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[steamboatwilly]

Can anybody please provide a cross sectional drawing of a typical cheddar type oil seperator, ie approx 70mm by 30mm, showing the internal layout,  as  unable to source, and I have the raw materials.  Understand there are three connections, ie  a steam inlet, steam  outlet and air vent. Dia of connection pipes would also be appreciated. Many thanks.

[wideawake]

Can anybody please provide a cross sectional drawing of a typical cheddar type oil seperator, ie approx 70mm by 30mm, showing the internal layout,  as  unable to source, and I have the raw materials.  Understand there are three connections, ie  a steam inlet, steam  outlet and air vent. Dia of connection pipes would also be appreciated. Many thanks.

Other members have much more experience than me in these things!   However I made a separator recently, which seems to work, from a bit of 1 1/2 inch diameter copper tube .   Basically it has the steam outlet to the funnel taken from the centre of the top plate.  The other two connections are steam inlet and condensate outlet (not air vent).   The steam inlet goes into the side just below the top and the tube is extended inside the drum curving round to encourage the steam to swirl round the drum rather than heading straight for the outlet.   The condensate outlet is taken from side near the bottom plate but can equally well be fitted to the top plate with the tube extended to near the bottom of the drum.   That's the way Cheddar did their version.

Sorry it's a description not a drawing

HTH

Guy

[steamboatwilly]

Many thanks Guy.Thanks for correcting me on the air pipe incorrect terminology.  Have drawn it out as suggested, and now wonder if the condesate outlet is required, ie I am thinking that perhaps a steam inlet and steam exhaust only would work, or have I got it wrong?  Since your post, I have made up a 75mm length of 35mm tube with endcaps from standard endfeed plumbing fittings, the bottom soft soldered, and the top removable for easy emptying, and for easy checking of oil level.

[boatmadman]

You need to have a method of emptying the condensate from the vessel.
 I know of 3 methods:
1. no drain and you use a syringe with a length of tube to draw out the condensate after each run, nice and easy.
2. drain connected to a length of tube that empties into an external collector. This method required a little valve on the drain, and a method of shutting off the steam vent. To operate this type, you need to open the drain and close the steam vent with the engine still running to use the exhaust pressure to blow out the condensate into the collector vessel, a little more complicated.
3. drain and pipe allowing the condensate to drain out by gravity to a collector, this will need a little valve as well.

Hope this helps.

Ian

[wideawake]

Many thanks Guy.Thanks for correcting me on the air pipe incorrect terminology.  Have drawn it out as suggested, and now wonder if the condesate outlet is required, ie I am thinking that perhaps a steam inlet and steam exhaust only would work, or have I got it wrong?  Since your post, I have made up a 75mm length of 35mm tube with endcaps from standard endfeed plumbing fittings, the bottom soft soldered, and the top removable for easy emptying, and for easy checking of oil level.

I see where you're coming from Will.   All the separators I've seen have a fixed top lid and therefore need an outlet pipe.    Also they're usually fixed down in the boat so emptying would otherwise be difficult.   I think, using your idea, you'd need to fix the top down firmly to stop steam leakage.   There's quite a bit of pressure in the tank.   In fact enough to empty the condensate via the outlet pipe just using steam pressure once the outlet cock is opened.   However if you can arrange a simple means of emptying the drum like a syringe then I'm sure your idea will work.   I like the simplicity of using end feed stop ends as top and bottom!  

Cheers

Guy

[derekwarner]

mmmmmmmm    must remember that these oil seperators are not pressure vessels & should not be subjected any restriction above atmospheric pressure....Derek

[steamboatwilly]

Dereck. Sorry, but being a new boy and on the bottom rung of the ladder, I do not understand the restriction part of your posting. Could you kindly explain a little more fully. Thanks.

[boatmadman]

Derek is absolutely right, I was misleading in part of my last post.

What he refers to is that your condensate separator has not been designed or built to operate as a pressure vessel. Consequently, there should be no attached fittings - eg valves, that can restrict the venting of the vessel to atmosphere, as this could allow the internal pressure to rise above atmospheric pressure creating the potential for catastrophic failure - read burst! with the associated risk of injury.

Further, pressure vessels have to be tested to prove integrity, just as does your boiler and refillable gas tank.

Re reading your posts, I see you used soft solder, its more usual to silver solder steam plant, as this has a much higher melting temperature. Boilers constructed using soft solder have been known to fail for this reason.

Off the top of my head I dont know what temperature condensate will be at, but if its near the melting temp of soft solder---- you guessed the potential for problems.

Hope this helps, and sorry for the confusion.

Ian

[steamboatwilly]

Thanks for comments Guy. Should have explained about construction a little more fully. A copper blank disc was soldered internally into the bottom end of the tube.  An end cap was soldered onto a square copper base plate. The tube is  then  just a push fit into the base for removal and emptying. The other end cap, also a push fit, INITIAL THINKING, could then easily be removed for emptying. In view of your comments I may well have to solder in place. I will set up and test, and if the end cap blows off, then I will fit condensate pipe and solder lid in place, and use a syringe to empty as boatmadman, thanks, suggested.
PS. Just seen a picture of a Monahan plant with a horizontal seperator, with Just steam in and steam out, and a screw fitting on top, presumably for drain purposes?

[steamboatwilly]

Hello Boatmadman. Thanks. Point taken. I do silver solder the boilers I make , unless a pot boiler type, ie Mamod. where pressures are below 40psi, thenI use soft solder and spritlamps or fuel tablets.  I was working on the theory that the exhast steam pressure /temp would be in this order, and I had not considered it as a pressure vessel. So please tell me if it is a pressure vessel? I honestly do not know. The way I was looking at it was that steam enters,swirls around, and exits through the top outlet pipe. As there was no expansion of steam, I assumed an outlet pipe of identical size to the inlet would not restrict steam flow, and a slightly larger one would make the escape steam vent easier. But , please gentleman, do put me right if my logic is wrong. Thank you to you all for your help and advice so far. A very constructive forum.

[tobyker]

I'm no engineer, but surely using words like "condensate" confuses the issue. We are referring here to an oil separator, which ensures that your model does not plow across the water spitting drops of oil out of the funnel as it goes. So the separator is merely providing a gap in the exhaust pipe into which any oil carried through the engine can drop. If it were a condenser, wouldn't it have a vacuum inside to pull the piston up (or down), and an air pump to maintain the vacuum despite the presence of air carried through the engine with the steam?  

An open steam outlet will prevent any positive or negative pressure building up, and a pipe taken to the bottom of the separator will allow for removal of the oil and of any water from condensed steam. So that's 3- in, out and drain.

[boatmadman]

Tobyker,

You are not wrong in what you say, but there is more to it. A condenser is, as you say, for turning exhaust steam into water for re using in the steam water cycle. You can and do get atmospheric pressure condensers, but they are very inefficient when used with steam plant. The most efficient system is a vacuum condenser, as you say. The reason for this is that the better the vacuum, the lower temperature you can take steam before turning back to water and hence more work is extracted from the steam.

A good vacuum condensing system will allow exhaust steam to enter the condenser, as steam, at a temperature below 30deg c. This is dependent on the level of vacuum and the temperature of the cooling water used to cool the condenser.

The vacuum does not assist in pulling a piston up or down, what it creates is a bigger pressure differential between the steam inlet pressure and exhaust pressure, thus enabling more useful energy to be extracted from the steam = greater plant efficiency. The same principal applies to steam turbine plant.

Willy, in general terms you can consider a vessel to be a pressure vessel if the internal pressure can rise above atmospheric pressure and if there is no unrestricted vent to atmosphere.

You are right about the pipe diameters, but at the volumes of steam used on small model plant, I think it is safe to use the same diameter exhaust pipe from the engine, to the oil trap and out to atmosphere. A larger dia pipe at the final outlet will slow the exit steam velocity and increase the cooling and condensing of the exhaust steam. This may result in water (condensate) spitting out of the end of the exhaust.

Ian

[steamboatwilly]

Hello Boatmadman. Thank you for the clarification, which is much apprciated. I shall work on the principle of it being a pressure vessel. That said, I will silver solder. I will also use identical inlet/outlet pipes. I have, in the meantime,visited the Monahan site, and note that they use  a horizontal layout more than the vertical version. So will try that in preference to the vertical one I was going to build. Interestingly they only appear to use an inlet and outlet pipe with no apparent vent pipe, but a screw fitting on top, presumably for drainage via a syringe. It will be interesting to build as theirs, and then screw in a pressure gauge and see what reading I get. Many thanks to you all for your interest. Will.

[Brooks]

If you just want to make a quick and easy separator, you can use a prescription plastic pill container with a screw-on lid. I used one 3 cm dia. x 6 cm tall for a single cylinder oscillator steamboat (Midwest's Heritage engine & boiler package). I drilled 2, 1/8" holes in the polyethylene lid, and poked 2 short pieces of 1/8" Cu pipe through the holes. Friction holds the pipes in place. Since I was going to lay down the container, I first bent the pipes 90 deg. One pipe sticks up when the container is lying on the deck, providing the steam exhaust pipe; the other pipe accepts the exhaust from the engine. Silicon tubing connects the engine to the separator. To empty the container, I just turn it upright, unscrew the lid, and dump out the water/oil collected (not in the pond, obviously). The separator must be emptied after about 20-30 minutes of running (2-3 voyages with this boat). It's about 1/2 full at that point.

Photos of the steamboat and separator can be seen in post#15 here. I eventually painted the separator black, but in the photos for #15,  it's still in it's prescription glory of orange plastic and paper label. Later photos (post #34) show it in black, lying on the deck between the RC crates and the engine platform:
http://www.rcgroups.com/forums/showthread.php?t=1153159

[derekwarner]

Guys....there is still a misconception here.....the model oil trap condenser as we describe is not a pressure vessel - technically it does not require silver solder & the following are generalities

1. model boiler steam discharge temperature ~~~~~~~150 degrees C @ ~~~~~~ 2Bar
2. model engine exhaust steam temperature ~~~~~~~75 degrees C
3. melting point of common 50/50 soft solder = 278 degrees C

So based upon these values we see a FOS [factor of safety] [278 divided by 150] = 1.85:1...in accepted engineering calculations for pressures & fluids, the FOS should be 4:1...so clearly we see that the use of soft soldered construction methods are not acceptable for pressures or temperatures as noted @ 1.

In the case of the oil trap condenser we have [278 divided by 75] = 3.7:1 which is ~~~~~close to our recommended FOS of 4:1

Having said this.......if a model maker was experienced with & had the equipment to silver solder such brass or copper components why would he bother to go down an alternate process?

Next point is the pressure gauge test…..common pressure gauges [both industrial or model] will display ZERO pressure when open to atmosphere which is approx 1Bar or ~~~14.7 PSI

It is only compound or specialist absolute gauges that display atmospheric pressure when open to the atmosphere

From here I suggest we understand that we experience pressure losses in pressure lines due to pipe size & length…we also experience a restriction in exhaust lines due to pipe sizing & length, however in model applications adding a pressure gauge in a T line to the discharge to atmosphere of the spent steam would not  register any value on the pressure gauge………

I have used the term ‘pipe’ here as most do….however pipe in engineering terms is a nominal bore pipe schedule eg., ½”nominal bore pipe 21.3mm OD

All of the material we use in steam model applications is ‘tube’ as measured by the OD be it imperial or metric ……  Derek
 

[gondolier88]

Hi Steamboatwillie,

Here's the drawing you wanted.

Greg

[gondolier88]

Hi,

Heres the drawing you wanted- also with a drawing on the right of what I did with mine.

Greg

[steamboatwilly]

Greg. Just what I wanted. My sincere thanks. May I also thank everbody else who kindly replied, also Graupner who confirmed that the drain vent should be closed when not in use. Will

[Canopus]

I actually use an old metal "Andews" tin as I found the volume on the Chedder oil separator only just sufficient with my Puffin unit. The Andrews tin follows the design of the Cheddar unit with the exhaust steam entering high at the side so it will flow round the inside of the container, centrifugal force dumping any condensate and oil to the outside. The effect is to create a central colum of clean stem which can then be exhausted through the funnel without splattering the model with crap!

I have a top pipe for the funnel connector and one at the very side reaching almost to the bottom and either empty using a syringe or by pinching the rubber exhaust hose and using residual pressure to flush the condensate out.

On Canopus all the connnections were done using epoxy glue and I have experienced no problems in five years usage.