
Thanks MJM.

Yes indeed - they will be.

gary
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 08, 2019, 09:14:53 AM
... wind as much as you can into the coil for more heat transfer area.  I suspect the smallest radius you can bend the tube to will determine how many coils you can fit.


MJM - by this do you mean that the pipe should be bent into as many separate coils - parallel to each other,  'clover leaf' style - as will fit into the body of the separator?

I had just envisaged one single coil with as many turns as possible, but am open to ideas. What do you think?
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on October 08, 2019, 11:02:18 AM
Hi Gary, I am suggesting one long tube wound in a coil like a spring.  However, as the connections are side by side in the lid, instead of returning straight back to parallel to the inlet, you might be able to just continue winding more turns in a second layer so there is more of the tube wound into the coil to maximise heat transfer area.  Itís a matter of what is practical.

If you look in B and Rís book, you will see how their coils were arranged. 

I strongly recommend against parallel coils where the flow splits into parallel paths.  Even in full size with the greatest care to achieving symmetry of the coils, it is still difficult to get equal flow through each path.

MJM460
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 08, 2019, 12:05:16 PM
That's great, MJM.

Thank you again for your clear advice and for sharing your knowledge.
Title: Re: Developing a Small Steam Plant
Post by: doubletop on October 08, 2019, 08:58:27 PM
Gary

I was lookng at your sketch and reflecting on 'dry steam to chimney'. If the condenser does its job there should not be much in the way of dry steam as its temperature will have dropped. It will then be converted to hot water coming out of the drain. That water will have oil in it but if you could work on an oil seperator you could then feed the hot water back to the water tank.

Just thinking.....

Pete
Title: Re: Developing a Small Steam Plant
Post by: ChuckKey on October 08, 2019, 09:49:27 PM
If you make the exhaust steam inlet tangential to the drum rather than radial, you will get something of a cyclone effect, as in Dyson vacuum cleaners, centrifuging out water droplets.
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 08, 2019, 10:46:36 PM
Thanks guys.

@ Pete - well, that makes sense! I was thinking that only some of the steam would condense, with some left over to send up the chimney to draw the flame (I have found that the blower - when used - sometimes helps focus a kerosene, alcohol or even gas flame into the bottom of the boiler). From what you are saying I guess that if anything does come out of the exit end of the separator it might be quite a gentle flow and that might actually be quite good to just gently pull up the flame. But we shall see. Your point has got me thinking that the thing for me to do is to first trial it without connecting the outlet to the chimney. If nothing is coming out there won't be much point in hooking it up, but if there is some outflow - event slight - I think it would be worth routing up tthe chimney.

@ ChucKey - agreed. Or like the cyclonic separator in a shop vac system. Already part of the plan!   :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 08, 2019, 11:10:01 PM

 That water will have oil in it but if you could work on an oil seperator you could then feed the hot water back to the water tank.

Just thinking.....

Pete

That's a thought, Pete, though I'm not sure I want to take this plant that far.

gary
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 09, 2019, 10:25:02 PM
Wahey!

Silver solder day.   :Mad:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840857.jpg)

Below: the top half. The brass cap was silver soldered on to the copper tube. This picture shows the steam inlet pipe - which enters the vessel at a tangential angle -  just before I soft soldered it into the hole. This was the only soft soldering I did today.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840856.jpg)

The main body of the separator is pretty much done. All of the joints on the bottom half are silver soldered, but the middle joint is left as a push fit so that the vessel can be opened up for cleaning and so on. If there is any leakage from this I'll cross that bridge later, perhaps with some silicone. As noted above, this isn't a pressure vessel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840855.jpg)

I'm waiting for an outlet valve with matching bush to arrive. When they do, the end cap of the 90 degree bottom tube will be drilled and the bush soft soldered into it. The next step after that will be the coil.

I'm not the neatest solderer in the world, hard or soft. I guess a lot of it is just practice. However, I'm not unhappy with the overall result, especially since most of it will be hidden inside the aluminium stand.
Title: Re: Developing a Small Steam Plant
Post by: crueby on October 09, 2019, 10:29:02 PM
Your WorkMate looks like mine - pile of partly broken fire bricks, some scorches on the wood... Well lived in!
 :popcorn: :popcorn: :popcorn:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 09, 2019, 10:34:38 PM
I'm in good company then!

The first time I silver soldered it took me by surprise - I set my actual shop bench on fire. Plastic containers on the shelf above were melting with the heat from the torch and it was raining stainless steel cap-head screws...

 :Mad: :Mad: :Mad:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 11, 2019, 12:05:14 AM
The steam valve and bush arrived today so this evening I was able to drill the end of the drainage pipe, soft solder in the bush and trial fit the valve. Again not the neatest soldering in the world (everything runs - maybe I need thinner solder wire?) but it will be fairly well hidden when it's done and at least the valve hasn't ended up crooked. For the delicate soft soldering of the steam in pipe and the valve bush I bought a cheapo fine flame blowtorch at B&Q yesterday and I must say it's excellent for this kind of work:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840934.jpg)

Then the chickens came home to roost. I had begun to get the idea that I might have been premature in silver soldering the cap on to a fairly long tube section before fitting the coil, as it was going to be a faff trying to fit and tighten up the union nuts on the coil inside the cap when the coil was in the way. I got the first end done easily enough before I wound the coil:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840933.jpg)

Then with that end still attached I wound the coil round a bar of acetal held in the vice. The entire length of the coil used my remaining length of 3/16" pipe with nothing to spare:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840931.jpg)

But getting the coil into the tube was a mission to say the least, as I was working against two straight verticals and the 3/16" tube was work-hardening by the minute. I had thought of putting an elbow at the bottom which would probably have made life easier - but I didn't. This was probably not the best way to go about it but I think it all goes back to my earlier step with the cap. A simple flanged cap as MJM suggested would have been much easier to manage. The first union nut that I had tightened worked loose as I manhandled the coil, so now I have the awkward job of reaching in past the coil and tightening all three, including the one on the vertical steam out pipe in the centre of the cap. I have nothing that will reach in there so I'm going to have to make a long thin right angle spanner for each of the two sizes of nut.

The other issue was that I could only push the coil so far into the cap before the straight sections prevented it from going any further. In the picture below, although you can't see it, the top of the coil (before it turns into a straight run) is only just over a third of the way up the top half of the vessel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/840932.jpg)

This bothered me at first as I feared a loss of efficiency, but the idea then dawned on me that probably all I need to do is to make the bottom end of the central steam out pipe longer so that it goes down quite far through the coil towards the bottom of the vessel (though clearly not so far down that the end will be immersed as soon as condensate starts to collect!). That way the steam will have no option but to descend into the depths of the coil before it can find its way out of the separator.

It also occurred to me that the bit of empty space above the coil where the steam comes in might not be such a bad thing either as it may give the steam a chance to build up a bit of a cyclone witthout interference when it first enters the vessel. This last point might be wishful thinking on my part - I'd be interested in any views on this. And on the rest of it of course...

So I need to make two tools to tighten the nuts, but other than that it seems to be goiing ok if my hypotheses above are correct. As a by-product, I have also realised that winding the simple coil for my flash steam plant (featured in another thread) should be a breeze...
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 14, 2019, 11:37:46 PM
Not the most inspiring pictures tonight, unfortunately.

Because of my design issue of making the top section too long, it was a right game tightening up the union nuts on the coil on the underside of the cap. You can imagine. I tried making a right angle spanner-like tool out of a bit of steel, but that proved to be too flimsy and it bent even though I had hardened it. In the end I just took a perfectly nice 10 mm spanner, put the business end of it in the vice and  bashed it into a right angle with a hammer. For shame! Sheer vandalism, but it did the trick and I was able to get the internal coil connections to what I believe to be watertight.

With that done it was even trickier to tighten the connection on the central steam outlet pipe, so I re-thought it and drilled and tapped the central hole in the cap M12, then turned an elongated bush from brass with a slight taper on one end and an M12 thread on the other. This was drilled through for a sliding fit on the 1/4 " OD pipe and screwed into the hole in the cap. The threads fit nicely, but a hank of PTFE tape and a blob of Stag Wellseal will ensure that no stray steam escapes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/841301.jpg)

I then ran a length of the pipe through the bush with the bottom end at what I guess to be about the right depth in the vessel and plenty to play with sticking out the top. A union nut and nipple were added at the top and the assembly was silver soldered up. Here it is in situ:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/841300.jpg)

This more or less completes the working assembly of the steam separator / feedwater preheater. I will use some of my self-amalgamating tape to make a seal between the top and bottom halves of the vessel, which will be ok because it won't be seen. I'll also insulate the main part of the body with ceramic fibre - ditto. The aluminium stand will cover a multitude, and that is what I'll tackle next.

Shiny toys!
Title: Re: Developing a Small Steam Plant
Post by: Ye-Ole Steam Dude on October 15, 2019, 12:05:21 AM
Hello Gary,

Still following and watching  :popcorn:

Have a great day,
Thomas
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 15, 2019, 12:07:29 AM
Many thanks Thomas.
You too   8)
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on October 15, 2019, 06:36:25 AM
Hi Gary, good to see you managed to get the coil in.  Well done on that.  I was wondering how you would do it after soldering the top on to the cylinder first.

Remember that the water inside the coil is at full boiler pressure, so silver solder as many of the joints in that tube as you can.  All the joints which only see exhaust steam operate essentially at atmospheric pressure, so are the easier ones to seal.

MJM460

Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 15, 2019, 09:21:26 AM
Hi MJM.

Getting the coil in was a mission, to say the least - both actually getting it in there, then tightening the nuts. Serves me right for not thinking it through properly. I don't think it's too bad a job in the end, though.

There are only two connections in the coil, and these are where it joins the cap. They are made with pipe nipples silver soldered on to the ends of the pipe and secured with union nuts. The unions are screwed into threaded holes in the cap. It's the tightening of the union nuts that makes the seal, and I *think* I managed to get them watertight (probably steamtight in fact though they don't need to be). I'll test these connections with an engine run under steam before final assembly though.

The joints at atmopsheric pressure shouldn't present too much of a problem, as you say.

 :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 17, 2019, 11:12:18 PM
Just back from working away from home, but managed to squeeze in a little bit of shop time this evening.

Milled a notch into the thick-walled aluminium tube that will act as a stand and jacket for the separator to provide access for the steam inlet pipe and to centre the separator in the stand:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/841505.jpg)

Like the steam inlet pipe, the sides of the notch are tangential to the bore of the stand.
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 20, 2019, 09:57:19 PM
The housing (a better term for it than 'stand') for the separator is quite tall, and when combined with the height of the chuck on the rotary table it is beyond the capacity of every machine in my shop apart from the big floorstanding drill press:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/841648.jpg)

The plan is to make a bolt circle in order to attach the cap to the housing. I'm going to use M2 cap head screws for this, with a tapping drill size of 1.6mm. The chuck on the drill press won't hold anything that small, but it will hold a very small Jacobs chuck that I have, which will in turn hold the drill bit. This arrangement produces a certain amount of runout, but I think the centre drill which you can see here will counteract that. The dividing plate attachment on the rotary table enables the correct spacing of the six holes. Note the mill table which I have fitted to the drill press - it's a very handy addition. Recommended!

I got as far as centre drilling  the holes (as in the photo below) before I had to leave to go away until midweek. Once they are drilled and tapped I'll use transfer screws to mark out the positions on the cap.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/841647.jpg)
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on October 23, 2019, 11:00:48 PM
So.

Holes drilled and tapped:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/842082.jpg)

So far so good. But next comes a comedy of errors. Because I had already silver soldered the top half of the separator to the cap, and not having any long series drills, I decided it would be necessary to drill the clearance holes for the fixing screws in the cap from above to avoid a foul-up between the drill chuck and the top half of the separator. I put four transfer screws into the holes in the housing, turned the cap assembly upside down and set it all up to transfer the holes by giving a wooden block placed on the other end of the housing a sharp tap with a wooden mallet:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/842081.jpg)

However, it didn't occur to me that the position of the steam inlet pipe would be a problem. It should have, but it didn't. The four holes transferred nicely (I only have four M3 transfer screws), but due to the fact that I had positioned the holes in the housing somewhat randomly relative to the notch for the pipe, the position of the notch caused the pipe to lever the cap round and throw the holes in the cap out of alignment with those in the housing when the cap was turned the right way up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/842080.jpg)

Rookie error!   :facepalm:

I initially thought of widening the notch, but then decided to try to bend the tube to a more forgiving angle. The tube did not bend. The soft solder sheared, and the tube came out:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/842079.jpg)

 :facepalm: :facepalm:

I'll have to solder it back in again at a better angle, after which I'll transfer and drill the two remaining clearance holes.

Not a major disaster, but the result of not thinking through the sequencing issues properly, and it's striking how a mistake early on can make its presence felt through subsequent steps.

Still, at least I now shouldn't have to widen that notch in the housing, and the drilling, tapping and transferring of the holes seems to have gone well...
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 03, 2019, 10:04:24 PM
Managed to make some reasonable progress before I went on holiday and today having just got back.

The cap is now in situ, fixed with stainless M3 pan head screws:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843069.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843068.jpg)

Work then began on the aperture at the bottom through which the drain valve will protrude.

Centering the housing on the drill press:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843067.jpg)

Cutting the aperture with a hole saw. This went quite well, and overall the aperture looks fairly neat. Inside the housing there is a gouge at each side as the hole saw cut vertically through the sides of the tube. I'm going to leave this be as any attempts to tidy it up will probably just make it worse. In any case the gouging is pretty much internal and doesn't really harm the overall look. It's visible on the finished assembly but you have to peer a bit to see it. No big deal.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843066.jpg)

I had a nice thick brass ring left over from a failed attempt at making a meths burner housing. This just needed a little drilling to convert it to a base for the separator housing. I centred it by eye under the housing and marked it out...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843065.jpg)

... then drilled three clearance holes to allow it to be fixed to the bottom of the housing courtesy of three corresponding holes drilled and tapped M3. These three holes are a bit out of alignment with the existing outer holes but that won't matter as only the outer holes will be seen. They will be used to fix the asssembly to the base board of the plant.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843071.jpg)

I used both transfer punches and transfer screws to mark out the various fixing holes in the cap and the base. They are extremely handy for accurately transferring hole positions.

Finally, the basic assembly in a more or less complete state:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843070.jpg)

There are still a few bits and pieces to attend to and the whole thing will benefit from a bit of a shine up. Getting there though...



Title: Re: Developing a Small Steam Plant
Post by: MJM460 on November 04, 2019, 04:39:29 AM
Looking good Gary.  Great to see progress already after returning from your travels.

One thing to note, that combination of metals will over time give you corrosion problems if it ever gets wet, which it almost certainly will.  The Aluminium tube will do a great job of protecting the stainless screws and the brass by sacrificing itself.

Fortunately there is a simple solution.  You might know that most yacht fittings are stainless steel, while masts and booms are mostly aluminium.  Any yacht chandler will have a small tube of paste to use as an insulating barrier.  It works well even in salt water environments.

So when you get to your near final assembly, put a smear around the top of the aluminium stand and a dob on each screw before you insert it.  It works very well, and will avoid unsightly corrosion, and ensure that you can always pull it apart if necessary.  The one I use is green, just wipe off the excess with a paper tissue or rag, but other brands may be a different colour.

Looking forward to the next steps.

MJM460

Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 04, 2019, 09:02:21 AM
Hi MJM, and thanks for your input once again.

My knowledge of the dark metallurgical arts only extends so far as knowing that 'some metals in contact with each other can cause corrosion', but without any real clue about what metals will do that. Your advice, therefore, is very helpful. There are a couple of yachting chandlers near where I live so it should be easy enough for me to get some of the goo you recommend.

Cheers...

 :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: Bluechip on November 04, 2019, 09:56:26 AM

 'some metals in contact with each other can cause corrosion', but without any real clue about what metals will do that.


Electrode potentials.

The greater the potential, the greater the risk of corrosion. There does need to be an electrolyte ( usually water ) present.

http://www.efunda.com/materials/corrosion/electrochem_list.cfm?sort=com

From the table copper is about +0.5v and zinc - 0.75v so if you poke a bit of each in a orange / potato / whatever you'll land up with a 1.25V - ish battery.  :)
No great current draw possible but it will drive a red LED, or sometimes a very small  motor

From memory the copper will eventually disappear hence the expression 'sacrificial anode'.

There is a fair bit more to it but I've long since forgotten ....  :old:

Oops .. starts here:

http://www.efunda.com/materials/corrosion/corrosion_basics.cfm

Dave
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 04, 2019, 09:28:57 PM
Thanks Dave.

I have no doubt that this information will be useful in many other projects too.

gary
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 10, 2019, 10:53:07 PM
I had to redo the soft soldering of the steam outlet pipe because I got all the angles wrong first time round. This was a messy and time consuming business but I got there. I then water tested the connections on the coil at the top of the separator and they appeared to be watertight. So, the way forward was clear...

The top and bottom halves of the main vessel were pushed together and the join covered with self-amalgamating tape. But for MJM 460 I wouldn't know this stuff existed, but it seems ideal for the job in hand, bearing in mind that this is not a pressure vessel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843748.jpg)

Next, the separator was lagged in ceramic fibre insulation material secured with fine copper wire:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843747.jpg)

And, bar a few lotions and potions, that's pretty much it. I'll call it done for now:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/843746.jpg)

Given that all of the main components are now done, the next step is to think about the layout of the plant as a whole and consider what material I'm going to use as a base board.

Will be interested to know what other people would use!

gary
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on November 11, 2019, 08:54:56 AM
Hi Gary, thatís a fine looking separator.  Now to see how it performs. 

I am not sure that I would have used the self amalgamating tape for that purpose, but it is very useful for a layer of insulation on the steam pipes.  However, as you say, it is not a pressure vessel.  Now that you have started soft soldering, you will have difficulty doing any further silver soldering, but again, it is not a pressure vessel.  I think I would have put a few rivets in, even if only loose, just to hold things in place and then soft soldered the seam.  Perhaps next time.  But there are many lessons in the journey to a handsome feature of your steam plant.

I just use a piece of chipboard for a base board, either melamine covered as in typical kitchen shelving to keep it waterproof, or just a few coats of polyurethane, again to make it waterproof.  Otherwise it tends to swell and disintegrate due to the inevitable water spills.  Ideally, eventually, I would like to tidy them up by adding brick like trim or more paint to make it look like brick or concrete, but perhaps that will wait until my model making skills are more advanced.

It is interesting that you chose to insulate the separator vessel inside the aluminium stand.  You are using the exhaust heat for boiler feed water in the coil, so donít want to loose it unnecessarily, but then you are discharging the exhaust, so the more that condenses, the less moisture into the shed, assuming you are in a shed.  Perhaps another area for some experiments, by trying a few runs with that insulation removed once you see what it does with the insulation.

MJM460

Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 11, 2019, 09:12:56 AM
Thank you MJM. Glad you like the look.

Apologies - I should have made it clear that your recommendation of the self-amalgamating tape was related to something else, not this. However, I have a feeling it will be ok in this application as the two sections of pipe that comprise the vessel make a really tight push fit. It can be quite hard to pull them apart by hand so unless that changes under heat, the tape is really just to close off any odd gaps round the perimeter.

I also thought about the dilemma of the insulation, and opted for your first point, i.e. to maximise the heat going into the feed water by preventing it from escaping through the walls of the vessel. But yes, as you say the condensing effect on the exhaust will be compromised. I guess it's a case of 'suck it and see' and trying it with and without the lagging.

Regarding the base board, my ideal would be a piece of the kind of smooth black slate that is often used to make fireplace hearths. That would look great, but it would be (a) expensive, (b) heavy and (c) unforgiving of any drilling errors.

I might prefer plywood to chipboard, possibly with a dark stain to camouflage any scorch marks. Or a slab of aluminium perhaps...

All ideas welcome!
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 20, 2019, 10:35:47 PM
I decided on a piece of plywood 20 mm or so thick for the baseboard. It will be varnished in a dark mahogany colour when it's done. The basic layout is below. I intend to put a displacement lubricator between the separator/preheater boiler and the engine - I'll probably just buy it rather than make one. I also have a tiny electric motor which will hopefully work as an engine-driven generator powering a small led lamp - these will be placed at the front of the board (the bottom in the picture). Some components will be screwed to the board from above with wood screws; others will be fixed from below with machine screws, in which case the holes will be countersunk and/or counterbored on the underside of the board. Counterbored holes will be reinforced with washers epoxied in. I think that this will suffice rather than making threaded inserts. As a final touch, some kind of angle bead will be fixed round the outer edges of the board.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/844788.jpg)

Starting to take shape but there's still plenty of plumbing and other stuff to do yet...

gary
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on November 20, 2019, 11:49:34 PM
Hi Gary, looking good. 

You can see that the complexity builds quite quickly when you set out to make a complete steam plant.  It would be worth making a sketch schematic ( I.e not to scale) to show where all your piping must go to get all the components in the right order.   Piping runs will determine (along with access) the orientation of components.   Piping runs can be much simpler and tidier if the location of components is carefully chosen.

Remember the lubricator must go in the steam line between the boiler and engine, preferably close to the engine and with its outlet equal or higher than the engine steam inlet.  You donít want oil in the boiler.

Thirty eight already here and itís only 10:30 am and only November.  Not even summer yet.  Hardly need a preheater for the boiler.  But we are expecting a cool change later in the afternoon which should drop the temperature to a more comfortable level quite quickly.

MJM460
Title: Re: Developing a Small Steam Plant
Post by: crueby on November 20, 2019, 11:53:30 PM
Good tips on the piping from MJM, be bad to get most of the way through and have two pipes or fittings inrterfere. There is the high-tech route with drawings in 3D, down to the old school (and sometimes fun-ner) way of mocking it up with something like pipe cleaners. I remember mocking up sailboat cockpits with boards, crates, and extension cords.
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on November 21, 2019, 12:01:58 AM
Donít mock the pipe cleaners, Chris.  We used to build whole refineries with plastic tube and moulded fittings, and made up pressure vessels all to perfect scale.  Then attached labels with the dimensions and went direct from that to isometric drawings of individual pipes with material lists for the welders.  No layout drawings.

Main problem was the plastic tended to melt if we tried to fire it up to see if it would run.  Also turbines were lacking in internal detail!

That was real 3-D modelling, way before all this virtual stuff.

MJM460
Title: Re: Developing a Small Steam Plant
Post by: crueby on November 21, 2019, 12:17:17 AM
Donít mock the pipe cleaners, Chris.  We used to build whole refineries with plastic tube and moulded fittings, and made up pressure vessels all to perfect scale.  Then attached labels with the dimensions and went direct from that to isometric drawings of individual pipes with material lists for the welders.  No layout drawings.

Main problem was the plastic tended to melt if we tried to fire it up to see if it would run.  Also turbines were lacking in internal detail!

That was real 3-D modelling, way before all this virtual stuff.

MJM460
I am not mocking them, I am serious about using them! In a mock-up. I would mock trying to put steam through them!
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on November 21, 2019, 12:30:33 AM
Yeah, pipe cleaners would not even handle low pressure air.  Come to think of it while our plastic tubes would have been ok for low pressure air, the elbow and tee fittings, valves etc were all solid.  Fortunately we had other methods to check that things were likely to work. 

MJM460
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 21, 2019, 07:34:20 AM
Hi guys -

My temporary lapse of thinking regarding the position of the displacement lubricator (now corrected above) notwithstanding, I believe I have a reasonably clear image in my head of the piping. However, the pipe cleaners mockup is a great idea. Don't think I have seen a pipe cleaner for decades but they are no doubt still out there (after all, what else would people clean their pipes with? While I suspect that pipe-smoking has gone into decline as vaping has ascended, surely it cannot be extinct!). Amazon is my friend...

Intriguing, MJM, that you would build small scale models of whole refineries using Blue Peter methods and materials.     :)

Hot in Australia, cold here in Britain. I tend to prefer the cold but a happy medium would be good...

Thanks both for your input.

gary
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 21, 2019, 08:11:20 AM
Pipe cleaners ordered!
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 26, 2019, 09:56:34 PM
The pipe cleaners have not yet arrived, so rather than pace up and down fretting I transferred my attention to making a handle for the boiler feed pump:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845174.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845173.jpg)

The grip is aluminium, the shank a random piece of steel of unknown kind that I inherited with a lathe I bought a few years ago.

I'm pleased with the chunky undercut thread on the shank and the curved profile of the shank (which took quite a lot of work with files and abrasives in the lathe). The overall finish is reasonable and I can always go back to it again if I decide to. I am definitely not pleased that the slot at the bottom of the shank (to fit over the brass handle of the pump) is off-centre. I have no idea how this happened. I used an edge finder on the insides of the vice jaws and the 1/2 function of the DRO before cutting it with multiple passes of a small endmill.. Maybe I wasn't as accurate with the edge finder as I should have been - I don't know. I'll get away with it because it's only a pump handle and the slot will be covered by a collar. I most certainly will not get away with it when I get to building my second engine, so I need to address this.

I also reckon that some people may feel that the handle asssembly is a bit big and somewhat out of scale with the rest of the plant. On the other hand, it should be a nice chunky handle to pump water with.

Still on track, the inevitable imperfections notwithstanding...
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 27, 2019, 05:48:11 PM
Well, since none of you  have talked me out of using that handle on the basis that it's visually too big for the plant, I've decided that I might as well talk myself out of it. It's too big for the plant. Or is it? Dammit, I don't know...depends on how you look at it... but certainly I have thought of other applications in which I could use it, so we'll see...

Meanwhile, here's my little oil refinery in development. Welcome to pipe cleaner heaven:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845232.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845231.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845230.jpg)

Looking at it might make you go crosseyed, but I think it more or less makes sense. The photos make some of the pipe cleaners look as though they are angled all over the place, but in fact they are pretty much arranged in right angle bends (I have a few elbows in my box that might be nice to use). The red pipe cleaners represent lagged pipes, the blue ones bare copper. The spiral bits are just where I have wound the pipe cleaners around existing pipes, and the bit of blue near the engine represents the displacement lubricator (winging its way as I type).

Apart from any other comments any of you may have, I only have two questions:

1. I have designated the pipe routing steam up the chimney from the separator as lagged. Should it be so?

2. How do I get water and steam to flow through the pipe cleaners? I have looked and they don't seem to be hollow in the middle. Can't for the life of me figure that one out...
Title: Re: Developing a Small Steam Plant
Post by: JC54 on November 27, 2019, 07:52:54 PM
Ask Santa to bring you some very thin long Drills?
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 27, 2019, 08:52:53 PM
Ah... so that's how it's done! Yep, makes sense...
Title: Re: Developing a Small Steam Plant
Post by: crueby on November 27, 2019, 10:29:28 PM
Ask Santa to bring you some very thin long Drills?
Aircraft extension drills....   :Lol:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 28, 2019, 12:33:14 AM
Amazon is my friend...
Title: Re: Developing a Small Steam Plant
Post by: JC54 on November 29, 2019, 10:57:04 PM
My vote is keep pump handle as it is. I think it is in keeping with the engine,, something different. :ThumbsUp: :old: :DrinkPint:
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on November 29, 2019, 11:55:44 PM
Hi Gary, looks like itís time to make up some tube connectors, and bend some copper tube, now you have the 3-D patterns.

You asked about insulating the outlet from the separator/feed water heater.

Insulation is normally applied for one of two reasons, or perhaps even both.  The obvious one is for heat conservation, and the other is for personal protection.  In this case, heat conservation is not really required, though if the outlet steam gets to the top of the stack before it condenses, it will more readily be dispersed into the atmosphere as extra humidity rather than raining inside your workshop.  So I would suggest in this case the main issue is personnel protection.

In the oil industry, and I assume power generation is similar, personnel protection is required if the surface is both accessible for accidental touching and above 65 deg C, above which burn injuries are considered likely.  Probably a bit of a safety margin in that, especially if you are an experienced welder with tough skin, but the line has to be drawn somewhere.

You might be interested to know what happens if the pipe is hot enough to cause injury, but process reasons require cooling.  In such cases, a cage is made from expanded metal mesh and supported of the pipe by appropriate brackets in the accessible areas, for example where the pipe passes through a platform.

The exhaust steam in that pipe will be a mix of steam and air, so the final temperature after the feedwater has absorbed what the available heat transfer area will allow, is a bit hard to guess, but it will probably be a little above 65, but certainly less than 90.  Considering the nature of the plant as a whole it is probably not the biggest injury risk you need to be aware of, so I suggest that you can take your choice.

MJM460



Title: Re: Developing a Small Steam Plant
Post by: derekwarner on November 30, 2019, 04:22:22 AM
Gary......

I found the DuBro 1/8" & 5/32" OD bending spring & wasted so many bends as being inaccurate in the set of and badly rippled inner surfaces, despite pre annealing the bend area

I finally purchased a pair of DuBro tube benders for the above sized tubes and find the K&S 1/8" & 5/32" OD brass tube can require 2 or 3 annealings until red hot, then air cooling after each annealing can achieve a smooth 90 degree bend with absolutely minimal surface rippling on the tube inner radius surface

If you read & view images of older  :old: full sized steam plants pipe work, you will note 90 degree bends, with pipe spools set in 3 principal  planes.....yes 'vertical', 'horizontal' and 'across

Parallelisim of pipe runs is also an aspect point as viewed that follows for the 3 planes mantioned

There is no use of 135 degree bends  :facepalm: or angular set of any pipework

So after realisation of the above my scale tubework [generally] follows these principals

Derek

Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on November 30, 2019, 04:24:12 PM
Hi All.

Many thanks for your input.

@ JC54 - on the handle - you have emboldened me! It's quite a big handle but it's not like the plant is a 'model of' anything, so there's no predetermined look for it to spoil. And yes, I suppose it does sort of go with the engine, so I am now one step closer to keeping the handle as is.   :ThumbsUp:

@ MJM460 - educational, as always. I'm not too worried about the safety angle in this instance. As you suggest it's relatively minor (and I have been burned too many times to care...). What I'll do is run it with the pipe in question left bare, see what it does and then decide whether or not to lag it.

@ Derek - I agree with you about the 90 degree bends. It's certainly my intention to keep everything as square as possible. However, I have these:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845454.jpg)

I have quite a few of these elbows and straight connectors for both pipe sizes (3/16" and 1/4"). Using elbows instead of at least some of the bends would probably make life easier in that cutting straight pipe lengths and silver soldering nipples on to them will be easier  to keep accurate than full pipe runs with several bends in them.  However, will using elbows instead of bends impair efficiency by creating more drag on the steam passing through? Or would the difference be insignificant in a plant of this size?

And why do I find myself thinking that that last question has MJM's name on it...?   ;)

@ Derek - thanks for posting the photos. Great looking plant! What is that you used for the pipe insulation?
Title: Re: Developing a Small Steam Plant
Post by: derekwarner on November 30, 2019, 07:32:42 PM
Gary.......the advantages of using those demountable elbows you show are many indeed, the single biggest disadvantage is in the hot steam tube to the engine & the mass of the fitting body, tails & nuts all consume more heat energy that a bent tube...same naturally applies to straight unions........a Golden rule is to keep the hot steam line a short as is reasonably practicable

In many installations, you may have a lubricator and then a regulator in the steam line between the boiler & the engine....so these must be considered & also lagged if possible

So the greater the material mass of the hot steam tube reduces the temperature of the steam & increases the formation of condensate/water

There is certainly a lessor issue with return lines, although it is best maintain the hottest exhaust steam temperatures the let the de-oiler perform its task

The tube insulation is pretty simple.......cotton twine [1.5 mm diameter] + a drop of Superglue......then wound progressively over the tubing....around the bends as needed & ended with another drop of Super glue........layer & paste a Home Brand Celulose type Polyfiller over the cotton twine to your required thickness....I chose say 2 mm deposit, then sand with 140 grit paper gently and progressively in sheet or tube format until you end up with a uniform thickness of ~~ 1.5mm depth......paint with oil based primer + oil based top coat

Derek
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on December 01, 2019, 11:39:57 AM
Ah yes, that makes sense, Derek.

Not so much about friction/baffling effects; more about heat loss. Right enough, now that you point it out it's a bit self-defeating to lag pipes then stick a big heat sink in the middle of them. so... I will use the elbows where it doesn't matter (e.g. the cold water feed) and bend the others.

Thanks also for the recipe for lagging the pipes. Not sure I will do it the way you describe, but will certainly consider it.

Cheers,

gary     :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: MJM460 on December 01, 2019, 11:37:04 PM
Hi Gary, a bit slow on taking my cue, itís been a busy morning.

On the pressure drop, yes, a change of direction involves more pressure loss than the same length of straight pipe, though as you suggest itís not a lot in the great scheme of things.  The component of velocity in the direction of the straight pipe is reduced to zero, involving the loss of one velocity head of energy, and it is a loss, not converted to extra pressure.  Then the flow has to be accelerated in the other direction, which takes another velocity head.  Obviously the two occur in a gradual transition rather than in sequence, but the total effect is similar.  The important thing to appreciate is that velocity is a vector and has direction.  Maintaining the same speed of flow around a bend does not avoid the issue.

If you have a sharp bend, such as the intersection of two drilled passages in a solid fitting, there is even more energy lost in turbulence created.  There is less turbulence in a smooth sweeping bend so less energy loss.  The standard data for a forged pipe bend of the standard radius is about 13 times the equivalent length of straight pipe.  So for 1/4 in. tube, about 3 inches of extra length.  You can see why I say overall it is not much.  But bending the tube avoids the cost of the fitting as well as in principle being the right direction on energy losses if you are after the last bit of performance.  You do what fits when you have plenty of pressure which you are dissipating in a control valve to run an engine slowly, as pressure loss is not a problem.

On the heat loss issue, Derek is quite right that it takes heat to get the extra metal in those fittings up to steam temperature.  That certainly results in extra condensate when you are starting from cold.  However, providing you insulate them well, the extra heat loss once warmed up is only due to the extra surface area, and easily managed by a bit of extra thickness of insulation, so again, not much of a problem in the grand scheme of things, especially with that good condensate separator you have made.

It might not be immediately obvious just why refinery piping is always run parallel in the three orthogonal directions.  Cutting across at an angle would obviously involve a shorter length, hence lower cost.  Basically the parallel runs allow the most usable space for future additions, while the remaining open space is more friendly for cranes and other maintenance equipment, so not only to look tidy.  A singly line across a pipe trac at an angle can block hundreds of meters of otherwise useable space where the pipe supports are already in place.  In your plant you may prefer graceful curves in keeping with your engine design.  Itís up to you.

MJM460
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on December 03, 2019, 10:56:26 AM
Thanks MJM.

Putting this all together, I reckon I'll try to avoid using couplings where it's reasonable to do so, but not be too phobic of them for the tricky bits and where it doesn't matter.

As for the aesthetics - good point. Graceful curves are nice, but then so is a bit of juxtaposition of organic and geometric. I'll play it by ear...

Fascinating to learn about allowing space for service vehicles etc among refinery pipework. Obvious if you are in the know, I suppose, but what lay person would have thought of it?

All the Best,

gary

 :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on December 05, 2019, 10:30:56 PM
The displacement lubricator arrived today. PM Research LUB-2, 2" long, 3/16" x 40 thread. All the way from the USA. Here it is, along with the tee by which it will be connected into the system, lying on the baseboard which is now looking pretty good after five coats of water-based gloss woodstain/varnish in a 'dark mahogany' hue:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/845975.jpg)

I guess I could have had a go at making a lubricator myself but it strikes me as being something of a mission and I'd rather devote the required amount of time, energy and angst to something more substantial.

As for hooking it up, here's exactly how I plan to do it (3:35 to 5:07):

http://www.youtube.com/watch?v=y9o6dXWGE10

Now that I have this part and the baseboard is varnished, I can finalize my layout and start screwing things down and piping them together.

 :cartwheel:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on December 07, 2019, 05:38:06 PM
It appears to be green at this end of the planet too.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/846061.jpg)

Duralac Green. Preventing Corrosion Between Dissimilar Metals. In a Shed. Near You. Now.

Another handy tip (one of many) from MJM460.

 :ThumbsUp:
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on December 08, 2019, 08:43:13 PM
A bit of progress today.

Yesterday the original flat brass handle of the water pump was glued into the slot in the new steel shank with Loctite 638. Today, I drilled two cross holes and tapped them M5. Two M5 screws were then secured in these holes using Loctite 2400 Threadlocker (blue in colour):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/846192.jpg)

Tomorrow or the day after, when all the adhesive has set, I will cut off the ends of the scews and grind them flush with the shank. After that the plan is to machine a brass sleeve just long enough to cover this joint and fix it in place witth 638.

A locating ring for the water reservoir was machined, and this was fixed to the base board, as was the steam separator/feedwater preheater. The undersides of these (which directly contact the board) were smeared with silicone to prevent water from being drawn under the parts by capillary action. All points of contact between dissimilar metals (aluminium, brass and stainless steel screws) were treated with the ghastly green goo. Where the part fixed to the baseboard is brass, stainless steel screws were used, and where the part  is aluminium, the screws are brass. Just for the contrasty look. Having a couple of the main elements fixed to the board feels like a real step forward:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/846191.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/846190.jpg)
Title: Re: Developing a Small Steam Plant
Post by: propforward on December 08, 2019, 09:21:46 PM
Some beautiful work in this thread Gary. Nice job.
Title: Re: Developing a Small Steam Plant
Post by: gary.a.ayres on December 08, 2019, 11:43:54 PM
Thank you very much Stuart. Very kind of you.

gary